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Portions of this document may be illegible electronic image products. Images are produced from the best available original document. Creating artificial reefs from decommissioned platforms in the North : review of knowledge and proposed programme of research

Aabel, J.P.1, Cripps, S J.2, Jensen, A.C.3 and Picken, G.4

* Dames & Moore Group, , . 2 RF- Research, Stavanger, Norway. 3 University of Southampton, Southampton, UK. 4 Cordah, , UK.

Southampton Oceanography DAMES & MOORE /Centre-- A DAMES & MOORE GROUPCQMBANy I

i. Preface

During recent years the subject of decommissioning redundant oil and gas structures has been receiving increasing attention within the industry, regulatory authorities, pressure groups and the public in general. An increasing awareness of the technical problems that are involved, including the great expense (both to the and the tax payers of several nations), and the environmental and social consequences (both positive and negative), has led to the discussion and exploration of a range of, sometimes innovative, potential solutions to the problem. One such scenario that has been suggested is to use suitable, cleaned parts of some of these structures to create artificial attracting reefs. The Decommissioning Communications Project (ODCP) of the E&P Forum, the international petroleum industry federation, convened an Artificial Reefs / Marine Workshop on the 20 November 1996 at their offices in . As a result of considerable interest in the potential of “rigs-to reefs”, four research and consultancy institutes that lead independent R&D work within the decommissioning of offshore structures, were commissioned to produce a report. The aim of this report, presented here, was to summarise work conducted in the field to date, evaluate what further information is required in order to reliably estimate the likely potential for offshore structures as artificial reefs in the , and propose work that would fill those gaps in knowledge. August 1997.

Jens Fetter Aabel Simon Cripps Antony Jensen Gordon Picken Managing Principle Senior Scientist / Reader Senior Research Fellow Director Dames & Moore Group RF-Rogaland Research University of Cordah Southampton Kirkebakken 8, RF Decommissioning Department of Kettock Lodge, N-4012 Stavanger, Unit, Oceanography, Aberdeen Science and Norway. PO Box 2503 Southampton Technology Park, Ullandhaug, Oceanography Centre, Bridge of Don, N-4004 Stavanger, European Way, Aberdeen, AB22 8GU, Norway. Southampton, 5014 3ZH, UK. UK. Tel +47 51 89 08 50 Tel +47 51 87 52 18 Tel: +44 1703 593 428 Tel:+44 1224 414 202 Fax +47 51 89 08 49 Fax+47 51 87 52 00 Fax: +44 1703 596 642 Fax +44 1224 414 250 [email protected] [email protected] a.jensen @ soc.soton.ac.uk [email protected]

pH Dames l moorf . 1. EXECUTIVE SUMMARY T

1 Executive summary

The case for R&D work on North Sea artificial reefs Artificial reefs, man-made structures for attracting or protecting animals, usually fish, or for protecting the environment, have been used world-wide for many centuries. In the North Sea there is no doubt that currently operating and redundant offshore oil and gas structures do attract fish. Whilst there is some information on artificial reefs in general, platform reefs in the Mexican Gulf in particular and general information on the environment around North Sea platforms, there are insufficient data on which to reliably estimate the consequences of a rig-to-reefs programme in the special conditions of the North Sea. There are potentially many benefits that can be derived from platform reefs, for example as an aid to increased yield for commercial fishermen, a means of enhancing fish stocks and protecting habitat from physical damage. In addition there may be a reduction in decommissioning costs for the oil industry (and so tax payers) and in negative environmental impacts inherent with land-based decommissioning techniques. We need however, to be able to answer questions with some degree of reliability. What are the best uses for a reef and how can it be managed within the common resource of the North Sea? What form should such a reef take? How great will be the benefits to fishermen and how can they best achieve them? Will the benefit of a reef as a protection zone against, fishing be significant either in the , or within the as a whole? To what extent would the ecosystem as a whole, and rare species in particular, benefit from such a habitat protection device? There is also the potential for negative impacts, such as loss of fishing area and changes in the ecosystem. Questions to be asked include: is the loss of access significant? Will the socio-economics of the fishermen be changed for the worse? Will the remains of the platform constitute a source of on the sea bed that will detrimentally alter the ecosystem in the region? How will we assess that change? There is much talk about platform reefs in the North Sea, both positive and negative, but little data on which to base any assertions. The work proposed in this report is not a repetition of old studies, it is not purely of academic interest and it does not contain work that is not strictly relevant. The work proposed will build up a picture of how platform reefs function in the North Sea, allowing an assessment of their advantages and disadvantages, if they are likely to be a viable proposition, and if so how they can best be used. This work will need to be of a high academic quality in order to stand peer review from the oil industry, scientist and critics alike. It will be focused towards practically applicable results that will aid the decision making process.

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Without such a programme of work there will be insufficient data on which decision makers, such as legislators, politicians, policy makers, environmental groups and those responsible for managing the marine habitat, can base their judgement and advice. Users of the shared marine resource and interested parties will need open, independent information in order to assess the likely benefits or problems that may result. Information, such as that to be published from this study, will go a long way to aid the assessment of the potential of platform reefs and will greatly assist communications, leading to a more open, realistic discussion based on facts rather than conjecture and suspicion. It is therefore strongly recommended by this independent project group that the proposed study programme be implemented as soon as possible in it entirety. Artificial reefs Marine artificial reefs have been defined in 1996 by the European Research Network (EARRN) as: submerged structures deliberately placed on the seabed to mimic some characteristics of a natural reef. The use of artificial reefs as fishing sites has a long history. Their use for enhancement and coastal zone management is more recent. In general, the abundance and diversity of species at an artificial reef depends on suitable living conditions, a supply of recruits and a higher recruitment and immigration than mortality and emigration. Suitable living conditions may include: access to food resources, shelter from predators and currents, orientation, and normal environmental conditions that are at least within the biological tolerances of the species. Artificial reef designs Artificial reefs have been constructed from many types of material, both natural and man-made. They range, in size and material, from simple wooden , to engineered steel and structures, as well as "materials of opportunity" such as car tyres, old cars and abandoned offshore installations. The majority of artificial reefs have been deployed in inshore, shallow waters. In a European context there is a preference for reefs to be made from concrete, which is a prime building material. There is a philosophical opposition to recycling, on the basis that no dumping of ‘waste’ should be allowed. Distribution Japan has been one of the leading countries that have used artificial reefs as tools, primarily fisheries yield enhancement, dedicating at least 10 % of its coastline to marine enhancement devices, and $750 million on artificial reefs in particular, between 1976 - 1988. Japan has invested considerable effort into the optimisation of reef layouts and . The use, by the Japanese, of artificial reef components resembling jacket structures, has increased during the last few years.

OWES 4 MOORE The USA has also appreciated the opportunities of recreational fishery enhancement derived from artificial reefs and has initiated a national artificial reef programme. Each coastal state develops reefs using both engineered reefs and materials of opportunity. Despite the large investment in artificial reefs in certain countries, the ecological basis behind their function and biology is poorly understood but is actively being researched in and the USA. The variety of materials used and the broad range of conditions in which reefs are deployed limits the conclusions that can be made. Nevertheless, at artificial reefs, high fish densities, biomass and catch rates, in addition to rapid colonisation, are well documented and are often found to be higher on artificial reefs than on natural reefs or randomly selected bottom controls. Rigs-to-reefs in the North Sea The concept of “rigs to reefs” is just one specialist aspect of artificial reef technology. It is generally understood to mean the use of decommissioned offshore oil and gas platforms as artificial reefs. The possibility of using platforms as reefs first arose in the : existing manned structures off the coast of attracted significant numbers of game fish, forming the basis of a substantial sport . There are more than 6500 offshore oil and gas related structures world-wide. While most of the structures are in the Gulf of Mexico (4000), the biggest and most complex structures are found in the North Sea. Within EU and Norwegian waters there are 609 offshore platforms. Most are small steel platforms in the southern part of the North Sea that, by international convention, will need to be totally removed to land. In the deeper, harsher water of the northern North Sea there are steel platforms of up to 65,000 and concrete platforms of up to 850,000 tonnes. Of the 420 platforms in the North Sea, approximately 210 are in the UK sector. In the Norwegian sector there are about 70 working and planned structures, all located in the central and northern North Sea. Only a few structures in the North Sea have stopped production, but several fields and structures are to be taken out of service in the near future. A date for a halt in production for manyof the larger, or new, fields has yet to be decided upon. Artificial reefs programmes in the Gulf of Mexico, using materials of opportunity from decommissioned oil platforms, have proved highly successful and cost-effective. Oil platforms appear to be close to ideal reef components for some purposes, and, if carefully selected, can satisfy many of the design criteria for artificial reefs constructed to attract fin-fish. Though the majority of work on rigs-to-reefs to-date has been carried out in the Gulf of Mexico, care must be taken when applying these findings directly to the North Sea, which represents a different, and in some ways a more hostile, environment. To date, there has been no rigs-to-reefs initiative in the North Sea. There are no high profile steel reefs in the UK sector of the North Sea. The appreciation of how such reefs might function is derived entirely from the study of existing working platforms.

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Previous studies Several short-term studies have been executed around platforms in the North Sea to identify whether these structures are acting as effective de facto artificial reefs. The results of these studies strongly indicate that North Sea platforms do have higher concentrations of commercially valuable fish associated with them, compared with the surrounding habitat. Fish were found at platforms under both ambient and artificial lighting, at all times of the day, and at all seasons. Shoals of saithe, and Norway pout were seen to move slowly around and within steel jackets. Large shoals of saithe were seen around some structures on successive days, and, although there is no proof that these were the same fish, it is clear that fish were spending some time, at least, in the close vicinity of the structure. Observation indicated that fish densities and variety of species were much higher close to platforms than at distances of more than 50 -1,000 m away. Fish densities did not decline gradually with increasing distance from the platform, instead, there was usually a sharp demarcation at the edge of the shoal. How important are any installation-based fish likely to be to the overall North Sea stock? If the fish densities found around the structures surveyed in 1990 were present around the majority (50 % - 80 %) of other installations in the northern and central North Sea, these structures would “retain” around 4,000 to 18,000 tonnes of saithe and 450 to 3,600 tonnes of cod. All the evidence obtained to date indicates that fish living in the vicinity of structures are in at least as good a condition as those collected from the open sea. There is indeed evidence to show that fish frequenting platforms may be in better condition, and growing more quickly, than those at open sea sites. The platform fish studied so far tend to have higher concentrations of hydrocarbons in their muscle tissue than open sea fish, but in only a few cases could these elevated concentrations be attributed to low-toxicity oil- based drilling muds. Such fish have not been found to be tainted. Missing data It would therefore appear that the immediate platform environment is one which fish find acceptable and to which they are attracted. They may find extra food there, shelter from currents, and a reference point for efficient station-keeping. To date though, there is insufficient data to substantiate any or all of these theories. Within the 500m safety zone they will also escape fishing pressure. The structures scattered throughout the North Sea therefore provide local ‘reef ’ utilised by fish for a time. The limited evidence to date suggests that the existing working platforms are having a small, probably beneficial effect, on local fish populations. The extent to which these habitats are having any long-term, or significant effects on the total populations of these species will only be gauged when a fuller understanding of the temporal utilisation of platforms by fish and their possible movement between platforms is achieved. It is clear, however, that a reef effect has been created around platforms, and it

DAMES & MOORE influences the behaviour of commercially important species to some, unknown, extent. The significance of the results of these studies in terms of either the benefit to fish populations or the benefit to fishing operations are difficult to assess and remain to be fully investigated. Implementation in the North Sea Three different scenarios are discussed. They represent a range of different solutions for the creation of one or more artificial reefs based on the structures in the North Sea: In situ toppled reef emplacement: every structure will be toppled in place individually. Clustered reef emplacement: one or more sites for construction of one or more artificial reefs will be established. When a structure is abandoned, it will transported (if this is feasible) to one of the designated sites. Abandon in place: the structures are left in place, probably after the equipment has been removed and the structures have been secured. This scenario is currently only being considered for large concrete structures. If any of these scenarios are to be realised it is obvious, given the current climate of significant concern about disposal of waste at sea, that there is a need to demonstrate that chosen actions are the best environmental options. There is pressure from the fishing lobby to remove all obstructions to , so this must be properly assessed and subsequent actions, justified and planned to provide maximum benefit, be it environmental or fishing related. Benefits of artificial reefs At present there is insufficient data available to assess the “rigs to reefs” options available in the North Sea. The distance offshore and the strictly enforced exclusion zones around production platforms has prevented much qualitative data being gathered. Oil platforms were seen as good sports fishing locations in the USA and so a need to preserve that amenity was seen as important. In where some structures are regularly harvested for platforms are seen as being potentially useful in (Barcelona convention). The absence of a proven function or utility for users other than the oil industry in the case of the North Sea platforms is a problem in that there is no incentive from outside the oil industry for assessing their potential to provide a management tool for fishing or fishery or nature conservation management. Current knowledge does not allow an effective assessment of whether the creation of artificial reefs from the jackets of North Sea platforms can/will have benefits to fishing, fisheries management, the environment (in the form of habitat provision and protection) or coastal community socio-economics. Evidence tentatively suggests that artificial reefs can be used either to benefit fishermen, as an enhanced fishing site, or the fishery, as a protection area. The two uses are largely mutually exclusive. The work proposed will attempt to provide data that will allow the most suitable usage to be decided,

KGAMES* MOORE given various parameters including reef design and location. Offshore and inshore reefs are likely to function in very different ways.

Proposal for further work Research is urgently needed to provide an appreciation of the current status of jackets as artificial reefs and provide information on fish residency and behaviour, the physical environment and the benthos. This will support the modelling of possible artificial reef creation scenarios where jackets provide the major structural components. Without such data it is unlikely that a North Sea “rigs to reefs” proposal will succeed, as there will be insufficient information to evaluate a proposal one way or the other. The proposal will be perceived merely as a cost cutting exercise by the oil industry During the proposed study programme it is intended to gather data relevant to two possible modelling options: • that jackets are used to create artificial reefs offshore to facilitate habitat, fishing and/or fishery management • jackets are moved inshore to provide artificial reefs for fishing and other exploitation as well as having a possible role in coastal fishery resource partitioning. The proposals encompass: • The creation of a demonstration inshore steel lattice reef to allow evaluation of the economic benefits of such a structure for coastal communities • The investigation of an offshore, “cold” platform to evaluate, over three years, fish presence, site loyalty, rate of recruitment, behaviour in relation to water movement, feeding and food sources, growth rates and population structure around a platform in contrast to a control site (Fig. 1). Consideration of the fouling community, physical environment and benthos will allow an appreciation of possible nature conservation benefits of reef creation. With these data, reef creation scenarios will be modelled and assessed for benefit to the fishery, fishing yield and/or nature conservation and an effective course of action proposed for the creation of artificial reefs from steel jackets. Further, a reef management plan incorporating optimal usage, fisheries management, socio-economic and ownership aspects will be proposed, based on the results of the field study programme. Formation of a technical advisory group with membership from interested parties to provide a communication pathway between the scientific working group and NGOs, fishermen’s associations, government, environmental organisations and the like, is proposed. The total provisional cost for the full 5 year offshore reef research programme is £ 2,411,200, though substantial reductions in cost are possibly if vessel charter can be sourced outside of the programme. The total

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provisional cost for the full 5 year inshore reef research programme is £ 1,352,00, though sub-programmes are also proposed.

ARP2000 plan of work Offshore reef

Benthos for Quantify fish Measurable Juvenile Sustainable Effect on energy or retention? benefit? protection? fishery? vicinity? conservation

Artificial reef fisheries management model / plan

Measure of Positive vs. Estimate of Management usefulness to negative best useage plan fish & fishery impacts

Figure 1: Summary of offshore reefplan of work

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Contents

I. PREFACE...... I

1 EXECUTIVE SUMMARY...... * ...... 1

2 PICTORIAL GLOSSARY...... 11

3 INTRODUCTION...... 18 3.1 General background and history...... 18 3.2 Rigs to reefs...... 21

4 ARTIFICIAL REEF TECHNOLOGY AND RELATED EXPERIENCE IN THE NORTH SEA AND NE ATLANTIC...... 25 4.1 General introduction...... 25 4.2 UK sector...... 25 4.2.1 Historical overview...... 25 4.2.2 Fish aggregation...... 26 4.2.3 Numbers and variety of fish at a deep, submerged structure ...... 30 4.2.4 Monitoring the residence times and movements of fish at platforms...... 30 4.2.5 The contamination and taint of fish at platforms...... 31 4.2.6 Health and growth of fish around oil platforms...... 37 4.3 Norwegian sector...... 38 4.4 Other artificial reef activity in the North Sea...... 41 4.5 Conclusions...... 42

5 REVIEW OF ARTIFICIAL REEFS WORLD-WIDE...... 44 5.1 Japan...... 44 5.2 USA...... 45 5.3 ...... 46 5.3.1 UK...... 46 5.3.2 ...... 47 5.3.3 ...... 50 5.3.4 Portugal...... 51 5.3.5 Spain...... 51 5.3.6 ...... 53 5.3.7 ...... 53 5.3.8 Finland...... 53 5.3.9 The European Artificial Reef Research Network (EARRN)...... 54 5.4 Other countries...... 54

6 BENEFITS OF ARTIFICIAL REEFS...... 56 6.1 Summary of benefits ...... 56 6.2 Fisheries management: a benefit for managers...... 56

III Dames A moore 6.2.1 Justifying the use of offshore structures for fisheries enhancement...... 57 6.2.2 Functioning of a reef within a fishery...... 57 6.3 Fish concentration and stock enhancement: a benefit for fishermen...... 57 6.3.1 Fish behaviour ...... 57 6.3.2 Stock enhancement...... 59 6.4 Fishing effort reduction: an economic benefit for fishermen...... 61 6.4.1 Commercial fishing...... 61 6.4.2 Recolonisation...... 62 6.5 Fish stock protection: a benefit for future stocks ...... 63 6.6 Aquaculture / ranching: a benefit for farmers...... 64 6.7 Biodiversity, habitat protection and restoration: a benefit for the environment...... 64 6.7.1 Biodiversity management...... 64 6.7.2 Provision of new habitat ...... 65 6.7.3 Restoration of damaged habitat ...... 65 6.7.4 Protection of existing habitat ...... 65 6.8 Reef productivity: a limited local benefit ...... 66 6.9 Artificial reefs within the EU : a benefit for the fishery...... 67 6.10 Transfer of management, ownership and liability: a benefit for fishermen and the current operators...... 67 6.11 Changes in fishing practice: a further fisheries benefit ...... 69

7 IMPLEMENTATION OF THE RIGS TO REEFS CONCEPT IN THE NORTH SEA...... 71 7.1 Introduction...... 71 7.2 Scenarios for artificial reef creation from jackets ...... 72 7.3 In situ toppledemplacement...... 72 7.4 Clustered reef site...... 72 7.5 Abandon in place for CGBS...... 73 7.6 Potential locations for reefs...... 74 7.6.1 UK sector...... 74 7.6.1.1 In situ toppled reefs...... 74 7.6.1.2 Clustered toppled reefs...... 75 7.6.2 Norwegian sector...... 77 7.6.2.1 Installations...... 77 1.6.2.2 Suitable areas in the Norwegian part of the North Sea...... 79

8 PROPOSAL FOR FURTHER RESEARCH...... 82 8.1 The need for further work ...... 82 8.2 Inshore Reefs...... 84 8.2.1 Introduction and purpose...... 84 8.2.2 Proposed Reef...... 84 8.2.2.1 Proposed site...... 84

GAMES 4 MOORE COKDil I S iMhMMUUlM TU

5.2.2.2 Consultation...... 85 8.2.2.3 Site description...... 86 5.2.2.4 Proposed reef module...... 86 5.2.2.5 Flotation and deployment...... 87 8.2.3 Proposed Programme of Work ...... 87 8.2.3.1 Introduction...... 87 8.2.3.2 Proposed programme of scientific research...... 88 8.2.3.3 Provisional inshore reef programme budget ...... 89 8.3 Offshore reefs...... 91 8.3.1 The aims of further work ...... 91 8.3.2 Studies proposed...... 93 8.3.2.1 Acoustic survey of fish shoals...... 93 5.3.2.2 Acoustic telemetry...... 93 8.3.2.3 Physical water column...... 95 8.3.2.4 Fish size, feeding, growth and contamination...... 96 8.3.2.5 Size frequency analysis...... 96 8.3.2.6 Stomach contents analysis...... 96 8.3.2.7 Instantaneous growth rate...... 97 8.3.2.8 Tainting and contamination...... 97 8.3.2.9 Fisheries...... 98 8.3.2.10 Commercial fishing...... 102 8.3.2.11 Benthic sampling...... 104 8.3.2.12 Assessment of epifauna on the jacket ...... 106 8.3.2.13 Plankton ...... 106 8.3.3 Site justification...... 106 8.3.3.1 Wrecks as unsuitable sites...... 106 8.3.3.2 Non-operational platforms as suitable sites...... 108 8.3.4 Survey programme...... 108 8.3.4.1 Aims...... 108 8.3.4.2 Planned activities in 1998 ...... 110 5.3.4.3 Planned field-work during 1999 ...... 110 8.3.4.4 Planned field-work during 2000...... 112 8.3.4.5 Planned field activities in 2001...... 112 8.4 Technical Advisory Group...... 118

9 CONCLUSIONS...... 119

10 REFERENCES...... 122

|H DAMES 1 MOORE 2. PICTORIAL GLOSSARY 11 2 Pictorial glossary

Figure 2: The components of a steel-piled platform. Figure 3: The main components of a multi-legged concrete platform (). Figure 4: Toppling the steel jacket after the removal of topsides (1). Figure 5: Toppling the steel jacket after the removal of topsides (2). Figure 6: Creating a 55m clearance by cut and place after the removal of topsides. Figure 7: Schematic diagram of a reef cluster (not to scale).

|H DkMESI MOORE topsides

0 100

Figure 2: The main components of a steel-piled platform.

gCMtrSA MOORE metres 100

Figure 3: The main components of a multi-legged concrete platform (Condeep).

HI DUMB i MOORE level

sea seabed

the

on

lands

structure

pull

by

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winch

initiated

from topple

hinges

metres for

removed

de-ballastod

except

cut legs

topsides piles

Figure 4: Toppling the steel jacket after the removal of topsides (1). n level

sea seabed

the

on

lands

structure

pull

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winch

initiated

from topple

cut

metres piles removed

and

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Figure 5: Toppling the steel jacket after the removal of topsides (2). 16

Figure 6: Creating a 55m clearance by cut and place after the removal of topsides. 17

deck sub-structure with navigational aids

sectional elevation on A - A'

Figure 7: Schematic diagram of a reef cluster (not toscale).

counnn jUj DAMES A MOORE 3. INTRODUCTION 18

3 Introduction

This chapter will set the scene for further discussions, by describing what artificial reefs are, how they originated, what uses they have been put to, how they are thought to function. The concept and history of using oil and gas structures as artificial reefs (rigs-to-reefs) will be briefly introduced.

3.1 General background and history Any structure that, deliberately or not, provides the effect of a natural reef, may be denoted an artificial reef. Marine artificial reefs have been defined in 1996 by the European Artificial Reef Research Network (EARRN) as: submerged structures deliberately placed on the seabed to mimic some characteristics of a natural reef. Stephan et al. (1990) state that, "artificial reefs represent a tool by which man can elicit changes in the ecosystem to achieve benefits". Many different artificial reefs have, for a long time, been placed in many different environments throughout the world. The use of artificial reefs as fishing sites has a long history, presumably arising from chance observations of fish being attracted to objects placed in the water. An European example comes from Italy; in Sardinia tuna have been caught for hundreds of years in complex floating net traps weighted with stones. At the end of each season the stones were cut loose and fell to the seabed. Fishermen noticed how many fish species were attracted to these accumulating piles of weights and fished these “accidental” reefs outside of the tuna season. Artisanal fishermen in tropical countries without any scientific or assistance have probably built the majority of inshore artificial reefs and fish attracting devices (FADs). Such reefs increase catches in local fishing grounds using simple, readily available, materials such as rocks, trees, bamboo and scrap tyres. Artificial reefs are habitat enhancement devices placed in the marine or freshwater environment to provide, in the best examples, a specific habitat preference for target species. By increasing the carrying capacity of the natural environment their purpose is to increase the overall productivity. Artificial reefs have been used for centuries by coastal communities and have become popular fisheries management tools world-wide (De Silva, 1989; FAQ, 1990). Traditionally, artificial reefs have been constructed for fishery enhancement, but they are now built to serve a number of purposes: • improvement of fishing catches and quality; • provision of spawning areas, and protected juvenile and finfish habitats; • shellfish and finfish ranching to protect natural stocks; • shore protection and control of beach erosion; • breakwaters;

BQwrs&Moofii: • preventing trawlers from using certain areas; • restricting fishermen from shipping lanes; • reduce fishing pressure on defined stocks; • mitigation and restoration of degraded habitats; • amenable SCUBA sites in sheltered areas; • waste disposal options; • scientific experimental grounds; • recycling of nutrients in areas where bivalves (molluscs) are farmed; • resolve potential conflicts between user groups of the marine resource. Artificial reefs function as fishery enhancement devices because they resemble natural reefs. In general, they show a similar species composition and community structure to natural reefs in the same area, assuming they are subject to the same environmental conditions (Ambrose & Swarbrick, 1989; Bohnsack & , 1985; Matthews, 1985). and invertebrates usually colonise new reef materials fairly rapidly. The final composition and abundance of the artificial reef community may vary considerably, depending on the composition of the substrata, the season the material was deposited and numerous environmental variables, including water movement, water temperature and water chemistry. The depth at which the reef is situated is also important, especially with regard to algal colonisation. After initial colonisation, populations often fluctuate cyclically or seasonally. Assemblages of biological communities may be affected by competition, predation and physical disturbance (Bohnsack et al., 1991). Fish also recruit rapidly to an artificial reef, sometimes within hours of installation (Bohnsack & Sutherland, 1985). They often reach a climax population size within a few months of deployment, creating an enhanced fishing zone up to several hundred metres from the reef. Larger catches are however, generally limited to within 60 m (Mottet, 1981). An equilibrium community structure is usually achieved within 1-5 years, although there are often seasonal variations in the number of species and individuals. A wide variety of environmental cues are thought to play an important role in attracting fish to such devices, including: current patterns; shadows; species interactions; ; touch; pressure; and visual cues of size, shape, colour and light (Bohnsack & Sutherland, 1985). Different species exhibit different behavioural preferences throughout their life cycle. In particular, several fish species have been shown to stay near artificial structures for protection when small and vulnerable to predation (Anderson et al., 1989). An artificial reef can be important for the fish stocks of a much larger area than the reef itself, because it gives protection to the fish during their most vulnerable stages. Some Japanese reefs, for example, are built to improve spawning, recruitment and survival of animals during the early stages of their life histories (Mottet, 1981). In general, the abundance and diversity of species at an artificial reef depends on suitable living conditions, a supply of recruits and a higher recruitment and immigration than mortality and emigration. Suitable living conditions may include: access to food resources,

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"" "™ shelter from predators, and normal environmental conditions that are within the biological tolerances of the species (Bohnsack et al., 1991). Artificial reefs have been constructed from many types of material, both natural and man­ made. Theyrange, in size and material, from simple wooden constructions, to engineered steel and concrete structures, as well as "materials of opportunity" such as car tyres, old cars and abandoned offshore installations (Kjeilen et al., 1994). An artificial reef area can be composed of single reef units, groups of units, or a larger reef complex comprising several groups of reef units. The majority of artificial reefs have been deployed in inshore, shallow waters (Kjeilen et al., 1994). Japan has been one of the leading countries that have used artificial reefs as fisheries management tools, dedicating at least 10 % of its coastline to marine enhancement devices. Japan has invested considerable effort into the optimisation of reef layouts and construction. The USA has also appreciated the opportunities of recreational fishery enhancement derived from artificial reefs and has initiated a national artificial reef programme, each coastal state develops reefs using both engineered reefs and materials of opportunity. Despite the large investment in artificial reefs in certain countries, the ecological basis behind artificial reef function and biology is poorly understood. The variety of materials used and the broad range of conditions in which reefs are deployed limits the conclusions that can be made. Nevertheless, at artificial reefs, high fish densities, biomass and catch rates, in addition to rapid colonisation, are well documented (Bohnsack et al., 1991; Bohnsack & Sutherland, 1985), and are often found to be higher on artificial reefs than on natural reefs or randomly selected bottom controls (Ambrose & Swarbrick, 1989; Bohnsack et al., 1991; Bohnsack & Sutherland, 1985; De Martini et al., 1989; Fast & Pagan, 1974; Hueckel et al., 1989; Laufle & Pauley, 1985). Also, artificial reefs generally serve to attract more commercially valuable species than those associated with soft sediments (Seaman et al., 1989). This has been attributed to the greater complexity offered by artificial reefs. Overall, artificial reefs are thought to aggregate existing scattered individuals and allow secondary biomass production by (Bohnsack & Sutherland, 1985; FAQ, 1990): • increasing survival and growth of larvae and juveniles by providing a settlement substratum, shelter from predation and additional food resources; • creating new food webs through the provision of new spaces, habitats and colonisation patterns; • protecting the sea-bed and nursery grounds; • recycling energy byretaining a localised ecosystem. There is concern that artificial reefs can cause over-fishing. In some instances this has occurred (Polovina, 1989). Evidence from several researchers however, indicates that reef deployment increases the fish populations of particular species without interfering with the natural fisheries of adjacent habitats (Alevizon & Gorham, 1989; Bohnsack & Sutherland, 1985; Stone et al., 1979). Over-exploitation of reef-associated fish stocks is generally not expected as a consequence of artificial reef deployment (Bohnsack & Sutherland, 1985),

Wjs dames 4 moore because artificial reefs can generally be expected to provide both fish aggregating and biomass producing qualities (Bohnsackef al., 1991). Research scientists are active throughout the world, working on a wide range of reef related questions in what is a fairly new branch of marine science. The majority of the work has focused on establishing what happens when a reef is deployed, considering speed and “naturalness” of colonisation by animals and plants and the implications of this for habitat protection or fisheries exploitation. Scientists frequently work on artificial structures placed for one purpose in order to investigate other uses. In an European context we see fisheries investigations around reefs placed to protect habitat and behavioural studies on reefs places as material test sites. This does not negate the value of work done but it is important to realise that a lot of results are derived from “structures of opportunity” rather than reefs purpose-built for the scientific project being undertaken. International communication between scientists is maintained by a four yearly international conference and, recently in Europe, by the European Artificial Reef Research Network (EARRN). Engineering interests have become involved in the design and deployment of artificial reefs (as seen in Spain, Hong Kong and Japan) where civil engineering companies see a commercial market developing for such structures. Such companies can be very influential in design and construction, seemingly often designing reef structures without formal research into the requirement of target species, relying on trial and error and human aesthetics for manydesign developments. In summary, artificial reefs are used to enhance fisheries by creating fishing opportunities, reduce user conflicts, save time and fuel, reduce fishing effort, make locating fish more predictable, increase public access and safety by deployment near ports, and increase fish abundance at deployment sites by attracting dispersed fish and producing a new fish biomass. It has been suggested that the most likely applications for artificial reefs in commercial fishing are to create or expand existing nursery or spawning grounds for some species (Sheehy, 1985) though the latter is unlikely in the North Sea. Stocking in specially prepared and enhanced areas can also improve the initial survival and growth of juveniles (Sheehy, 1985).

3.2 Rigs to reefs The concept of “rigs to reefs” is just one aspect of artificial reef technology. It is generally understood to mean the use of decommissioned offshore oil and gas platforms as artificial reefs. The possibility of using platforms as reefs first arose in the Gulf of Mexico and stemmed from the fact that existing manned structures off the coast of Louisiana attracted significant numbers of game fish, forming the basis of a substantial sports fishing industry where none The "rigs-to-reefs" concept is one specialised aspect within the field had previously existed (Harville, 1983). Recent experience shows that jacket-like, open lattice work structures exhibit good reef characteristics, attracting a variety of mid-water and species. The use, by the Japanese, of artificial reef components resembling jacket structures, has increased during the last few years (Grove et al., 1991).

||jj O wes t moofie In general, platforms make good artificial reefs because they provide: • hard substrata habitats; • an abundant food supply from attached and motile species; • a visual, tactile or auditory reference point in an otherwise unstructured environment; • structural openness permitting adequate circulation of water within the interior; • a large surface area, which in conjunction with water circulation, encourages abundant biofouling arid benthic hard-bottom species; • physical design complexity providing shelter from strong currents and predators; • a range of habitats throughout the water column allowing different species to remain at their most favourable depth and increase their range vertically; • spawning and nursery grounds. The degree of importance of each of these factors depends on the particular species and life cycle stage of the species involved (Driessen, 1985). Operating oil platforms are unique as artificial reefs because they extend throughout the water column, providing benthic, mid-water and surface habitats. Fish studies around Gulf of Mexico platforms have revealed that fish are present at all depths, with the greatest variety in the range 30 - 70m depth (Ditton & Falk, 1981). It is believed that the platforms provide the basis for a substantial and that their presence has changed relatively unproductive areas into diverse, dynamic and highly productive ecosystems (Driessen, 1985). There are more than 6500 offshore oil and gas related structures world-wide (Gurney, 1992). The structures are concentrated in different areas, with the majority (4000) occurring in the Gulf of Mexico (Gurney, 1992; Reggio, 1987a). Other important areas include the west coast of the USA, the China Sea, the and the North Sea. While most of the structures are in the Gulf of Mexico, the biggest and most complex structures are found in the North Sea. By far the greatest concentration of oil-related artificial reefs is found in the Gulf of Mexico. These reefs consist of jackets or topsides which have been totally submerged in situ or at another chosen location, for the specific purpose of creating an artificial habitat (Bleakley, 1982a; Bleakley, 1982b; Gurney, 1992; Parker & Henkhaus, 1989; Quigel & Thornton, 1989; Sheehy & Vik, 1982; Stark, 1990). Both operational platforms and decommissioned structures deployed as artificial reef components have been investigated. Both were found to exhibit the same reef characteristics (Seaman et al., 1989; Stanley & Wilson, 1991). The species composition on Gulf of Mexico platform reefs resembles the nearby natural reef communities (Seaman et al., 1989) although species diversity, in some instances, was found to be slightly lower, perhaps because of the relatively young age of the platforms (Hastings et al., 1976). On the other hand, it has been estimated that there are 20 - 50 times more fish around platforms than at soft bottom control areas of the same size, and 5 times more fish than on nearby natural reefs (Driessen, 1985). Several investigations have revealed that trophically independent, transient fish are often dominant in terms of biomass, but habitat faithfulness has been identified for some pelagic and benthic species (Seaman et al., 1989). One hundred and fifty species that were unknown in the Gulf of Mexico 30 years ago have now been identified at platforms (Driessen, 1985). Numerous species of fish and invertebrates at the hatching, juvenile and nesting stages have also been observed around Gulf of Mexico platforms (Driessen, 1989). Artificial reefs programmes in the Gulf of Mexico, using materials of opportunity from decommissioned oil platforms, have proved highly successful and cost-effective. It is well known that desirable fish species are associated with the structures, and there is even talk of the damage that could be done to fisheries by the total removal of platforms which are already acting as de facto reefs. Although some materials of opportunity represent a compromise in design, oil platforms appear to be are close to ideal reef components for some purposes, and, if carefully selected, can satisfy many of the design criteria for artificial reefs constructed to attract fin-fish. By the year 2,000 it is expected that 1,625 platforms will have been removed from the of Louisiana. The high cost of removal and the potential loss of this commercially important habitat have been the incentives for rigs-to-reefs initiatives. Under new US federal policy guidelines, many of these platforms will be used for artificial reef construction (Reggio et al., 1986; Reggio, 1987a). Without these structures, offshore sport fishing activities in Louisiana would be greatly reduced. There are certainly differences between the Gulf of Mexico and the North Sea, but there are also some similarities. The sea-bed area is mainly featureless, soft bottomed and flat, with no natural reefs. In the North Sea however the temperature is lower, the depth is greater and the fauna is different, but the same pattern of aggregation, protection and increased growth of fish may be expected. Due to the greater distances to shore, compared with the Gulf of Mexico, little recreational fishing is expected, and the benefits in terms of increasing standing stocks of fish will mainly accrue to the commercial fishing industry. Platforms in the Gulf of Mexico increase local fish stocks because they provide hard bottom habitats that are important for fish and other marine life. Increase in local fish stocks is primarily a result of fish aggregation, but also increased biomass production, as a result of decreased mortality and increase in fish size, is possible. In recent years, offshore oil and artificial reef developments off the coast of Louisiana and have been recognised as having a significant direct positive effect on offshore recreational fishing, commercial hook and line fishing, as well as SCUBA diving (Reggio, 1987a; Reggio, 1987b). Recreational fishing, worth millions of dollars, has developed around offshore installations and artificial reefs, especially off the coast of Louisiana (Driessen, 1985; Reggio et al., 1986). Commercial catch landings, particularly of shrimp, in the Gulf of Mexico have shown a substantial increase (Driessen, 1989). The majority of the 4,000 Gulf of Mexico oil and gas structures are placed in water depths ranging from 30 - 100 m, at distances of 2.5 - 143 km from the shore (Bleakley, 1982a; Corcoran, 1995; Driessen, 1985; Driessen, 1986; Harville, 1983; Seaman et al., 1989; Stanley & Wilson, 1991; Williams, 1995; Reggio et al., 1986). It has been estimated that these platforms account for 28 % of the known hard bottom habitat in the Gulf of Mexico

||j CWtfESA MOORE

*■ " " (Driessen, 1985; Reggio et ai, 1986). Three thousand seven hundred of these platforms are placed off the coast of Louisiana, providing an estimated 90 % of the hard bottom habitat in this state (Reggio, 1987 a; Reggio, 1987b; Stanley & Wilson, 1990).

SSciAMiStMOailE 4. ARTIFICIAL REEF TECHNOLOGY AND RELATED EXPERIENCE IN THE NORTH SEA AND NE. ATLANTIC 4 Artificial reef technology and related experience in the North Sea and NE Atlantic

In this chapter, the knowledge and information that is useful in describing the functioning of artificial reefs in northern European and their effectiveness in attracting fish, is presented. This includes studies both on reefs themselves and on a wide range of aspects pertaining, but not directly related to artificial reefs, such as fish and contaminants distributions.

4.1 General introduction There are no high profile steel reefs in the North Sea. appreciation of how such reefs might function is derived entirely from the study of existing working platforms or structures that have been accidentally sunk without being planned as an artificial reef. The following sections describe the results of several studies and surveys undertaken in the North Sea over the period 1987 to 1997, which can be grouped under the following headings: • studies on the presence, abundance and at platforms; • studies on the contamination and taint of fish at platforms; • studies on the health and growth rates of fish at platforms.

4.2 UK sector

4.2.1 Historical overview Several research studies, funded by the Offshore Operator’s Association Ltd (UKOOA) and individual operators, have been undertaken to investigate the interaction between fish and oil-related structures in the North Sea. In 1987, the numbers and variety of fish species found in the vicinity of installations were ascertained by examining incidental fish activity seen on videotapes taken during annual sub-sea inspections. The results of this study were then complimented by a special survey at a deep offshore wreck in the Beryl Field (1988), to examine fish activity at a structure which was inactive and did not penetrate into the photic zone. Knowing that several species of fish were commonly found in very close association with working platforms, a study of the flavour and tissue hydrocarbon content of fish caught at platforms was carried out in 1988, and this expanded on the findings of an earlier study from 1987. Preliminary work was also undertaken with a view to initiating a study which would assess the actual utilisation that fish may make of both active and inactive structures, by monitoring the presence and movement of fish around the structures using acoustic tracking. In the period 1987-89, a two year research programme was carried out which used biochemical techniques to determine the growth rates and condition of fish found living close to platforms in comparison to fish caught in the open sea. Finally, a -based sonar survey of fish activity, combined with a study of fish contamination and taint, was completed in 1990. Together, these studies have extended knowledge on the interaction between platforms and their associated fish, and on the likely response of fish to, and their utilisation of, large inactive oil-related structures at offshore locations.

4.2.2 Fish aggregation The aims of these studies were to determine the extent of fish aggregation at offshore oil and gas platforms, to identify which species were present, to ascertain what their depth distribution was on the structure, and to assess sizes and number of individuals. The operators of fifteen platforms in the UK North Sea (Table 1) provided randomly selected videotapes from recent sub-sea inspections, and these were reviewed by a biologist. Platforms selected for this survey were chosen to represent the main of the North Sea (southern, central, northern and central inshore) and the two types of structure in the UK sector, steel piled jacket and concrete gravity platform. In addition, videotape inspections of pipelines in the northern North Sea, central North Sea and southern North Sea were reviewed (AUMS, 1987a). Table 1: Structures and pipelines studied in the four areas of the UK North Sea (AUMS

Area Structure Pipeline Northern North Sea Thistle A Magnus to Ninian Central Heather A North Brent A Brent Flare Central North Sea Brae A Forties A to Forties C Forties A Fulmar to Clyde Tartan A Beryl Bravo Beryl Condeep Beryl Flaretower Beryl SPMII Central North Sea, inshore Beatrice AD Beatrice AP Southern North Sea West WB West Sole to Easington

Of the 134 videos viewed, 103 (77%) showed some degree of fish activity. The quantitative data on major species found around structures in the northern and central North Sea are summarised in Tables 2 and 3. Table 2: Depth range, abundance and density for the major species recorded around structures in the northern North Sea. Major Species Depth Range Max. No. Max. (m) Observed Densities Observed Saithe -21 to seabed 2000 2.0 m"3 Cod -40 30 0.2 m"3 Ling -100 to seabed 50 0.5 m'3 Norway Pout -140 to seabed 5000 5 m"3

Table 3: Depth range, abundance and density for the major species recorded in the central North Sea. MajorSpecies Depth Range Maximum Numbers Maximum Densities (m) Observed Observed Saithe -2 to seabed 500 3.0 m"3 Cod -12 to seabed 100 0.2 m"3

Steel structures in the northern and central sectors had shoals of saithe , swimming around and within the lattice work of the steel jacket. Shoals of up to 2,000 individuals at densities of 3 m'3 were observed in the depth range -21m to the seabed. Individuals were generally in the size range 40 cm to 60 cm indicating that they were probably 2 to 3 years old. Other fish seen at these depths included {Melanogrammus aeglefinus) and whiting { merlangus). Saithe shoals generally declined in density with increasing depth, but at the base of the jacket up to perhaps 15 m from the seabed, further smaller shoals of saithe were found. Other species were also found in this lower zone, including cod Gadus morhua. Cod were seen in shoals of up to 100 individuals at densities of 0.2 m"3, with individuals up to 100 cm long. Immediately above the seabed, and around any small pieces of debris lying within the confines of the jacket, a variety of species was found including ling (Molva molva), wolf­ fish (Anarchichas lupus), Norway pout (Trisopterus esmarkeii) and red fish (Sebastes marinus). Large shoals (5,000 individuals, density 5 m"3) of Norway pout were seen near the seabed, and at short distances away from the platform. In the southern North Sea, saithe and cod were less abundant, but the variety of species near the seabed in an around platforms increased, with (Pleuronectes platessa), dab (Limanda limanda), bib (Trisopterus luscus) and sole (Trisopterus minutus). Concrete structures also had small shoals of saithe swimming in the mid-water region, and numerous fish close to the horizontal tops of the tanks at about 70 m depth, and the usual variety of species around the base of the platform on the seabed.

DAMES & MOORE Fish could be found at platforms under both ambient and artificial lighting, at all times of the day, and at all seasons. Shoals of saithe, cod and Norway pout were seen to move slowly around and within steel jackets; when disturbed by the ROV they moved to one side, but clearly remained orientated or fixed on the structure. At no time was the impression gained that the ROV had just happened to observe fish which were ‘passing by’ the structure, having encountered it on their normal movements. Large shoals of saithe were seen around some structures on successive days, and, although there is no proof that these were the same fish, it is clear that fish were spending some time, at least, in the close vicinity of the structure. Observation indicated that fish densities and variety of species were much higher close to platforms than at distances of more than 50 - 1,000 m away from them. In some of the videotapes, all four faces of small structures could be seen at one time, and it was clear that the shoals of saithe, in particular, were concentrated around the platform. Fish densities did not decline gradually with increasing distance from the platform; instead, there was usually a sharp demarcation at the edge of the shoal. Videotapes taken along pipelines revealed that elevated densities of fish near the seabed did not extend more than 20 - 50 m beyond the platform. ‘Background ’ densities were achieved very quickly when following the pipeline away from the platform. A second survey of fish numbers and densities was conducted by sonar in 1990. Four installations, Brae Bravo, Maureen, MCP-01 and Tartan, were visited to provide a range of structural types for the hydroacoustic survey, which was undertaken using a transducer deployed from a bow crane. The vessel was manoeuvred around the installations to position the transducer in various positions around and at different distances from the structure. Open sea areas were also surveyed for comparison. The printed echograms produced by the Simrad EK500 system were then analysed to determine the characteristics and distribution of the fish around the installations. The size range of saithe caught at the different locations were broadly similar, mean length 46.2 cm - 53.5 cm and mean weight 1.4 kg - 2.1 kg. Their diet was composed entirely of natural food items such as sandeels and small shrimps. The cod caught at Maureen, mean length 66.3 cm, mean weight 3.1 kg, were generally larger than those from the open sea, mean length 49.8 cm, mean weight 1.4 kg. Three types of fish were observed in the echograms generated by the hydro-acoustic survey. The first were fish closely associated with the seabed either as individuals or small shoals. The second were individual mid-water fish and the third were mid-water shoals. The latter categories were termed pelagic because of the mid-water habit. The fishing activities suggest that the pelagic shoals and at least some of the pelagic individuals were saithe whilst the demersal, bottom fish were for the most part cod. The abundance of increased near the installations at three sites. This aggregation was restricted to a large extent to within 100 m of the structure. The bottom fish which were much less abundant also exhibited aggregation. Based upon these results an estimate of the overall abundance of fish in the aggregations around the installations was determined. These results are presented in Table 4. It should be emphasised that many assumptions were included in these calculations and that although the qualitative aspects of the data are accurate the quantitative estimates should be considered indicative at this stage. The aggregations of saithe were estimated to contain around 70,000 to 115,000 individuals and 100 - 250 tonnes of fish. A similar area of open sea may contain around 500 individual fish amounting to around 1 biomass. It was also estimated that between 8,000 and 17,000 bottom fish were found within 100 m of the structures, representing between 10 and 50 tonnes. The densities of fish in the shoals was estimated at 3 x 10'2 fish m"3 with individual fish at between 3 x 10"3 to 8 x 10* 4 fish m "3. Open sea fish were at a density of around 8 x 10"5 fish m"3.

Table 4: Abundance and biomass estimates for within 100 m of each installation and for an equivalent water volume in the open sea, for comparison Pelagic fish Demersal fish

Platform Abundance Biomass Abundance Biomass Fish Kg Fish Kg Brae bravo 4,140 5,796 10,764 23,681 Maureen 115,128 253,281 16,848 50,544

Tartan 78,804 110,340 — — Mcp-01 79,815 95,778 7,956 10,353 Open sea 565 1,131 (7,000,000 m3)

The presence and characteristics of fish around the installations appeared to mirror the natural behaviour of the different species. Saithe are known as a shoaling fish which is attracted to discontinuities such as wrecks and rock outcrops in the sea. Cod in the North Sea tend to be more solitary and only aggregate at spawning times. Much discussion in other studies of fish aggregation has focused upon possible attraction mechanisms. The evidence from this study suggested that the installations merely provide a large structure which is naturally attractive to fish, particularly saithe. A question which is often raised is how important are any installation-based fish likely to be to the overall stock. If the fish densities found around the structures surveyed in 1990 were present around the majority (50 % - 80 %) of other installations in the northern and central North Sea, these structures would “retain” around 4,000 to 18,000 tonnes of saithe and 450 to 3,600 tonnes of cod. The overall stocks of saithe and cod are each estimated at 600,000 tonnes. Therefore, the aggregations that might be present around fixed platforms in the central and northern North Sea may account for 0.7 % to 3 % of total saithe stocks and 0.08% to 0.6% of total cod stocks. It should be remembered that the quantitative estimates reported in the UKOOA 1990 study should be treated with caution, as they are indicative estimates not accurate predictions. The standing stock on a reef compared with

Hi OWES & MOORE the total North Sea stock is though by no means the most important parameter of possible reef success, as will be discussed in chapter 6.

4.2.3 Numbers and variety offish at a deep, submerged structure Factors that may attract fish to working platforms include noise, light, heat, vibration and additional food, either from fouling organisms or wastes from human habitation. In order to determine the relative attraction of an inactive structure at a deep offshore location, the wreck of the semi-submersible 3 (T3) was specifically examined by ROY in June 1987. The wreck lies in 110 m of water about 8 km SW of the Beryl Field and has a vertical profile of about 40 m; no part extends into the photic zone and being inactive it has none of the additional stimuli that might attract fish. It was found that the seabed in the immediate vicinity of the wreck, and the water column within about 15 m around and above the wreck were frequented by a much greater and abundance of fish than the seabed or open sea away from the wreck at this location in the North Sea. The wreck was frequented by saithe, Norway pout, haddock, ling, cod, wolf fish, pollack (Pollachius virens), lemon sole, , bib, codling and whiting. Shoals of 500 to 1,000 saithe were observed swimming slowly around the vertical legs and in the water column between and immediately above the legs. Very few fish were seen at sites more than 30 m away from the wreck. The quantitative data on the major species observed at T3 are given in Table 5.

Table 5: Quantitative data on the major species observed around Transocean 3 (AUMS 1987b). Species Average Size Depth Range Maximum Maximum (cm) (m) Shoal Size Density (m3)

Saithe 40 to 50 -50 to -108 1000 2.0 Norway 15 to 25 -95 to -108 1000 10.0 Norway 20 to 25 -95 to-108 20 5.0 Haddock Ling 80 to 100 -108 10 0.1

The study of fish activity at the deep wreck T3 showed that deep structures at distant offshore locations in the North Sea also have the effect of aggregating fish. Since the T3 structure was inactive, and only lightly fouled, this finding strongly suggests that it is principally the physical presence of the wreck in an otherwise empty area of seabed which has the effect of attracting and concentrating various species of fish (AUMS, 1987b).

m&WCS&MOOnF- 4.2.4 Monitoring the residence times and movements of fish at platforms Studies at working platforms and at Transocean 3 had shown that many fish may be found at such sites. Although visual observation suggested that the fish were spending some time in the vicinityof these structures (fish swimming slowly; orientating around the structure; not moving away from it when disturbed by ROV’s; large shoals seen on successive days), there was no proof that individual fish were spending significant lengths of time at a platform. In order to understand fully the effect of platforms on fish behaviour, and consequently on their ecology and health, it is important to have more accurate information on their residence times at such structures. In 1988 a preliminary feasibility study was carried out to ascertain if small acoustic transmitters of the type that could be implanted in fish such as saithe and cod, could be successfully monitored in the marine environments of working North Sea platforms. If they could, then further studies would then be possible, involving the acoustic tagging of a small number of fish and monitoring their presence/absence around a platform or wreck for 10-20 days using a remote receiver/data-logger placed on the seabed. The feasibility study was carried out in September 1988 around the Beryl Field, to determine the effective range of the transmitters. A receiver/logger was deployed at Transocean 3 for 36 hours, with two transmitters at distances of 1 m and about 150 m. A second deployment was carried at Beryl A for 24 hours with a remote transmitter deployed at distances of 100 - 200 m from the receiver. The receiver was successfully recovered after each deployment by activation of an acoustic remote release. This feasibility study was entirely successful with both transmitter and receiver functioning well around the platform and wreck. Data analysis showed that the effective range of the transmitters was in excess of 500 m around wreck and platform except in the worst of weather conditions when it was reduced to about 100 m. In view of the fact that previous studies have shown that elevated concentrations of fish rarely extend more than 100m from the platform, it is concluded that acoustic monitoring of the presence of tagged fish would be feasible. Such a programme would determine if marked fish stayed close to the structures, disappeared entirely and never returned, or made periodic excursions form the platforms (to another platform or structure?) before returning to the platform site again.

4.2.5 The contamination and taint of fish at platforms With the recognition that significant numbers of demersal fish were spending some time around working platforms, a study was carried out in 1988 to analyse the tissue hydrocarbon content and the flavour of selected species of fish caught near platforms, and compare them with fish caught in areas well away from the platforms. The species studied was the saithe. “Platform” fish were caught from a supply vessel at a multi-well production platform in the northern North Sea where low-toxicity oil-based mud had been used during development drilling. “Open sea” fish were caught by a commercial fishing boat at a site about 40 km SE of Sumburgh head, Islands. A small number of saithe were also caught at the platform MCP01 in the central North Sea, where no drilling whatsoever had been undertaken.

jHH DWES A MOORE All the platform fish appeared to be in good condition when landed with no skin blemishes, spots or lesions, or any other sign of -health. None of the fish was sick or moribund. Great care was taken in the landing, handling and sub-sampling of all fish to avoid contamination and to ensure that the fish arrived in the laboratory in good condition and without spoilage. Platform fish were treated within 3 hr of capture by biologists on board the supply vessel. They were gutted, the liver cleanly removed for separate storage in a solvent-washed aluminium tube, the body cavity washed with ice and the whole fish packed in ice in a clean fish box which was stored in a refrigerated container on board. Open sea fish were treated by the crew of the fishing boat, who had been properly briefed on the stringent handling requirements. These fish were gutted and then packed in ice in the usual way. On landing, platform and open sea fish were blast frozen after equivalent periods (4 days) storage in ice, and then stored at -30°C. Samples for flavour assessment were cut from frozen fish and prepared for taste assessment using a standardised protocol recommended by the MAFF Tony Research Station, Aberdeen. Flavour was assessed by the Tony Research Station taste panel in a series of 7 sessions 4 of which comprised a random presentation of platform fish and open sea fish, 1 a selection of platform fish and fish from the pumping station, and 2 of platform fish alone. Each panel consisted of between 8 and 10 members who were asked to assess the flavour of the fish in relation to their previous experience of the flavour of the species, and to rate any taint on a 5-point scale. Taint was defined as “a flavour or odour foreign to the product”, and following normal protocol for such flavour assessments, a fish was judged to be tainted if at least 50% of the panel members recorded some level of taint in the sample. Tasters were asked to assess flavour, note and quantify the presence of any taint, and comment on the smell, quality and texture of the fresh. Forty-five platform fish, 20 open sea fish and 5 fish from the pumping station were presented to the taste panel. No platform or open sea fish was found to be tainted by the criterion described above. Several assessors remarked on the “full flavour” or “strong flavour” of the platform fish, one commented on a possible “tarry” flavour, and one on an “oily flavour”. The appearance, odour, texture and consistency of the flesh of platform fish were no different from those of the open sea fish. Both platform and open sea fish achieved similar low scores on taint assessment, consistent with the random hits that might be expected during such assessments. All platform fish were therefore judged to be untainted, entirely acceptable and no different in quality, appearance, smell or texture from the open sea fish. Tissue hydrocarbons were analysed by Gas Liquid Chromatography. The typical aliphatic profile for Saithe from the open sea site comprised n-alkanes peaking at nCza to nCi9, with varying quantities of pristane and squalene. Fish from the pumping station and the platform had n-alkane distributions similar to this. The range of total n-alkane concentrations in the flesh of fish from the open sea site was 488 ng.g"1 to 824 ng.g"1 wet weight with a mean value of 648 g.g* 1. The concentrations of n-alkanes in the flesh of fish from the pumping station were higher, with a range of 600 ng.g"1 to 2,479 ng.g"1 and a mean of 1,477 ng.g"1. The concentrations of n-alkanes in the flesh of fish from the platform were similar to this, with a range of 633 ng.g"1 to 3,920 ng.g" 1 and a mean of 1,851 ng.g'1.

The concentrations of n-alkanes in the livers of fish from both the pumping station and the platform were much higher than in the flesh, and this was expected. Highest concentrations were found in the livers of fish from the pumping station, which had a range of 7,600 ng.g'1 to 90,689 ng.g and a mean of 31,074 ng.g"1 wet weight. The livers of platform fish had n-alkane concentrations ranging from 6,200 ng.g"1 to 40,950 ng.g"1 with a mean of 15,423 ng.g'1. No livers of open sea fish were examined as they were not retained by the fishermen who gutted the fish. Oil-based drilling muds have been widely used in the North Sea, and the accumulation of oily cuttings on the seabed at the base of platforms has an obvious impact on the seabed and its fauna. The impact of these cuttings piles on the benthos is well described and quantified (see, for example, Addy et al., 1984; AUMS 1987a; Davies et ah, 1984; Mair et ah, 1987). The effect of the cuttings may be detected as elevated hydrocarbon concentrations in the sediment, and as impoverished or stressed benthic macrofaunal communities, up to distances of 2,000 m from the platform (Davies et al., 1984). The possible effect that the discharge of oily cuttings may have on fish in the area around the platform has not been studied so intensively. The most comprehensive published work in the UK North Sea has been an examination of the flavour and tissue hydrocarbon concentration of dabs Limanda limanda caught in the immediate vicinity of the Beatrice Platform (Lat. 58° 08 ’ N. Long. 03° 06’ W.) (McGill et ah, 1987). Beatrice stands in 45 m of water 20 km offshore in the Moray , , and at its base there is a pile of cuttings which has been produced while drilling with low-toxicity oil-based muds. Dabs naturally spend considerable periods of time in direct contact with the seabed and spend considerable periods of time in direct contact with the seabed and tend to remain within a local area, and so it is highly likely that flatfish caught close to Beatrice had frequent and prolonged contact with the pile of cuttings under the platform. Dabs were caught in two areas around Beatrice, the first 550 - 860 m from the platform, the second 1,000 - 1,870 m away from the platform. The study found that there was a definite significant tendency towards the presence of an oil taint in the fish caught in the 550 - 860 m zone compared with those from both the 1,000 - 1,870 m zone and a control site situated some 20 km away from the platform. Analysis of the tissue hydrocarbon burden in such possibly tainted fish revealed the presence of two unresolved complex mixtures (UCM), which were absent in the traces of fish from the control site 20 km away. It was concluded, however, that although the fish caught closest to the platform had some signs of contamination by petrogenic hydrocarbons, the presence of an oil taint was minimal and too low to be recognised by the consumer at large. In the 1988 study, the total n-alkane concentrations in the flesh of fish from the pumping station, where there had been no drilling, were broadly similar to those in the flesh of fish from the platform, where there had been drilling using low-toxicity oil-based muds. On the basis of total n-alkane concentrations there was therefore no obvious indication that the additional hydrocarbon burden of fish from the pumping station and the platform was caused by petrogenic hydrocarbons. The qualitative results, however, indicated that for two of the platform fish the hydrocarbons in their tissues were in part due to a weathered

HjcMMUt MOORE low-toxicity base oil, which may have derived from the cutting at the base of the production platform. The n-alkane concentrations in livers of fish from the pumping station and the platform were much higher than in the flesh from the same fish, as was expected, but there was no correlation between flesh n-alkane concentration and liver n-alkane concentration. Concentrations of n-alkanes in livers of fish from the pumping station were, however, significantly higher than those of the platform fish, and there is no obvious explanation for this difference. Petrogenic hydrocarbon components were not found in the livers of three platform fish. In two of these fish the petrogenic component again consisted of UCM in the region nCu to nCi$. Despite the presence of petrogenic components in some fish, and the indications that some of the hydrocarbon burden may have been derived from weathered low-toxicity base oil, there was no evidence to suggest that the presence of these components was responsible for the different flavours experienced by the testing panel. Examination of the results from the taste panel assessment of flesh flavour and the analysis of aliphatic hydrocarbons in flesh and liver revealed that there were no correlations between mean taint score and total n- alkane concentration in flesh or liver. The taste panel remarked that many of the samples from the platform had strong, full flavours. These comments were mostly made in the earlier sessions when only platform fish were being assessed, and refer to the strength of the typical sweet, creamy, meaty flavours of fresh Saithe, and they are different from the atypical flavours recorded as taints. The presence of these stronger typical flavours is, however, another example of the difference in flavour between fish from the open sea and fish caught near platforms. It is known that fish flavour may vary throughout the year depending on the availability of food, with, typically, weaker flavours being found when food is scarce or when the fish are not feeding. The difference in the strength of normal flavours between platform fish and open sea fish may therefore be related to the availability of different types of food at the platforms due to marine fouling or human habitation, or perhaps to differences in behaviour and feeding patterns in the platform fish. There was, however, no evidence to suggest that this different flavour was due to the effects of petrogenic hydrocarbons. It is interesting to compare hydrocarbon concentrations found in the 1988 study with those reported in previous studies, although previous data are limited and include only one value for Saithe (Table 6). The n-alkane concentrations in the flesh of fish from the open sea site in the 1988 study were higher than those of the solitary saithe and the cod reported by Whittle et al, (1977), or the cod reported by Hardy et al. (1974). They were, however, in the same concentration range as the haddock (Whittle et al., 1977), which has a lipid content similar to that of saithe and cod. The concentrations of n-alkanes in the flesh of fish from the pumping station and the platform were, however, higher even in relation to two “fatty” species, and horse mackerel. The n-alkane concentrations of livers of fish from the pumping station and the platform (calculated excluding nCsi to nCss because of the presence of alkenes) were noticeably higher than those recorded for both the white and the fatty fish reported in the previous studies (Hardy et al, 1974; Whittle et al, 1977). It therefore appears that the hydrocarbon burdens of both the flesh and livers of fish from

|H Dkmes i moore ~35 the pumping station and the platform tend to be greater than those reported previously for fish from the open sea.

Table 6: Comparison of the n-alkane concentrations of flesh and liver from the 1988 UKOOA study and past studies.

Source 1988 UKOOA study Whittle et at., 1977 Hardy et al. 1974 Open sea Pump st. Platform Open North Sea Aquarium Species Saithe Saithe Saithe Saith Cod Haddock Mackerel Horse Cod e mackerel No. 4 65 10 1 4 2 3 3 3 analysed

FLESH Range: 488-824 600-2749 633-3920 100-200 300-1700 600-1400 300-3300 Mean: 648 1473 1851 100 200 1000 1000 1500 200

LIVER Range 7600- 6200- 1400- 2800- 1800- 1700- 90,689 40,950 4600 3900 6300 7500 Mean 31,074 15,423 3,000 3,000 3300 4100 5300 3400 Values indicate fhisto nC^ng.g1 wet weight.

A second survey of fish contamination and taint was carried out in 1990, when saithe and cod were caught at Brae Bravo and Maureen. Unfortunately insufficient cod were caught at Brae Bravo and so only cod from Maureen were analysed. Full quotas of saithe were achieved at both sites. Reference fish were caught on the Bressay Shoal to the north of the installation sites. Fish were again caught close to the platform using rod and line and in the open sea using conventional gear. Once on board ship, samples of flesh and liver were taken to subsequent analysis of hydrocarbon, mercury and cadmium levels. Samples of flesh were also taken to enable an assessment for the presence of a taint as the result of contamination by hydrocarbons. The size, weight and stomach contents of the fish caught were also noted. The majority of the flesh samples and all the liver samples of both cod and saithe exhibited hydrocarbon contamination with a composition indicating low toxicity base oil used in drilling muds as the source. The highest levels of hydrocarbon contamination in saithe flesh were observed from Brae Bravo, followed by Maureen and then the open sea fish. A similar trend was found for saithe liver samples but with little difference between the fish from Maureen and the open sea site (see Table 7). The cod caught at the open sea site had higher levels of hydrocarbons in their livers but lower levels in their flesh compared to levels found in the fish caught at Maureen.

RQcwMES t MOOflE No relationship could be determined between the levels of contamination in cod and saithe from the same site. Nor could the levels of hydrocarbon contamination in the liver and flesh of fish or the degree of contamination with size and therefore age be correlated.

Table 7: Results of analysis of hydrocarbons and metals in fish sampledin 1990 UKOOA survey of platforms (IOE, 1990).

Site Species Mercury Cadmium n-alkane mg kg' 1 mg kg' 1 tissue type cone ng g"1 Open Sea Saithe 0.032 0.007 Flesh 70 Liver 6,405 Cod 0.033 0.008 Flesh 79 Liver 7,986 Maureen Saithe 0.026 0.005 Flesh 188 Liver 5,066 Cod 0.054 0.016 Flesh 266 Liver 3,580 Brae Bravo Saithe 0.025 0.012 Flesh 434 Liver 9,676

In all the fish analysed the concentration of hydrocarbons was higher in the liver than in the flesh. This trend would be expected since the liver is known to accumulate lipid soluble contaminants such as hydrocarbons. The mercury and cadmium levels in both saithe and cod, caught at the two platform sites and the open sea site, were low. The mercury and cadmium in saithe and cod were within the range of values recorded in fish surveyed in different areas of the North Sea and landed by commercial trawlers. All the mercury levels recorded were within the lower category (less than 0.1 mg kg' 1) set by the Joint Monitoring Group. All the cadmium levels recorded were well below the limit normally expected in fish by MAFF (less than 0.2 mg kg" 1). There were no significant correlations between the levels of mercury and the levels of cadmium in any of the fish analysed. The results of the taint analysis clearly showed that both saithe and cod caught at the Maureen and Brae B platforms and at the open sea site were not tainted, and that the flesh flavour was not affected by any factor that could be related to petroleum products. The petrogenic hydrocarbons which were identified in 16 of the 25 flesh samples analysed had not affected the flavour of the fish. All the fish tasted were classified by all the assessors as having no taint. Any differences in flesh flavour were considered by the taste panel as being within the range of flavours usually associated with these two species.

|j|j OWES i MOORE The results of the second UKOOA survey in 1990 indicated that there was a contamination of fish by hydrocarbons indicative of the low toxicity base oil used in drilling muds. The source of the weathered low toxicity base oil in the flesh and livers of fish caught at the Maureen platform and the open sea site (more than 40 km from the nearest platform), was not determined. It was unlikely that the Maureen site was the site of origin for the low toxicity muds detected; the Maureen wells had been drilled with diesel-based muds, and the cuttings were removed prior to the installation of the gravity platform over the drilling template. If depuration rates are slower than the time needed for fish to reach the open sea and Maureen locations from the site of contamination, then it is possible that the fish caught at the open sea site and Maureen could have derived their hydrocarbon burden elsewhere. This would presumably be a site of relatively recent low toxicity mud use and with 112 exploratory wells and 35 development wells drilled in the year before the survey in the UK sector of the central North Sea and 70% use of oil based muds, there would have been many potential sites available. It is also possible that the widespread hydrocarbon contamination found in the fish tissues resulted from accumulation of hydrocarbons from background levels in the water column or from feeding on other marine organisms which have themselves been contaminated by petrogenic hydrocarbons. There are insufficient data presently available, however, to arrive at a definitive conclusion regarding the mechanisms at work in these fish. The contamination of fish away from known sources also suggests that the fish are not generally resident at a particular site, but move, encountering sources of contamination from time to time. A comparison was made between the results of the 1990 survey and the results of earlier studies of saithe contamination. The comparison showed that the tissue hydrocarbon levels in the saithe from both the platform sites and the open sea site were higher in previous studies than those recorded in the 1990 survey. These differences might simply be a result of the two surveys being conducted at different times of the year and of variability in contamination levels between populations of fish. It is possible, however, that these differences in hydrocarbon concentration recorded in the two were related to a general decrease in the discharge of oily cuttings from 18,500 tonne in 1988 12,310 tonne in 1990. It appears that no taint results from the levels of contamination found in the fish and it appears that no enhanced levels of mercury and cadmium are present.

4.2.6 Health and growth offish around oil platforms Having established the fact that fish commonly congregate around offshore oil platforms and may be found there at different seasons of the year, the question arises as to the consequences of living in close proximity to platforms. The effects that the platform environment may be having on individual fish were investigated in a study on fish growth and condition, funded by Mobil North Sea Ltd. The first aim of this study was to estimate the growth rates of individual saithe caught around drilling platforms within the Beryl field at different times of the year. Growth is the ultimate expression of fish health or condition because it integrates all the biotic and abiotic factors acting on an organism, and reflects any secondary impacts of chronic stress. It was therefore envisaged that relative growth rate estimates could be compared, effectively using the fish as biological indicators of habitat condition. Pre-determined laboratory-based biochemical correlates of growth rate for saithe were used to estimate growth rates. Various biochemical indices have been used to evaluate the instantaneous growth rate of fish, and the indicators measured in this study included the ratio white muscle RNA:Protein, and the activity of white muscle enzymes (citrate synthase, cytochrome oxidase and lactate dehydrogenase). In addition, condition factor, relative caeca! number and relative gall bladder size were measured. Seven different indicators (6 biochemical and caecal-somatic index) were used to estimate the growth rates of the oilfield fish and comparisons were made between them. Secondly, the platforms fish were compared with fish of the same species caught at the same time in other open sea sites, away from potential hydrocarbon pollution and any “reef’ influence of the physical presence of a platform, using the same biochemical and physical measures. During 1988 and 1989 six fish collecting trips were made at three different locations; four visits were made to the Beryl Field, one to the wreck of Transocean 3, and one to Loch Ewe on the west coast of Scotland. All fish were caught by line fishing, killed on site and samples taken within a few minutes of capture. This study yielded detailed information concerning biochemical indicators of growth rate, and also the relative growth and condition of fish found at platforms and in the open sea. Details of the findings are given in Mathers et al., 1992a and b. In summary, it was determined that RNA concentration in the white muscle of fish varies with season; slow growth or weight loss in winter is accompanied by low RNA concentrations, whereas higher growth rates in summer are accompanied by higher RNA concentrations. Seasonal patterns in enzyme activity and physical condition factors were also found, but not all could be clearly related solely to changes in growth rate. It was therefore concluded that the most reliable method of estimating growth rate was RNA content expressed either as a concentration within the muscle or as a ratio. Comparison of the growth rates of fish caught in August 1988 from the Beryl field and from Transocean in showed no significant differences. In the 1989 samples, however, the growth rates of the fish from Beryl were higher than those caught at the same time at Loch Ewe, after the effects of body size had been taken into account. It was therefore concluded by the research team that, on the basis of the evidence from this study, it did not appear that the saithe found in the Beryl field were growing any less well than saithe found at the other sites sampled.

4.3 Norwegian sector The first studies carried out in the Norwegian sector on the importance of oil and gas installations as potential artificial reefs, were done by Olsen & Valdemarsen (1977) and Valdemarsen (1979). The first study, carried out during one week in May 1977, sampled fish using traps, jiggers and vertical baited lines at different distances and directions from the installations of the Ekofisk complex. The results indicated that cod were aggregated in substantial numbers in

H Games 4 moors the proximity of the installations, whereas only scattered concentrations were present in the surrounding areas. It was noted that (Meganyctiphanes norvegicus) dominated the stomach content in cod demonstrating that organisms living on the structures did not contribute significantly as a food source. The study gave the following recommendations: • reliable methods should be developed for estimating fish density gradients; • annual variations in the fish distribution should be investigated; • total amount of the different species inside the safety zone should be investigated; • organisms near the installations should be compared with reference areas; • residence times for fish around platforms should be established. A second study in the same area was conducted in August 1978 (Valdemarsen, 1979) and both gillnet, fishing, longlining, jigging and echo-surveying were used as . All methods used in the study indicated that demersal fish aggregate around oil platforms. The greatest fish densities (both demersal and pelagic) were observed in the vicinity of the structures, being 3 and 10 times higher for cod and saithe respectively in the distance interval 0 - 200 m from the structures, compared to a reference area >500 m from the platform. It was concluded that, with a possible exception of one gillnet setting which resulted in good catches of saithe, catches with the different gears were probably too small for commercial fishing around a platform. A study on the experiences on artificial reefs world-wide, and especially in the North Sea region was performed in 1994 (Kjeilen et al., 1994). The study included an overview of different types of reef structures, suitable exposure areas, optimal size and shape, stability problems etc. Several artificial reef experiments world-wide were described in detail. A joint venture between RF-Rogaland Research, ICIT and AURIS reviewed the ODIN platform in the Norwegian sector of the North Sea as a potential Artificial Reef (Kjeilen et al., 1995). Both the steel jacket and the topside elements were evaluated. The study also included legislative background and the rigs-to-reefs history as well as a description of the environment in the area and the platform itself. Impacts, both positive and negative were evaluated as well as mitigating actions. Different management scenarios and a complete 5 year monitoring programme were defined and discussed. Financial discussions were also included and the report concluded: • the site was suitable for an artificial reef due to the water depth, the lack of oil based muds, an unlevelled and featureless seabed; • • the lifetime for the jacket was estimated to be approximately 100 - 150 years and the jacket did not require any treatment before placement on the seabed; • if topside modules were to be used, they required total stripping which would probably be costly; • the presence of the reef would not cause significant negative impacts on the physical and biological environment;

Hjjj Dames & moore • the reef would attract a variety of fish species from the surrounding area; • the total standing stock of fish in a reef made from the jacket alone is estimated to be 30 - 35 tonnes; • the creation of a reef at the ODIN site presented an ideal opportunity to obtain essential data, hitherto lacking for the North Sea. Around 25 structures from the Ekofisk area were evaluated as elements in one or several artificial reefs in a study by Cripps et al. (1995). The study covered aspects on the environment in the area, structural description and a scenario discussion. Both immediate in situ toppling, delayed in situ toppling, immediate clustered reef creation, delayed clustered reef creation and abandon in place were evaluated. The report gave some conclusions and recommendations including: • The area was suitable for reef creation, however some of the sites contained large piles of oil based drilling muds and should be avoided as reef sites. • All steel structures, including bridge supports and flare towers, had a configuration that was optimal for use a reef modules. • The presence of the reef may enhance standing stocks of fish in the area. Based on numbers of fish around some working platforms in the North Sea, a conservative estimate of the standing stock of fish at the reef composed on jackets only was more than 1000 tonnes. • If the structures and the sediments on which the reefs were placed were properly decontaminated prior to reef creation, no negative impacts on the biological community would be expected from the reef. Some leaching of metals, such as iron, would occur when the structures were deteriorating, but the effects would be negligible. • A clustered reef configuration comprising several installations and modules was likely to be of great potential and would also reduce the region covered by reef components, so reducing the negative impacts to other users of the sea. • Possible reef sites where the jackets should be clustered were suggested. Two recent studies have been conducted on fish populations around jackets in the Norwegian sector of the North Sea. A general report on fish stocks in the ODIN area was published in 1995 (Furevik & Valdemarsen, 1995), while ROV recordings were used to study fish aggregations around a cold steel jacket (Cripps & Aabel, 1995). The study from the ODIN area concluded that the field is characterised as of medium importance with regard to fisheries. The field is not an important area for trawl fisheries, and does not prevent trawling or other important fishing activities significantly. The Odin field is, however, situated near a generally rich fishing area and the platform as a structure will probably concentrate significant amounts of fish (Furevik & Valdemarsen,1995). The preliminary study conducted by Cripps & Aabel (1995) used ROV recordings from around a cold jacket as a tool for giving a qualitative and semi-quantitative estimate of the fish populations. A total of 27 hours ROV recordings were available for visual analysis and

atKMES&MOORE a method was proposed for optimising the monitoring of fish species, number and behaviour. • Red fish (Sebastes viviparus), saithe (Pollachius virens), whiting (Merlangius merlangus) and ling (Molva spp) were most frequently observed. • ROY structural survey videos were adequate for the estimation of species, location and, in most cases, the number of fish associated with various parts of the jacket. • Red fish {Sebastes viviparus) were frequently observed singly or in groups closely associated with the structure. They were seen in the deeper parts of the structure from 71 m to the bottom at around 96 m. The majority of the red fish were at the deepest parts of the structure, on or just above the sediment. • Saithe {Pollachius virens) appeared the most numerous fish around the jacket. As a large pelagic species it was commonly seen in shoals in the open spaces between the structure members and lying off the outside of the structure a few meters. The majority of broad-view camera shots showed the presence of saithe. Shoals were often small, numbering less than 10 fish, though occasionally large shoals comprising several hundred fish were sighted. Whilst the majority of observations of this species were made whilst the ROY was near the bottom, the fish themselves were frequently in much less deep water around mid- to upper-depth. This species appeared to be greatly concentrated around the jacket compared with expected off-structure water. » Two other species of fish identified, albeit rarely, were thought to be whiting {Merlangius merlangus) and ling {Molva spp.). These two species were so infrequently identified that no conclusions as to preferred location or quantity can be reliably made. Various other species of fish, such as cod, may have been present, but due to distance or definition problems it was not possible to accurately identify all individuals seen. Due to the short time scale of the project it was not possible to analyse in detail diurnal migrations and changes in occurrence. A controlled time and location dependent protocol was also not followed, i.e. the ROY was at different locations during a day, thus limiting conclusions regarding changes in fish location. It was however evident from the videos that the pelagic fish were absent or difficult to locate during the night and morning. Most of these fish were seen in the middle to late afternoon, strongly indicating a diurnal migration to and from the structure. No substantial diurnal migration with respect to depth was observed. It was considered that the videos did contain sufficient information to at least semi-quantitatively estimate on-off jacket migration phenomena.

4.4 Other artificial reef activity in the North Sea Artificial reefs have been deployed off the SE Scottish (Tomess), Dutch () and the east English (East ) coasts. Details are given in section 5.3. The Tomess reef has not proven to be a success as a commercial fishery site, strings of pot and netting do yield a catch but is not of sufficient volume to make the reef a preferred fishing site. This is thought to be a result of material (large boulders ) and location (the reef is swept by strong currents). The coastal defence structure off has succeeded in developing a beach behind the structures and so protecting the short stretch of coastline but the plans for the remaining structures have been modified to improve to feed beaches down- of the reefs. The success of this project has encouraged MAFF to continue with its emphasis that future reef deployment should be multi-functional, with the general idea that reefs built for coastal defence should be designed to assist in fisheries enhancement. This is primarily a financial argument, the coastal protection section of MAFF fund coastal defence schemes in and Wales costing several millions of pounds each year, it would be cost effective to combine one of the interests of the fisheries section with this activity. The Dutch reef project has recently ( 1997) submitted its final report. Results have shown good epifaunal colonisation rates and attraction of fish and commercial species. The fate of the structure has yet to be decided; there is a strong possibility that it will be removed. This would satisfy the two vociferous lobby groups, the shrimp fishermen who see any seabed obstruction as a threat to their living and the ’’environmentalists” who object to ’’foreign” material being placed in the sea and disturbing a so called pristine sandy habitat. The latter is an interesting viewpoint from a country that exists because of its hard substrata sea defences. Elsewhere around the North Sea coast there are varying amounts of interest in the concept of artificial reefs. Philosophically the Germans oppose the placing of reefs on the basis that they upset the balance of a natural sediment area. The Danish are currently running an appraisal programme to decide if reefs could be an aspect of their fisheries management programme in the future. They too have concerns about introducing new, hard habitat into predominately sedimentary areas and may well opt for a type of habitat replacement; using reefs to replace habitat lost by the old practice of’’stone-fishing” for building materials. All of the reefs mentioned and even those being considered will use natural stone. One issue dominates the question of using waste material, that of ill-considered dumping. Northern European opinion is very sensitive to the concept of artificial reef creation being used as an excuse for dumping environmentally unacceptable waste, and/or in the case of jackets as being a money saving operation for governments and the oil industry without environmental or fishery benefit. In the North Sea, as in the Gulf of Mexico, a jacket will have to be part of an agreed, planned, assessed and effective reef deployment programme before it can be placed on the seabed. Whilst there are similar environmental concerns in the there is a greater degree of pragmatism. The Barcelona convention on dumping in the Mediterranean allows the use of jackets for artificial reef development when combined with aquacultural activities. This difference may well reflect the important role large reef structures can play in preventing damage to habitat and aquacultural facilities by illegal trawling.

4.5 Conclusions A variety of commercially important fish species are found in the close vicinity of many working platforms in the North Sea. Although these individuals may derive additional food from the structure and its fixed and mobile fouling community, it is likely that the

IllJtHWfSiMOOfiE principal attracting feature of the structures, the cause of the aggregating effect, is the physical presence of a large structure at the offshore location. All the evidence obtained to date indicates that fish living in the vicinity of structures are in as good a condition as those collected form the open sea. There may indeed be evidence to show that fish frequenting platforms are in better condition, and growing more quickly, than those at open sea sites. The platform fish studied so far tend to have higher concentrations of hydrocarbons in their muscle tissue than open sea fish, but in only a few cases could these elevated concentrations be attributed to low-toxicity oil-based drilling muds. Fish caught at platforms where no drilling had taken place exhibited broadly similar concentrations of hydrocarbons in flesh and liver to those caught at multi-well production platforms. There were indications that the flavour of the fish caught at production platforms was ‘fuller ’ or ‘stronger’ than that of open sea fish, but they were not tainted and there was no correlation between their mean taint scores and the hydrocarbon concentrations of flesh or liver. No damaged, sick or moribund fish has been observed or caught in the course of these studies. It would therefore appear that the immediate platform environment is one which fish find acceptable and to which they are attracted. They may find extra food there, shelter from currents, and a reference point for efficient station-keeping. Within the 500 m safety zone they will also escape fishing pressure. The structures scattered throughout the North Sea therefore provide local ‘reef habitats ’ utilised byfish for a time. Evidence to date suggests that the existing working platforms are having a small, beneficial effect on local fish populations. The extent to which these habitats are having any long-term, or significant effects on the total populations of these species will only be gauged when we understand more fully temporal utilisation of platforms by fish and their possible movement between platforms. It is clear, however, that a reef effect has been identified around North Sea oil platforms, and that jackets do influence the behaviour of commercially important species. The significance of the results of these studies in terms of either the benefit to fish populations or the benefit to fishing operations are difficult to assess and remain to be fully investigated. Evidence to date suggests that there will be a net benefit to local fish populations.

I! DAMES t MOORE 5 . REVIEW OF ARTIFICIAL REEFS WORLDWIDE 5 Review of artificial reefs world-wide

5.1 Japan The Japanese are the world leaders (by a considerable margin) in artificial reef technology for commercial fishing enhancement and have been creating artificial reefs since (at least) the 18th century. Currently Japan is in the third phase of artificial reef development, that of creating entire fishing grounds where there had been none before, a significantly more sophisticated philosophythan the patch work development of structures seen elsewhere in the world. This programme commenced in 1974 with the goal of diverting Japanese fishing effort from distant water fishing (where it was meeting increasing resistance) to mariculture and resource management in Japanese waters. Government investment has been substantial; for example in 1988 US $150 million was allocated to subsidise the construction of 2.2 x 106 m3 of fishing reefs, 10% of the coastline has been influenced by artificial reef deployment or other modifications designed to enhance yield of sea food. Deployment of artificial reefs in Japan is well regulated. The engineering and design aspects of Japanese artificial reefs are well refined, and make use of many different lattice type shapes. These are apparently effective in attracting mid-water and demersal species and large, high profile lattice structures have been developed. Designs such as the Kobe steel reef, N-F reef, NSC type steel reef and NSM steel reef, in the region of 11 m3 weighing 33 tonnes, resemble small oil production platforms. Quality standards regarding building materials, design, location and construction exist which must be complied with if structures are to qualify for government certification and subsidy. However, the biological appraisal of artificial reef performance is not so well advanced. Some workers have concluded that there are insufficient biological and economic data for judging the cost effectiveness of manyof the reef deployment operations. The Japanese judgement is more pragmatic, the artificial reefs work (in that they provide effective fishing locations) and are worthy of development because they enhance the harvesting of food from the sea, a major component of the Japanese diet. Japanese reef development is linked to the use of concrete and steel (and some GRP) as the main construction material. In general waste materials are not used, although plans are well advanced to use pulverised fuel ash for banks, a significant new material for a fairly ambitious project. By indicating a preference for steel and concrete the Japanese government are effectively directing significant reefs subsidies into domestic industries providing this material, a useful spin-off from reef development. Artificial reefs are frequently managed by coastal communities in Japan. The social structure of interaction within and between fishing communities is well defined and each has historic rights to harvest specific areas of the seabed. By developing reefs within this existing effective and transparent system the fisheries managers in Japan have a proven management structure in place as soon as the reef is deployed.

gUg CtkMES & MOORE 5.2 USA American experience of reef construction dates back over 100 years and in that time a variety of (mostly waste) materials have been used including: concrete, rock, construction rubble, scrap tyres, cars, railway carriages and . Recent high profile examples have been battle tanks and fighter aircraft deposited in the Gulf of Mexico. The USA is "home" to the original "rigs to reefs" programme. The USA has a national artificial reef plan but no government funding commitment. Funding has come from the Federal Aid in Sport Fish Restoration Program, which may provide up to 75% of reef construction costs, with individual States providing the rest. In 1987 more than US $140 million was provided by the Federal Aid Program. The most active state is that of which has placed over 100 structures along its Atlantic and Gulf coastlines. The artificial reef programmes of many maritime States are run to benefit recreational sports fishing, SCUBA diving, commercial fishing, assist with waste disposal and provide environmental mitigation. Artificial reefs are generally perceived as a "good" thing in the USA and whilst scientific evidence is part of the appraisal process for environmental mitigation, the sports fishing reefs are judged to a large extent by "customer satisfaction" criteria. Artificial reefs are most frequently deployed to improve sports fishing which is recognised as an important industry with significant socio-economic benefits to coastal communities. It is important to recognise that recreation in the USA is of much greater importance and is taken much more seriously than in Europe. In the USA artificial reefs have been encouraged on a "low or no cost basis". With the help of national legislation coastal states have defined sites where reefs may be deployed and in many cases a small group of state employees or enthusiastic volunteers have been involved with the acquisition of materials to create reefs. More often than not these are "waste" materials or "materials of opportunity” and the cost of deployment is absorbed by the organisation "donating" the materials. The process follows fairly simple economics; does placing a suitable material in the sea, after cleaning, cost less or a similar amount to onshore disposal or recycling, given that politics and PR are in support of the idea? If so then reefs will be deployed. Reefs have been constructed from a wide range of materials such as old vessels, battle tanks, computer hard disks, old toilets, building rubble tyres and so on. This type of deployment gives rise to the complaint that reef creation is just a legalised method of dumping waste at sea, something that reef legislation (and most credible reef researchers) seeks to prevent. The general aim has been to create new sites for sports fishing that are convenient in that they are close to ports, well marked and provide good catches of fish on rod and line. "General purpose" artificial reefs are created because knowledge of the required target species habitat is limited as is choice of materials. Criterion for success are based on rod and line catch, number of people fishing or using the reef and "charter boat satisfaction" (which translates into tourist dollars) rather than a hard "cost benefit analysis" based on commercial fisheries. The use of rod and line appears to pose no serious threat to the fish populations attracted to these structures. Little concern is expressed by other than researchers as to how the systems work and why. Such generalised reefs appear to increase the overall local biodiversity, another factor that is seen as "good".

j|j| DAMES & MOORE cORnan The use of jackets in the Gulf of Mexico is an extension of this philosophy. This area holds the majority of the world's production platforms, some 4000 compared to about 400 in the North Sea. Platforms tend to be much smaller than those in the North Sea and they have been in place for much longer. The use of obsolete jackets to create artificial reefs is based on a "mutual benefit" philosophy unique to the USA and it's historic way of creating artificial reefs from "waste" materials.

5.3 European Union At present most reefs are still associated with scientific research of some type. In Europe artificial reefs were pioneered in Monaco for nature conservation in the late 1960s. Artificial reef research programmes have now been initiated in eight countries of the European Union (EU) (Italy, Spain, Portugal, the UK, Germany, the Netherlands, Finland and France). In addition, countries such as Ireland and Greece have a strong interest in artificial reefs, although no structures have, as yet, been placed (as far as is known). A Greek reef programme exists, deployment should happen soon. Outside the EU, Poland has deployed experimental structures in the Baltic, Turkey has a small experimental programme based in Ege University. Romania has placed some reefs for experiments into biofiltration in the Black Sea near Constanza. Israel has been active in the field for some time, deploying tyre structures in the Mediterranean and having an interest in structures placed in the . Russia is involved with reef interests in the Baltic and has built reefs in the , the SADCO-SHELF programme. Reef building has, until recently, been carried out nationally, with little cross-border co­ operation. This is changing; in 1991 Italian artificial reef scientists formed an Italian reef group to encourage liaison between research groups. An association of Mediterranean artificial reef scientists now exists. Artificial reef research in Europe has reached a stage where scientific priorities for the future need to be developed in the light of previous research and experience. This is the aim, and the reason for the creation, of the European Artificial Reef Research Network (EARRN) funded by the European Commission "AIR" programme.

5.3.1 UK. Two deliberately placed marine artificial reefs now exist in the UK, one in Poole Bay, on the central southern English coast deployed in June 1989, and off the south eastern Scottish coast near Tomess, deployed in 1984. In addition one of the few European riverine reefs has been deployed in the brackish waters of the River Ouse in East Anglia and a series of coastal defence structures are being built off the coast of East Anglia . The Poole Bay reef was deployed as a material test experiment. The reef consists of blocks made from stabilised Pulverised Fuel Ash (PFA), a waste material from coal fired power stations bound with cement and aggregate. The reef has been continuously monitored to investigate the biological colonisation and the fate of the heavy metals bound within the coal. Results suggest that the heavy metals are secure within the blocks, that colonisation is rapid and that reefs do provide a good habitat for and other commercial shellfish. The Tomess reef was constructed from quarried rock derived from the construction of a nuclear power station. The reef is investigated infrequently to determine biological colonisation, fin-fishery potential and shellfish fishery potential. To date the reef has not been found to support significant amounts of any commercial species although biological colonisation has been good. The Ouse reef was designed as a "mattress" of branches and straw to promote invertebrate biodiversity in a barren, dredged river bed. In this aim it was successful, numbers of invertebrates increased over a three year period. A series of sixteen artificial reefs are being constructed off the coast of East Anglia as a means of coastal defence. This programme is the first of its type in the UK. Other workers in the UK are interested in the utilisation of artificial structures for stock enhancement and the decommissioning of North Sea oil rigs in such a manner as to provide artificial reefs, some for fishery enhancement.

5.3.2 Italy Italy has seen considerable artificial reef activity. The Italians were among the first serious European users of artificial reefs and are well organised on a national basis. Many programmes have been assisted by 50 % EU funding and both local government and fishermen's organisations are involved in encouraging the programmes. Several programmes are predominant. Loano artificial reef An "anti-trawling" reef system was set up in the during 1986 to protect the natural environment and in particular Posidonia beds from bottom fishing gear towed by trawlers. Trawling is prohibited in waters shallower than 50 m in the western Mediterranean (Italy, France and Spain) and 100 m off the northern Spanish coast. Researchers based at Genoa University have studied the effectiveness of the protection as well as investigating the settlement of benthos and colonisation by fish. Seasonal and successional changes of the reef communities have been noted. Of late, interest has developed in the possibility of repopulating reefs with commercial species such as lobsters, transferring the juveniles from other places or from hatcheries. Results show that the reef units provide effective protection against trawlers. Cement panels immersed at different depths revealed 117 species of sessile animals and 76 algal species had colonised. Sixty-six species of fish and cephalopods were listed, some of these utilising the reef for reproduction. Endangered species such as groupers {Mycteroperca rubra; Epinephelus marginatus) appeared in the vicinity of the artificial reef. They are very rare in the Ligurian sea. CENMARE - Coal ash for artificial reefs There is an interest in the constructive use of power station waste (Pulverised Fuel Ash, PFA) for artificial reef construction. As in the UK great emphasis has been placed on the environmental suitability of such material and a large tank trial was undertaken by workers from Genoa in 1990 and 1991. Epifaunal settlement on the ash blocks proved greater in

I OWES & MOORE quantity and better in quality than that on the control (concrete blocks). Biomass measurements confirmed the qualitative and quantitative differences seen in the biological indices between the epifaunal communities. Given the biological colonisation and the physical and chemical stability PFA seems to be a suitable material for artificial reef construction. Gulf of Castellammare (North west Sicily) The project run by the government funded CNR laboratory has evaluated benthic and nekton colonisation, the fishing yields and the trophic relationship between the resident fish and the benthos in the reef area. Benthic settlement was characterised by low percentage cover of algae and a large amount of filter feeders. An increase in number of species and species diversity was observed in the nekton assemblage in the reef area in comparison with the control area. Fishing yields were slightly higher in the reef area than in the control area. Resident fish species were observed in the reef area. Stomach content analysis revealed that Sparid fish appeared to prefer feeding around the reefs rather than on natural substrata. and mussels culture has been successful. Mazara del Vallo reef (South west Sicily) This reef was constructed with planned deposition of shipwrecks on the seabed. The overall aim of the project, initiated in 1989, was to investigate the effectiveness of shipwrecks as artificial reefs in the Mediterranean. The project evaluated nekton assemblages by means of fishing surveys using a trammel net; two years of fishing data have been collected detailing the species composition of the waters around the reefs. Stomach contents and the sagittal otoliths of all the most abundant species caught were extracted. Fishing yields in the reef area were higher than in other areas off the Sicilian coast. The analysis of the species composition showed a high diversity due to heterogeneity of the seabed. At present at least 11 artificial reefs exist along the Italian Adriatic coast. Seven of these (Porto Garibaldi 1, Rimini, Cattelica, Senigallia, Portonovo 1 and 2, Porto Recanati) were constructed with the scientific support of IRPeM-CNR of Ancona. The reef at Porto Recanati was deployed on behalf of IRPeM in 1974 and it was the first Italian reef to be scientifically planned. It is placed at about 13 - 15 m and is made of concrete cubes (2x2x2 m) assembled in pyramids each formed by 14 cubes. The cubes provide holes of different shape and size to offer shelter to the different species of fish, and molluscs. Their surface is rough to facilitate the settlement of bivalve larvae. The pyramids were deployed about 50 m from each other and two old vessels were sunk amongst them. The aims of the scheme were: anti-trawling protection, re-population of biota and development of new sessile biomass, especially mussels and , through the introduction of suitable surfaces. Data obtained showed that initial costs were recovered three times over in about four years through small scale fisheries and collection of the mussels settled on the artificial substrata.

|pj OAMfS & MOORE coRnan In 1983 IRPeM deployed the experimental artificial reef of Portonovo (Portonovo 1). It is placed in about 11 m of water and made of 4 pyramids; each one of 5 concrete cubes of the same type of those used at Porto Recanati. The reef was used by CNR Ancona for experiments on suspended and immersed shellfish culture ( and oysters culture). The artificial reefs at Porto Garibaldi (1 and 2), Rimini, Cattolica, Senigallia, Portonovo (2) were constructed in the years 1987-89. Five of them (Porto Garibaldi 1 and 2, Rimini, Cattolica and Portonovo 2 were deployed on behalf of local fishermen's associations and represent large scale commercial systems. The aims of reef deployment were prevention of illegal trawling, re-population and mariculture. At these sites, fishing surveys with a standard trammel net were started one year before reef deployment and continued for a few years after. The aim was to compare the effectiveness of the reefs in the different areas in terms of fishing yield and their impact on the fish assemblage of the original habitat. The scientific results obtained from the overall research can be summarised as follows: a) The effects of artificial reefs are more evident at sites far from natural hard substrata. b) Species richness, species diversity as well as fish abundance increased after reef deployment. This increase was particularly appreciable for reef-dwelling nekto- benthic species (eg Sparids and Scienids). The increase in average catch weights recorded for these species three years after deployment of the artificial reefs were 10 - 42 times the initial values. These increments seem to be directly correlated to the reef dimensions in terms of volume of immersed materials and inversely correlated to the distance between the oases. c) Higher catch rates are reported from the artificial reefs in comparison with unprotected areas (Senigallia zone). d) The fish assemblage at the artificial reefs is affected by seasonal fluctuations as well as in the all coastal area. The lowest values are generally recorded in winter, when most of the species migrate to deeper, warmer waters. e) Eventual collapses of fishery stocks living on reefs seem to be mitigated inside the artificial reefs complexes in comparison with unprotected areas. f) In eutrophic waters the new biomass of bivalve molluscs (e.g. mussels and oysters) settled on the artificial structures finds suitable conditions for developing and creates mariculture opportunities. Gulf of Trieste The Miranare Reserva Marmara reef in the Gulf of Trieste was placed (in 1978) on a muddy bottom in 18 m of water. Biologists from the University have monitored benthic colonisation and fish populations. Whilst sedimentation has limited benthic colonisation (characterised by low % cover of algae) fish are plentiful. A range of species has utilised the reef for reproductive purposes. A seasonal and successional pattern of colonisation has been recorded. From 1988 concrete pyramids have been deployed off the site of the laboratory at the University of Trieste. The site has been studied to provide data on

|H Games t moore settlement and colonisation of periphyton and other ecological parameters. In addition the effectiveness of such structures in preventing trawling activity has been researched. A reef was deployed in 1994/4 at Dosso, Santa Croce (Gulf of Trieste) Cement structures have been placed to ensure fish repopulation and to deter ecologically unsound fishing techniques such as trawling.

5.3.3 France French activity started in the 1970s with both car bodies and concrete cubes being used in early constructions. Much work focused on the benefits that reefs could make to mariculture, an important element in French coastal economics. French research workers placed more artificial reefs off the French coast (Bouches-du- Rhone, Alpes-Maritime, Languedoc-Roussillon) in the early 1980s. The Bouches-du-Rhone reefs were integrated into local government plans to promote marine life. In all some 3600 m3 of artificial reefs were deployed, Beauduc (>600 m3), Cote bleue (2500 m3) and La Ciotat (460 m3). Natural rock and concrete armed pyramids were used in construction, with an emphasis on anti-trawling reefs (as requested byinshore fishermen). The Alpes-Maritime reef focused on biological validity of reefs and their socio-economic importance in coastal waters. The use of reefs for habitat amelioration was a particular feature of this programme. Results from these programmes concluded that artificial reefs provided good fish habitat, the artificial reefs sometimes holding more fish than comparable natural reefs. The results from the third of these reef programmes, that of Languedoc-Roussillon had a significant impact on the direction of artificial reef research in France. This programme, initiated by IFREMER, placed substantial reef, 6000 m3 of material on a soft seabed in the Golfe du Lion. Commercial net fisheries (mainly for flatfish) were assessed for 16 months before and 16 months after placement of the reef material and the conclusion was reached that although variety of species caught increased in only the second year after deployment, no overall increase in commercial catch could be seen (conflicting with the Italian experience at Senigallia). This result, apparently from a relatively short term study of a poorly placed reef and of species most of which do not require hard substrata, reduced the willingness of the French government research organisation IFREMER to fund research (The protocol of this study, together with the siting of the reef has since been critically reviewed by other workers). However, other French organisations maintain significant scientific interest in the field, with scientists continuing to work on existing reefs like those at Port Cros, others collaborating with European based groups such in Monaco and Italy as well as working in the Middle East. Work has recently started on new reefs in the Golfe du Lion, interest being focused on fish behaviour and the possibilities of shellfish culture on reefs. The work is in progress at present and results are not available. Recent contacts with IFREMER suggest that the organisation is reconsidering its decision to halt artificial reef research

pScRMFSAMOORE coRna 11 5.3.4 Portugal Two programmes are active in Portugal, one off of Madeira, the other on the southern mainland. The reefs off Madeira are in a developmental stage. Since 1983 car bodies, tyres and wooden boats have been used to create artificial reefs in two sites. The aim of the project is to enhance the fisheries potential of the areas and surveys are currently being carried out to establish oceanographic data. On the mainland a the single programme is looking at two reefs off the Ria Formosa, an important estuarine system on the Algarve coast. The aims of the programme are to evaluate the impact of artificial reefs at both ecological and fishing levels and to determine in which way the artificial reefs in the Algarve can be useful as an instrument for fish stock management and to increase coastal resources. An artificial reef complex costing $3.5 million is to be deployed soon in this area. Results show that the structures of concrete blocks are physically stable, maintaining reef structure. Biological colonisation of the reefs was rapid during the 1st year after deployment. Seventy-nine fish species were collected on the reef, most of them related with the fish populations of the neighbouring lagoonal system (depending on seasonal migration to the sea). Chemical studies show a significant increase of productivity in the reef zones.

5.3.5 Spain There is extensive reef building activity throughout Spain, over 100 reefs have been placed, co-ordinated by national government with considerable input from local government and 50 % funding from the EU in most cases. Forty-seven artificial reefs have been constructed, some very extensive in area, mainly with habitat protection (anti­ trawling) and/or artisanal fishery enhancement as the main aims. Not all reefs are subject to scientific monitoring but 5 areas are worthy of note. Balearic coastal waters Reefs were deployed to examine the fisheries enhancement potential, the processes of benthic colonisation and the role of artificial reefs in the regeneration of damaged sea bed. The project has assessed the colonisation of the reefs by benthic organisms and the presence and abundance of nektonic species around the reefs since 1991, as well as measuring some oceanographic water parameters. Results show that artificial reef boulders are naturally covered by benthic flora and fauna from the first year, a sequence in species and shapes of the organisms is observed. The fish population of the area has increased since the deployment of the reef. The biological "behaviour" of the reef differs significantly between the various study areas. Differences in artificial reef shape and structure have decisive effects on the biological communities found around reefs of different form. El Campello (Alicante, Iberian South-eastern). Here artificial reefs have been used to protect meadows of the Posidonia oceanica from damage caused by illegal trawling activity. In the studied area, trawling effects can be

j||l>MES&MOOnE seen from 13 to 30 m. Due to the importance of P. oceanica meadows to local littoral ecology and fisheries an "anti-trawling" artificial reef has been installed. The reef comprises 358 blocks, in 47 squares, each square being 300 m2, and 21 dispersed blocks. Work started on the project in 1990, the reef being deployed in 1992. Blocks were arranged in an attempt to protect the maximum area of Posidonia meadows against illegal trawling. The protected area is about 5,400,000 m2, 45 % of which held damaged Posidonia meadow. Since artificial reef installation, in November 1992, no trawling activity has been detected in the area. A three year research programme is under-way. Results of this programme will allow comparison of the effect of the reef on protected and unprotected meadows. Tabarca Island (SE Iberian peninsula) This reef was created in 1989 to protect seagrass meadows (25 anti-trawling modules of 8 tonnes) and includes some experimental structures to attract/concentrate pelagic and demersal fish. Oceanographic parameters and planktonic populations were studied in addition to biological colonisation, fish population dynamics and sea grass meadow recovery. Galicia, Ria de Arousa, (Province of Pontevedra, NWSpain). Preliminary work led to the implementation of a 2 year artificial reef research programme, starting in July 1993. The need to compensate for the lack of scientific artificial reef research conducted in Galicia has been the main motivation. The influence of depth, degree of exposure and level of organic matter on the floor on artificial reefs will be studied. Artificial reef modules have been installed in two different areas, one at a depth of 20 m and the other at 12 m below sea level. The monitoring plan involves gathering monthly samples at each location with the purpose of carrying out the following: evaluations of the periods in which different types of benthonic flora and fauna occupy the artificial reefs, numerical estimates of the commercial species based on photographic means, while at the same time marking and following the movements of crustaceans as well as surveying the population of bivalve molluscs located in the substratum which is protected by the reefs. Programa Plurianual de Arrecifes Artificiales. Arrecife artificial de Arguineguin (Gran Canaria, Islas Canarias). Located in Santa Agueda Bay, to the south of Gran Canaria Island, this reef was placed in the water in 1991, following baseline surveys which started in 1989. The artificial reef is composed of 84 concrete modules of 5 different types. Initial results show that benthic and pelagic communities in the reef area changed dramatically compared those seen in the baseline study. An overall increase in species diversity and biomass has been noted. New species were still colonising the reef two years after deployment. Seasonal and successional patterns of colonisation have started to emerge. The reef biota is now much richer than that on a nearby natural reef, as a consequence of higher sediment abrasion in the latter case. Several species have utilised the reef for reproductive purposes: mating (cephalopods), laying eggs (cephalopods and fish) or releasing larvae (fish). Some

D*MES L MOORE fish species have found the reef to be a suitable habitat and become resident. Pelagic fish have been observed feeding around the modules. The reef modules are physically stable.

5.3.6 Germany The only project in Germany is not so much an artificial reef as a test for environmental acceptability of artificial materials in environments. The project, started in 1992, has determined the amount and succession of colonisation on natural stone and blast furnace slag used in river bank reinforcement in Harbour, River . Measurements of pH in interstitial water of the newly constructed river bank reinforcement showed that between the blast furnace slag the pH increased from 6.8 (interstitial water of natural stones) to 8.5. Initial experiments dealing with the biological settlement of algae on plates of natural stone and slag indicated that settlement on artificial stone is retarded. Replicates of this experiments are showing no significant difference in the quantity or quality of algal species settling on the plates. Heavy metal analysis indicates different patterns of metals in periphyton grown on different substrata.

5.3.7 Netherlands Noordwijk artificial reef In September 1992 an experimental artificial reef consisting of four, more or less circular, heaps of basalt blocks in a row perpendicular to the prevailing current direction was placed 8.5 km off the Dutch coast at Noordwijk. Each 'sub-unit' is about 1.5 m high and about 10 m in diameter, and consists of about 125 tonnes of basalt, the blocks having a diameter of 20 - 80 cm. The aim of the project is to investigate the colonising capacity, possible morphological effects on the surrounding sea bottom, and potential modification of the distribution of biomass in the area caused by the reef. Fish and benthic fauna in the area were assessed before the reef was placed. The species composition and biomass on the reef, as well as fish and benthos up to 1 km from the reef are being monitored 5 times per year. The physical stability of the construction is also watched. Developments on the reef show a steadily increasing biomass and diversity. Monitoring will continued until the end of 1996. Results are currently being assessed and hopefully decisions be made about the usefulness of the artificial reef concept in combination with several management options such as coastal defence, aquaculture and fishery management. At the same time laboratory investigations on the usefulness of different waste materials as reef building material are commencing. Owing to very strict rules in The Netherlands, as well as funding problems, this aspect is not (as yet) developing very well.

5.3.8 Finland The reef programme in Finland is in its infancy (started in late 1993) and linked to the problems of fish farming waste management, pioneered in Russia. The main aim is to

|H OWES* MOORE experiment with the possibility of using artificial reefs in nutrient and biomass removal. The project will study whether the growth capacity of fouling communities in the Finnish , is high enough to be used in catching significant amounts of nutrients released by the fish farms. Fish farming is an expanding industry in the Finnish Archipelago. Nutrients released due to overfeeding and fish faeces are causing of the area. Different materials and reef structures are being experimented with as substrata for filamentous algae and epifauna. The recruitment rate, growth rate and the efficiency with which nutrients are taken up by the fouling communities are being recorded. The results will be compared with the nutrient amounts released by the fish farm in the experiment. Mass balance of the entire system will be calculated. The possibilities of using the reef biomass as fertiliser and animal food will be investigated. The programme will run until 1997.

5.3.9 The European Artificial ReefResearch Network (EARRN) The EARRN, started officially in May 1995, consists of 51 scientists from 31 laboratories throughout the EU and will run initially for 3 years. It is co-ordinated by Dr. Antony Jensen, Department of Oceanography, University of Southampton. All four authors of the current report are members or associate members of the network. A 5 day conference in late March 1996, focused on 4 topics: management of coastal resources (including fishery enhancement), socio-economic impacts and legal aspects of artificial reefs, research protocols and reef design and materials. The meeting is being followed by a number of topic specific workshops. It is felt that scientific priorities for the future should be achieved in an European context (rather than national), and currently the European Commission funding allows scientists within the European Union and affiliated trading partners to initiate this work. Collaboration on a wider scale (EU countries plus Romania, Poland, Russia, Israel, Turkey and Monaco) is also being undertaken through the preparation of a book reviewing European artificial reef research (Jensen, 1997).

5.4 Other countries Elsewhere, artificial reefs have been developed according to local requirements, using materials judged to be suitable, usually using availability and cost criteria. Only Japan and the USA have a national development plan. Countries such as the Philippines have developed reefs for use by fishing communities often using waste materials such as tyres, but also much shorter lived locally abundant materials such as bamboo. Such reefs are placed to provide fishing locations for coastal populations and are often short lived. The importance of pelagic fish to these coastal communities has led to the widespread use of FADs again often built from bamboo and lasting for a season or two. Scientific monitoring is often absent, being beyond the resources of the fisheries scientists. The attitude to “waste materials” seems to be that they would be acceptable if environmentally benign This is also the case in where reefs have frequently been built from "materials of opportunity" such as tyres and redundant ships. These reefs have been used primarily as a focus for recreational angling with some SCUBA diving. In Taiwan many fishing vessels (made obsolete by government policy to reduce the size of the fishing fleet) have been sunk to provide new habitat. Artificial reefs are a definite component of Taiwanese fishery policy and are widely used. Obsolete ships are a favourite material for creating attractions for SCUBA divers and recreational fishermen. The practice is seen world-wide and frequently is supported by tourist authorities. One artificial reef with a more sombre purpose is formed by the wreck of the ’’Rainbow Warrior”, sunk by as a memorial to her crew members killed in a bomb attack on the ship whilst visiting . Current initiatives in Hong Kong seem likely to result in a significant artificial reef programme to protect marine parks from illegal fishing and provide new fishing locations for exploitation. The programme is being led by the fisheries department who will use contractors to design and deploy structures within Hong Kong waters.

IH DAMES i MOORE 6 . BENEFITS OF ARTIFICIAL REEFS 55

6 Benefits of artificial reefs

6.1 Summary of benefits Having discussed what artificial reefs are and shown that they have been widely used throughout the world, this chapter will itemise the advantages that they confer. By clearly stating what use North Sea reefs can be put to and indicating any areas of uncertainty, their implementation can be better planned, efficiency accurately monitored by permitting the correct choice of assessment parameters and need for more information identified. It is a well established fact that offshore structures do attract fish (Olsen & Valdemarsen, 1977; Valdemarsen, 1979). This is however an oversimplification of the situation as several aspects are associated with the creation of an artificial reef. The interaction between these aspects, e.g. biology, engineering, safety, social, management, politics, etc., is complex. The potential benefits can be summarised as follows: • greater density of fish; • decreased fishing effort; • increased catch security; • protected juveniles - increased recruitment of young fish to a catchable size • protected adults - more secure stock, so population less likely to crash; • provision of new habitat; • restoration of damaged habitats; • protection of existing habitat; • a technical conservation tool within the EU’s CFP; • a means to transfer management to the fishermen themselves. It should be noted that not all the benefits can occur at the same time on the same reef. Actual benefits that accrue will be dependant on many factors including: the use to which the reef is put; its “efficiency” as an attractor or protector; and the environment in which it has been placed.

6.2 Fisheries management: a benefit for managers The following discussion is primarily based on presentations to the E&P Forum’s Artificial Reefs Workshop in Nov. 1996 (Cripps, 1996) and on Cripps et al., (1996).

!|| CV^MESi MOORE 6.2.1 Justifying the use of offshore structures for fisheries enhancement It is a well established fact that offshore structures do attract fish (Olsen & Valdemarsen, 1977; Valdemarsen, 1979). This is however an oversimplification of the situation as several aspects are associated with the creation of an artificial reef. The interaction between these aspects, e.g. biology, engineering, safety, social, management, politics, etc., is complex. Partly because of the lack of hard data to aid the discussion, the likely operation and advantages of artificial reefs has often been misinterpreted bythe popular press, giving rise to exaggerated claims and a misunderstanding of the possible benefits. Section 5 will attempt to predict likely artificial reef operation, efficiency, impacts and management.

6.2.2 Functioning of a reef within a fishery Artificial reefs represent a tool by which man can elicit changes in the ecosystem to achieve benefits (Stephan et al., 1990). They are habitat enhancement devices placed in marine or to provide a specific habitat for target species. By increasing the carrying capacity of the natural environment their purpose is to increase the overall productivity. Artificial reefs have been used for centuries by coastal communities and have become popular fisheries management tools world-wide (De Silva, 1989; FAO, 1990), as described in section 3. Artificial reefs function as fishery enhancement devices because they resemble natural reefs. In general, they show a similar species composition and community structure to natural reefs in the same area, assuming they are subject to the same environmental conditions (Ambrose & Swarbrick, 1989; Bohnsack & Sutherland, 1985; Matthews, 1985). The depth at which a reef is situated is important, especially with respect to algal composition. Fish may recruit rapidly to a reef, sometimes within hours of installation (Bohnsack & Sutherland, 1985), some species reaching a climax population size within a few months. This recruitment may create an enhanced fishing zone up to several hundred metres from a reef. Larger catches are however, generally limited to within 60 m (Mottet, 1981). An equilibrium community structure is usually achieved within 1 - 5 years. Seasonal variations in the number of species and individuals present on a reef are common.

6.3 Fish concentration and stock enhancement: a benefitfor fishermen

6.3.1 Fish behaviour A wide variety of environmental cues are thought to play an important role in attracting fish to such devices, including: current patterns; shadows; species interactions; sound; touch; pressure; and visual cues of size, shape, colour and light (Bohnsack & Sutherland, 1985). Different species exhibit different behavioural preferences throughout their life cycle. In particular, several fish species have been shown to stay near artificial structures for protection when small and vulnerable to predation (Anderson et al., 1989). An

jjjjjlj OWES S. MOORE artificial reef can be important for the fish stocks of a much larger area than the reef itself, because it gives protection to the fish during their most vulnerable stages. In general, oil and gas platforms are thought to make effective artificial reefs because they provide: • hard substrata with associated habitats; • an abundant food supply from attached and motile species; • a visual, tactile or auditory reference point in an otherwise unstructured environment; • structural openness permitting adequate circulation of water within the interior; • a large surface area, which in conjunction with water circulation, encourages abundant biofouling and benthic hard-bottom species; • physical design complexity providing shelter from strong currents and predators; • a range of habitats throughout the water column allowing different species to remain at their most favoured depth; The degree of importance of each of these factors depends on the particular species and life cycle stage of the species involved (Driessen, 1985). Operating oil platforms extend throughout the water column, providing benthic, mid-water and surface habitats. Fish studies around Gulf of Mexico platforms have revealed that fish are present at all depths, with the greatest variety in the range 30 - 70 m depth (Ditton & Falk, 1981). Work conducted in the North Sea (ICIT, 1991; Cripps & Aabel, 1995) corroborates this conclusion. It is believed that the platforms provide the basis for a substantial food chain and that their presence has changed relatively unproductive areas into diverse, dynamic and highly productive ecosystems (Driessen, 1985). Once attracted to a natural or artificial structure, fish tend to assume one of three particular positions relative to the structure (Ogawa, 1986). The species found around North Sea structures may approximately be assigned to the following patterns: 1. Upper and mid-water swimmers, such as saithe, congregate over or around structures. They tend to hover, remaining in the upper layers as a shoal. 2. Bottom layer swimmers which gather around the structure, but are not sedentary, such as cod (Gadus morhua) and Norway pout (Trisopterus esmarkeii). 3. Sedentary fish which inhabit holes and spaces, such as ling (Molva molva), wolf-fish (Anarchichas lupus) and redfish (Sebastes spp). Platforms do not provide all the food necessary to sustain the high densities of fish living around them. The presence of fouling on the submerged structure is not essential in attracting or retaining populations of fish. The many thousands of fish found around North Sea structures must therefore continue to derive the bulk of their food from off-reef sources (Mottet, 1985; Todd & Bentley, 1991). In general, it is likely that a combination of factors gives rise to the observed distribution of fish around platforms, the species-specific aspects of behaviour being at least as important

HnWvtCS&MOOflE

* as installation-related features. The immediate platform environment is one which fish find acceptable and to which they are attracted, and one which apparently produces no adverse effects in terms of physiology, biochemistry or commercial value. A growing body of evidence indicates that offshore platforms can create new habitats and augment carrying capacities, therefore increasing the diversity, numbers, range, size and growth rates of desirable commercial fish. If they do attract juveniles, which is currently unknown, the platform reefs may allow more individuals to reach adulthood than was previously possible. The structures scattered throughout the North Sea are therefore likely to be providing local reef habitats that are intermittently utilised by fish. The likely range and scale of benefits to the North Sea fishery is an issue that is more complicated than may at first sight appear. It involves aspects of fish Concentration, stock enhancement, fishing effort and fisheries management. Much has been promised from artificial reefs in the past. Exaggerated estimates of potential benefits has lead to disillusionment and distrust, particularly amongst fishing interests. These over-optimistic claims have probably resulted from a misunderstanding of the likely functioning of a reef.

6.3.2 Stock enhancement Despite the large investment in artificial reefs by certain countries, the ecological basis behind their functioning and biology is poorly understood. The variety of materials used, and broad range of conditions in which reefs are deployed, limits the conclusions that can be made. Nevertheless, at artificial reefs, high fish densities, biomass and catch rates, in addition to rapid colonisation, are well documented (Bohnsack et al., 1991; Bohnsack & Sutherland, 1985), and are often found to be higher on artificial reefs than on natural reefs or randomly selected bottom controls (Ambrose & Swarbrick, 1989; De Martini et al., 1989). Overall, artificial reefs are thought to aggregate existing scattered individuals and allow secondary biomass production (Bohnsack & Sutherland, 1985; FAO, 1990) by: • increasing survival and growth of larvae and juveniles that utilise hard substata by providing a settlement substratum, shelter from predation and additional food resources; • creating new food webs through the provision of new spaces, habitats and colonisation patterns; • protecting the sea-bed and nursery grounds; • recycling energy by retaining a localised ecosystem. A major uncertainty associated with a justification for the establishment of artificial reefs is the degree to which reefs concentrate fish, and what the effect will be on the fish stocks in the region as a whole. Estimates of the density and quantity of fish (the standing stock) around a North Sea reef can be made using data from the surveys of fish at working North Sea platforms. The weight of fish per unit volume of enclosed space within the reefs created by the presence of platforms in the North Sea ranges from 0.055 kg m"3 to 0.62 kg m'3. Other estimates from the UK sector suggest approximately 0.3 kg m"3 amounting to about 70,000 pelagic fish and 9,000 demersal fish aggregating within 100 m of each installation (ICIT, 1991). The average weight of fish per unit volume of enclosed reef is then about 0.3 kg m* 3. A rough

[XWFS& MOORE estimate for a reef made of the jacket structures only, indicates a capacity to hold approximately 1 tonne of fish per 3,000 m3 of jacket volume. In general, the number of fish found around working North Sea platforms, although locally high, is still very small in relation to the overall stocks of fish in the North Sea. The total allowable catch (TAG) for North Sea saithe in 1992 for example was 110,000 tonne (Holden, 1994). Depending on the effectiveness of the fishing technique employed, the reef stock would be expected to be caught in a short time, or if the stock proved difficult to catch, then small returns would be expected over a longer period. In either case, given the current level of knowledge regarding standing stocks around oil installations as reefs, the premise of the provision of increased stocks would seem inadequate on its own to motivate the establishment of such an artificial reef. Arguments based on this single premise could be open to misinterpretation, resulting in a too pessimistic assessment of the several other benefits which could be achieved. There is currently no evidence to suggest that North Sea reefs would produce significant amounts of new fish of commercially fished species, i.e. breeding would take place there. The spawning behaviour of the major commercial species such as cod, (Clupea harengus) and plaice (Pleuronectes platessa) does not require the presence of a reef substratum. Spawning grounds without such features are currently well established in the North Sea. An increase in the number of juvenile fish that would not have survived the early, high mortality, life stages, may however occur around North Sea reefs, depending on their location, because of the protection they would offer. Also, there will be a better protection against predators, especially fishermen, for fish at all life stages. It is therefore possible that, in practice, new biomass will be recruited to a catchable size (produced), not because more fish are spawned, but because less potentially viable juvenile fish die. It is likely that non-commercial North Sea species, that are adapted to breed around submerged structures, such as rocks, may breed and spawn on artificial reefs. Such individuals may act as prey for the commercial species. They are unlikely to compete with commercial species for space on the reef because the latter are either mid-water or demersal. Any localised increase in commercial and non-commercial fish stock density around a reef in the North Sea is likely to primarily result from the fish concentrating effect as a consequence of its attractive features. Some increase in fish stock can also result from increased survival rates and production of new fish. The extent and possibilities for the increase in production is however not currently possible to predict, but it is likely to be much less than the fish concentrating effects of the reef. As will be described in section 6.5, what the jackets offer now, and artificial reefs will offer in the future, is protection from fishing pressure. Reduced fishing should result in increased survival that should result in a larger recruitment of fish into the fishery. This needs to be quantified by research. North Sea artificial reefs are therefore likely to primarily attract and concentrate fish, and only to a lesser extent produce new individuals. Whilst this, at first sight, may seem to limit the application of this technology, there are never-the-less still many advantages to be gained from the establishment of a reef. It is though important to make the differentiation between production and concentration, so that the functioning and efficiency of reefs are not misunderstood.

IH O wes 4 moore An artificial reef can then be used for protecting fish from fishing mortality (section 6.5) or for helping fishermen to catch fish more efficiently (section 6.4). These two uses are largely mutually exclusive: the former aiding fish stocks and the latter aiding the socio­ economics of the fishermen. These two uses must be distinguished if the functioning of a reef is to be fairly assessed.

6.4 Fishing effort reduction: an economic benefit for fishermen

6.4.1 Commercial fishing Artificial reefs as fish concentrating devices can make fishing easier. The quantity of fish caught around reefs can be greater for the same effort compared with fishing in open sea. This is because the reefs can increase the density of fish present. It is in the fishermen's interest to catch the required weight of fish in as short a time as possible and by travelling as short a distance as possible. Catch security is also an important consideration, i.e. an increase in the probability of being able to catch the required weight of fish in a given period. The limited increase in standing stock in the region as a whole, the increase in catch security and decrease in fishing effort indicate that artificial reefs may act as fishermen's rather than fisheries management tools. This is a subtle but important distinction which summarises the likely functioning of the reefs, and is not exactly as commonly envisaged. Put simply, whilst artificial reefs in the North Sea have not yet been proved (because they have not yet been studied) to increase fish stocks (the fisheries perspective), they may make the fishermen's job easier (the fisherman's perspective) (Cripps et al., 1996). The determination of a suitable fishing effort for a reef will be an important management parameter. When considering fisheries stock management options within a region such as the North Sea as a whole, the concept of Fmax is commonly applied. Fmax is the fishing effort, e.g. in terms of days fishing with a particular type of gear, that produces the maximum yield, i.e. fish caught. Figure 8 indicates the relationship between increasing effort and catches and is called the yield per recruit curve. If fishing is not great then few fish are caught and these tend to be of a larger size because they have a good chance of surviving, i.e. escaping fishing mortality, from one year to the next. As the effort increases, more fish are caught, but fewer large fish survive. There then comes a point where so many fish are caught that only small fish growing from one year class to the next (recruiting) remain to be caught and a lot of effort must be expended to catch these few fish. This is similar to the law of diminishing returns. Though only an untested theory, is possible that the assessment of Fmax for artificial reef stocks will be a special case of the regional fisheries model explained above. Instead of fish merely recruiting into a catchable size class as a result of growth, fish will move on to the reef from the surrounding fishery. In such a case the yield per recruit curve (Figure 8) may be skewed to the left for reefs. Catches per unit effort may be greater on a reef, as explained above, but as the stock is small and localised it will be relatively easy to fish-out, leading to an efficient use of fishing resources and inefficient economics. The rate of

m OWES & MOORE CORDail im — decline in catches with increasing fishing effort above Fmax will be dependant on the re­ colonisation rate of the fish after fishing.

Fishing effort

Figure 8: Standard and speculative artificial reef yield per recruit curves (adapted from Holden, 1994). A management plan for an artificial reef will therefore need to incorporate the concept of the special reef case of Fmax and more usefully Fo.i for which a high yield is maintained for a significantly lower fishing effort. There is some danger of over-fishing stocks in the region around an artificial reef. Such stocks are already under considerable pressure from multi-national fishing fleets harvesting to quotas that are generally above those recommended by fisheries scientists as being optimum. There may well be a need to regulate fishing in prescribed areas around the reefs, at least until sufficient data have been accumulated to estimate the possibility, if any, of . Data from American studies indicate that the possibility of overfishing is •not great, though artificial reefs there are primarily used for sports fishing which has a lower intensity than commercial operations. If current fish landing quotas are adhered to, there should be no chance of over-fishing stocks in the North Sea as a whole. The same quantity of fish will be removed as that prior to the creation of a reef, but as discussed above, the effort and time used to catch them may be reduced.

6.4.2 Recolonisation The quantity of fish on a reef at any time is obviously an important criteria determining the usefulness of a reef to commercial fishermen. A further important and currently unknown factor influencing both usefulness and reef fisheries management, is the re-colonisation rate. A fast rate would mean that a reef could be fished more frequently than a slow rate. The change in the re-colonisation rate with the stock present on the reef would also

Mm immes a Moore * ———— determine the optimum reef stock density that should be maintained by fishing pressure. It is vital to the estimation of reef fish-aggregation efficiency and to the preparation of fisheries management plans that the re-colonisation rate for oil installations in the North Sea is studied and quantified.

6.5 Fish stock protection: a benefit for future stocks It has been suggested that the most likely applications for artificial reefs in commercial fishing are to create or expand existing nursery or spawning grounds for some species (Sheehy, 1985). Protection, though an emotive subject with fishermen, may be a more important justification for establishing artificial reefs in the North Sea than merely stock enhancement. This would be especially so if the standing stock on the reefs proved to be small. Depending on current, often politically based, North Sea fisheries priorities, protection alone may be sufficient to justify the existence of reefs. The principle of the protection policy is that artificial reefs can be used to preserve currently over-fished stocks. This can be achieved by preventing access to a particular area, such as where spawning or juvenile stocks are known to occur, by limiting the type of fishing gear that can be used, or by offering shelter from both fishing and natural predation. There is already a precedent for the use of closed or restricted fishing areas for particular seasons within the current legislative framework of the EU’s common fisheries policy and national governments regulations. “Several orders” giving fishing rights for a certain species to a group of fishermen, and areas such as the “mackerel box ”, where fishing with certain types of gear at particular times of the year was banned in order to protect juvenile mackerel, are not uncommon. There is an enormous natural loss of eggs and juveniles of commercially fished species in the North Sea. About 95 % are lost in the early stages and of these a further 70 % die in the second year. Commonly, natural mortality rates (deaths due to natural causes such as predation and disease rather than fishing) of fish decrease with age. There are therefore a large number of juvenile fish produced to counteract losses, as the number of fish in an age class declines with age. A female cod (Gadus morhua), for example, sheds between 3 and 7 million eggs during each spawning (Tail, 1981). Rather than protecting the spawning adults, the majority of fisheries management policies act so that mortality, through fishing, of the numerous young fish is reduced. Within limits, the size of the spawning stock is unimportant to the production of new fish (recruitment). A large year-class recruiting to the fishery results in a very large increase in catches (Holden, 1994). It required only 2 or 3 young to survive each year instead of 1 as previously, from the millions of eggs laid, to produce the massive increase in cod catches seen a few years ago. Artificial reefs could then be a means of allowing more individuals to grow to sizes in which natural mortality rates are less. Protection of breeding and juvenile fish using reefs could therefore be a means to enhance commercial stocks. It should though be noted that an increased concentration of small fish may attract predatory fish of the same or different species. Also, the presence of the reef may affect the sediment character of the spawning grounds and so render them unusable, a factor that needs investigating. Limiting access and fishing efficiency, by the presence of potentially ensnaring structures causing less efficient or harmful fishing gear to be used, may also be a means to protect damage to the benthos and improve the sustainability of a fishery. This does however partially argue against the positive implications of reef creation by improved fishing efficiency, described above. There are two main potentially negative impacts associated with the use of reefs for fisheries protection. Firstly the location of reefs and recommended exclusion zones would need to be well marked on-site and on maps, for safety reasons and so that costly damage to fishing gear could be reduced. Secondly, the establishment of exclusion zones is an emotive subject with commercial fishermen, who fear a reduction in their potential fishing area and hence loss of earnings. The benefits to the fishery as a whole, in terms of an increased recruitment and density would need to be emphasised, to compensate for a perceived loss in working area.

6.6 Aquaculture / ranching: a benefit for farmers Artificial reefs can serve several roles in fisheries management; from the enhancement of described above to more intensive aquaculture systems. Settlement of mussels on reef structures in the Adriatic led to research that identified a route for exploitation . Stock density can be intensified by adapting the well established "suspended rope" system of mussel cultivation that is practised throughout the world, stringing seeded ropes of mussels between artificial reef units. Reefs here provide anchorage for fairly standard aquaculture activities. The important factor is that without the reefs providing anchorage and protection from disturbance the mussel culture would not be possible. Suspended rope is also used for culture in Japan. In Japan specially designed artificial reefs are used for the culture of kelp, urchins and abalone. Combined systems for all three have been constructed where the kelp supplies food for the urchins and abalone. There is interest in developing aquaculture systems to develop abalone as a cultured species in Europe and artificial reefs may play a part in this. In more general ways artificial reefs can provide protection for more conventional net- based aquaculture facilities from damaging trawling activity. The use of jackets has been suggested in preliminary discussions of aquaculture developments off Tunisia. Toppled to provide fishing structures the jackets would prevent illegal trawling damaging nets holding fin-fish.

6.7 Biodiversity, habitat protection and restoration: a benefit for the environment

6.7.1 Biodiversity management The contribution that artificial reefs can make in biodiversity management is that of habitat manipulation. This has the potential to increase the number of species in a given area and to provide specific purpose-designed habitat for target species. 6.7.2 Provision of new habitat Artificial reefs are usually constructed to provide elevated hard substrata where formerly there was none. Artificial reefs mimic natural reefs but can be built to provide greater surface area, elevation, current shadow/disturbance, or niches/crevices to favour target species. An early European artificial reef study was that by the Association Monegasque pour la Protection de la Nature off Monaco in the 1970s. Artificial reefs, (2 m3) made from hollow blocks or tiles cemented together, were laid on a muddy seabed within a marine reserve. These attracted a good settlement of epifauna and provided a habitat and refuge for spiny lobster. Following on from this work, specifically-designed cave habitats for rare red coral have been successfully developed by the Institut Oceanographique at Monaco. The placing of artificial reefs on a muddy/sandy seabed will smother and kill infauna directly under the reef. Some 100 infaunal species were replaced by more than 250 epifaunal species within two years in the Poole Bay artificial reef. The infaunal populations in undisturbed sediment around the reef were unaffected by reef deployment. The lowest estimates of epifaunal biomass per unit area were equivalent to that of previous infaunal biomass. However, the greater surface area available on the reef (2.5-3 times ground area lost) gave a higher biomass estimate than from the seabed that the reef covered. This new habitat led to a rapid increase in species numbers and diversity. After 4 years the epibiota provided a food source for molluscs, lobsters, crabs and fish. These in turn were predated by cuttlefish and predatory fish. The reef is a site for reproduction by corkwing wrasse and whelks ().

6.7.3 Restoration of damaged habitat Modem techniques have increased the environmental impacts of fishing; powerful vessels use heavier fishing gears (such as "rockhopper" trawls).This has led to the destruction of some seabed habitats. As an example, in the province of Kerala (SW ) a successful attempt to restore damaged fishing grounds the coastal communities have used a variety of local materials (stones, cast concrete and bamboo) successfully restoring bottom habitat diversity and fish catches. Around the UK coast there are several offshore sites where waste has been dumped under licence. Off Blyth coal flyash from coal burning power stations has been dumped for many years. This has resulted in the smothering of rocky outcrops with a sterile blanket of ash, covering ideal lobster and crab habitat and fish feeding grounds. While dumping ceased in 1995 it will be many years before this area will return to full productivity. One restoration method would be to continue dumping coal ash as stabilised ash blocks (tested in the Poole Bay reef) to restore habitat diversity and accelerate the re-colonisation process. Another concept would be the use of jackets from decommissioned platforms in the North Sea

6.7.4 Protection of existing habitat In the Mediterranean Sea most artificial reefs have been placed as nature conservation and/or habitat protection structures. At least 100 artificial reefs have been deployed for habitat protection by Israel, Italy, France and Spain. Reef complexes range in size from a

|H O wes i moo « few hundreds of square metres to several square kilometres. Their prime role is to prevent the destruction of sea-grass meadows by trawling. Sea-grass is a valuable habitat for many commercial species of fish, providing nursery grounds and shelter. Such protection reefs may be placed and left to function, others are used to enforce the creation of marine reserves or parks where activities are regulated. One example of such a protective reef or barrier can be found off the new port of Loano (NW Italy). Here Posidonia sea-grass has been protected by an artificial barrier about 3 km 2 in area, deployed in 1986. Most of the anti-trawling barrier consists of 350 1.2m3 cubes placed on the seabed. In the centre of the artificial barrier a number of concrete block "pyramids" made from 2m3 blocks provide additional height to the structure and are a focus of scientific research. The whole barrier construction is a marine reserve created by the Comune di Loano (local government), the regulations of which are supported by active policing. Research scientists have documented the colonisation of the barrier structures by a variety of epifauna and epiflora and the arrival of shoals of fish attracted to the barrier. The reintroduction of spiny lobster and grouper into the area is planned. The creation of marine parks may well have implications on fisheries outside the park boundaries. Work in New Zealand suggests that marine parks may effectively, by acting as a refuge of limited size, provide a steady supply of animals into a fishery close to its borders. It is not established whether this could work with pelagic fin-fish, but in theory any respite from fishing pressure that provided feeding opportunities could improve the size and/or fecundity of fish in the long term. This in turn could improve sustainability of catches. In the North Sea such a park would have the added benefit of protecting the seabed from disturbance and so promoting the re-development of the infaunal community. The Spanish approach to creating their “anti-trawling” reefs is to place reef units in a calculated pattern over areas of several km 2 and allow the physical presence of the reef units to deter trawlers. An additional effect in waters where a variety of fishing techniques are used is to effectively partition the marine resources, biasing fishing effort away from trawling, towards a smaller scale of activity.

6.8 Reef productivity: a limited local benefit Artificial reefs have a long history and are used world wide to promote fisheries but the basic understanding of their role in marine ecosystems is limited. There is still a fundamental argument as to whether artificial reefs increase total productivity of fish or simply attract stock from surrounding areas. It is likely that the answer is species specific; a reef in Japan did not enhance flatfish catches as planned, the population near the reef just re-distributed itself on the surrounding seabed. However, octopus landings were increased by 1.8 kg m3 of reef per year after 50,000 m3 of reefs were deployed. This was considered a net increase in total stock and there was no evidence of re-distribution. As octopus are often habitat limited the creation of new habitat with suitable dens was thought to be the major influence behind the stock increase. The subtlety of reef effects may make a scientific answer to the production question very difficult to achieve. In the case of animals that use a reef as a breeding site factors such as egg production (which are relatively easy to estimate) may be used. Where pelagic or non-

||| Dames & moore 67 reef breeding fish are considered the challenge is to estimate growth rates and/or survivorship during their stay on the reef and then try to ascertain what aspects of the reef have contributed to any differences from the control values. Whilst artificial reef activity is a global reality, the importance of such activity in the coastal zone varies from country to country.

6.9 Artificial reefs within the EU Common Fisheries Policy: a benefit for the fishery Researchers may well come to consider an artificial reef to be, at worst, of insignificant negative impact, and at best, a benefit to a fishery. However, in order to get to the implementation stage as a fisheries enhancement device, the concept must be acceptable to either the fishing industry or the fisheries management authorities, and preferably both. Offshore reefs in the North Sea will, by virtue of their tend to fall within the remit of either the EU or the Norwegian government. Whilst there have been many disagreements between EU and Norwegian fisheries authorities and both groups differ in their choice of technical conservation methods, their basic political aims, in terms of maintaining as large as feasible viable national fishing fleets, are similar. To achieve this socio-economic aim, the biological principles of retaining fish stock sizes within “biological safe limits” and preferably at a maximum sustainable yield should (though are often not) be followed. A goal of “relative stability” is also sought though has not yet been achieved. It is then possible that if the use or management of an artificial reef is suitable or permissible under the EU Common Fisheries Policy (CFP) for the North Sea then it will also be a viable proposition within Norwegian fisheries limits. Largely because of ever increasing criticism of the CFP, the EU is currently accepting suggestions and examining new ways of managing and conserving stocks that can be implemented from 2002. All new initiatives must though be legal under the current legislation. The planning of the use of redundant offshore structures as artificial reefs then comes at a particularly auspicious time. There is currently a precedent under national and EU regulations for the implementation of closed or restricted fishing zones. Further work and consultations are required to confirm that artificial reefs are a strategy that could be adopted or even prioritised by fisheries authorities. It should be stressed that integration of artificial reefs into fisheries management policies is as much a socio-economic issue as it is a biological conservation measure, because of the practical aims of the authorities, stated above.

6.10 Transfer of management, ownership and liability: a benefit for fishermen and the current operators Artificial reefs can be used for either protection or enhanced fishing purposes. If an offshore reef is to be used for enhanced fishing then a fishing plan will need to be developed and managed. Though the plan will need to take into consideration technical conservation measures, such as those used fo prevent the fishing mortality of undersize fish

111 OWES & MOORE and the small possibility of over-fishing in the surrounding region, management will, as with the fishery as a whole, be primarily aimed at socio-economic factors. To be justifiable as a fishing enhancement reef, there must be a net economic benefit accrued by the fishermen using it. The management plan will attempt to determine the conditions that will produce an economic benefit, e.g. total allowable catch limits for the reef, fishing pressure, gear and replenishment time between fishing. The alternative to reef-specific management would be to allow the reef to be exploited as any other area in the fishery. Market forces in the form of fishing yields may then govern fishing on the reef, though exploitation is unlikely to be optimal, thus diminishing the potential benefits used by the petroleum industry as a motivation for this form of decommissioning. If it is agreed that to obtain the maximum benefit from a fishing enhancement reef then some form of management is required, then the question of which group should do the management arises. The following groups may be considered: 1, national fisheries ministries; 2, the EU within the CFP; 3, a scientific reef advisory committee; 4, the original operator; 5, a contracted commercial group; 6, a fishermen’s co-operative.

Groups 1 and 2 do not need to justifyreef creation and as such do not have such a vested interest in optimising performance other than as what they may consider to be a small part of the overall fishery. Whilst they may join option 3 they may not prioritise an individual reef high enough to justify the expense of management. Option 3 may be feasible, especially if an element of R&D is involved. Option 4 is probably the least preferable alternative as petroleum companies do not have experience or the wish to be fisheries managers, irrespective of fishing industry opinion which is likely to be against such a move. Option 5 is also feasible but will represent a continuing cost for the industry. For option 6 management and responsibility for the reef is handed back to the fishermen. This, in theory, can be done in 3 ways, through: • national fishermen’s organisations; • specific fisherman / boat / company; • a reef co-operative. It is unlikely that a national organisation will consider the reef of sufficient size to warrant attention. It is highly unlikely that an individual could legally purchase or gain access to exclusive fishing rights in what is traditionally a common resource. It would be highly controversial.

jH CHWES 4 MOORE From a purely practical viewpoint, returning management of the reef to a fishing co­ operative has much to commend it. The fishermen themselves, who know best how to fish, then take care of the reef and associated stocks. At present such an option is unlikely to be legally feasible, but as it is an attractive proposition it deserves further consideration at a time when the CFP is being reviewed and new radical alternatives are being sought. There have been several calls, by fisheries experts within the previous few years for a return to a greater degree of ownership in the fisheries resource than is currently perceived by fishermen. Models to enable this, range widely from: the practice in Pacific artisanal fisheries, whereby smaller groups of fishermen are allowed exclusive rights within certain areas; to individual transferable quotas (ITQ) for each fishing boat. The former Director of Fisheries Research for MAFF in England and Wales even suggests a more creative interpretation of the CFP that may help the current situation (Garrod, 1994). He not only suggests that fishermen should be given a greater share of ownership so that they have a vested interest in the fishery, but goes on to suggest that in the centre of basins such as the North Sea there should be a refuge for core stocks and indeed the ecosystem as a whole. Such areas would provide a pool of recruits to sustain national fisheries in coastal areas. Whilst he states that such areas would be totally closed to fishing, he details the advanced verification techniques that would be required to police such an area. This refuge idea is exactly that proposed for artificial reefs. Reefs have the added advantage that, by their very structure, they tend to attract fish and obstruct fishermen. The main disadvantage of using reefs in such a context is that they may not be large enough to cause the necessary beneficial effects. They could however either form the core of a refuge, or a clustered reef comprised of several structures could be formed to cover a larger area. Further work is required to examine the socio-economic and legal potential of such a transfer of management strategy and whether ownership and liability transfer would be included.

6.11 Changes in fishing practice: a further fisheries benefit As stated previously, current fishing regulations serve to preserve the livelihood of fishermen rather than the fish themselves. Due to the current poor status of many of the stocks in the North Sea drastic action has been recommended by the EU and Norway in order to save these stocks from crashing. To improve the status of the fisheries there are basically two choices, both of which require changes in fishing practice and hence the socio-economics of fishermen: • reduction in the number of small fish caught • reduction in fishing effort Traditionally, regulation has centred on the former option, primarily because this was the politically easier option to implement. Technical conservation measures in this respect include: total or partial fishing bans in defined areas, gear limitations such as minimum

H DAMES & MOORE mesh size restrictions. A major problem associated with measures limiting fishing effort and hence fishing mortality is the difficulty of enforcing them. It can be seen that artificial reefs could be used as just such a means to enforce much needed restrictions on fishing effort in a particular areas. Due to the presence of the decommissioned structure itself, access will be denied within the reef zone. Further, if fishing is conducted in the vicinity of the reef then gear such as long-lines may prove more feasible than demersal trawls. Again, there would seem to be a use for artificial reefs within the current fisheries management policies, though changes in traditional fishing practice and hence socio-economic adjustments would be required. How large and extensive these changes would need to be as a result of a fairly small area of reefs in the North Sea as a whole has yet be determined.

fyl [MACS & MOORE 7. IMPLEMENTATION OF THE RIGS TO REEFS CONCEPT IN THE NORTH SEA 7 Implementation of the rigs to reefs concept in the North Sea

7.1 Introduction The purpose of this section is to: • examine some concepts for the creation of artificial reefs from platforms in the North Sea; • outline the advantages and disadvantages of different scenarios for reef creation in the North Sea; • identify the types, locations and numbers of platforms that might contribute material to these different types of reefs. If jackets are to be utilised as artificial reef materials a range of deployment options and locations are possible. These range from toppling in place to movement of jackets to form reef clusters or “fields” inshore. Such reefs may be used to provide an area (or areas) , within a planned overall management strategy, where trawling pressure is minimised by the physical difficulty of fishing without damaging gear, to reefs designed to provide opportunities for fishing either offshore or inshore. In all scenarios, the dominant influence seems to be that of fishing and fisheries. It must be remembered that in addition to these there will be nature conservation advantages, such as the provision of hard substrata in an otherwise sedimentary area and/or the protection of the sea-floor from physical disturbance and the subsequent development of an undisturbed benthic community. These in turn may well provide a food source for both commercially important and other fish species. There are 420 platforms in the North Sea, of which approximately 210 are in the UK sector. In the Norwegian sector there are approximately 70 working and planned structures, all located in the central and northern North Sea. The structures are fairly large and are placed in water depths ranging from 70 to 300 m. The Troll platform now built will be placed at a depth of 302 m. Other structures in the North Sea area (about 150) are mainly small and situated in the shallow southern North Sea. They are mostly owned by Dutch and Danish interests (Corcoran, 1995; Laver, 1992; NOU, 1993; Williams, 1995). The majority of structures in the North Sea are constructed of steel. Only 26 structures are concrete. Of the concrete structures, 15 are in the Norwegian sector, 10 in the UK sector, and there is 1 Dutch structure (Corcoran, 1995; Williams, 1995). Only a few structures in the North Sea have stopped production, but several fields and structures are to be taken out of service in the near future. In the Norwegian sector, the expected end of production for the following fields are: East-Frigg, 1995; Frigg, Heimdal, Edda, Cod and Tommeliten Gamma, 1997; West Ekofisk, 1998; Gamma North and Gyda South, 1999 (Fjells&, 1994). ODIN was shut-down on the 1st August 1994 (Anon, 1994). Production on North East Frigg stopped on the 8th May 1993. A date for a halt in production for many of the larger, or new, fields has yet to be decided upon, but it is expected that several of the structures in the Ekofisk field will be abandoned within the next five years.

7.2 Scenarios for artificial reef creation from jackets Three different scenarios are discussed in this chapter. They represent different solutions for the creation of one or more artificial reefs based on the structures in the North Sea. Some of the scenarios will, for different reasons, be difficult to realise, but it is necessary to discuss them all to give a complete overview. Many intermediate solutions exist between the scenarios, so it is impossible to discuss all of them. The three scenarios discussed are: 1. In situ toppled reef emplacement - every structure will be toppled in place individually. 2. Clustered reef emplacement - one or more sites for construction of one or more artificial reefs will be established prior to abandonment of the first platform. When a structure is abandoned, it will transported (if this is feasible) to one of the designated sites. 3. Abandon in place: the structures are left standing in place, probably after the equipment has been removed and the structures have been secured and cleaned. This scenario is only being considered for large concrete gravity base structures (GBS).

7.3 in situ toppled emplacement The design of the reefs laid out according to this scenario will have to be adjusted to existing platform locations and activities, thereby excluding the most beneficial layouts, because toppling directions will be limited. This may also include using unfavourable sites in terms of sediment characteristics and contamination from drilling operations. One advantage of this scenario is that a reef community has the opportunity to develop at several reef sites without any fishing pressure, because the sites will be protected from fishing byexisting safety zones around working platforms. Some optimisation in reef configuration may be possible if groups of linked or closely positioned structures are toppled in pre-defined directions according to a reef design determined prior to toppling of the first structure.

7.4 Clustered reef site Reefs will be created by bringing together various cleaned structures from different locations that have been identified as being suitable reef components. Structures, such as different jackets will be disconnected from the sea bed and transported, either above or below water, possibly even from another field. The structures will be placed in a juxtaposition that will produce an overall design that optimises the aims of the reef.

HU CKMESt MOORE The clustered reef option will give fewer, but larger, reefs compared with in situ toppling. It will be possible to avoid the most unfavourable sites. Decommissioned structures will have to be moved away from the operating platforms. This will be a benefit in terms of avoiding the more contaminated areas as reef sites, but it is likely that the total costs will increase compared with all other reef creation options, because most structures will have to be moved to a new location. Creation of clustered reefs will, in the long run, be less of a hindrance to the fishing industry because the total area covered by reefs and surrounding avoidance zones will be less, and also more defined. Reef sites should be placed in the vicinity of some platforms, so avoiding the need to move all structures. A structure that cannot be moved or is difficult and dangerous to move would be particularly suitable as a reef nucleus. This will reduce costs as well as disturbance to the seabed and existing biological communities.

7.5 Abandon in place for CGBS For the abandon in place option the CGBS jacket is left standing in place after it is abandoned. The deck structures and top-side modules will be removed, or stripped and cleaned of all contaminants. If this scenario is defined as "disposal" of the structures it is covered by the London Dumping Convention and the IMO Guidelines. According to the IMG Guidelines, structures standing in less than 75 m and weighting less than 4000 tonne in air (jackets without decks and superstructures) will have to be removed. It is not clear whether the piles, anchoring the jackets to the sea bottom, can be included in the jacket weight according to the IMO guidelines. If it is accepted that abandonment in place may serve as an alternative use of the structures, then it is a favourable solution from an environmental point of view, as nothing has to be done with the jacket. From an artificial reefs point of view, the effect of a standing concrete structure will probably be less than a steel lattice structure. The topside units will generally be removed, or flushed and cleaned if not removed, whilst the jackets left will have to be maintained to ensure safety and environmental requirements. This will be a costly operation conducted from a land base. Navigation equipment must also be maintained. Standing structures could be a risk for small boats as these might try to use the structures when crossing the North Sea. Even if a safety zone is maintained, this will be impossible to control. A distinct advantage of abandoning CGBSs in place is that they could be used as the nucleus or hub of a larger reef complex, to which other steel platforms could be brought. The hub would then act as part of the reef, clearly mark the area and could be used as a base from which to study the reef and monitor its exploitation. In addition, it is feasible that monitoring equipment on the hub could advise fishermen on the current exploitation potential of the reef.

msDAMfSAMOORf. 7.6 Potential locations for reefs

7.6.1 UK sector The potential for using the 205 operating fixed steel UK sector structures in the scenarios outlined in section 7.2 is briefly reviewed below.

7.6.1.1 In situ toppled reefs Of the 205 fixed structures, only 23 stand in water deep enough to yield the required 55 m clearance if the whole structure were to be toppled such that its largest basal dimension was rising vertically from the seabed (Table 8). If these 23 platforms were toppled individually as reefs they would cover some 150,000 m2 of seabed at 20 separate sites. Platforms which are considered to be located at one site are: Ninian North and South; Alwyn North and South and Bruce D and PUQ. Table 8: List of UK fixed steel platforms in water deep enough to give 55 m over the toppled remains of the whole jacket (Cordah, 1996)

Name Jacket Decomm. Water Base Estimated Weight year Depth Dimensions End. Vol. (t) (m) (m) (m3) Magnus 34,440 2005 186 85 x 85 877,455 Thistle 28,000 1999 161 85x82 738,990 Piper B 22,555 2001 145 72x60 448,920 20,500 2011 167 100x80 885,100 Murchison 20,300 2000 156 75x75 590,850 Comorant N 20,050 2020 161 77x75 626,049 18,650 2010 157 80x70 602,880 Ninian S 18,000 2008 141 75x75 534,038 AlbaN 17,000 2014 138 80x60 474,720 Heather A 17,000 1999e 143 61x61 379,451 Scott JD 16,131 2011 145 70x55 411,075 Alwyn NAA 15,900 1999 130 70x65 414,050 AlwynNAB 14,500 1999 130 66 x 64 386,100 Tartan A 14,500 2000 140 66 x 64 415,800 Brent A 14,225 2011 140 70 x 70= 470,400 Ninian N 14,100 2008 143 75 x 75= 541,613 Saltire A 13,687 2005 144 75 x 75= 545,400 Beryl B 13,250 2006 120 60x55 291,600 N W Hutton 12,662 1999= 144 86x60 532,512 Bruce PUQ 9,600 2018 118 45x36 164,610 9,500 2012 145 45x42 221,850 East Brae 9,200 2015 116 42x37 153,468 Bruce D 7,700 2018 118 40x40 155,760 e = estimates. 7.6.1.2 Clustered toppled reefs It is envisaged that steel jackets may be clustered around fixed concrete structures. The steel jackets that may be arranged in this way could, for the purposes of this assessment, be the same as those listed in Table 8 as capable of having a 55 m clearance in situ when toppled This provision would ensure that if, for any reason, jackets could not be transported to the concrete “hub ” of the cluster reef after they were toppled, they would, at least, have the required 55 m clearance above them. Table 9 lists the concrete structures standing in more than 75 m of water in the UK North Sea with their proposed decommissioning dates. If cluster reefs were to be created around them, all reef building activities would have to wait until the proposed “central hub ” concrete structure had itself been decommissioned, or at least had ceased production. Table 9. List of concrete structures in more than 75 m of water in the UK sector of the North Sea.

Platform Substructure weight Decom. Water depth (t) date (m) Ninian Central 345,000 2008? 133 Beryl A 200,000 2006? 117 Brent B 165,664 2017 139 Brent C 287,542 2017 141 Brent D 177,809 2017 142 Comorant A 294,655 1999 150 Dunlin A 228,611 1999 151 MCP01 N/A N/A N/A Pumping station

If the criteria of cluster reef creation include the specification that the steel jackets are transported the shortest possible distance to the proposed concrete hub, then one possible scenario is that 6 hubs would be designated with 23 steel jackets grouped around them in clusters of 4 — 6 platforms. The total enclosed volumes of the clustered steel jackets at each hub would range from 765,438 m3 to 2,810,175 m3 (10). If MCP01 cannot be used as a hub, its steel platforms could go to Beryl making a large cluster of some 3 x 106 m3 enclosed volume. Under this scenario a total of 381,452 tonne of structural steel would be moved.

pH DAMES & MOOIIE Table 10. Potential arrangement of cluster reefs for steel jackets in the UK North Sea, Central Hub decom. Steel Steel Estimated Total estimated hub date componentdecom. date end. Vol. enc. vol. (m3) (m3) Dunlin A 2007 Thistle 1999 738,990 Murchiston 2000 590,850 Magnus 2005 877,455 Eider 2010 602,880 2,810,175

Comorant A 1999 Comorant N 2020 626,049 Tern 2010 885,100 NW Hutton 1999? 532,512 Brent A 2010 470,400 2,514,061

Ninian 2009 Alwyn A 1999 414,050 Central AlwynB 1999 386,100 Heather 1999 379,541 Dunbar 2012 221,850 Ninian N 2008 541,613 Ninian S 2008 534,038 2,477,102

Beryl A 2006 Bruce PUQ 2018 164,610 Beryl B 2006 291,600 East Brae 2015 153,468 Bruce D 2018 155,760 765,438

MCP01 ? Piper B 2001 448,920 Saltire A 2005 545,400 AlbaN 2014 474,720 Tartan A 2000 415,800 Scott JD 2011 411,075 2,295,915 Total estimated enclosed volume (m3) 10,862,691

jUjoAMrSi MOORE 7.6.2 Norwegian sector

7.6.2.1 Installations The oil and gas installations in the Norwegian sector vary from small sub-sea templates weighting 20 tonnes to the large concrete structures weighting several hundred thousand tonnes. Obviously not all of these structures are usable as elements in artificial reefs. As stated previously, elements with open lattice work structures show good reef characteristics and attract a variety of fish species (Grove et al., 1991). Such elements will therefore constitute the major parts of artificial reefs. The following types of oil and gas structures are found in the Norwegian sector: Floating production units

Two platforms and five loading systems are found in the Norwegian sector. None of these are evaluated as artificial reef elements as they will easily be removed after production close down. Sub-sea installations Approximately 50 sub-sea installations weighting from 20 to 1500 tonnes are found in the Norwegian sector. Some of the templates could be used as elements of artificial reefs, but being small, the best place to use them may be as elements in a shallow artificial reef. Steel installations Altogether, 67 steel installations are found in the Norwegian sector, 30 of these are either standing in less than 75 m of water or with a structure weight of less than 4000 tonnes in air. The weight varies from 800 tonnes for some of the tripods to 26000 tonnes (Brage platform). All these installations could be used as elements in artificial reefs due to the lattice structure. Table 11 presents steel platforms in the Norwegian Sector of the North Sea, standing in more than 75 m of water, or with a structure weight of more than 4000 tonnes in air. These structures are most suited as elements in artificial reefs.

^ DAMES & MOORE Table 11: List of jackets standing in more than 75 m or with a structure weight of more than 4000 tonnes in air.

Name Operator Jacket Water Base Estimated Weight depth Dimensions Enel. vol. fx 1000 tonnes) fm) fm) fm3) Brage 26 137 650000 * Oseberg C Norsk Hydro 18 110 550000 * Oseberg B Norsk Hydro 14 109 69x55 556452 Frery Elf 6 119 150000 * Heimdal Elf 16 120 550000 * Frigg (QP) Elf 7 97 180000 * Frigg (DP 2) Elf 9 97 180000 * Veslefrikk Statoil 10 175 55x55 308108 Sleipner East Statoil 4 83 45 x 45 222915 16/11 S Statoil 8 70 180000 * 16/11 E Statoil 4 70 100000 * 2/4 S Statoil 7 77 42x42 92170 Valhall (DP) 6 69 120000 * Valhall (PCP) Amoco 5 69 120000 * 2/4 G Amoco 2 77 33x41 62500 Ula BP 5 71 41x41 155923 Gyda BP 9 66 180000 * 1/6 A Phillips 7 70 50x65 182300 2/4 F Phillips 7 78 50*65 182360 7/11 A Phillips 4 78 44x76 192600 2/7 C Phillips 7 71 50 x 66 189000 2/4 B Phillips 5 74 46x62 151000 2/4 C Phillips 6 77 50 x 62 184000 2/4 FTP Phillips 5 77 46x61 149700 2/4 H Phillips 3 77 46 x 46 118000 2/4 K Phillips 20 74 67x93 319800 2/4 P . Phillips 1 77 34x40 69515 2/4 Q Phillips 1 77 34x40 69500 2/4 R Phillips 3 77 35x63 119700 2/4 W Phillips 1 77 29x33 39900 2/7 A Phillips 7 71 50x65 182360 2/7 B Phillips 7 71 50x65 182400 2/7 FTP Phillips 4 71 35x65 117400 2/7 D Phillips 5 70 30x36 60680 2/4 E Phillins 5 76 50 x 65 176000

* : volumes not confirmed

Steel elements such as flare stacks and bridges have not been included although they may be suitable as elements in artificial reefs. Their total volume is however insignificant compared to the jackets.

Homes iMoont * '* Concrete installations Thirteen operating concrete installations are found in the Norwegian sector. None of these are, due to their closed structures, suitable as artificial reefs. They may however function as centres of artificial reefs as they may be impossible or very difficult to refloat and remove. Table 12 lists the concrete installations on the Norwegian Sector of the North Sea. The Ekofisk Barrier Wall is excluded from the list. Table 12: Concrete installations in the Norwegian Sector of the North Sea

Name Operator Structure Water Comments Weight depth fx 1000 tonnes) (m) 2/4 T Phillips 235 74 Weight in place Draugen Norske Shell 245 270 Frigg (TCP 2) Elf 164 104 Gullfaks A Statoil 340 142 Substr. weight in air Gullfaks B Statoil 173 134 Substr. weight in air Gullfaks C Statoil 846 217 Substr. weight in air Oseberg Norsk Hydro 321 110 Sleipner Statoil 205 82 Statijord A Statoil 320 145 Towout displacement Statfjord B Statoil 824 145 Towout displacement Statfjord C Statoil 764 145 Towoutdisplacement Troll Statoil 656 330

7.6.2.2 Suitable areas in the Norwegian part of the North Sea An evaluation of possible areas for artificial reefs in the Norwegian sector of the North Sea suggests four areas where oil and gas installations can be clustered around concrete structures to form larger units. The following criteria have been used: • the area must hold a large number of steel jackets, otherwise it would be too expensive to form a reef;• • the area must hold one or more concrete installations as these could prove difficult to remove and would act as a hindrance to e.g. trawling; • the area should not interfere with known spawning grounds for fish stocks. Based on these criteria, the following areas in the Norwegian sector of the North Sea could be suitable for construction of artificial reefs based on clusters of oil and gas installations: Area 1 - The Ekofisk area This area has a high density of platforms suitable as elements in an artificial reef. Except for the Ekofisk tank (2/4T), all jacket structures and tripods/flare towers have configurations that are extremely suitable as reef components. The larger structures will contribute most to the enclosed volume of a reef, which as previously stated, determines the total expected yield from a reef.

H| DAMES 4 MOORE Volume should be the main reef component selection factor. If structures are going to be moved from their present location to become part of reef clusters, the location of the larger structures should be selected as the destination for the reefs if the contamination status of the area around them is within acceptable limits. This will reduce costs and disturbance to the sea bed, as well as simplifying toppling and movement operations. Area 2 - The Oseberg area This area has four large steel jackets that could form a cluster of platforms around the Oseberg concrete structure. Two jackets from the Oseberg complex (Oseberg B and C), the Brage platform and the Veslefrikk platform would all contribute significantly to an artificial reef. Area 3 - Statfiord/Gullfaks area This area has a high density of concrete platforms, three at the Gullfaks area (Condeep 4 shafts) and three at the Statfjord area (both Condeep 3 and 4 shafts). Steel jackets have to be brought in from other fields but the area, including the UK sector, has a high density of steel jackets which makes it possible to create a large artificial reef. Creating one or more artificial reefs in this area must be seen in connection with potential artificial reefs around Ninian Central (UK), Comorant A (UK) and Dunlin A (UK). Area 4 - The Fries area Four jackets could be clustered around the TCP 2, forming an artificial reef. This should be discussed in connection with a potential reef around Beryl A (UK). An overview of the different clusters and the estimated total volumes is given in Table 13.

H DAMfS & MOORE Table 13: Potential arrangements of clustered reefs for steel jackets in the Norwegian Sector of the North Sea.

Central Steel Estimated Total estimated hub component end. vol. end. vol. tm3) fm3) 2/4 T 2/4 K 319800 1/6 A 182300 2/4 F 182360 2/7 C 189000 2/7 A 182360 2/7 B 182400 2/4 E 176000 2/4 P 69515 2/4 C 184000 2/4 Q 69500 2/4 FTP 117400 2/4 H 118000 2/4 G 62500 2/4 R 119700 2/4 S 92170 2247005 Oseberg Brage 650000 Oseberg C 550000 Oseberg B 556452 Veslefrikk 308108 2064560 TCP 2 Fray 150000 Heimdal 550000 Frigg QP 180000 Frias DP 2 180000 1060000

More elements could be moved into these designated reef areas, especially to the Ekofisk area. Which elements to be incorporated will be a function of aspects such as distance to the reef centre and decommissioning date.

rm OS DAMFS 4 MOORE counnn 8. PROPOSAL FOR FURTHER RESEARCH 8 Proposal for further research

8.1 The need for further work This report has indicated that whilst some studies have been conducted of artificial reefs in different parts of the world and of the general environment around North Sea platforms, there is insufficient data available to assess the benefits, consequences and feasibility of a “rigs to reefs” strategy in the North Sea. The distance offshore and the strictly enforced exclusion zones around production platforms has prevented much qualitative data being gathered by marine user groups who were the initial movers in the development of the USA rig utilisation programme. Oil platforms were seen as good sports fishing locations in the USA and so a need to preserve that amenity was seen as important. In southern Europe, where some jackets are regularly harvested for mussels, platforms are seen as being potentially useful in aquaculture (Barcelona convention). The absence of a proven use in the case of the North Sea platforms is a problem. There has been no incentive from outside the oil industry for assessing their potential to provide a management tool for fishing, fishery, or nature conservation management. There are no large steel artificial reefs in , so there is nothing to compare them to either. In short, current knowledge does not allow an effective assessment of whether the creation of artificial reefs from the jackets of North Sea platforms can/will have benefits to fishing, fisheries management, the environment (in the form of habitat provision and protection), or coastal community socio-economics The work outlined below provides for an appreciation of the current status of North Sea jackets as artificial reefs and will provide information on fish residency and behaviour, the benthos and the physical surroundings. This will support modelling of possible artificial reef creation options in which jackets provide the major structural components. Work can be divided into two, largely separate, programmes of work covering inshore and offshore reefs. These two classes of reef are expected to have different modes of operation, uses, designs and logistics, and hence are treated as separate entities. Figure 9 summarises the stages of work involved within the two programmes and indicates how far each programme has progressed to date. The study is intended to gather data relevant to two possible modelling options: 1. that jackets are used offshore to create single or complex artificial reefs to facilitate habitat, commercial fishing and/or fishery management; 2. jackets are moved inshore to provide artificial reefs for commercial and sports fishing and other exploitation and/or a possible role in coastal fishery resource partitioning. Not only does the proposed work aim to estimate the potential advantages and disadvantages of reefs constructed from platforms in the North Sea, but much of what is

||gDAMU&MOORf. currently occurring around operating structures will also described. The body of work will therefore be of considerable interest irrespective of the artificial reef options. Results from reproducible, independent, peer-reviewed research published openly can be used by: • the oil industry to determine the feasibility of using artificial reefs as a decommissioning strategy; • service companies and operators - to plan the optimal design of reef to maximise benefits and minimise costs; • regional authorities - to estimate if local benefits can be accrued; • national and multinational government organisations - to estimate if the reefs are in the national interest and that their positive impacts justify any negative impacts; • pressure groups - to aid in the balancing of the costs and benefits and to better inform the public Depending on the original viewpoint, without such a research programme as proposed below, it will either be difficult to justify the use of reefs or it will not be possible to reliably estimate the likely impacts. For rigs-to-reefs in the North Sea to be at least a proposition worth political evaluation, the following research is urgently required.

C ho ice of cold platform ______)

Phase 1 preliminary

Phase 2 l___main research_ ___ /

Research programme Reporting t reccomendotions

R eel removal

Figure 9: Flow diagram of project stages. Shaded region indicates currently completed stages.

HI Owes 4 MOORE 8.2 Inshore Reefs

8.2.1 Introduction and purpose A one year feasibility study has been completed, to establish the requirements for the design, siting and scientific investigation of an artificial reef intended to enhance the fisheries productivity and the economic prospects in areas of the UK where these would otherwise be low (AURIS, 1995). CORD AH environmental management consultants now propose to build and study a high profile steel reef off the coast of the , Scotland (CORDAH, 1997). The creation of artificial reefs is one of the specific support actions for fisheries of the Highlands and Islands Regional Plan (Scottish Office, 1994) and is incorporated into the UK Fisheries Sectoral Plan. Consequently, the proposed pilot reef is intended as the UK’s investigation site on the long-term utilisation of high profile artificial reefs for fisheries resource management, establishing the basis for technology transfer and diversification to other suitable locations in the UK and Europe. The purposes of the proposed programme of work at the inshore reef are as follows:- • to construct the first UK high profile steel reef; • to study the response of fin fish to the presence of the reef; • to apply, evaluate and develop methods for assessing fish populations and fish movements around high profile steel reefs in the North Sea; • to acquire reliable data with which to determine the potential benefits, if any, of creating such artificial reefs in the context of near-shore fisheries in the UK; • to examine ways in which such reefs might be exploitable by the communities they serve; • to create a test and research site that would provide data and knowledge on this topic to a wide and diverse range of interested parties. A licence to deposit material on the seabed, as required by the Food and Environmental Protection Act 1985, will be sought from the Scottish Office Agriculture, Environment and Fisheries Department. As required by the UK Department of Transport, the site of the reef will be advertised and all interested parties will be notified of its location before the reef is put in place. The exact location of the module will be published in a “notice to mariners”, and marked on navigation charts. It is understood that it will not be necessary to mark the reef permanently with a buoy.

8.2.2 Proposed Reef

8.2.2.1 Proposed site The selected site is an area of inshore and gravel seabed 8.5 km off the coast of Brora on the Moray Firth, with a water depth of 40 m. It was selected after the completion of an exclusion mapping exercise which involved assessment of a wide range of physical,

gl DAMES & MOORE biological and commercial attributes of the whole region of the Moray Firth, and extensive consultation with many interested parties. Conservation organisations, the local port authorities, the Scottish Fishermen’s Federation, local fishermen’s organisations, and the Department of Transport have agreed in principle to the siting of the reef at this location. The views of the Crown Estate Commissioners have been sought and guidance obtained from them. This systematic process identified the north west coast of the Moray Firth as an ideal region for an artificial reef development because there is: • a clear socio-economic incentive to create and use a reef, arising from the declining traditional fishing industry, high unemployment, rural depopulation and generally low per capita incomes; • sport angling potential, resulting from an expanding market for recreational fishing, the existence of several local businesses who already provide charter vessels for sea angling, the capacity of other small, local fishing vessels to adapt to working the reef good access to the site from local ports, and apparent benefits to the wide range of local businesses who could supply goods and services to sea anglers; • deep water close to shore (40 m depth) and a suitable hydrography; • a fairly level topography with a suitable firm, sandy substratum; • limited trawling in the area; • minimum risks to shipping because the proposed site is outside the main shipping lanes; • an adequate distance between the proposed site and areas that are already highly productive. The general area in which the reef could be sited was identified and consultations then held with the Scottish Fishermen’s Federation and the local Fishermen’s Associations. Three sites were initially identified by the local Fishermen’s Associations, and the site off Brora was finally selected because it was most suitable for the local fishermen.

8.2.22 Consultation A wide range of organisations and individuals were consulted by AURIS about the desirability of creating a pilot artificial reef at the proposed location. All of the parties have indicated that they have no objections, in principal, to the construction of a reef at the proposed site. In particular, Scottish Natural Heritage has given its approval for the reef which may become an integral part of their Moray Firth Initiative.

||j CftMtSi MOORE 8.2.2.3 Site description Location The site lies within a 10.8 km 2 sea area bounded by the co-ordinates: 58°1.5 ’N 3°44’W 57°59.75 ’N3042.25’W 58°1.9 ’N 3°41.75’W 58°0.5 ’N 3°40.5’W The physical environment The area is characterised by low energy diurnal , weak tidal streams, an average tidal range of approximately 3.5 m, and peak current velocities of less than 0.5 m s'1. At the site, the topography is fairly level and sedimentary, with patches of coarse sand, brittlestar beds and compacted sand with small surface ripples and worm casts. The biological environment A survey of the seabed at the proposed site, carried out in conjunction with Scottish Natural Heritage during AURIS’s feasibility study, did not reveal any biological features of conservation significance. The sediments tended to be fairly mobile and there were few sessile epifauna. In relation to local inshore fisheries, the catch is low, with fishing being mainly restricted to sport angling. The principal species caught are cod, haddock, whiting, plaice and lemon sole, and ling around natural reefs. The area provides seasonal feeding, spawning and nursery grounds for cod, whiting, plaice, sole and herring. Scallops are fished locally, and crab and lobsters are caught along the rocky coastal margin. Grey and common seals are locally abundant. Bottlenosed , harbour and white-beaked dolphins are also observed in the area, and sea otters are widely distributed along the coastal margin. The Moray Firth is one of the most important sites for , wintering waders, wildfowl and sea ducks in Europe and holds nationally and internationally important bird concentrations, as well as several species at the limit of their geographical range. The site of the pilot artificial reef lies within the proposed Moray Firth Special Area of Conservation. In relation to conservation, SNH has given their approval to AURIS’s proposals which may become an integral part of the Moray Firth Initiative (a coastal zone management plan of which SNH is a participant).

8.2.2.4 Proposed reef module It is proposed to construct a single reef module from a redundant crane tower (dimensions 19.5 m x 17.1 m x 53 m, weighing approx. 400 tonne in air) to be provided by BARMAC Limited, Nigg. The tower is of an open, steel, tubular, lattice work design which is recognised as an important feature in determining the effectiveness of the reef for shoaling 87 finfish, and incorporates the desired design characteristics of a pilot reef. The enclosed volume of the crane tower is 17,673 m3 and it would cover approximately 1,034 m2 of the seabed. It is estimated that its average life-expectancy is greater than 60 years (based on an average corrosion rate for steel of 0.2 mm per year in seawater). The redundant crane tower is an ideal high profile reef module. It incorporates the desired design characteristics of an open, lattice-work reef for shoaling fish, contains no environmentally damaging substances, will be structurally stable, and offers a significant cost benefit over a new-build structure.

8 2.2.5 Flotation and deployment The reef module is currently stored at BARMAC’s Fabrication Yard, Nigg, . An initial inspection has indicated that no environmentally damaging substances are present on the module and no anodes are fitted. Nevertheless, before deployment, the unit will be checked for contaminants and some light steel work will be removed. It is proposed that a new research and development company, Prosyst Limited, will carry out the flotation and deployment of the module, bymeans of a new system of controllable buoyancy air bags. The company has secured funding for the design, building and testing of their bags, but it is essential that they are used on a demonstration project. The DTI and Scottish Enterprise support their technological development. The bags will enable the module to be floated out from Nigg to the reef site, and to be lowered accurately into position on the seabed The vessel used for tow-out will be equipped with satellite navigation equipment (GPS or DGPS) to ensure that the unit is placed at the approved location. The reef module will be placed horizontally on the seabed in a water depth of 40 m, giving at least 20 m surface clearance for local inshore shipping traffic, as stipulated by the Department of Transport. One or two large conventional anchors may be used to fix the reef to the seabed as added protection to ensure that it does not roll or move from its site. At the end of the monitoring period, the buoyancy bags will be used to refloat the reef and transport the module back to shore for dismantling and recycling.

8.2.3 Proposed Programme of Work

8.2.3.1 Introduction The feasibility study constructed preliminary models for the ecological productivity and economic utilisation of the pilot artificial reef. Cost-benefit analysis has indicated that recreational sea angling could be a commercially viable use of the pilot reef, adding significant new revenue to the local economy. In contrast, the sustainable catch from the small-scale experimental reef would be limited and unlikely to provide a viable income for commercial fishing vessels. With respect to commercial fishing, however, there may ultimately be benefits in scaling up the reef to form larger reef complexes. In addition, the reef would provide valuable data from which to determine if the materials of opportunity that will become available when North Sea oil platforms are decommissioned could be used as reef components. Inaccessible to mobile fishing gear, the reef could also act as a refuge area for fish and shellfish populations, providing benefits for fisheries conservation. The study of the pilot reef is intended, therefore, to field-test the models established in the feasibility study. In particular, it is proposed to investigate: • species biomass, abundance, spatial distribution and community interactions before, during and after the pilot project, for the benthic and epibenthic biota, as well as the sessile and free-living biota on the reef; • recruitment, standing stocks and the dynamics of fish and shellfish populations before, during and after the pilot project; • sustainable yields for the various types of fishing activity; • environmental costs and benefits; • social and economic costs and benefits; • a forecast of the consequences of scaling up the reef to form a reef complex.

8.2.3 2 Proposed programme of scientific research The programme of scientific research will be carried out over a period of five years to assess the colonisation and succession patterns on the reef. After a baseline site investigation, to be carried out prior to installation, the reef and surrounding sea area will be monitored during the study period by ROV surveys, benthic surveys, diver surveys, sonar surveys, fish tagging, capture/recapture and tracking, telemetry and remote sensing, and possibly seal tagging and tracking. A comparison will be made with nearby reference areas at representative seabed locations and on natural rocky reefs and wrecks. Since there is no practical means of preventing fishing at the site, it is intended that the reef will be fished by local sea angling charter vessels throughout the study period. The proprietor of one of these businesses has agreed to provide catch records (which will be regularly validated on board by the scientific team), collect socio-economic census data from the anglers, and enable scientists to collect fish samples during the study period. Fish taken from the reef will be assessed in the laboratory for weight, length, age, sex, growth, fecundity and tainting. Years 1 and 2 of the monitoring programme will mainly involve observational techniques; invasive monitoring such as tagging will be restricted to the final three years of the programme to allow the fish stock to assemble and stabilise. Tagging could be attempted at an earlier date if the reef community became well-established. No measures will be taken to prevent predation by seals during the study period. The field survey will parallel a study on the social and economic conditions relating to the use of inshore reefs. The field data will provide an input into the development of a fisheries model for the reef, a social and economic cost benefit analysis, an ecological analysis of the spatial utilisation of the site, an ongoing assessment of the environmental effects, and a GIS database for managing the environmental and socio-economic data, trend evaluation and forecasting.

HI DAMES & MOORE 89

8.2.3.3 Provisional inshore reef programme budget Tables 14 and 15 indicate the proposed budget for the inshore reef research programme. Table 14: Proposed project budget

Component Pre 1 2 3 4 5 Post Tot. Reef Creation Engineering overview 20 0 0 0 0 20 0 40 Deployment(capital) 0 200 0 0 0 0 0 200 Retrieval (capital) 0 0 0 0 0 0 50 50 Scrap value (capital) 0 0 0 0 0 0 (15) (15) 0 10 10 10 10 10 0 50 Maintenance etc. 0 2 2 2 2 2 0 10 Contingency (capital) 0 20 0 0 0 0 10 30 Annual sub-totals 20 232 12 12 12 32 60 Subtotal for reef creation 365 Study of fish presence, movements Res Sci./PhD fees & subsist. 0 15 16 17 18 19 10 95 Materials & Equipment (capital) 0 25 100 50 25 25 0 225 Static fishing surveys 12 24 24 24 24 24 12 144 ROV surveys 5 15 10 10 10 10 5 65 Diving surveys 0 6 6 6 6 6 0 30 Annual sub-totals 17 85 156 107 83 84 27 Subtotal monitor fish presence 559 Study of fish growth & health Res.SciVPhD fees & subsist. 0 0 0 17 18 19 10 64 Materials & Equipment (consumm) 0 0 0 30 20 15 0 65 Annual sub-totals 0 0 0 47 38 34 10 Subtotal assess fish growth 129 Associated fish analyses Hydrocarbons & metals 15 30 0 30 0 30 15 130 Flesh taint 0 0 3 0 0 3 0 6 Annual sub-totals 15 30 3 30 0 33 15 Subtotal assoc, fish analyses 136 Associated Environmental Surveys Benthic surveys 25 0 0 0 0 29 0 54 Bio-fouling surveys 0 3 3.5 4 4.5 5 0 20 Annual sub-totals 25 3 3.5 4 4.5 34 0 Subtotal assoc, fish analyses 74 Academic/Comm support/Reports 5 7 11 7 11 7 10 58 Visits/meetings/conferences/papers 0 3 3 5 6 6 8 31

Annual capital costs 0 245 100 50 25 25 45 490 Annual staff & consummb costs 77 115 88.5 162 129.5 205 85 862 Total annual cost (£K) 77 360 188.5 212 154.5 230 130 Total annual cost (% total budget) 5.7 26.6 13.9 15.7 11.5 17 9.6 Total Cost for Syr programme 1,352

§J§[S4.MOORf. Table 15: Summary costs

Major expenditure £K % total To create and remove reef 365 27% For core fish studies (presence, biomass, movement) 688 51% For associated fish studies (growth, taint etc.) 136 10% For complimentary environmental surveys 74 5.5%

For academic/comm, support, reports, conferences 89 6.5%

Preliminary budget for full 5yr programme of scientific study at an inshore reef in the Moray Firth. All numbers £K. Key: Pre = pre-deployment work; Post = post removal work; 1-5 = year’s of study Commentary This is the draft budget for the creation of a reef and the completion of a full five year programme of scientific research. Having created such a valuable study site, the maximum benefit should be derived from it terms of scientific research. This is an expensive programme, but credible data needs to be obtained. Please Note 1. The cost of deployment may be reduced by the use of the Prosyst controlled variable buoyancy bags, and this is presently being pursued. 2. The bulk of the research would be carried out by University-based research students (MSc & PhD), not consultancy staff at Cordah. This is very cost-effective and ensures the work is firmlyin the body of on-going international scientific research. 3. The associated programme of environmental study is not essential to the study of the performance of the reef with respect to fish populations and possible benefits of inshore reefs to local communities. It does, however, provide data with which to assess any positive or negative effects that the reef may cause in the nearby environment. 4. A 5 year study programme would be ideal, given the predicted timing for the development of a stable, mature reef community at the site, but a minimum 3 year programme would be acceptable. 5. Depending on local collaboration, some cost savings might be possible with respect to the provision of boats for sampling, fishing and diving. On the basis of these comments, a preliminary costing can be indicated for the following possible options (Table 16).

Beowrs— &__ Moonc 91 Table 16: Costs of different programme options

Possible Programme Cost £K For programmes lasting 5 years

A. Full programme as described 1,352

B. As in A, but withoutassociated fish studies/environmental surveys 1,142 C. As in B, but withoutstudy of fish growth 1,013 For programmes lasting 3 years D. Full programme as described 1,034 E. As in D, but without associated fish studies/environmental surveys 894 F. As in E, but without study of fish growth 799

8.3 Offshore reefs

8.3.1 The aims of further work The aims of the proposed programme of work at an offshore site are as follows: 1. to determine if, and for how long a platform reef retains a fish population, and the size of that population; 2. to determine if the platform reef is having any measurable beneficial or detrimental effect on the health, growth and commercial value of the fish it retains; 3. to determine if the platform reef enhances fish reproduction and/or gain in tissue weight; 4. to determine if the platform reef is used by juvenile fish; 5. to determine if the platform reef is having any measurable effect on the pelagic (water column) and benthic environments in its immediate vicinity; 6. to assess if a platform reef could be fished sustainably by commercial fishermen; 7. to describe and evaluate the “fouling organisms” on the platform reef as a food supply for commercial species and for nature conservation value. To achieve these objectives, an integrated programme of work is proposed, with an emphasis on fish as these species are perceived as the most significant from an exploitable resource viewpoint. In outline, the programme will: A. Select a non-operational steel jacketed platform which could be used with minimal hindrance as a survey site B. Determine, by means of an initial ROV/sonar survey, that the selected platform has a rich and diverse “resident” fish population suitable for the purposes of this study C. Carry out a three year programme of survey, sampling, measurement and analysis, to address the main topics of research listed above. This programme would involve periodic offshore surveys and sampling from a vessel. On these occasions a wide range of samples would be obtained in order to maximise the value

CKMB& MOORE of the ship’s time. Some samples would be analysed immediately, others might be archived for possible future study. There would also be routine, longer term monitoring by remote equipment on the seabed or on the platform A summary of the work planned in the offshore reef programme is presented in Figure 10.

Aims Benthos for Juvenile Effect on Quantify fish Measurable Sustainable energy or retention? benefit? protection? fishery? vicinity? conservation

Artificial reef fisheries management model / plan

Figure 10: Summary of offshore reefplan of work

OWES & MOORE counan §5 8.3.2 Studies proposed

8.3.2.1 Acoustic survey of fish shoals Aims

Semi-quantitative estimates of the fish populations around an artificial reef and at a reference site, are vital for estimating the significance of fish aggregations around a platform reef. Previous studies (e.g. Olsen & Valdemarsen, 1977; Valdemarsen, 1979) used a variety of different fishing methods to compare number of fish, while newer studies (e.g. ICIT, 1991) used acoustic methods. None of the methods exclude the other and several will need to be used together when surveying the steel jacket. Methods The Simrad EK500 Scientific Sounder System for the acoustic assessment of fish densities around the installation, will be used, because it can accurately identify the strength of the signal from a selected target, thereby providing more detailed analysis of fish size and numbers. A new concept is used by the echo sounder receivers so that an instantaneous dynamic range of 160 dB is achieved. The echo-sounder can observe the horizontal position of individual fish within the sound beam, enabling the study of fish behaviour. Acoustic surveys will be conducted along transects from the jacket and at the reference site. The distribution and number of fish will be observed on at least three cruises each year. These techniques will allow an overall estimation of shoaling behaviour and size, but will reveal little information about the response of an individual fish to environmental stimuli and, most importantly, its residence time in terms of its period of absence and return to the platform reef. To achieve these data, which are essential to the overall assessment process, acoustic telemetry will be used (see next section).

8.3 2.2 Acoustic telemetry Aims Fish are known to congregate around platforms, this has been confirmed by snapshot surveys and diver observations through time. As yet no long-term data exists to provide information on variations in shoal size and location over time or on the behaviour of the shoal members. Whilst sonar surveys are the best technique for establishing shoal size and numbers of fish, only telemetry will allow the determination of an individuals behaviour (how it makes use of the structure) and residence time. Their behaviour through a day in relation to the structure, tidal currents, light and food will provide indications of how the jacket may benefit the fish, for example the jacket may provide shelter from currents or create eddies that disorientate prey species. Residence time is a key factor in ascertaining the potential for the structure to provide benefit to the fish, if the fish do not spend a significant time close to the jacket then any possible positive effect will only be negligible to the overall success of that individual. Residence time would be a key factor in modelling the potential for jackets or clusters of jackets to produce benefit to the fish population.

j|| DAMES & MOORE Methods

The only certain way of determining individual behaviour and residence time is by marking that individual and tracking it. Conventional tagging would not be logistically feasible as the method relies on being sure of recapturing the individual, as does the sophisticated data logging tags used to gather long-term data on other species such as . Telemetry allows animals to be followed in their natural environment, their location being given by signals from a tag on or in the body of the subject. In the sea, acoustic signals are commonly chosen because radio signals are rapidly attenuated in sea water. In the sea, the best technique is acoustic telemetry either with constantly transmitting tags (pingers) or intermittent transponding tags. The latter requires a more complex tag and interrogator / receiver, but provides a longer lifetime for the tag. Acoustic telemetry, in combination with sonar surveys, would be a powerful method, enabling the positive identification of schools of fish from the relative position of single tagged individuals. A three phased approach to using acoustic telemetry can be envisaged: Phase 1 The simplest initial approach would be to capture fish and fit pingers either externally or in the stomach (in line with animal husbandry guidelines) then release and follow with a manually operated directional hydrophone for a few hours or days. This would help determine the range of detection of the tag in the acoustic conditions around the platform and establish the “blocking effect” that the platform structure will have to the acoustic signals. Initial data on these aspects as well as fish movement would assist in the design of the phase 2 equipment deployment. Phase 2 An array (minimum of 3) of linked (radio or hard wire) hydrophone receivers would be deployed around the platform which could determine the XY position of the tagged fish. By using a variety of frequencies more than one fish can be tracked, allowing several individuals or species to be followed at the same time. The depth of the individuals (the 2 element of position) would be measured by a pressure transducer within the tag and transmitted with the identification signal. This could either be used with a single hydrophone receiver or multiple array. It is likely that an array of receivers would be deployed for a few days during a field survey. Longer term monitoring could be carried out with a sub-surface package comprising a single hydrophone receiver & data logger with acoustic release, the latter allowing the package to be retrieved at a later date. This would establish the residence period of marked fish for some of the time between field surveys (tag life is limited by battery size to days or weeks) and would show, assuming the tag was retained whether fish left the jacket only to return at a later date. If necessary, a more complex system would be a linked array of such receivers which would provide information on the direction in which fish left and returned to the jacket. During Phases 1 and 2, basic environmental parameters such as current velocity and direction, light and temperature would be logged by an instrument package.

gOVMESAMOORC cOHna i * Phase 3 This would be triggered by results from Phase 2 equipment which indicated residence periods that were longer than the battery or an acoustic tag lives. To allow monitoring to continue an improvement on Phase 2, but with development implications, would be to move to a telemetry system that used transponding tags. These tags would be useful for long term monitoring, since these effectively only consume power when interrogated. If fish were tagged during one field survey and were still resident months later the tag could be expected to respond, unlike pingers which have short lifetimes. This approach would also be valuable for the single listening station deployed alongside a platform to record fish presence/absence. Four annual site visits are required for deployment of the telemetry system with each deployment lasting for 5 days (weather conditions permitting). An additional deployment at a control site would allow for on and off-reef behavioural comparisons. There will be a need for an initial site visit to establish the viability of, and plans to use, acoustic telemetry. Deployment of the long-term data-logging monitor will take place as soon as fish are tagged with acoustic tags. Development to deployment of Phase 3 will depend on Phase 2 results and is not envisaged until spring of Year 2. Fish behaviour around the platform reef is likely to be influenced by water movement and food availability. In turn the presence of the platform will potentially influence both these factors. Current needs to be measured whilst the telemetry is taking place.

8.3.2.3 Physical water column Aims One of the major factors that may influence the behaviour of the fish around a jacket, and that will influence the success of epibiota settlement and survival on the surface of the jacket, is water movement. The jacket can be expected to disrupt the flow of water by its physical presence, so providing shelter from the main force of water flow (in the lee) and creating eddies of water as the current passes through the lattice structure. These areas of shelter and swirling movement may serve to give the fish a bioenergetic advantage when they are in areas of shelter, because they do not have to swim so hard, or a feeding advantage, if prey species are disoriented by the swirling water. Methods The instrument of choice for measuring water column movement is a 300 kHz, ship mounted Acoustic Doppler Current Profiler (ADCP) which will give a resolution of 10 cm to a depth of 75 m. This would be deployed during a research cruise around the jacket for full tidal cycles at neap and spring tides, so giving the range of effects. Deployment at a control site, remote from a platform, will allow comparison. Linking fish position (from telemetry) with water column movement and stomach contents analysis will provide a unique insight into the way that the jacket structure is used by the fish and help in assessing whether swimming in the vicinity of a jacket does provide benefits to fish in terms of, for example, growth potential.

jyjj Dames & moore ■ "* 8.3.2.4 Fish size, feeding, growth and contamination Aims Some of the main issues in evaluating the effectiveness of a jacket as an element in an artificial reef are to demonstrate whether the presence of the structure: • attracts a different size frequency distribution of fish from that at a control site; • attracts a particular target species; • increases the fish biomass in the area; • causes fish to feed on animals living on or near the structure. It is therefore of great importance to try to quantify the energy budget of the different trophic levels. It is also necessary to demonstrate if fish living in and around a structure feed on prey from the same area or just use the jacket as a safe haven and feed in other areas. Methods Fish can be captured by using hooks, nets or traps. Experience suggests that to obtain fish from close proximity to the platforms this is best achieved byrod and line, with nets being next best. Traps have been used around platforms but with mixed success. For the purposes of examining stomach contents, fish caught at depth should be retrieved with care to the surface in order not to cause inversion of the stomach through the rapid expansion of the swim bladder. For all other purposes, the fish can be used whatever their condition. Care must though be exercised to avoid contamination of tissues during landing and preparation, if the fish are to be used for chemical examination. Detailed protocols for the handling landing, preparation and storage of fish and tissue samples have already been worked out and can be applied to this study without great modification.

8.3.2.5 Size frequency analysis Aims These data will allow a comparison of the physical dimensions of individuals in the fish populations in the vicinity of the platform reef with those at the control site. Logging of data with that of stomach contents analysis, age, growth rates and contamination will build up a full picture of fish condition. Methods Simply achieved by measuring and weighing each individual involved.

8.3.2 6 Stomach contents analysis Aims This will provide information on where the fish feed and also which prey species dominate their diet.

jj|| OMISt MOORE Methods contents will be compared between fish around the platform reef and the control site. Both pelagic and demersal species will be sampled and at least 25 individuals of each species selected. Key species in the North Sea are the pelagic or semi-pelagic species cod (Gadus morhua) and saithe (Pollachius virens), while demersal fish species include Ling (Molva molva) and dab (Limanda limanda). Fish with wounds will be discarded because their normal feeding may be disrupted. As soon as the fish is landed, it will be bled, measured and weighed. The stomach will be opened, the contents weighed, preserved in 4 % formaldehyde and buffered with borax. Identification of, for example, crustaceans from stomach samples is a difficult task, but as far as possible, the stomach content will be identified to genus or family and, where possible, to species level. Different statistical methods will be used to identify trends and patterns in the material and to identify differences between the different stations.

8.3.2J Instantaneous growth rate Aims The instantaneous growth rates of two species, saithe and cod will be assessed. The most important implication of assessing instantaneous growth rates will be the need to set up laboratory control populations of fish with which to determine “baseline ” growth rates of fish fed known rations of food over time. Although baseline data is available for saithe, these would need to be repeated and levels set for cod. Methods The fish caught at the offshore site will be sampled according to the protocols of Mathers et ah, (1991a; 1991b). This would require the setting up of tanks in controlled laboratory conditions, rearing and maintaining several different groups of fish species with carefully controlled intakes of energy, and sampling them periodically to determine the biochemical correlates of growth and assess these against physical measures such as change in weight and length. The methodology for biochemical assays and determinations has been established and probably does not require further development.

8.3.2.8 Tainting and contamination A study of the flavour of selected species of fish at the site will be carried out to determine if any detectable taint is present in the reef fish. Although it is likely that the study site will be one at which little or no drilling has been carried out, it will still be necessary to acquire sound data on the health and taste of fish that will aggregate at the reef and which, under different circumstances, might be exploitable by commercial fishermen and sold to the public. The taint study will therefore: • assess the level of any tissue contamination in selected species; • determine the possible origin of any contamination found; • assess the flavour of fish by presentation to a taste panel;

|| DWES& MOORE • investigate any possible relationship between levels of tissue contamination and any taint detected in the fish; • attempt to investigate the potential for chronic, low level contamination of reef fish flesh by the inputs from sacrificial anodes on the structure. Numbers of fish will be caught during annual surveys and analysed for contamination and taint. In addition, a specific sampling exercise will be undertaken at one point in the study, to sample the water immediately adjacent to anodes. The purpose of this exercise will be to determine any possible elevations in the concentrations of metals and other contaminants derived from anodes, in the water within 1 - 10 m of anodes. One of the fish sampling exercises should be timed to coincide with the water column sampling effort, to provide complimentary data on the levels of contamination in the fish flesh and liver.

8.3.2.9 Fisheries Aims This section deals with how the various surveys and experiments described above will be combined to estimate various parameters associated with fish stock assessment and management. Section 8.3.2.10 will deal more specifically with methods for the commercial exploitation of these stocks. There are 2 main questions that need to be answered in order to estimate if an artificial reef has a value within the fishery. 1. Does the reef function as a significant refuge for fish, especially juveniles? 2. Alternatively, can the reef be used so that it is an aid to commercial fishing? This section will primarily deal with question 1. Whilst various associated parameters will need to be examined to give an overall view of the impact of a reef on the fishery, survey protocols will be mainly aimed at determining the standard fisheries equation, for the reef as described by Russell (1931) and Beverton and Holt (1957): S2 = S, + (A + G) - (M + C) where Si and S2 represent the total weight of fish at the beginning and end of a defined period, A is the recruitment, G is growth, C is the fishing or capture mortality and M is the natural mortality. This is a simplification, but is an achievable first stage of reef assessment. To estimate even such apparently simple data from a multi-species fishery with open borders is notoriously difficult, so realistic aims must be adopted. Data will be used to estimate: • Quality - what species are present, what is their size distribution, which are commercially valuable? • Quantity - how many fish are present, and in what densities? • Growth - how fast do the fish grow, and does this differ from off-reef fish?

' I*™** p|f tXMES & MOORE • Natural mortality - what is the age of the fish present, are they older and therefore survive longer than off-reef fish? What level of intra and inter-specific predation is there?

• Location - where are the various species primarily located on and around the reef, is their position predictable, are they accessible to fishing gear, how far from the reef does a sphere of influence extend? • Movement - how long do fish spend on a reef, at what times of day and which seasons are the fish on the reef? Answers to these questions should give a picture of which fish use the reef and to what extent they benefit from it, if at all. It must be stressed that fisheries science is inherently complex, with parameters that are highly variable, even chaotic. Within the proposed field programme it should be possible to quantify certain key elements, e.g. growth rates on and off reef, and build-up a picture of the functioning of a reef. Quality Fish quality will need to be determined by sampling individuals (see 8.3.2.4). For this work the fish need not be returned alive and so the sampling method can be more active, such as netting. The species, length and weight will be measured and general condition prior to sampling will be assessed. A representative sample of fish, in terms of size and species will need to be taken. Sufficient numbers will need to be sampled to give a representative size frequency distribution. Duplicate surveys will be conducted at a station at a distance of not less that 10 km from the reef, but in the same region and depth of water as that of the reef. This will act as a control and allow an estimate of the effectiveness of the reef. Quantity The number of fish both around and inside a reef will need to be counted. This can, in principle, be done using an acoustic visualisation of shoals or mark recapture techniques (see section 8.3.2.1), though the later technique will not be logistically possible. From a fisheries management viewpoint it would be most useful to determine diurnal and seasonal changes in numbers. This necessitates the need for multiple or continuous counting techniques. Acoustic surveying using proprietary “fish-finders” will need to be conducted in order to estimate the number of fish on and near the reef. From the instrument readout the number of fish in a region will be counted as accurately as possible and this figure will be used to calculate the density of fish per m3 and the total standing stock at any one time. Growth Growth is a vital element to consider in the quantification of the benefit derived by a fish on a reef. It is also required to assess changes in standing stock biomass and hence the potential for exploitation. In some instances growth can be estimated by capturing individuals, measuring their weight and length (see 8.3.2.5) marking them and returning them unharmed. It is then hoped that it will be possible to recapture these individually marked fish at a later date and determine a growth interval. Recapture of the same fish is inherently unreliable, especially in the middle of the North Sea where commercial fishing pressure is high. As recapture rates would be expected to be very low this technique is therefore not recommended. Alternatively growth can be estimated from the measurement of annual incremental growth rings on the otoliths (ear bones) of fish. The size of increments is correlated with fish size and hence growth. Standard techniques have been developed for this purpose. The fish need to be destructively sampled as described above. A range of fish ages and species will need to be sampled and measured. Growth of fish caught on the reef will be compared with a control site without a reef, to indicate relative growth. Natural mortality In fisheries studies, the natural mortality (M) of a stock cannot be estimated directly. It must be determined as the residue of the total mortality coefficient after fishing mortality (F) has been estimated separately. Such a technique is not practically feasible within this study, so some other, possibly more qualitative, method of estimating M on and off reef is required. Mark recapture techniques are unlikely to be accurate as it will not be possible to reliably differentiate the fish that died of natural causes from those that merely left the reef area and did not return. A qualitative estimate of M can been gained from an examination of the stomach contents of the fish . This will indicate the size and types of fish eaten. Results will need to be combined with acoustic surveys and telemetry data to indicate the probability that the fish were eaten whilst on or off the reef. Further, survival relative to off-reef areas may be possible to estimate from differences in the age structure of reef and ambient fish as determined by sampling and otolith studies. Location Acoustics (8.3.2.1) and telemetry (8.3.2.2) data will be used to describe the movement and positioning of the fish around and within a reef and thus indicate their accessibility to fishing gear. Ideally, in a reef used for protection it would be hoped that the majority of juvenile fish remained within the reef whilst in a fishing enhancement reef it would be hoped that there would be a large sphere of influence allowing access to fishing gear. Movement In order to build up a picture of the use of reefs by fish, including when and where they feed, the length of time they spend on a reef must be estimated. Diurnal and seasonal movements will indicate the benefit that the fish derive from the presence of the reef and also their susceptibility to fishing. For example, fish that have been found to grow faster on the reef or have a full stomach, but yet are shown likely to have remained in the vicinity of the reef must therefore have fed on the reef. Alternatively fish that are shown to make diurnal or intermittent feeding forays off-reef derive their benefit from the reef in other ways such as a reduced risk of predation or a reduced energy requirement. A stock that moves off a reef intermittently for significant periods may nevertheless become a target for fishing even though the reef area itself may be used as a protected zone. Diurnal movements will need to be determined using acoustic surveys (8.3.2.1) continuously through several daily cycles. Additionally video recordings from either a fixed camera or an ROV have been shown to be a useful means to indicate changes in fish abundance and hence movement to and from the reef. Telemetry and repeated acoustic surveys can be used to show longer term movements of, in the former case, individual animals and in the latter case, shoals. Summary of fisheries work required In summary, in order to obtain data that will be required to both estimate the benefit of a reef to the fishery and to subsequently propose a suitable management plan, various parameters must be combined. These form other parts of this overall study and so the fisheries work can be considered as a integration of data, rather than the need to conduct separate fisheries fieldwork. Figure 11 summarises the fisheries work proposed in relation to other work described in section 8.3.

Aims

Achievable outcome

Figure 11: Summary chart of the fisheries management assessment of an artificial reef

§|i GAMES & MOORE 8.3.2.10 Commercial fishing Aims

This sections deals with methods associated with the commercial exploitation of the artificial reef fish stock. An artificial reef can be used either to protect fish from fishing pressure or as a fishing enhancement device. If a reef is to be used for fishing then the following attributes are required: • large standing stock, therefore dense shoals; • fast replenishment after fishing; • compliment of high market value species; • fish of sufficient size to be caught by regulation gear; • accessibility of gear to stocks. Ideally, for a reef to be of value to fishermen, the catch per unit effort and the catch security will both be high. In other words, a fisherman who the reef will achieve his target catch size in as short a time as possible and will have a high degree of confidence that he will not get a poor catch, respectively. In order for such an estimate to be made, the following 8 criteria will need to be assessed during this study: 1. standing stock size and shoal density; 2. location and movement of stocks; 3. species present; 4. size frequency distribution of the commercially valuable individuals; 5. stock replenishment time after fishing; 6. most suitable gear; 7. catch per unit effort; 8. sustainability of fishing. The first four aspects have been described previously and so data will be available, assuming the other parts of this study are conducted. The final four aspects then require further study. Field work Several types of gear can be operated on or around artificial reefs, depending primarily on the proximityto the reef that the gear will be used. Phase 1: will take the form of a discussion with commercial offshore fishermen, as it is they that have the greatest practical knowledge and experience of setting gear in a range of locations and conditions.

|||o*MES4MOORE Phase 2: having estimated the type of gear that is most likely to be suitable, the reef will be fished commerciallywith observers aboard. The following parameters will be noted: • catch size; • time (effort) taken to obtain catch; • market value of catch; • gear and technique used most efficiently; • location of largest catch; • fluctuation in catch retained; • by-catch quantity. It should be noted that fishing away from the reef at a control site will have little comparative value because the gear and techniques used on the reef are unlikely to be the same as that used in open water. Phase 3: using either acoustic or video surveying (preferably continuous) a semi quantitative estimate of the rate of re-colonisation of the reef will be made. It will hopefully be possible to plot a curve of resident fish number vs. days after fishing. Phase 4: after a period determined from analysis of the results from phase 3 (possibly 2 months) a second commercial fishing cruise will be conducted. The same gear and techniques will be used as in phase 2. Results from phase 2 and 4 will be compared in order to determine if the composition of the catch has altered and to corroborate survey evidence from phase 3. Phase 5: acoustic or video surveying will again be used to qualitatively estimate of the rate of re-colonisation of the reef, for comparison with phase 3 results. Phase 6: the following parameters will be calculated, estimated or noted, • stock replenishment time after fishing; • most suitable gear and technique; • catch per unit effort; • sustainability of fishing; • subjective preference of the fisherman to fish on or off reef. Permission will be required from the fisheries authorities if fish are caught outside of a quota and from the platform operator to enter the exclusion zone. Extra insurance may be required to cover liability on entering this zone. Summary Such a study, using a limited number (two) of cruises with commercial fishermen should result in achievable data that can be used to determine parameters described above that are vital to the assessment as to whether fishing on an artificial reef is likely to be a feasible and an attractive economic proposition for commercial fishermen. Without such

SWISS! knowledge, one of the main justifications for establishing a platform reef will remain unknown, and as such, the case for establishing the reef will be greatly weakened. The commercial fishing study is summarised in Figure 12.

Figure 12: Summary of the commercial fishing fieldwork

8.3.2.11 Benthic sampling Aims It is possible that the physical presence of the platform may be having some effects on the benthos immediately around it, altering the composition of the infauna and so food supply. In the future, artificial reefs in the North Sea may well act as barriers to trawling activity, so protecting the fragile benthos from the physical disturbance it now copes with. The current exclusion zone may mimic this effect to some extent. Previous benthic surveys may provide the required data. However, a series of samples from the seabed at different distances from the platform will be taken to determine if there is any gradient of effect is detectable, and secondly if this can be linked with any confidence to either natural or anthropogenic aspects of the environment. For the purposes of this plan, it is assumed that the platform or site chosen has not been subject to recent deposition of drilling muds and is sufficiently far away from known drilling sites to show no effects whatever from the discharge of cuttings or cleaned oily cuttings onto the seabed. In such circumstances, any gradients in the epifauna and infauna of the benthos could with confidence be attributed to natural variations, or the localised influence of the platform and its associated reef effect. Methods The most cost-effective way of obtaining samples would be to use a remote grab, to sample the sediment to a depth of about 15 cm. Standard protocols for the use of grabs, and for the subsequent analysis of physical, chemical and biological samples, are well established and these should be used. This will permit the data collected at the reef site to be assessed against the large body of information already obtained from many platform and reference sites around the North Sea, and from other, non-oil related studies in the North Sea. Samples should be analysed for the following parameters: • particle size characteristics - to determine the nature of the seabed and one of the significant influences on the composition of benthic communities; • sediment metal concentrations - to assess if there are any gradients of effect centred on the platform and its anodes. In the absence of a cuttings pile, the steel structure and anodes would appear to be the only source of such anthropogenic inputs. It would be valuable to attempt to determine anode-related inputs to sediments; • sediment hydrocarbon concentrations - to assess if there is any gradient (to ensure that there is not), but also to provide site-specific data for the platform. It is thought that hydrocarbon concentrations in sediment have risen in parts of the North Sea specifically as a result of oil and gas activities. Examination of a non-drilling site would provide some data relevant to this question, as well as being of direct relevance to this study; • • assessment of benthic communities - dependent on the type of sediment at the site, the benthic community will comprise various proportions of surface dwelling (epifauna) or sediment dwelling (infaunal) species. It is likely that the sediment will be mud or muddy sand and that the majority of species will be infaunal. It would therefore be appropriate to examine the community by means of grab samples. The numbers of different species and the total numbers of individuals in different species should be determined. A standard multivariate analysis can then be carried out to examine the relationship between the community found and the underlying physical and chemical parameters that might influence its composition.

jHH DAMLS & MOORE 8.3.2.12 Assessment of epifauna on the jacket Aims There has been the suggestion that fauna on the jackets of offshore platforms provide an additional source of food for fish. Analysis of the stomach contents of captured fish may provide further evidence to support or refute this supposition. The fauna (and flora) on the jacket are also of value in their own right and should be assessed in order to effectively describe the community and its nature conservation value, given that the steel substrata of the jackets are an unusual habitat in the North Sea which will be destroyed when the jacket is removed to land or placed on the seabed. Methods There is already a body of qualitative and quantitative evidence describing the fouling communities on many platforms throughout the North Sea and, in the past, samples of fouling communities have been taken by divers and examined. This information should be reviewed and the composition of platform reef epifaunal communities compared with other epifaunal populations to provide an indication of nature conservation value (and volume of fish food, if fish are found to be feeding off the reef epibiota). Of particular importance for the future assessment of communities on jacket based artificial reefs are the species present on the base of the jackets as it is these, rather than the communities close to the surface that will dominate the deep water reef surfaces. It would be prudent to examine the fouling on the structure using ROVs during frequent surveys of the platform and its fish, with emphasis on the deeper portions of the structure.

8.3.2.13 Plankton Aims Plankton form the basis of the food wed for marine animals. Some assessment of population structure through the water column is needed to provide baseline information on the variation of available plankton. This comparison will provide some indication of the plankton found at the surface and that just above the seabed. When this is linked to benthic biomass data it will give an indication of the epifaunal biomass supportable on a toppled jacket, as opposed to a vertical structure. Methods Plankton is extremely variable and so vertical plankton net hauls and water samples for chlorophyll analysis will be needed during each cruise, during the day and night. Standard techniques and equipment have been developed for this purpose and are available to the project.

8.3.3 Site justification

8.3.3.1 Wrecks as unsuitable sites It has been suggested on several occasions that a study of existing shipwrecks in the North Sea could provide valuable data with which to assess the potential benefits of offshore artificial reefs. It is therefore appropriate to examine here the possibilities of using existing wrecks as study sites. Much has been made of the fact that there are many wrecks around the UK coast and that these could provide “models” for the effects of reefs. Examination of the available sites, however, reveals that the options for wreck study may be very limited. For the purpose of identifying wreck sites that could closely mimic an offshore reef site, the wreck data from a large area of the North Sea have been examined. The area analysed was bounded by the coast of Europe to the east, latitude 51°N to the south, latitude 62°N to the north, and approximately longitude 4°W to the west. It therefore included most if not all of the UK, Norwegian, Dutch, German and Danish sectors of the North Sea and is more than 500,000 km 2 in area. Within this area the Hydrographer of the Navy (Wrecks Department) have catalogued some 8,000 wrecks of more than 25 tonne weight. Not all of these wrecks are suitable for the purposes of providing a “model” site to investigate the effects of reefs. Ideally, a survey site should possess some or all of the properties of a decommissioned or partly decommissioned steel platform. Since the focus of any “rigs to reefs” study is on those large, deep water platforms in the central and northern sectors of the North Sea, the list of wrecks was further screened to highlight sites with the following characteristics: • the wrecks should be located in the central or northern sectors - for the purposes of screening this was defined as an area bounded by 5°E, 55°N, 1°W and 62°N; • the wrecks should be located in water depths greater than 75 m; • the wrecks should be of more than 1,000 tonne weight; • the wrecks should be of steel, not wooden, construction. Examination of the listed wrecks against these criteria reveals that there are 22 wrecks with these attributes, excluding the remains of , and the wreck of the semi- submersible Transocean 3 near Beryl. They range in size from 1,002 t to 6,336 t, and lie in water depths of 65 m to 187 m. The earliest of these wrecks dates from 1914 and the latest from 1940. Some of these wrecks may provide a site at which the reef effect could be studied but there are two main drawbacks to this. Firstly, the wrecks of vessels, with hulls of solid vertical and horizontal plate steel, which may have partially or totally collapsed in on themselves, do not provide a good approximation to the open lattice work structure of steel jackets. The amount of enclosed volume in such wrecks which is accessible to fish is relatively small in comparison with a jacket; the water circulation through the wreck is likely to be restricted and fish access to the interior of the structure is likely to be limited. Secondly, given their age and location, most of the wrecks are likely to have been fished, either deliberately or accidentally, at some time in their lives; they may even be fished from time to time at present. In addition to altering the natural population of fish in and around such wrecks, the fishing activity may have resulted in the wreck becoming snagged by nets which have been discarded but are still “fishing”. This “ghost fishing” and the presence of dead and rotting fish makes the reef unattractive to fish and may considerably reduce the efficacy of the reef.

p§ H umes t Moore S.3.3.2 Non-operational platforms as suitable sites It therefore seems likely that any offshore studies would be best focused on existing non- operational platforms. This proposed programme outlines the scope of work for such a study. A test site for the full-scale experiment should be selected based on several criteria: • The platform should be in a cold phase. Several papers have focused on the possibility that factors such as light, noise, vibrations and/or waste could explain the accumulation of fish around a platform. Recent studies (Cripps & Aabel 1996) have demonstrated that non-operating jackets also attract fish in large numbers. Further, it will probably be easier to get access to the safety zone if the platform is in a cold stage. • There should be a minimum distance of at least some km to the nearest structure, natural or artificial reef to avoid interference that could mask the scientific results. • The distance to operating platforms should not be too far as that might exclude the use of supply vessels from these platforms. • There should be an accessible deck structure on the jacket where necessary scientific recording and sampling equipment could be mounted or stored. • To minimise the impact to commercial fishing, the jacket site should not be in an important spawning or heavily fished area. Several areas in the North Sea are in accordance with these specifications. One possibility might be the Albuskjell with the platform 2/4 F as a centre for the study. This platform was shut down several years ago. The jacket weights approximately 7300 tonne (piles included) and has a volume of 182,000 m3. The distance to the nearest platform (1/6 A) is 8 km and the distance to the Ekofisk Centre is approximately 13 km. This makes the 2/4 F platform an excellent base for performing full scale scientific experiment.

8.3.4 Survey programme

8.3.4.1 Aims This section summarises the planned practical work during the period 1998 - 2001, a total of 3.5 years. Together with the Gannt diagram (Table 17) this will outline the planned study. The provisional proposed budget is presented in Table 18. A substantial part of the total budget of £ 2,411,200 could be reduced if the offshore industries provide assistance in the form of ship-time, e.g. loan of supply vessels. To get the best possible picture of the positive and negative impacts from an artificial reef based on structures from the oil and gas industry, a comprehensive sampling programme is planned. Results from this programme will be used to describe attempts to quantify the different trophic relationships on and around an artificial reef, the physical parameters and the commercial fishing and fisheries aspects, as described in section 8.3.2.

. OWES & MOORE coima i * It should be noted that milestones are used to divide the practical work. They will be logical breaks in the programme (due to seasonal restrictions or end points of a survey), which can be used to evaluate progress to date and discuss further action. They are not necessarily the end points of an activity, because several activities, out of necessity, extend over several years. A summary of the practical work milestones is shown in Figure 13.

Milestone 1 ROV and acoustic studies background information on fish stock distribution and composition site suitability determination

Milestone 2 Acoustic & telemetry studies quantification of fish shoals observation of fish behaviour Fish sampling size, weight and quality Stomach contents

Milestone 3 Background data Hydrography Plankton Growth on structure Benthos Milestone 4 Fish behaviour movement and residence time distribution and structure of fish populations Fish taint

Milestone 5 Sediment analyses metals and hydrocarbons grain size

Milestone 6 Fish behaviour movement and residence time distribution and structure of fish populations

Milestone 7 Commercial fishing study usefulness of a platform reef best techniques to employ efficiency of capture management strategy ______2002

Figure 13: Practical work milestones - offshore reef study

HI DAMES 4 MOOflE 8.3.4.2 Planned activities in 1998 Only limited field activities are planned in 1998. A project would be conducted to review existing ROY surveys to gain an overview of fish populations around selected jackets. The report from this investigation will be evaluated as the first milestone in the project. The project will cover the following aspects: • species composition around specific jackets; • size of individuals and shoals of fish; • position in the water column, as a function of distance from the jacket and time of day. In addition to this desk-top study, there will be a one week cruise, focusing on acoustic survey methods. The main objective of the acoustic work will be to observe fish shoals around the jacket and to compare the results with sites along a transect from the jackets.

Milestone 1 Based on results from the ROY and acoustic studies, general, but vital background information on fish stock distribution and composition around an installation will be determined. This will be used as the basis for further study and to determine if the chosen study site is likely to be suitable as an example of an artificial reef.______

These first surveys will be limited to quantitative estimates on fish populations around the jackets. Important questions relating to e.g. fish migration, fish behaviour, food chain, re­ stocking etc., will be covered in the following studies. A workshop is planned for the end of 1998 when the results from the ROY study and the acoustic survey can been reported. Costs arising from the 1998 work are presented in Table 18.

8.3.4.3 Planned field-work during 1999 After reviewing the results from the 1998 survey and ROY study, the programme for 1999 and the following years will be further defined and adjusted. The focus in this part of the programme will be on fish behaviour and benefits accrued: • what proportion leave and return, as a function of time? • do the fish benefit in terms of growth and/or increased survival rate? • do they breed on the reef? • do juveniles live there? • is it likely that fish can get contaminated or tainted while living in or close to the reef ?

pjjj DAMES & MOORE The 1999 study can be divided into two main activities: Fish data Fish data will be collected using several methods. The “passive” methods are telemetry and acoustic observations (8.3.2.1 and S.3.2.2). The “active” methods will employ different fishing techniques. The methods most likely to be used are gill nets, traps, trawl and lines (8.3.2.4).

Milestone 2 The following elements will be covered: • quantification of observed shoals of fish using acoustic observations; • observation of fish behaviour by telemetry observation; • size, weight and quality of the fish captured using the different survey fishing methods; « stomach content (as input data to the food web and benefits calculations).

The data obtained through these elements of the programme will be evaluated in a workshop by the end of 1999. The results will be reported as preliminary conclusions. The workshop will also discuss the programme for the forthcoming years and suggest eventual changes to the programme in light of new information. Background data

Milestone 3 This study will seek to determine adequate background data to estimate energy transfer through the food web on an artificial reef. These data can be used to determine if energy is more effectively utilised on a reef compared with a reference site. Indications of the attractiveness of a reef to fish should also be possible.

Species living outside reef communities probably use more energy for prey hunting, while parts of this energy could be used for growth if the species lived on a reef. There will be three surveys, late January, late May and in October. Elements to be covered will be: • Hydrography (temperature, , oxygen); • Plankton (both and to be able to quantify primary production on a reef and on a reference site); • Marine growth on the structure (from previous studies it is unlikely that this is a major food source for the fish living on the reef but it may play a significant role in the total food web and the reefs “attractiveness”); • Benthos (some fish species predate on bottom living animals, so a quantification of available biomass in the bottom sediments is necessary). Benthos will only be sampled on the May cruise.

||j OAMES& MOORE

1 ““ Costs relating to the 1999 work are presented in Table 18.

8.3.4.4 Planned field-work during 2000 The tentative programme for 2000 will be a natural continuation of the 1999 programme. There will be a background data part and a fish documentation part. In addition to the elements suggested for the 1999 cruise, the following elements will be included: Fish data Data on metals and hydrocarbon concentration in the fish tissue will be collected. The fish will also be surveyed for taint. From previous studies (AUMS, 1989; Aabel et al., 1990) it has though been demonstrated that tainting is unlikely to occur in species living in the water column near oil and gas platforms. The surveys in 2000 are planned late January, late May and in October. As in 1999, the data obtained through the 2000 surveys will be evaluated in a workshop by the end of 2000. The workshop will evaluate the data from the three previous years. The workshop will also discuss the programme for the last year of the planned programme and will suggest eventual changes to the programme in light of new information.

Milestone 4 The work will be aimed at continuing the study of fish behaviour (e.g. movement and residence time) and the distribution and structure of fish populations, as this will require more than one year of work. Additionally, fish taint studies will be conducted.

Background data

Milestone 5 Data on metals and hydrocarbon# in the sediment will be collected, together with data on grain size, in order to give a better understanding of the ambient environment, under which conditions the artificial reef functions.

Costs relating to the 2000 studies are presented in Table 18.

8.3.4.5 Planned field activities in 2001 The programme for 2001 will follow the programme for the two previous years with continued focus on the issues described above. There will be a background data element and a fish documentation element. Additionally a commercial test fishing programme will be started. Although this a vital part of the overall study, as it will indicate the practical usefulness of a fishing enhancement reef to commercial fishermen, it must be conducted last, because a large proportion of the sample stock are expected to be removed in six fishing phases (8.3.2.10).

Eli GAMES & MOORE Milestone 6 The work will be aimed at continuing the study of fish behaviour (e.g. movement and residence time) and the distribution and structure of fish populations, as this will require more than one year of work.

Milestone 7 A commercial fishing study using professional fishermen will indicate the usefulness of a platform reef to fishermen, the best techniques to employ, the efficiency of capture, and indicate the most suitable management strategy.

The surveys in 2001 are planned late January, late May and in October. There will also be a workshop by the end of 2001 to sum up the results from all cruises. The conclusions from this workshop will be used when the final report is written in 2001/2. Costs relating to the 2001 work are presented in Table 18.

j$j DAMES &MOOR£ Table 17: Gannt diagram charting the progress of the proposed research programme.

1998 1999 2000 2001 2002 No Activity 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 Planning, mobilisation * * 2 Field work Hydrography * * * + ♦ 4t Plankton * * * * * * * * .... *"™ ...... Benthos ...... * * Marine growth * Fish (ROV, acoustic) ...... * .... * * * * * * ...... * * *""" ..... *" Commercial fishing * * * ....* ....

3 Reporting Progress reports ... * .... * * * Final report, review * * *

4 Meetings ...... -...... Work shops « * * * * ....it” Project meetings | * * * * * * * *

OWES & MOORE 115

Table 18: Proposed project budget

Unit No of Cost/ Total Frequency Total units/ unit 1998 1999 2000 2001 2002 No Activity year £ .£ no. no. no. no. no. £ 1 Planning, mobilisation man-days 20 450 9,000 i i i i 36,000

2 Sampling / field-work Development and testing of equipment man-days 20 450 9,000 0 i i 18,000 ROV videos man-days 30 450 13,500 1 0 0 0 13,500 Main surveys (plankton, benthos, marine growth, fish registrations) Cruise man-days 48 450 21,600 0.5 3 4 2 205,200 Boat lease days 10 7000 70,000 0.7 3 4 2 679,000 Equipment lease lump sum 40,000 1 1 1 1 160,000 Fishing (only plankton in addition) Cruise man-days 20 450 9,000 0 3 2 3 72,000 Lease days 6 3500 21,000 0 3 4 2 189,000 Commercial fishing (commercial fishing boat, various types of gear)

Cruise man-days 20 450 9,000 0 0 0 3 27,000 Lease days 6 800 4,800 0 0 0 3 14,400

3 Analysis Plankton sample 30 100 3,000 0 3 3 3 27,000 Benthos sample 50 200 10,000 0 1 1 0 20,000 Marine growth sample 10 100 1,000 0 1 1 0 2,000 Fish stomach (fish identification and measures will be done on board) man-days 20 450 9,000 0 3 3 3 81,000 Organic compounds from sediment and biota sample 200 150 30,000 0 0.5 1 0.5 60,000 Metals in sediment and biota sample 200 150 30,000 0 0.5 1 0.5 60,000 Tainting man-days 50 450 22,500 0 0 1 0 22,500

1 DAMES & MOORE 116

Table 18: Proposed project budget cont.

Unit No of Cost/ Total Frequency Total units/ unit 1998 1999 2000 2001 2002 No Activity year £ £ no. no. no. no. no. £ 4 Data handling, evaluation etc. ROV videos man-days 30 450 13,500 i 0 0 0 13,500 Plankton man-days 7 450 3,150 0 3 3 3 28,350 Benthos man-days 10 450 4,500 0 0 1 0 4,500 Marine growth man-days 10 450 4,500 0 0 1 0 4,500 Fish man-days 20 450 9,000 1 3 4 2 90,000 Commercial fishing man-days 25 450 11,250 0 0 0 1 11,250 Chemical analysis man-days 20 450 9,000 0 2 2 2 54,000 Technical support man-days 200 300 60,000 0.3 1 1 1 198,000

5 Reporting Progress reports days 20 450 9,000 1 2 2 2 63,000 Final report, review, articles days 150 450 67,500 0 0 0 0.3 0.7 67,500

6 Meetings Work shops man-days 20 450 9,000 1 1 1 1 36,000 Project meetings man-days 8 450 3,600 0 1 1 1 1 14,400

7 Travel, transport of equipment Lump sum 20,000 0.2 1 1 1 64,000

8 Administration, co-ordination man-days 48 450 21,600 0.5 1 1 1 75,600

Total sum per year 195,600 686450 860550 617,750 50,850 2,411,200

| Dames & moore 117

Table 18 comments: 2 8 days sampling, 6 scientists on the main cruise 6 days sampling, 2 scientists on the fishing and commercial fishing cruises If a supply vessel could be used on the main cruises (necessary fishing gear etc.), sponsored by the industry, the costreduction will be GBP 100 000, the fishing cruises should probably use a commercial fishing boat. Two of the scientists on the main cruise could be replaced by people from the industry, reducing the overall cost by GBP 20 000 3 Chemical analysis in 1999 and 2001 only from biota 4 Data handling includes all statistical treatment 5 Based on 4 progress reports 6 1 workshop, 10 scientists a year 2 project meetings a year, one in connection with the workshop, 4 scientists and the E&P Forum 8 0.5 man-day/week to co-ordinate the activities Cost reductions: A strong involvement from the industry itself could reduce the total cost by £ 100,000 - 200,000.

DAMES 4 MOORE 8.4 Technical Advisory Group A Technical Advisory Group (TAG) is suggested, including members from the petroleum industry, fishermen’s organisations, regional and national authorities and from research. This group would oversee the work, especially in its initial planning stages, in order to ensure that all of the concerns from interested parties were considered and that a high standard of research was being conducted. 9. CONCLUSIONS 9 Conclusions

Artificial reefs 1. Artificial reefs have for centuries been used to assist fishermen, enhance fisheries, or protect the local environment 2. Artificial reefs can be purpose built or made of waste materials. Their size and design varies with target species, available material and local conditions. 3. Japan and the USA have invested considerable sums in the establishment of artificial reefs. Rigs-to-reefs 4. Decommissioned offshore oil and gas structures have been shown to have been put to good use as artificial reefs in the Mexican Gulf. 5. Conditions and structures in the Mexican Gulf and North Sea are so different that few valid comparisons can be made. 6. Several structures in the North Sea may be suitable as platform reefs. Open lattice work structures with a large accessible volume are particularly suitable from a fisheries perspective. 7. Previous studies indicated large shoals of several species of fish, particularly saithe, in the vicinity of operating and redundant platform jackets. 8. Fish appear to derive some sort of benefit from being in the reef region, but is unclear as to exactly what this is. 9. Prior to reef creation, structures will need to be cleaned, toxic, loose and unsuitable structures removed, and possibly to some extent dismantled. 10. Platform reefs can be implemented by: toppling structures in situ; clustering several structures at one site, possible near an immovable structure; or abandoned in place in the standing position. 11. The clustered reef scenario would appear to have the greatest potential, because of the likely benefits in terms of fish protection and reduced spread of sea floor litter. 12. Reef creation should not be confused with offshore dumping, which is a very different proposed solution to the problem. Reef creation is the planned construction of structures that are designed to optimally achieve their aims, such as fish protection, using only suitable, cleaned parts of platforms and topsides.

j|| D/HMES& MOORE The benefits of platform reefs 13. It is possible that platform reefs can be used to decrease fishing effort and increase catch security: the chance of catching an adequate quantity of fish. 14. Alternatively platform reefs may be used to protect fish, preferably juveniles, from fishing mortality, thus increasing the stocks available to the fishery. 15. There are precedents for the establishment of protected zones within EU policy. 16. The current political climate within the Common Fisheries Policy of the EU is currently in favour of measures that restrict fishing effort rather that catch quantities. Platform reefs are such a technique. 17. Platform reefs, by affording both protection and a more diverse range of habitats may also enhance ecosystems locally. Such changes are not always considered beneficial. 18. The environmental impacts of implementing a platform within a reef cluster may be less than other decommissioning options such as dismantling on land. Reef creation may also be seen as socially more acceptable than land disposal. 19. Other likely benefits of platform reef creation compared with other disposal scenarios, such as cost savings and safety issues are beyond the scope of this report. The case for further R&D work 20. Information available at present is insufficient to reliably estimate the extent of these expected benefits, or even to judge if these benefits are realistic. 21. Two parallel studies are proposed: deployment and monitoring of a small steel lattice inshore reef, and an investigation of an inoperative platform to describe its reef-like characteristics and model possible scenarios for creating artificial reefs from steel jackets. 22. Both the inshore and offshore studies will provide new data which will allow the evaluation of reef creation scenarios. They will be highly goal orientated towards quantifying the environment around a platform reef in order to build up a picture of the benefits of the reef to fish, fisheries and the local ecosystem.. 23. Only when such data is available will it be possible for decision makers to reliably assess the potential of platform reefs, both as a means of habitat or fisheries enhancement and as a suitable decommissioning option. 24. Information from this study will be published in peer reviewed journals. Such open access to data will allow others to assess the results and promote informed decision-making and communication

HI DAMES & MOORE 25. In view of the great importance of the decommissioning issue, the potential advantages, the need to base discussions on hard facts and the desire for free and open communication, it is strongly recommended that the scope of work proposed in this report be implemented. 26. The total provisional cost for the full 5 year inshore reef research programme is £ 1,352,00, though sub-programmes are also proposed. 27. The total provisional cost for the full 5 year offshore reef research programme is £ 2,411,200, though substantial reductions in cost are possibly if vessel charter can be sourced outside of the programme. 10. REFERENCES 10 References

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