Kenya Diani Marine Reserve Expedition 1993: Report on the Distribution of Habitats and Species of the Diani Coast - Part 1

Home , Arothron meleagris, Conus consors, Hemitaurichthys zoster, Phymanthus crucifer, Pyramid butterflyfish

Kenya Diani Marine Reserve Expedition 1993: Report on the Distribution of Habitats and Species of the Diani Coast - Part 1.

Item Type Report

Publisher Universities of York & Hull

Download date 27/09/2021 21:10:40

Link to Item http://hdl.handle.net/1834/7240 KENYA DIANI MARINE RESERVE EXPEDITION. 1993

REPORT ON THE DISTRIBUTION OF HABITATS AND SPECIES OF THE DIANI COAST.

PAR T 1.

MAY, 1994 UNIVERSITIES OF YORK & HULL, UK. 2

PAR T 1

EXECUTIVE SUMMARY CON TEN T S PAGE PART 1 EXECUTIVE SUMMARY. 2

l. INTRODUCTION 8

2. THE SURVEY AREA: GENERAL CHARACTER AND TOPOGRAPHY 19

3. HABITAT DISTRIBUTION SURVEY 22 4. IMPACT STUDY 28 5. CORALS AND REEFS 47

6. FISHES 57 7 . INVERTEBRATES- 92 8. CONCLUDING REMARKS 105 3

REPORT ON THE DISTRIBUTION OF COASTAL AND MARINE HABITATS AND SPECIES OF THE DIANI COAST.

EXECUTIVE SUMMARY

1. INTRODUCTION

This report arises from field work carried out between November 1993 and December 1993 in response to recommendations made by Schoorl and Visser (1991) in their discussion paper 'Towards sustainable coastal tourism' environmental impacts of tourism on the Kenya Coast

\ commissioned by the Netherlands Minister of Agriculture, j Nature Management and Fisheries. Funding and support for J • this project was provided by the Royal Geographical Society UK, the Kenya Wildlife Service and various companies and trusts.

2. OBJECTIVES

Specific targets for the project were as follows:

1) To determine the occurrence and distribution of species which may be of conservational concern and/or which serve to indicate the general pattern of distribution of species within the study area.

2) To identify and map the occurrence and distribution of various coastal zone natural habitats including coral reefs and other sub littoral zones, Inter tidal, Mangrove, Estuarine and off-shore islands.

3) To prepare a coastal zone management plan which will suggest various methods of regulating use and other activities affecting the marine resources of the area.

4) To identify sites appropriate for the establishment of protected areas located so as to protect the best examples of habitats representative of Kenyan reefs and to make recommendations for the establishment, management and operation of these areas.

5) Working directly with Kenya Wild Life Service Staff a number of permanent environmental monitoring sites to be established. KWS staff to be trained in continuous monitoring techniques enabling these sites to act as stati:t)ns for biological monitoring, in particular for marine pollution of the whole Diani coastline.

The work presented in this report has been carried out under the direction of Dr. Rupert Ormond, Director of the Tropical Marine Research Unit at the University of York, York, UK, on behalf of Kenya Wildlife Service. Much of the field work was assisted by the involvement of specialist consultants. 4

During the course of the 6 weeks field work, 16 sites were surveyed on the reefs between Chale island in the south and the Mwechema river in the north.

3. METHODOLOGY AND OBSERVATIONS

Survey work was carried out at three different levels of detail or intensity, with the more superficial forms of study applied over very large areas, or at a large number of sites and detailed observation restricted to a small number of selected sites. The three levels of study and their extent of observation were as follows:

Type of Study Extent of Application 1. Above water observations Applied over the whole study of critical habitats. area. (supplemented by exploratory snorkelling and diving)

2. Qualitative underwater 'Reefwatch' observations observations using the were made at 16 stations. 'Reefwatch' format.

3. Detailed Study Sites 6 Detailed Study Sites were detailed quantitative Sites were established observations taking 3 days at each site

This work has resulted in the production of a set of maps at a scale of 1:50000 showing the occurrence and extent of different off shore coral reef habitats and associated critical marine habitats.

Particular attention has been paid to the distribution .. ; and status of critical habitats. Critical habitats are those which either are highly productive and hence support dense populations of animals, fish, etc., either within \ them or in surrounding areas or are habitats that are the i breeding or nursery areas of species of commercial importance , , or scientific significance. The principal critical habitats within the study area are the coral reefs, mangrove stands, sea grass beds and inter tidal areas. 1 The coral reefs in the survey area were found to be highly productive providing food and shelter for many species of commercial fish and scenically of a quality that would compare favourably with sites in other parts of the Indo Pacific set aside for diving tourism. Coral communities are mainly distributed as an off-shore fringing reef which runs parallel and almost unbroken along the entire Diani Coastline. Sedimentation can inhibit coral growth and reef formation and this appears to be occurring on the reefs over the whole study area as a result of natural depositing of fine sediments from rivers and mangrove areas. The coral assemblages throughout the study areas appear to be very similar and naturally arranged in zones of similar 5

groups of species by depth and degree of exposure to wave acti9n. Small patch reefs and inner reef formations occur' within the lagoon formed by the fringing reef most prominently close to high energy areas at breaks in the 'reef crest. The coral cover of the seaward facing reef slope is often dominated by soft corals representing up to 70% of total cover.· Sarchophyton species being the most evident and much smaller proportions of hard corals represented mainly by Porites and Acropora species.

Extensive sea grass beds occur throughout the study area on suitable soft substrate in shallow water especially within the Lagoon and in the lee of the Chale island. Thalassodendron ciliatum and Thalassia. Halodule and Halophila species are widely distributed.

Small stands of mangrove occur within the inter tidal zone all along the estuary of the Mwechema river and on Chale island. Four species are common. Avicennia maria-OJ, and Rhizophora Mucronata being the most dominant. These sea grass areas and mangrove stonos are a major contributor to the nutrition of the coral reefs of the ares and provide nursery grounds for a large number of commercially valuable fish and shellfish. It is essential that a rational plan be developed to prevent pollution and damage to these areas not only to safeguard these processes but also to assure t: hatfhe--8t-a billslng-eTfecttheseplant-s·provldetot-h-e . environmentally extremely fragile estuarine systems will help to prevent estuarine erosion and the resulting sedimentation of the reefs.

Apart from studies of these critical habitats and of the plants and animals already referred to. observations have been made of marine fish, echinoderms. molluscs. crustaceans and 'other invertebrates.

The observations on fish have principally been of interest in providing a detailed quantitative account of the main components of the fish assemblage present on the reefs of the study area. The choice of species studied are based upon a list of key fish species that are included by the Tropical Marine Research Unit in their Reefwatch programme and used in studies undertaken in all parts of the Indo Pacific area. The occurrence and numbers observed of these key species is regarded as a good indicator of the quality of the reef in a given area. An additional advantage of adhering to a standard approach is that studies in one part of the Indo Pacific can be readily compared with other Indo Pacific locations and zoogeographic trends established.

Further studies were conducted to compare the populations of commercial fish species of the Kisite Marine National Park with those of the detailed study sites at Diani by adding calculations of, biomass to data provided by Reefwatch underwater site inspections. As the sites at Diani are similar to Kisite both topographically and in terms of the 6 form of coral reef habitat provided such 8 comparative study is an admirable basis to assess the status of the Diani sites.

The results of the study appear to give clear evidence of a serious deficiency in the survey area in that species diversity and abundance were much lower in the unprotected Diani sites by comparison with the Park. The calculated biomass of commercially important species was also far' smaller in the unprotected Diani sites and indicated a strong possibility of non sustainable impacts to the fishery.

Observations of echinoderms indicate that, as was found in earlier studies at Shimoni, populations of most species are very variable according to location and this includes the needle spine urchins (Diadema spp). There is some evidence to support earlier observations by other workers (Muthiga and McClanahan 1987) that exploited reefs are dominated by urchin populations due to lack of predators and are poor in fin fish populations and corals whilst protected coral reefs are typified by an abundance of both. The long spine (Diadema spp) and rock boring (Echinometra mathaei) urchins are present in large numbers within the lagoon and on the outer reef slopes. These urchins can cause extensive damage to corals and when found in excessive numbersis~~oftenan ind ic.ationof. a ser:i_QJ.I~_i_mJ~Q:l.a~c;.e :lJ:'l the natural condition of the reef.

Similar intensive surveys were conducted to assess the numbers and distribution of the Crown of Thorns Starfish (Acanthaster planci) a further species of echinoderm that in large numbers can cause extensive damage to live hard corals. Numbers throughout the survey area were very low and are considered to be at a level within natural mass and distribution patterns taking account of the low level of hard coral cover at the sites observed.

Observations of molluscs especially the Spider Conch (Lambis croceata) provided a quantitative account of the occurrence of these species in the study area down to 15 metres. The evidence of our studies indicates that there is a variable distribution and this could be linked to shell collecting of this commercially important species especially within the ~agoon.

4. CONCLUSIONS AND RECOMMENDATIONS

The reefs of the Diani coastline are rich, varied and beautiful and the main report to follow will provid~ a detailed account of the research that has allowed this conclusion to be reached. The rapid increase of both tourism and commercial fishing in the area indicates that this valuable resource has not been left unrecognised. . Such development is clearly very much dependent upon the maintenance of the environmental quality. It is unfortunate that there will be some evidence presented in . 7

-the report that shows that detrimental impacts have occurred . to the natural environment which can be associated with this development.

In summary the marine resource contained within the area of study is rich but is currently subject to ecological impacts which, if continued, could cause irreversible damage to the ecological status and possibly seriously affect the future commercial development of the area.

Taking the present situation into account it is essential that the current and future planning for the area is reviewed with regard to ecological impact and included in an integrated coastal zone management plan that will address negative environmental impacts and safeguard the coastal native and natural resources.

Part II of this report presents proposals for the management and conservation of renewable natural resources of the study area. These proposals are based upon our research and early recommendations by Schoorl and Visser (1991), following the Workshop on Sustainable Coastal Tourism (Mombasa 22 - 23 April 1991), published in the discussion paper "Towards Sustainable Coastal Tourism", Environmental impacts of tourism on the Kenyan Coast commissioned by the Netherlands M~n~~try of Agrittil~tife, Natur~ Management and Fisheries Nairobi (Second revised edition June 1991). 8

] J

SECTION 1

1 I l .

I N T ROD U C T ION

,.1 J Ja J

j I I. 9 INTRODUCTION

I· Origin of Report

This report arises from work carried out between the 16th November 1993 and' the 29th December 1993 as the second stage towards progressing a series of objectives and specific targets agreed with the Kenya Wildlife Service for the whole of the Kenya coastline.

The general objectives of the project conducted from the site of the proposed Diani Reserve were identified as follows: I 1) To provide an inventory of the natural resources of the I , coastal environment surrounding and including the proposed Diani National Reserve.

2) To reveal major threats to which resources are exposed.

3) To indicate those conservation measures which will contribute to the maintenance of the productivity of these resources and strengthen the stability of the ecosystems for the ultimate benefit of people living around the area and upon it.

The specific targets were identified as follows:

1) To determine the occurrence and distribution of species which may be of conservation concern and/or serve to indicate the general distribution of species within the study area.

2) To identify and map the occurrence and distribution of the various coastal zone natural habitats including:

Coral reefs and other sub littoral zones Inter tidal Mangrove Estuarine Off-shore islands

3) To compare the fish populations of the Kisite Marine National Park with those of the Mpunguti Marine National Reserve.

4) To identify all sites appropriate for the establishment of protected areas located so as to protect the best examples of habitats representative of the Kenyan reefs and to make recommendations for the establishment, management and operation of these areas.

5) Working directly with Kenya Wildlife Service staff a number of permanent environmental monitoring sites to be selected and established. KWS staff to be trained 10

in continuous environmental monitoring techniques enabling these sites to act as stations for biological monitoring, in particular for marine pollution in the whole survey area.

6) This project is a continuation of a series of studies which, over the next three years in co-operation with the Kenya Wildlife Service, will seek to provide a complete marine resource management plan for all Kenya's Marine Parks.

This report is divided into two separate parts:

PART I Report on the distribution of habitats and species of the Diani Coast

PART II Management of the Diani coast and recommendations for protected areas.

Personnel and Field Work Organisation

The work presented in the report has been carried out by the Project Leader, Les Holliday working under the direction of Dr. Rupert Ormond, Director of the Tropical N-a rim~--Research Unit-at-the Uni versi.tyo-fYork,Y-ork, UK. The field work involved a team of volunteer biologists and divers from the Universities of York and Hull assisted by Nr. Ali Kaka, The Senior Warden, Kenya Coast, and the four trained diver KWS park rangers located at Kisite Marine Park and Mpunguti Marine National Park. Valuable additional assistance was provided by Dr. Ken Bock.

Off shore survey work involved the use of two vessels, one of which was provided by the KWS, and a total of 430 Reefwatch related person dives were undertaken supplemented by a further 20 person dives devoted to site exploration.

Nethods

A variety of methods were used during the course of this project aid these methods are described below. First, however, it ~s important to give some account of the general strategy of work that has been developed to meet the requiremeats of the project. As will be realised, a detailed tnderwater biological survey of a difficult coastline covering an area over 69 square kilometres is not a task that can be accomplished easily in the time we had available using only a small team of experts as~isted by a group of enthusiastic partly trained but largely ~nexperienced KWS diver rangers. It is obviously not possible to stop at every point on the ground nor to carry out a detaLled examination of the flora and fauna at more than a limited number of sites. 11

Accordingly" a strategy was adopted involving survey work at three different levels of detail or intensity, with the more superficial forms of study applied over very large areas or at many sites while highly detailed observations were made at much fewer sites. The three levels of study and their extent of application were as follows:

Type of Study Extent of Applicatio~ 1. Above water observations Applied over the whole study of critical habitats. area. (supplemented by exploratory snorkelling ond diving)

2. Qualitative underwater 'Reefwatch' observations observations using the were made at 16 stations. 'Reefwatch' format.

3. Detailed Study Sites 6 Detailed Study Sites were involving detailed Sites were established quantitative observation taking 3 days at each site.

Analysis of the data from such a survey should allow a reasonable estimate of the habitats and species likely to be present at any point on the coast of the survey area. The exploratory-dives served to .. distinguish the .gl'ound-truth regarding habitats visible in aerial photographs and during direct observation from the air. The Reefwatch observations extend the identification of habitats under-water and include semi-quantitative counts of selected indicator species. The detailed study sites extend the information provided by Reefwatch observations to provide quantitative information about the distribution of a larger number of species within different varieties of the same habitat or within the same habitat on different sites.

The quantity of the data collected is not sufficient to guarantee that any site can be completely characterised, and in particular, detailed quantitative studies have only been completed on coastal coral reefs, not other habitats, and within the depth range 0 - 15 metres. Enough information has probably been obtained however to permit the general"assessment of the nature and biological significance of any site.

In relation to the need to rely on subjective or semi quantitative information from sites observed, especially on the Reefwatch basis, it must be stated that such an approach although not meeting the highest scientific standards, is unavoidable if one needs to assess the distribution of habitats and species over such a large area as covered in the project, in the time available, without an impossible number of scientific workers. As Kenchington (1980) has pointed out, the design of such a survey involves trade-offs between detail or coverage, area of coverage and cost.

=of. 12

It is interestihg to note that very similar problems have been encountered in planning the management of a number of other large complex areas of coastline, reefs and islands which alt~ough much larger in scale are comparable in logistic terms with the survey work included in this report, namely the archipelagos of Indonesia and of the Philippines, the Australian Barrier Reef and more recently, Saudi Arabian Red Sea. In each case there has been an urgent need to establish the location and extent of different habitats below as well as above water before planning and management can be initiated. Unfortunately the realities of scientific work particularly under water are that quantitative studies are very time consuming. Kenchington (1978) gives a useful table of the approximate amount of reef that can be surveyed per hour using different techniques. Typically, for example, it might be expected that a diving team of two biologists would need 7 - 10 days to complete a quantitative survey of just the coral species present over only 100 metres of reef.

In both the Philippines and Australia workers developed rapid and semi quantitative survey techniques similar to Reefwatch so as to assess the status of a large number of sites. Because the scale of these surveys was so large a further method was developed (see Kenchington 1980) involving the towing of an observer on a manta board over several hundred , metres to allow a subjectiveJl~~1',-essment of s~i-tedescrip~tion, I aesthetics, slope stJli!H:rat.e/sed imen t t depth, coral cover, mean colony size and coral species diversity. The first known use of manta boards for large scale surveying of coral reefs was by the present director of the Tropical Marine Research Unit (see Roads and Ormond 1971) who used the technique for estimating numbers of the Crown of Thorns starfish Acanthaster planci on reefs in the Sudanese Red Sea. The methods used in the present survey will now be described. 'Reefwatch' Underwater Site Inspections l The main type of underwater site inspection used, involved the completion of two simple record sheets asking firstly for information about the position of the site, the profile ] of the reef (in side view) and a series of assessments concerning the aesthetic and recreational values of the site, the abundance and diversity of corals and of fish and the extent and form of any impacts or pollution apparent.

Abundance of fish and corals were usually estimated as follows: to estimate coral cover on reefwatch sites the pair of divers would assess by eye an overall estimate of the amount of hard and soft cotal within a 2m. band over a 20m •. length of reef representative of the dive site within the dep~h range under study. Dive sites were generally divided by depth, a site coul' be representative of the Sm. to 10m. ~one, the 10m. to 15m. zone etc. Note was also taken of dominant coral species and species zonation as related to the general topography of the reef. - 13

Sea urchins and other invertebrates were recorded by searching for and counting the numbers present within 1 metre either side of twin 250m. weighted transect lines previously installed at each site at 10m. and 15m. depth levels. Divers used 1m. long light metal poles to accurately define the area of observation and by swimming parallel to the transect line holding the pole at right angles to the line were able to observe and record each side of the line easily.

Fish abundances were assessed by a pair of divers swimming along the weighted transect lines covering, approximately, a 500 metre by 10 metre band transect. Using two diver observers to record information directly onto pre-printed waterproof record sheets during this swim was found to be an accurate and successful means of obtaining counts of the species specified to be recorded. Due to the limitations of working with inexperience observers it was decided to dispense with identifying fish species only by Latin names and to substitute line drawings and the common names of each fish species on the waterproof record sheets. This allowed species to be more readily identified on site and assisted in the accuracy of the recording.

Similar visual censuses of fish using transect lines have been widely used in recent years (see Chave and Eckert, 1974; Alevizon and Brooks, 1975; Jones and Chase, 1975; Ehrlich et aI, 1977; Robertson and Lassig, 1980; Anderson et al 1981, and the accuracy of such estimates has been shown to be quite good for all save very small or cryptic species (Brock 1982). On most sites observations were made by up to eight pairs of divers and the results obtained compared favourably, one pair of divers with another, and with repeat scores where stEes-were-v i s fE-ed- on--niOre- Tnan-.. one· ·0 c Ca s i on • u _

At all sites separate counts were made of the fish families: Butterfly fishes (Chaetodontidae) and Angel fishes (Pomacanthidae), Trigger fishes (Balistidae), Puffer fishes (Tetraodontidae) and Porcupine fishes (Diodontidae), and Groupers (Serranidae), Emperors (Lethrinids) and Snappers (Lutjanids) •

Detailed Study Sites

Work at the Detailed Study Sites essentially involved a much more intensive and extensive application of methods similar to those described before for Reefwatch site inspections. The six sites were chosen because of some feature warranting closer and more detailed inspection or for their unique or scientifically significant nat~re.

The work at each site varied considerably due to the nature of the specific feature under study and the varied nature of the site topography. Detailed assessment of each site and the results of our observations are contained within later sections of this report. 14

These studies do indicate a number of purposes that some of the Detailed Study Sites seem likely to fulfil. Firstly it is clear that they may serve excellently as stations for biological monitoring of environmental quality in particular for marine pollution in their general region. Secondly a number of interesting theoretical findings have emerged as will be apparent when the results of these sites are explained in more detail.

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INTRODUCTION - BIBLIOGRAPHY

Alevizon, W.S. & Brooks, M.C. 1975. The comparative structure of two western Atlantic reef-fish assemblages. Bull. mar. Sci. 25 482-490.

Anderson, C.R.V., Ehrlich, A.H., Ehrlich, P.R., Roughgarden, J.D., Russell, B.C. & Talbot, F.H., 1981. The community structure of coral reef fishes. Am. Nat. 117, 476-495.

Blom, J. 1985. Decline of the Malindi/Watamu reef complex, Research report for the laboratory of aquatic ecology.

Brock, R.E., 1982. A critique of the visual census method for assessing coral reef fish populations. Bull. mar. Sci. 32, 269-276.

Bryceson, J. 19~0. State of the marine environment in the East African region, UNEP regional reports and studies. Chave E.N. & Eckert, D.B., 1974. Ecological aspects of the distributions of fishes at Fanning Island. Pacif. Sci. 28, 297-317.

----ne--Ge-or-ges;··-- P~A--;---TggO-~----La n (f-oBs-e-d-·poITut 1. ona-ncf"frs----rmpact ---- on coral reefs and related ecosystems, USAID.

Ehrlich, P.R., Talbot, F.H., Russell, B.C. & Anderson, C.R.V., 1977. The behaviour of chaetodontid fishes with special reference to Lorenz's "Poster Colouration" hypothesis. J. Zool. Lond. 183, 213-228.

IUCN., 1980. World conservation strategy livins resource conservation for sustainable development.

IUCN., 1990. World Conservation Union, a framework for the classification of terrestrial and marine protected areas.

Comez, F.D., Alcala, A.C. & San Diego, A.C., 1981. Status of Philippine coral reefs - 1981. Proc. 4th intnl Coral Reef Symp. Vol. 1- pp. 275-285. Marine Sciences Center, Univ. of Philippines, Manila, Philippines.

Jones, R.S. & Chase, J.A., 1975. Community structure and distribution of fishes in an enclosed high island lagoon in Guam. Micronesia 11, 127-148.

Kenchington, R.A., 1978. Visual surveys of large areas of coral reefs. In: Coral Reefs: survey methods. pp. ~49-161. (Eds. D.R. Stoddart & R.E. Johannes.) UNESCO, Paris.

Kenchington, R.A., 1980. The development of methods for selection and monitoring of tourist operators and sites. In: Marine and Coastal Zone Management pp. 179-189. (Ed. J.L. Munro) UNESCO, Paris. 16

Ormond, R.F.G.;, Dawson Shepherd, A., Price, A., Pitts, R.,1984. Report on the Distribution of Habitats and Species in the Saudi Arabian Sea. Saudi Arabia Marine Conservation Programme, prepared by IUCN.

Roads, C.H. & Ormond, R.F.G., (Eds.), 1971. New studies on the Crown of Thorns starfish (Acanthaster planci) from investigations in the Red Sea. Report of the 3rd Cambridge Red Sea Expedition, (1970). Cambridge Coral Starfish Research Croup, 124pp.

Robertson, D.R. & Lassig, B., 1980. Spatial distribution patterns and coexistence of a group of territorial damsel fishes from the Great Barrier Reef. Bull. mar. Sci. 30, 187-203.

Salm, R.V. 1984! Martine and Coastal protected areas, a guide for planners and managers.

Salm, R.V. 1986. Coral reefs and tourist carrying capacity, the Indian Ocean experience.

Schoorl, I and Visser, N., 1991. Towards sustainable coastal tourism , environmental impacts of t()l!E_:i:s m __~!! -.!h~__ I~RY a _~j)~s...t-. _ ------~------~------ UNESCO, 1983. Comparing Coral Reef Survey Methods. pp. 135-175. Report of a regional UNESCO/UNEP Workshop, Phuket Marine Biological Centre, Thailand. UNESCO Report in Marine Sciences, No. 21.

UNEP, 1982. Environmental problems of the East Africa region.

UNEP, 1982. Marine and coastal area development in the East Africa region.

UNEP, 1982. Marine pollution in East Africa region.

UNEP, 1985. Management and conservation of renewable marine resources in the East Africa region. 17

ACKNOWLEDGEMENTS

I should like to acknowledge the considerably help and assistance received from many people and organisations in the work leading to the preparation of this report.

I would particularly like to thank:

Mr. Ali Kaka, The Senior Warden, Kenya Coast and his staff from the Kisite Marine Park and Mpunguti Marine National Reserve including:

Abdalla K. Mwanderi Salim Tsumo Bakari Hamisi Jabu Mohammed S. Mohammed Salim O. Chonga Simba Mwabuzi

For every assistance with the arrangements and fieldwork at Diani and the provision of accommodation and a diving tender.

-----=-~ne---sl:af-r------of-t1fe-ir

Dr. Mary Stafford-Smith, Dr. Alec Dawson-Shepherd, Dr. Andrew Price for providing assistance and the original research into Reefwatch survey techniques.

- the specialist consultants who assisted on site,

Dr. Rupert Ormond (TMRU University of York). Dr. Ken Bock.

- the inhabitants of Diani and surroundings especially: Ranjit Sondi and Reef Hotels, Chris Modigell, Alliance Group Hotels and Mario Scianna, The Crab Dive Centre

for their generous hospitality and continuous support.

- members of the headquarters staff of the Kenya Wildlife Service at Nairobi who helped with advice and assistance, principally:

Dr. J. Else,

- organisations in Kenya that provided support and assistance before and during the Fieldwork, including:

Ted Goss (Eden Wildlife Trust), Nico W. Visser Agricultural Attache, Royal Netherlands Embassy and co-author of the discussion paper "Towards Sustainable Coastal Tourism, environmental impacts of tourism on the Kenya Coast". 18

I am greatly indebted to all of the volunteer members of the Diani Marine Reserve Expedition from the Universities of Hull and York:

Dr. Chris Payne, Megan Hobbs, Dr. Darren Kwee, and Nigel Procter

other specialist consultant expedition members from the UK:

Charlotte Scott and John Fetenby.

Finally, I must express my gratitude to the Royal Geographical Society, London, and the large number of commercial organisations in the UK. who provided sponsorship as cash support, materials and services without which the expedition would not have been possible:

Barclays Bank pIc, British Rail, American Express, One Earth Tours.

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., ) 19

SECTION 2

THE SUR V E Y ARE A

GENERAL CHARACTER AND TOPOGRAPHY i- .------.~..--~- --.-----.----~------,r I J.

1. I ./

J 20

THE SURVEY AREA: GENERAL CHARACTER AND TOPOGRAPHY

The area covered by the survey is the Diani coast line extending from Chale island in the south to the Mwachema river in the north, the site and boundaries of the proposed Diani Marine Reserve. The main survey area covers over 94 square Kilometres and the survey was concerned mainly within the shallow-water sublittoral environment down to a depth of about 15 metres and the adjoining intertidal zone. Special attention was paid to the mangroves and associated seagrass beds within the intertidal zone, which are primary producers of nutrients for the life on the off-shore reefs. The extent of the area in question is indicated in the map, Fig. 2.1, and further more detailed cover is included in the set of maps featured in following sections of the report. This present sectio~ serves to introduce the survey area and to provide some background.

Coastal Topography and Climate

Diani and its fringing offshore reefs are oriented East facing and due to the complexity of the coastal topography support a wide diversity of coastal marine biological habitats including off-shore coral reefs, mangroves and sea grass beds and various other intertidal habitats. Within the survey boundaries there is also the Island of Chale (lkm x O·sk, 0·5 sq.km), a low island of fossilised coral and not recent in origin. Due to the tides, which are semi-diurnal with amplitudes ranging from l·lm to 3·sm, large areas of reef flat are revealed at low tides. Annual rainfall is over 800 mm, the major part falling in the period between March and July. Rivers flood during this period pouring fresh water and sediments onto the coastal shelf area that variably affect the development of fringing coral reefs and encourage the formation of extensive mangrove stands.

These physiographic factors impose marked seasonal patterns on the physical and chemical conditions of the shallow reefs. Sublittoral Habitats

Extensive fringing reefs have developed along the edge of the relatively shallow coastal shelf with maximum depths of less than 30 metres. Other quite different habitats exist closer inshore in the lagoon formed by the fringing reef which reflect the lesser wind and current. Extensive stands of seagrass are to be found in these protected shallows, and patches of reef, predominantly Porites spp, in exposed areas and situations close to channels and breaks in the reef.

The intertidal zone is basically of two major classes of intertidal substrate; sandy beaches composed of calcareous fragments of coral and molluscs forming a fairly coarse coral sand backed by low cliffs of wind eroded fossilised coral, or locations less predominant, where estuarine conditions exist producing mud flats over a fossilised coral substrate. Because of their relative significance in terms of extent and productivity the range of intertidal communities has been included in the study by mapping their occurrence and 21 distribution. See section 3 Habitat Distribution Survey. Where inter tidal habitats and communities have interaction with reef communities this is discussed in the section dealing with individual sites.

Hard-bottom sea bed within the study area and the depth zone under consideration (less than 15 metres) is, with few exceptions, dominated by coral communities and the ecology of such areas is essentially that considered in the account of reefs and corals given in Section 5. The other major sublittoral habitat is formed by submarine areas of sand or sand-marl that are found in some parts of the coastal shelf, but are most conspicuous in shallow water in-shore. The most significant biological habitat developing in such areas is formed by stands of seagrass that occur generally in protected shallows (0·5 - 2·0 metres) where circulation is still sufficient to maintain water quality. The occurrence and distribution of these seagrass beds is included in the habitat distribution maps in the following section.

...... DIANI SURVEY AREA FIG. 2.1 ".

Mwachema River 4

Diani

• Galu

• Kinondo

Chale Island ...

o 1 2 KM . I I 8ITE INDEX AND LOCATION8

REF. 8ITE NAME LATITUDE LONGITUDE

1 Galu Village 04°20·178 39°30·63E 2 Kinondo Village 04°20·138 39°30·61E

_ .._._-_.-. 3 IcliaTeISTano-Sl:Ye r- ·0-4--0-25·085 -30 0 3o-·-59E ....

4 Mw;chema River 04°1S·308 39°3S·67E

S Leopard Beach Hotel 04°1S-268 39°3S·66E

6 Trade Winds Beach Hotel 04°1S-248 39°3S·6SE

7 Neptune Hotel 04°20-168 39°30-63E

8 Chale Island 80uth 8ite 2 04°20-078 39°30-S9E

9 The Crab 04°20·208 30 0 3S-64E 22

SECTION 3

H A BIT A T DIS T RIB UTI 0 N SUR V E Y

.~------_._.------~------~------ HABITAT MAP DIANI REEF PROJECT FIG. 3.1.

Mwachema River

i I

Diani

KEY Mangroves Chale Seagrasses Reef o 1 2 KM Rockycliff 1 1 23

THE HABITAT SURVEY

1. INTRODUCTION

The Diani coast region of Kenya is dominated by its long white sandy beach, broken only at the north end of the study area by .the Mwachema river estuary. It is here that a narrow belt of mangrove can be found situated between raised reef rock and the ri~er South from Mwachema the sandy beach is uninterrupted down to Chale Island except for isolated areas of exposed overhanging reef rock. At Chale Island mangroves are present on the leeward side of the island and on the mainland. They are also found further south towards Gazi although this area was not covered in our survey.

The lagoon extends the entire length of the study area. It is approximately 1 Km wide and up to 4-Sm deep, with the exception of the area south of Chale Island which reaches 8 - 10m in depth. The reefs studied at Diani were fringing reefs of hard and soft corals with similar r~ral communities found -.---_f..o_r..mi.n&-smaJ.Lp.at,c.1L_r..ae.f_~e...... la_&_o-..M~.L~--.------

2. HABITAT SURVEY METHODS

An assessment of the extent and diversity of mangroves, seagrasses and hard corals was carried out along the mainland coast and lagoon.

The mangroves were surveyed on foot, and where possible 10m 2 transect observations were carried out and the tree species noted. There was a difficulty in surveying all the mangroves in the Mwachema estuary due to security problems. ~

The lagoon was surveyed in t~o ways, profile transects were continued from those carried out on the intensive outer reef sites and the profile of the reef continued across the lagoon to the shore. This method was also used at The Crab site. The sea grass species, corals and substratum were noted every SOm in a 10m wide band, by a snorkeller assisted by an accompanying boat handler. This allowed for six detailed cross sections to be made of the lagoon. A longitudinal survey was also carried out the length of the lagoon with the use of a boat and limited u~e of snorkelling. The Eden Trust very kindly donated the use of a helicopter for the production of aerial photographs of the study site. These were used to compare with and add to the data obtained from the longitud~nal survey of the lagoon by boat.

The outer reef slope was surveyed with. the use of SCUBA ~..1 ~quipment and involved both intensive surveys and non-intensive Reefwatch surveys. 24

3. RESULTS/OBSERVATIONS

3.1 MANGROVE.S

Four species of mangrove tree were observed in the area surveyed. Avicennia marina known locally as Mchu was found to be the most common species of mangrove tree in the areas covered by the survey. It was found in sandy and muddy areas where its pneumatophores protrude from the substrate, it can be tall and has small and narrow leaves. The wood may be used for fuel or furniture making.

Rhizophora mucronata (Mkuko) had long dark viviparous propagules some of which could be seen embedded in the sediment below the parent tree. They have small white flowers and a rosette-like arrangement of leaves. The wood is in demand for building purposes and for fuel.

Ceriops tagal (Mkandaa) has buttress and knee roots but those found by the river in the sandy/mud substrate were not well developed. ~-ney-fiave very smarr-white fTOWers with 5 sepals and are easily missed. Its wood is again used for construction or for fuel.

Sonneratia alba (Milana) was found in the more sandy substrate, it has thick succulent leaves oppositely spaced on the stem with pneumatophores protruding through the sand.

At the Mwachema estuary all four species of mangrove tree occur with Avicennia marina found to be the dominant species. As the band of mangrove was only approx 10-15m wide little zonation between the different species was discovered. The stands of mangrove extended in a narrow belt along both sides of the river estuary inhibited from spreading landward by raised reef rock. The substrate was composed of sand with softer mud present near the river edge.

On the north side of the estuary there were more species present and a larger concentration of trees than on the south side. In a 10m 2 area surveyed, nine large, mature Avicennia ... marina were found with up to 200 seedlings (1m in height) present. Four large and 170 seedling Sonneratia alba were present in the more sandy substratum. Twenty Ceriops tagal with developing buttress roots and two Rhizophora mucronata were also observed.

In the southern belt the trees were found to be less dense, in a 10m 2 area surveyed, three large and thirty two seedling A.marina, one R.mucronata and two C.tagal were observed.

The maximum height of the trees was approximately 4m.

The fauna in this area was rich with numerous fiddler crabs, mud skippers and mud whelks were also observed. 25

At Chale Island mangroves were found on the leeward side of the island and on the mainland opposite. The mangrove belt on the island was again found to back on to a raised reef rock and so varied from only 5-20m wide belts, a 10m 2 area was again surveyed. Eleven mature and one seedling R.mucronata was observed with six S.alba present on the out er part of the mangroves. Only two specimens of C.tagal and one specimen of A. marina were recorded. To the west of the island S. alba tended to dominate over R.mucronata.

On the mainland opposite the island the mangrove density is low with only one R. mucronata and eight S. alba in a 20m stretch of coast. Most of these trees were mature with large trunks and with heights of up to 4-5m.

There was no evidence of recent cutting down of the mangrove for use as timber in the areas covered by the survey, though locals explained that most mangrove tree wood was collected in the area north of Gazi.

3.2 SEAGRASSES

The survey showed 4 species of seagrass to be predominant. These were Thalassodendron cilatum, Thalassia hemprichii, Halod u.l-e u-a-i-n-e,I'-V-i-s and Ha IG-ftR4-1a s t i P-\l~a~-~T-.,t-i-l-i-a-Wm~w-a-s,-- .-----,,--- . the most common species in the lagoon.

The distribution of seagrasses can be seen on the three coastal maps and on the lagoon profiles. A closer inspection of the profiles taken of the lagoon show a more detailed distribution of T.ciliatum, T.hemprichii and H. univervis. At Chale Island H.stipulacea, H.univervis and T.hemprichii were all observed to be small in size on the reef rock flat present between the mainland and Chale Island. This area is exposed at low tide with only small channels and pools retaining water, this probably influences the growth of the seagrasses.

3.3 MACROALGAE

A large variety of macroalgae was found growing in the lagoon, on dead corals, rock and rubble. Halimeda, DIva, Enteromorpha and Valonia (green algae) were present. The brown algae observed included Padina, Dictyota. Turbinaria and Sargassum.

The macroalgae also forms an important percentage cover on the outer reef slope, consisting of filamentous, encrusting and free-standing forms. Halimeda was observed frequently, with Valonia. Pad ina and Sargassum also present on the upper reef. slopes.

3.4 CORAL

The lagoon contains several small patch reefs, in these Porites lutea and P.lobata tend to be the most common species. These are found in massive, helmet shaped forms or as micro atolls where the low tide prevents further upward growth. 26

The coral showed signs of damage from propeller blades in the area that most boats exit the lagoon near Galu. Other genera that were found in the lagoon include Favia, Acropora, Pocillopora, Goniopora, Galaxea. Platygyra and one colony of Echinopora •. At the Neptune site hard corals were found on top of rock projections from the sand, here Acropora tended to dominate.

On the shallow mainland fringing reef the most dominant scleractinian coral was Porites both in the lagoon and on the outer reef slope. Pocillopora, Acropora. Echinopora, Astreopora, Galaxea. Favia and Platygyra were also important. Soft corals and algae tended to cover a larger percentage of the reef substratum.

----~------~- ---~~--~------~-'----_.. _,------_._"-_.. __._.. ---_._------_._-_.~---_... __ ..._------_.

- I Fig.3.1 THE COASTAL HABITAT ft'IAP

« ft'I\V ACIIEMA TO THE CRAB

" \I 5 .s S S s

oS S S 5 oS

Mwachema S 5 S

" S .. " V " " " \I ,. " ,. " " " " ...... C::J"

_u___~_.______.. ,--~~--~-~-_._-

" !i. " \I " " . ..5 " ,. S \ . ., .s \1 ", ,. "

.' " "

\I 'I " " ., S \I " ",

II ,, , I S " " v .. S " S II .,

\I " S S " " The Crab • I' " ,. .t

0 0·' 5 l' Okm· I I .KEY I ceo Deep CbaDDel _ MaDgrove Seagras5 s" SaDd ~ Reel Rock ." - Reel FiB. 3.2

. THE CRAB TO KINODO

• The Crab , I \I .1

1. " .. II

,I ., ., ., "

, I 1---~~~ ---~~--~------,-,------

II ,, \I

Galu •

\I " U

\ , I' I"\r"\,.... ,. s " I' ,. I' ,~ " I~ C) I' S S • 1 S ~ • I , S 1 . 5 .' .J II 1 • " " I'

• I " ,I I'

0"'5 .KEY °1 ______l_"_O_k_m i =:=> Deep Cbannel 1 • Mangrove " Seagrass S Sand ~ RedRock a, Reef Fig. 3.3

KINODO TO CHALE ISLAND

~ 1\

"1\ " ~ II II

" II

------l---I' I'

.s " 5 o 1_· O'i_5 1_'O_k_rnj .KEY c:<:) Deep Channel • Mangrove " Seagrass S Sud ~ RedRock .~... Red 27

SECTION 4

IMP ACT STU D Y ------~-

I I . ..J 28

THE ENVIRONMENTAL AND BIOTIC COMMUNITY IMPACT STUDY

1. INTRODUCTION

The Diani coastline has become a major tourist destination in Kenya and the marine resources of the area are the main tourist attraction. Recent concerns regarding impacts to these resources has encouraged proposals for the establishment of the Diani/Chale Marine National Reserve in order to manage and protect these valuable resources from destructive activities.

The destructive activities in the area have been assessed as falling into six main categories:

1. Illegal and destructive fishing methods. 2. Coral and shell collecting. 3. Reef breaking due to walking on the corals and anchor damage. 4. Uncontrolled numbers of tourist boats. 5. Uncontrolled numbers of Fisherman boats, net sizes and catches. 6. Pollution, litter, sewage and domestic waste water from hotels.

------'Fh-er-e-~i:_s_,_-however, i ft-s-tt-f-He-i: e fl t i-rrf.6Tma~i{)-fl-e fl the--P-l'-e-s-e-n-t--5-t-a.t\H3--- . and the magnitude of these impacts and threats to the marine resources of the area because of the limited research in the Diani region.

The Diani Marine Reserve Expedition was therefore initiated in response to this need to undertake the necessary research and provide a management report giving an inventory of the local resources, the threats to and health of the habitats and recommendations to limit the damaging consequences of increasing tourism in the region.

The key objectives of the impact study were regarded as follows:

1. To conduct research to establish human impact on Marine Resources and the environment generally.

2. Research to establish sustainable levels of the Resources especially fisheries, number of vessels or people, etc.,

3. Research to establish management practises that would ecologically promote recovery in the degraded, impacted and destroyed areas.

The first phase of the study involved assembling information on the area to be managed. The aim was to achieve a reasonable understanding of the nature and condition of the resources in the area and of their past, present and possible future uses. The three major habitats that were surveyed include mangroves, seagrasses and reef communities. Although these habitats are separated into distinct zones their ecology is interconnected; 29

mangroves and seagrasses provide important inputs of detrital material to adjacent communities and the coral reef may rely on these habitats for recruitment of fish, invertebrates and other fauna.

1.1 MANGROVES

The factors that influence mangrove distribution are largely physical. These include exposure to wave action, substrate type, temperature and salinity. Mangroves are essentially tropical and their distribution is comparable to that of corals: They face many impacts throughout the world from their direct destruction for the coastal development of tourism, aquaculture, agriculture and salt ponds as well as the clearfelling of wood for construction materials and fuel. Other threats to mangroves include nutrient enrichment, thermal pollution, hypersalinity and the effects of a high sediment load.

Although the mangrove forest has a remarkable ability to absorb nutrients with negligible or favourable effects to the health of the trees, this can lead to problems. Dentrification ------·_·--G-f--.e-x-c-e.s.s.--amm 0 D i aaD d D it..I:i..t.e---I:.e.q.uiLe.s.....-a--.l.a~ amount of .Qli~! _ Tbis can affect the mangal community, as mangrove soils are already low in oxygen. An input of sewage can reduce oxygen to a level that results in significant mortality of fauna. Sediment often accompanies this input, although rivers may contribute a significant proportion. Mangroves have adapted to tolerate a fair amount of sediment but are intolerant at levels where aerial roots are too heavily coated with fine sediments or particulate matter. If lenticels or pneumatophores become clogged, plants will die within a few weeks (Odum & Johannes, 1975). ..l Salinity changes can also be a problem for the stands. This is likely to be due to their mechanisms for exclusion or accumulation of salt being unable to tolerate high salt stress; the reasons for this are not fully understood. Some species can grow in water of extremely low salinity (Bowman, 1917; Davis, 1940 cited by Johannes, 1975), however, mangroves commonly thrive in coastal areas exposed to estuarine and seawater since the presence of salt under these conditions reduces the competition with other plant species (Johannes, 1975). Hypersalinity however is a problem to most mangrove species. An increase in salinity is associated 'with the restriction of circulation to the mangal, usually as a result of poor tidal circulation, low rainfall, high temperatures and high evaporation leading to an elevation of the soil salinity. This is often as a result of bunding for aquaculture or salt ponds, construction of roads or inputs of hypersaline water from desalination plants.

The human uses and impacts to the mangroves are a major threat to the well-being of this community. There are, however, a number of natural pressures on which we have no direct control. These include the effects of weather and wave action, for example storms, cyclones and hurricanes, tidal waves, also volcanic activity in some areas. Pests and diseases can also have a 30

major influence on the habitat, and population interactions such as competition and grazing are another significant factor in mangrove mortality (Fortes, 1988).

As well as it's socio-economic benefits the mangrove has numerous natural values. The harvest is used in house and boat .construction as well as for fish traps, fence posts, and for charcoal and fuel wood. These uses must be balanced against the value of mangroves in nature. The mangrove stands support a number of dependent species and serve as nurseries for many commercially exploited fish and shrimp populations. They are also a very important factor in coastal protection and sediment stability.

Rao. 1986 (Cited by Fortes, 1988) summarised these natural ~. values:

1. They aid soil formation by trapping debris. By reducing the local current speed the mangrove settles sediment that otherwise would impose on adjacent communities, especially corals that are particularly vulnerable to smothering by sediments.

2. They filter land run-off and remove terrestrial organic ------ma-~r·••c----- Mangroves, in particular the muddy substrate that they grow in, has a remarkable capacity to absorb nutrients, especially those from domestic sewage. Industrial effluent, although not a major problem in itself, heavy metals and other toxic chemicals associated with the waste can accumulate in the tissues of mangrove fauna which may be consumed by humans. "Mangroves can act as natural sewage treatment plants" (Gosselink et al., 1974 cited by Johannes, 1975).

3. Mangroves serve as a habitat for many species of fish, invertebrates and birds. Not only is the mangrove a very valuable habitat for mature individuals of various species, they have an essential role as nurseries for commercially important shrimp and fish species that are important to the diet and economy of many of these developing countries.

4. Mangrove forests are a major producer of the detritus that contributes to offshore productivity. The falling leaves and branches provide a continual input of nutrients, in the form of detritus, to adjacent communities. This is particularly important to reef building corals and their associated fish populations.

1.2 SEAGRASSES

On the Kenyan coast seagrasses have no specific protection. They are protected to some degree, however, if they exist within a marine park (Anon, 1985). The main environmental factors that influence the distribution of seagrasses include substrate type, water depth (usually related to light availability), 31

exposure to wave action and currents as well as tidal range and temperature.

Seagrasses are seen as a commodity in only a few areas and since, compared to other natural resources, their obvious value to humankind is limited there are not the same incentives to conserve them. They do not therefore, however, have the same problems that other resources face such as unsustainability. Although seagrasses now have few human demands, they have been put to a remarkable variety of uses in the past, (and still are in some areas). These include fodder for animals and less commonly as food for humans, chemicals have been extracted from them, they have been used for basket weaving, paper, fertiliser, packing materials and fuel for burning, even a cigar was tried amongst many other obscure functions (McRoy & Helfferich, 1980 cited by Philips & McRoy, 1980? As well as their limited threats from humankind they have few natural pressures, since the populations of their major consumers, the Turtles and Dugongs, have been decimated. Since seagrasses have no economic value to most cultures, their natural values are often taken for granted. The range of natural values that seagrasses provide are -li.sLe.Lh-J-W.o.D-LeL~_aL._fl..9-~_c_Lt-eJ:1_b..yJi...eJn.an_._i93_5J_. ------1

1. ~eagrasses have a rapid growth rate and high organic productivity. It is this resilience that is often taken for granted.

2. When alive they provide food for only a limited number of organisms since the decline of large Sea Turtles and Dugongs but as with mangroves they produce large amounts of detrital material that is a major input of nutrients to the surrounding ecosystem.

3. Numerous epiphytic organisms thrive on the leaves. This growth maybe comparable in biomass to the seagrass leaf weight and is grazed extensively by fish and invertebrates.

4. Seagrasses provide organic matter that initiates sulphate reduction and maintains an active sulphur cycle in the sediments.

5. As with mangroves the dense leaves diminish the current velocity near the sediment surface and promote sedimentation of organic and inorganic particles, these natural systems may also be a useful tertiary treatment for sewage.

6. Roots and rhizomes bind the substrate and stabilise the sediment thereby hindering erosion.

In addition to these functions the seagrass beds provide nursery and shelter for a variety of organisms. This community provides ideal conditions for breeding, concentration of larvae and juveniles and specific conditions for the developmental stage of many fish and invertebrates (Zieman, 1975). Many organisms use the beds for shelter; they offer the individual protection from currents and a hiding place from predators for highly edible fauna (Philips & McRoy, 1980). 32

Although this habitat is rarely exploited as a resource, it does suffer a number of human impacts. These include direct modification and development, run off from upland development and the effects of industrial pollution (Philips & McRoy, 1980). Damage is also caused by boat anchors and dredging. Seagrasses suffer from the effects of thermal pollution usually from electrical generation and desalination plants or enclosed lagoons heated by the sun. Sedimentation and turbidity, from rivers, possibly as a result of farming techniques and from dredge and fill operations may also affect the health of seagrass beds. The plants are relatively resistant to a number of toxic substances but its fauna are susceptible to many of these chemicals. Fully subtidal plants are undamaged by oil pollution but as oil sticks to the water surface exposed blades are killed (Zieman, 1975). .

Seagrasses exist in a wide range of salinities and their tolerance varies between species. The upper limit for their survival is around 64% but the optimum for growth is nearer 42%. Halodule species show the greatest tolerances to high salinities (up to about 52'5%), Syringodium is least resistant (35%) and Thalassia lies somewhere in between. Thalassia can tolerate as low as 3'5% (Macmillan & Moseley, 1967 cited by Zieman, 1975).

Seagrasses are also tolerant to a wide temperature range which is why they are found in many different climates and not limited to the tropics as are corals and mangroves. Although Thalassia is killed by temperatures greater than 35-40°C (Glynn, 1968 cited by Zieman, 1975), the rhizomes are not affected. Thalassia grows in temperatures of 20-30°C (Philips, 1960 cited by Zieman, 1975), but has an optimum of 28-30°C according to studies carried out in Florida (Zieman, 1975).

Seagrasses have a high requirement for light. The growth of epiphytic algae and phytoplankton, resulting from a large excess of nutrient in the surrounding water and substrate, diminishes the available light. Accompanying nutrient enrichment is an increase in turbidity and a subsequent reduction in the levels of oxygen. This ultimately results in a reduction of the density and coverage of the beds that usually become overgrown and replaced by Enteromorpha (Dong et al., 1972 cited by Zieman, 1975). The ·inevitable effect is reduced catches of fish and diminished crustacean numbers. Reduction of oxygen levels can affect species differently. After 24 hours exposure to anaerobic conditions Thalassia recovered completely whereas Halophila did not. The greater tolerance is likely to be attributed to the greater ability of Thalassia to store oxygen in its tissues (Zieman, 1975).

1.3 REEF COMMUNITY

"Reefs are the foundation, origin and protection of thousands of islands and protect the coastal margins of larger islands and continents. They are the basis of subsistence, security and culture of coastal and marine communities throughout the q 33

tropical oceans, yet reef degradation is widespread and increasingll (Kenchington, 1985).

"Media has taught the world about coral reefs; where they are, how to g~t there. Scuba has allowed even the most novice of swimmers to discover the underwater world" (Tilmant, 1987). Reef communities in marine parks around the world have, in recent years, been invaded by increasing research and exploration. More and more people are taking up diving and exploring parts of the world previously isolated from the many tourists by the expense of exotic travel. Even those not trained in scuba can now be taught at their destination by one of the many dive schools located in these regions, or experience the beauty of this unique ecosystem using simple snorkelling techniques or glass bottom boats.

In East Africa well developed fringing and patch reefs occur along major sections of the narrow continental shelf and around offshore islands (Wells & Sheppard, 1988). Apart from the effects of dynamiting, divers and snorkellers, and anchor damage, coral communities are being affected by pollution, the input of sewage in particular. The quality of light reaching these sub-littoral communities is subsequently diminished by an iricrease in plankton and algal growth.

The coral reef is the target of the diverse exploitation, both for extractive and non-extractive uses. The extractive uses include food, ornaments and curios as well as building materials in some parts. Several medical applications have been found for parts of the community; coral bone substitutes and an anti-pregnancy drug were discovered. The non-extractive purposes of many reefs include coastal protection and the treatment of wastes. In small quantities, sewage is broken down by marine bacteria and other elements in the system. In large quantities, the system is overloaded and a proliferation of algae, produces competition for space and available light (Marszalek), 1981), sediment and detritus-feeding echinoderms result (Kenchington, 1985).

There are also a wide range of impacts not attributable to humankind. Natural pressures as a result of fish foraging, urchins, storm damage, disease and sedimentation, although not • 1 a direct result of human activity are often amplified by human _interaction. The effect of fishing (removing the predators of corallivorous fish and invertebrates) means that certain fauna, previously controlled naturally, are thriving and hence imposing greater damage on this delicate community. Urchins often further extend the damage initiated by human activity, and pollution may weaken the resistance of corals to disease.

1.4 FISH

A major part of this study was to establish the health of fish stocks in and around the survey area. The survey, although highly selective, provided counts of important commercial fish, invertebrate predators and species effective at indicating the 34 general health of "the coral. The groups of fish that were counted include Groupers, Triggers, Snappers and Emperors, Butterfly ~nd Angel fish, as well as Puffers and some large Wrasse.

The main damage to coral is due to large fish such as Wrasse and Parrot fish. The dentition and powerful jaw muscles of the Parrot fish are especially well adapted for scraping algal turf from the limestone bottom. They are also well known for their foraging on coral polyps and associated zooxanthellae. Wrasse have a similar impact to massive form corals as the larger parrot fish but are generally omnivorous. Wrasse generally feed on crabs, small fish, gastropods, polychaetes, zooplankton and algae.

Butterfly and Angel fish feed on both hard and soft corals although the effect of their minute mouth parts is hardly comparable to those of the larger Parrots and Wrasse. This damage is more likely to recover rather than becoming infected with secondary growth of algae as is often the case with the larger fish damage. They also feed on a variety of other items such as algae and plankton.

Puffers and Trigger fish are well known for their damage to corals. The Puffer fish commonly feed on plankton or algae but characteristically b±-t-e~...--nps--off bI snelling eoral.-~-- Trigger fish have a similar characteristic nibbling behaviour. These are of particular importance in predation of invertebrates which themselves cause appreciable damage if left unchecked.

Groupers are extremely important commercially and are caught either by hook and line or by spear fishing. They feed on benthic (bottom-dwelling) predators such as small fish and invertebrates.

Snappers and Emperors are closely related to one another and have a similar diet of small fish, echinoderms and crustaceans. These important commercial species are often observed in huge shoals and are also major predators of invertebrates that cause damage if left uncontrolled.

1·5 WATER QUALITY

Ammonia, nitrite, nitrate and phosphate are typically associated with sewage input. Ammonia and nitrite are extremely toxic to fish, ammonia being more toxic and dominating in conditions of high pH. The reef communities are particularly sensitive to the quality of the surrounding water because of the nature of their metabolism (Carter, 1988). These compounds are, however, rapidly oxidised to less toxic nitrate in the highly oxygenated waters of an ocean. Nitrogen compounds are the critical limiting factor to algal growth and eutrophication in coastal waters. About twice the amount of phosphate as can be used by algae is normally present (Ryther & Dunstan, 1971). An increase in algal activity may result in higher pH in poorly mixed areas, degradation of nitrogen compounds is accompanied by a pH drop under similar conditions. 35

If in high enough levels, these nutrients can promote blooms of algae and plankton increasing the turbidity of the water column. Turbidity can be worsened by wave action and currents as well as by diver finning activity that liberates the settled sediment. S~diment not only attenuates light and diminishes the quality of illumination to corals. It may settle on the coral tissues and cause significant calix mortality (Personal communication & observation). Coral growth tends to be diminished in these conditions and silted substrates inhibit larval settlement (Johannes, 1975).

Oxygen is rarely limiting in the constant mixing of the ocean particularly where the continental shelf is so narrow as is the case in the Indian ocean. The levels of dissolved oxygen can, however, be markedly reduced in still water, for example shallow coastal water or in sites of coastal upwelling accompanied by an increased oxygen demand. The oxygen holding capacity of water is also influenced by certain physical factors, especially temperature. At higher temperatures oxygen comes out of solution, an increased salinity has a similar effect. A large input of freshwater from a river or an outflow would reduce the salinity -.-----LQC_ally . but again rapid mixing diminishes any maj or effect.

Analysis of water along, however, may be inadequate and misleading when studying marine coastal pollution. In a study of Kaneohe Bay, Hawaii, a bay known for its poor health, a statement was issued based on water quality tests that the bay was not badly polluted. This opinion was based on an examination of the water overlying the reefs, but not the reefs themselves (Johannes, 1971). A number of observations can be used to indicate a high nutrient load. This is usually the conversion of coral reef to benthic algae and filter feeders. Certain I invertebrates can also be used as indicators of pollution and ., nutrient enrichment. 1

2. IMPACT STUDY METHODS

The method used for fish, invertebrate and coral surveys involved laying two 250m leaded transect lines at 5 and 10m contours along preselected reefs within the Park and Reserve areas. Following this line, observations were recorded on appropriate slates. This method worked equally well for the impact assessments. Using several categories of damage, the ; damaged coral form was identified, quantifying the extent of 1 the damage with 10 x 10cm (100cm~) units. ! i Coral Form Damage Category .1 Branching Snapped/Crushed Massive Parrot fish - large/small Horizontal Plate Wrasse Vertical Plate Sediment/Diseased Encrusting Puffer/Trigger Free-living Inverted Columnar Mollusc Foliose Crown of Thorns Urchin REEF IMPACTS FIG. 4.1

Mwachema River

Diani

KEY

None Some Severe Chale Island o 1 2 KM & I I • REEF IMPACTS RATINGS FOR ALL SITES

IMPACTS REF. LOCATION SCORE HIPACTS

1 Village 22 Some Gat4u:~~t, 1 - , 20 I 2 Kinondo Village Some ~J ...... J,;,. ~ ~ , 3 Chale Island Site 1 21 Some t J 4 Mwechema River 23 Severe ., , 5 Leopard Beach Hotel 19 Some I ! 6 Trade Winds Beach Hotel 19 Some

7 Neptune Hotel 18 Some , J

8 Chale Island South Site 2 21 Some \ I 9 The Crab 25 Severe J 36

Snapping or Crushing of the coral was only identified on delicate coral forms, with branching corals being the most susceptible. Usually the branches were snapped half way down the branch and in certain circumstances the detached branch survived to develop independently, although this often was not the case and the damage was rapidly covered by algae, joining the remainder of the coral rubble.

Parrot fish damage was particularly common on large and small massive-form coral. The large parrot fish left a mark resembling a small bite out of an apple, often rapidly recolonised with filamentous algae. The damage from smaller parrot fish was not so severe and in some examples was not fatal to the coral tissue. These small beak scrapes were observed as scratches of lighter tissue on the coral.

, 7 Wrasse damage was similar to that of the parrot fish. The pattern on the massive form corals was, however, distinct from that of the parrot fish. Usually Wrasse damage took the form of a large scrape, imposed by the single upper incisor, and two separate scratches beneath this, caused by two sharp teeth at the bottom of their mouth.

It is difficult to distinguish between damage caused by sediment and that of disease. The coral tissue dies slowly, th1S 1S observed as a I1ne-merg1ng from healthy c:oral into rre-crd~~---- or dying coral tissue, observed as a rough border. There are diseases that can be identified from sediment especially White and Black band disease. These are characterised by white and black bands, respectively, around a region of damage thought to be caused by the growth of blue green algae (Cyanobacteria). This was not observed in Diani, though suspected disease or sediment damage was recorded. It is likely that much of this is as a result of stirred sediment.

Puffer and Trigger fish damage was characterised by the tips of branching-form corals bitten off. This was difficult to identify from other tip damage and the data for this is therefore unreliable. Following from the experience of the expedition it is easier to identify this, the tips of the coral are often marked with two small tooth marks.

The effe~ts of wave action and storms may result in colonies of coral being inverted. Although this was observed in branching, horizontal plates and some massive-form coral, it is more commonly associated with free-living coral species, for example Fungia.

Crown of Thorns (Acanthaster planci) has decimated many coral reefs and is hence a nightmare for park managers around the tropical seas. Damage caused by these starfish has-a distinct and very definite boundary. Only single individuals were observed and only small numbers recorded. They are usually seen more when they come out at night. In small numbers they are thought to be beneficial to the diversity of the reef by controlling the monopoly of the faster growing species. 39 and diversity, which are almost identical and general reef topography. This is another popular tourist diving site and again some damage was recorded at permanent anchorage points but to a lesser degree than was found at Galu.

Fish damage was very slight and a total absence of parrot fishes and very low numbers of large wrasses noted.

Reef cover of hard and soft corals was of a better quality than found at Galu and live corals extend further down the reef slope with significant sized communities of gorgonian corals at depths of 30 - 35m.

3.3.3 Chale Island

The Chale Island site is relatively shallow, the reef slope terminating on a sandy level substrate at 25m. Although used as a diving site the location is far less accessible than the locations described earlier and is not subject to the same order of impacts from divers. No permanent buoys are installed and dive boats anchor at various locations along a 1 km. section of the reef. Fishing from small dug outs and boats under sail was recorded on a number of occasions and the use of spearguns observed. Despite -t-h-e-se----pressures, there was little evidence of anchor damage or impacts caused by fishing nets or tackle on the corals.

This section of reef was the best recorded in terms of coral cover and diversity over the whole study area. Some fish damage was evident to both massive and branching forms of. hard corals but this can be considered to be within natural limits in relation to the fish populations present.

3.3.4 Mwechema River

The reefs in this area are complex in structure due to the effect of the fresh water input from the Mwechema river which causes a 0·5km break in the fringing reef and a 25m deep channel to the leeward side of the northern most extremities of the Diani reef section. The detailed study site was located on the leeward side of the reef on a site used regularly for tourist SCUBA diving.

The main activity found to be causing impacts to the corals was related to the fishing in the area. Large numbers of fishermen use the site and the shallow sections of the reef were heavily impacted; with anchor, net and line damage clearly evident. Evidence of diver damage was not so clear but it must be assumed that some of the broken branching coral could be so caused. The highest levels of recently killed coral and one of the lowest percentage cover of live hard corals was recorded at this site and the reefs appear to be exposed to impacts associated with over-fishing which are causing a rapid decline in the reef structure. 40

3.3.5 Neptune Beach Hotel

The detailed study site opposite the Neptune Beach Hotel was on the outer reef slope midway between the breaks in the reef at Galu and Kinondo villages. This gently sloping outer reef was poorly developed in terms of hard/soft corals with over 50% of cover comprised of extensive algal beds on reef rock.

This site was chosen principally as a control, initially, on which to base comparisons with other sites nearby which are more heavily used for both fishing and diving tourism. Features on the site did however suggest that this reef could be regarded as a further diving tourist site and assist in relieving pressure on the other popular sites close by.

Very few impacts were evident other than a small amount of parrot and wrasse damage particularly to some large Porites colonies located in the deeper section of the reef. The reef slope is very exposed as the reef crest at this location is poorly defined allowing strong wave action to sweep over the site during ------sJ:..o..I:..,m.....s....,.O-- ~ ------3'4 FISH COMMUNITIES

Since fishing is permitted without control along the whole of the Diani coastline both in the lagoon and the outer reef the numbers of commercial species of fish which were counted (Snappers, Emperor fish and Groupers) would be expected to be fewer in this area relative to the numbers found in a totally protected area such as the Kisite Marine National Park. A comparison of the relative mean total abundance of each of the Diani sites with the Kisite Park does therefore give some indication of the level of degradation in terms of fishing pressure.

From the counts taken there appears to be far smaller numbers in all of the commercial fish groups counted for each of the detailed study sites when compared with those for Kisite, as shown below:

Mean total abundance

Chale Neptune Kisite Galu Kinondo Island Mwechema Beach

Groupers 20 5 9 5 5 5 Snappers 511 16 78 7 7 19 Emperors 95 9 9 4 3 8

As crude as this measure may be, there is no doubt that abundance levels appear to be very low at the sites surveyed. A more detailed report of these studies appears later in the report in section 6.

Similar patterns apply with other fish species which serve 37

Urchin damage is similar to that of Crown of Thorns but urchins rarely feed on living coral polyps. Urchins usually expand damage already present by eating their way beneath damaged colonies burrowing into their calcium carbonate foundations.

It was often, however, difficult to identify the source of some of the damage. In such cases a description was taken of the damage and attempts have been made to identify it from discussion and literature.

Water quality monitoring

In order to assess the extent of threats imposed by inputs of nutrient and other terrestrial-source pollution, water samples were taken at intervals all along the coast. Significant peaks of nutrient are often only detectable in slow or still water, usually found at depth or in the shallows. For this purpose samples of water were taken from the outer reef as well as the lagoon. For the analysis of these samples Palintest water quality test kits were used. As well as measurements for ammonia, nitrite, nitrate, phosphate, dissolved oxygen and carbonate hardness, pH, temperature and salinity were recorded. The park rangers were also trained in the use of these kits to enable the work to-c~±ntte, prov±d±rr~ eaIly warn1n~rrr-s1gnlfi~t eutrophication.

Other observations were made which indicate elevated nutrient levels, as water quality tests alone can be inadequate and dangerously misleading (Johannes, 1971). These included notes of algal growth, turbidity, invertebrates, the presence of outfalls and other human activities.

3. OBSERVATIONS

3.1 MANGROVES

Mangroves were found to be present only in two small areas within the survey area located in the Mwachema estuary and on and around Chale Island. As these relatively small mangrove stands represent such an insignificant resource and are largely isolated little human impact appears to be occurring. However, as small as these mangal areas are they do provide an important contribution towards the ecosystems of which they are a part. Serious disruption would occur to the marine environment if, for example, the mangroves were cleared from the Mwachema estuary to accommodate an expansion in tourism. The stabilising effect these plants provide to the environmentally, extremely fragile, estuarine system is essential in helping to prevent estuarine erosion and any resulting sedimentation of the reefs. Similarly the mangroves in the vicinity of Chale Island are a major contributor to the nutrition of the coral reefs in the area and provide nursery grounds.for many of the commercially valuable fish and shellfish. 38

3.2 SEAGRASSES

Seagrasses, although having no obvious threats in this area, some evidence of damage from anchors and boat propeller blades was found at various locations within the lagoon. There is no control on this at present although permanent mooring sites have failed to be effective in the past because of the large size of the vessels.

3.3 CORAL REEFS

Much of the coral damage in the area results from the natural pressures of storms and fish predation. A number of damage incidents that were recorded, however, were more as a result of anchor and snorkeller/diver related damage, or from the expansion of such damage by urchins. The 'natural' damage has been amplified by imbalances in the ecology of the area resulting from fishing pressures or other human interactions. There was no evidence of damage thought to be due to the illegal activity of dynamite fishing, initiated by fishermen from Tanzania, who fish within the southern boundaries of the proposed reserve. -l 3.3.1 Galu Village i

At the Galu detailed study site damaged coral was surveyed on both the 8 and 15m transect. This site is an intensively used tourist SCUBA diving venue on the outer reef slope. Three permanent buoys are installed in order to avoid anchor damage which unfortunately contribute towards other impacts on the corals local to the anchorage points. Diving groups tend to assemble at the base of the anchorages and, inevitably, damage is occurring to the surrounding coral communities due to divers standing and ~ treading on the corals. The coral cover is, however, largely i of soft coral species which have much better and faster I regeneration powers than hard corals and the damage appears to be largely sustainable. Diver impacts elsewhere on the site were not noticeable and the areas of the reef frequented by them were in a similar condition to more isolated non-used areas. , Fish populations on the Galu site were relatively low and ! .J the absence of parrot fishes and large wrasses was mirrored by the low level of damage from such sources. On a number of occasions fishing boats were observed local to the site but there was little evidence of damage from nets and no lost traps or tackle observed on the reef.

The low levels of hard coral cover (less than 25%) and the relatively poor diversity (22 genera) are indicative of the exposed nature of the site which is subject to high energy wave action during the monsoon seasons inhibiting the colonisation of the reef by fragile and branching forms.

3.3.2 Kinondo Village

The detailed study site at Kinondo is in many respects similar to the Galu site and this was reflected in terms of coral cover j -1 41

as a crude indicator of the health of the reef. Butterflyfishes were chosen and significantly greater numbers were recorded at Kisite than at any of the Diani sites.

Mean total abundance

Chale Neptune Kisite Galu Kinondo Island Mwechema Beach

Butterfly 55 25 34 39 29 31 fish

Studies of the other species counted in the survey do not seem to show .any particular abundance patterns. 3.5 WATER QUALITY

In 1991 (Economic Survey 1991) records show that over 800,000 visitors came to Kenya and it is estimated that more than 50% of these visited the coast, a sizeable proportion of which, would be attracted to the Diani area. Numbers of visitors have steadily increased since 1991 and with numbers of this magnitude the consequences of not processing sewage waste from the hotel facilities at Diani, correctly, and allowing pollution of the marine enviIOllmellt ale votentiall, very gIave.

However, water sampling, using the test kits described earlier, detected very few anomalies both from samples taken at intervals along the Diani beach front to the lagoon and at outer reef sites. That all water samples were within their expected norms is a remarkable record given the number of hotels and visitors in the area. Similar tests in the Shimoni region recorded significant differences in pH, nitrites, nitrates and phosphates resulting from contaminated ground water from Shimoni village with a population of less than 2000.

Closer inspection of sewage disposal methods used by the hotels indicates that a large proportion of sewage waste is collected in holding septic tanks and removed for disposal by road sewage disposal tankers. Waste domestic water from showers etc, on the other hand, is allowed to disperse into the lagoon via soak away areas but appears to have little effect on salinity levels in the lagoon. These relatively small amounts of fresh water input do become insignificant when compared with the immense flushing effect of tidal changes when upwards of 85% of the contents of the lagoon can be replaced by fresh oceanic water from outside the reef each tidal change •

.. 42

4. DISCUSSION

4.1 MANGROVES AND SEAGRASSES

There was little difficulty encountered in undertaking a detailed and accurate survey of the mangroves due to the small areas involved. The detailed methods adopted allowed total sampling of some locations and tree by tree mapping of sizeable areas.

Seagrasses were far more difficult to assess and would require a significantly larger amount of time than was permitted to achieve detailed accurate results. Whilst survey methods were more qualitative than quantitative the data is an extremely useful indicator of the resources available and the level of impacts Reef and Lagoon profile studies were also selected to sample the areas of the reef and lagoon where it was considered the worst impacts could be occurring to ensure no large areas of impact would be overlooked.

4.2 CORAL REEFS

------=::---~:------=-"------:------:;;;-:---:--:--:----;------:------;------~ The work undertaken at Shimoni in the previous year proved very useful in allowing observations to be carried out with more expertise. Little work has been conducted in the past in identifying coral damage and techniques are still in the development stage. Coral damage was assessed by observations at detailed survey sites along SOOm of reef using a 1m long light metal pole to accurately define the area under observation which was a 1m wide corridor either side of the transect line. This involved estimating the area of damage in units of 10 x 10 cm 2 (100cm ) blocks. Whilst the data collection was very accurate and detailed the main problem remains the difficulty of precisely assessing the origin of some of the damage found.

4.3 FISH COMMUNITIES

The fish counts were designed to indicate the health of fish stocks and general fitness of the community. More account could have been made of natural impact species, such as Parrot" fish and large Wrasse, this would have enabled the fish predation on corals to be compared with actual numbers of fish responsible for the damage. Much of the damage suffered by the corals in the area was the result of grazing from large parrot fish. It would therefore be helpful to have a count of these fish. 1 Although a count was taken of large wrasse, also responsible I ! for a fair degree of the damage to massive form corals, the data ) was a little unreliable as it is suspected that the counts received of the wrasse were a little inaccurate due to the inexperience of some of those counting.

4.4 WATER QUALITY

Water quality testing in the area revealed few anomalies. This is mainly a result of the insensitivity of the test kits being used, but indicative of the low level of nutrients in the 43 surrounding waters. These kits were selected for the ease of use by KWS staff and are used primarily to test aquariums. Whilst not entirely satisfactory they nevertheless can register damaging input of nutrients resulting from localised eutrophication.

5. RECOMMENDATIONS

Recommendations for the management of the natural marine resources will be discussed in detail in the accompanying Part II of this report. In summary it appears from the level of impacts observed that a substantial part of the marine resources of the Diani coastline are in need of protection. It is important, however, that any measures taken are not in conflict with the needs of the area but at the same time should provide sufficient protection for the resources to ensure that future generations can benefit from them. If there is a conflict of uses the plan will not be workable. "Sustainable utilisation of coastal resources requires the manager to balance the cause and effect remaining alert to change and having skill to adjust. The paramount objective of coastal management is to devise a framework within which man may live harmoniously with nature" (Carter 1988).

To this end the main I ecomltie-rntg-tro-rr-oT-t1rrs-rev~ will tre the implementation of a coastal zone management plan. This will take into account the requirements of the region, in terms of tourism and other local needs. In addition the natural communities will be considered providing protection for those threatened by the increasing demands of mankind. 44

HABITATS AND IMPACTS - BIBLIOGRAPHY

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Davies, G.E., 1977. Anchor damage to a coral reef on the coast of Florida. Biological conservation 11, 29-34. den Hartog, C., 1970. The Seagrasses of the World. North Holland, Amsterdam.

Fortes, M.D., 1988. Mangroves and seagrass beds of East Asia: Habitats under stress. Ambio 17(3), 207-213.

Gomez, E.D., 1988~O~ervie~ of Environmental problems in the East Asian Seas Region. Ambio 17(3), 166-169.

Graham, R.M., 1929. Notes on the Mangrove Swamps of Kenya. Journal of the African, Uganda Natural History Society 36.

Hall, D., 1984. Conservation by Ecotourism. New Scientist No. 1399, 38-39.

Hawkins, J.P. &' Roberts, C.M., 1992. Effects of Recreational Scuba Diving on Fore Reef Slope Communities of Coral Reefs. Biological Conservation 62(3), 171-178.

Hutchings, P. and Saenger, P., 1987. Ecology of Mangroves, University of Queensland Press. 388pp.

Johannes, R.E., 1982. Traditional Conservation Methods and Protected Areas in Oceania. Ambio 11(5), pp. 258-261.

Johannes, R.E., 1975. Pollution and Degradation of Coral Reef communities. In: Ferguson Wood, E.J., & Johannes, R.E., (Eds). Tropical Marine Pollution. Elsevier Scientific Publishing, Amsterdam. 13-50.

Johannes, R.E., 1971. How to Kill a Coral Reef. Marine pollution Bulletin 2(1), 9-10 & 1(12), 106-107.

Johnston, R., 1976. Marine Pollution. Academic Press, 729pp.

Kelleher, G.G., and Kenchington, Richard A., 1982. 45

Australias Great Barrier Reef Marine Park: Making Development Compatible with Conservation. Ambio (5), 262-267.

Kenchington, R.A., 1988. Managing Reefs and Inter-reefal environments ~nd resources for sustained exploitive, extractive and recreational uses. In: Proceedings of the Sixth International Coral Reef Symposium, 1988, volume 1.

Kenchington, R.A., 1985. Coral Reef Ecosystems: A sustainable resource. Nature and Resource 21(2), 18-27.

Kenchington, R.A., and Hudson, Brydget E.T. (Eds.), 1984. Coral Reef Management Handbook. UNESCO.

Kenchington, R.A., Managing Marine Environments.

KUhhlmann, D.H.H., 1988. The Sensitivity of Coral Reefs to Environmental Pollution. Ambio 17(1), 13-21).

Liddle, K.J., & Kay, A.M., 1987. Resistance, Survival and Recovery of Trampled Coral. Biological Conservn. 42, 11-18.

Mackey, A.P. ,Hddgl<1nson, M. and itardel1a,·· R., 1992. "Nutrient levels and heavy metals inmangrove sediments from the Brisbane River. Marine Pollution Bulletin 20(8).

Marszalek, D.S., 1981. Effects of Sewage Effluent on Reef Corals. In: Proceedings of the Fourth International Coral Reef Symposium, Manila, 1981 vol.1.

Mergner, H., 1981. Man-made influences and natural changes in the settlement of the Aquaba Reefs (Red Sea). In: Proceedings of the Fourth Intgernational Coral Reef Symposium, Manila, 1981 - vol.1. Odum and Johannes, 1975. In: Ferguson Wood, E.J., & Johannes, R.E., (Eds.). Tropical Marine Pollution. Elsevier Scientific Publishing, Amsterdam.

Philips, R.C. and McRoy, C.P. (Eds.), 1980. Handbook of Seagrass Biology: An Ecosystem Perspective.

Ryther, J.H. and Dunstan, W.M., 1971. Nitrogen, Phosphorus & Eutrophication in C~astal Marine Environment. Science 171.

Salm, R.V., 1986. Coral Reefs and Tourists Carrying Capacity: the Indian Ocean Experience. UNEP Industry and Environment 9(1), 11-14.

Salm, R.V., 1985. Integrating Marine Conservation and Tourism. International Journal of Envmnt Studies 25, 229-238.

Salm, R.V., 1984. Ecological boundaries for Coral Reef Reserves: [ Principles and Guidelines. Environmental Conservation 11(3), .; 209-215. 46

Salm, R.V., 1983. Coral Reefs of the Western Indian Ocean: A Threatened Heritage. Ambio 12(6), 349-353.

Salm, R.V. assisted by Clark, John, R., Marine and Coastal Protected Areas: A guide for Planners and Managers.

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Wells, S.M. & Sheppard, C. (Eds.), 1988. Coral Reefs of the World, Volume 2. Indian Ocean, Red Sea and Gulf. UNEP Regional Seas Directories and Bibliographies. IUCN. Gland, Switzerland and Cambridge, UK./UNEP, Nairobi, Kenya.

Zieman, J.C., 1975. Tropical seagrass ecosystems & pollution. In: Ferguson Wood, E.J., & Johannes, R.E. Tropical Marine Pollution. Elsevier Scientific Publishing, Amsterdam. 63-74. 47

~) I \ SECTION 5

, -ll------G---G-R A L S-- A N B R E E F S

I j

,._JI

f .J 48

CORALS AND REEFS.

1. INTRODUCTION

The reefs found off the East African coast form a continuous band from the Equator to approximately 14°S latitude and the Kenyan coast extends just over 4s0Km along the East African coast. Mainland fringing reefs are the most common of reef type and form parallel to the coastline. The reef formations are restricted to a close band along the shore, since the continental shelf is narrow in this area. The fringing reef is approximately 200m wide and is separated from the coral sand beach by a lagoon of up to lKm wide and 4-5m deep. In this lagoonal area small patch reefs occur.

The study area covered the Diani coast from the Mwachema River to Chale Island. The reefs in this area consist of fragmented fringing reefs stretching parallel to the shore. These reefs may extend to 15 - 20m in depth and tend to have a gentle seaward slope with limited signs of spur and grove formation. 2. ffE'fHODS

This survey was carried out with particular attention to conserving, rather than depleting the coral reefs so non-invasive methods were used. Direct field observation was adopted using SCUBA equipment, combined with high quality photographic techniques. This enabled the scleractinian corals to be identified to genus or species level and the distribution and percentage cover of the corals to be noted.

Eight study sites were covered in total, five of which were studied intensively, these included Galu, Kinodo, Chale Island, Mwachema and Neptune. These intensive sites were surveyed as shown in the general methods, 1m 2 quadrates were taken (with the use of a 1m pole) every 10m along a pair of horizontal 250m lines~ Vertical transects were then laid at the end of each horizontal transect and the species noted up the line in 1m 2 quadrates. The species composition of the scleractinian corals were noted and the percentage ground cover estimated at each transect.

Three Reefwatch sites were also surveyed, where only one 250m horizontal transect was placed at approx 10 - 15m depth. Observations of 1m 2 quadrates were taken every 10m and the hard coral genera noted.

A profile study of the reef was carried out from 40 - sOm depth to the shore line at all of the intensive sites and the Crab site. Profile studies were based uvon observations of a 10m wide band of reef along which percentages of substratum cover were calculated and the main genera of hard corals noted. 49

3. RESULTS

3.1 CORAL FAU~A. INTENSIVE STUDY SITES.

The scleractinian coral fauna identified during the study are shown in Table 3A. A total of 54 reef building genera were recorded and this can be compared with studies in 1984 (Hamilton and Brackel) which listed 55 genera for East Africa as a whole. The number of genera found is likely to be an underestimation due to the intensive nature of the study methods. A more widespread and extensive survey would probably record many more genera.

The most prominent of these genera was Porites, found forming large colonies, mostly massive, with some branching forms. Other important genera were Acropora, Pocillopora, Astreopora. Echinopora. Favia. Favites and Galaxea.

Porites was found on all parts of the reefs from the exposed sUli zone, down to appreximately 10m. Seme formed massive, helmet-shaped colonies up to 2m across although most were found to be smaller. A limited number of colonies were present as small branched forms with encrusting bases.

Acropora was found as corymbose, arborescent or plate - like forms. On the Galu, Kinodo and Neptune reefs the Acropora colonies remained stunted and small but at both Chale Island and Mwachema reefs large plate-like and tabular forms were observed. Pocillopora was very common on all the reefs surveyed, - although colonies were all of small size. The largest species diversity was recorded on the Chale Island site.

Astreopora were frequently observed occurring more extensively along the more exposed shallow transects, and was usually in a massive form.

Echinopora was very common in an encrusting/foliaceous form • 1 the colonies were found both on shallow and deep reef areas ; becoming the main genera on some deeper parts of the reefs.

Both Favia and Favites were also common constituents of all the reefs studied as was Galaxea which frequently appeared although colonies were not extensive.

Lobophyllia was found in very large, mature colonies on the l deep transect at Chale Island, and to a smaller extent on Neptune . J and Mwachema reef.

~.J 50

3.2 CORAL FAUNA. REEFWATCH SITES

See Table 3Ai below for the reef building corals observed on these non intensive study sites.

Site 5: Leopard Reef

This seaward fringing reef ranged in depth from approximately 6 - 11m. The majority of substratum cover was algae covered rock with a large amount of soft coral present. A few massive Porites were scattered across the slope.

Site 6: Tradewinds Reef

This was another narrow seaward fringing reef, ranging in depth from approximately 8 - 15m with very little hard coral -present, Porites in the helmet-shaped form was the most common species. Soft coral and algae again dominated the substratum cover.

Site 8: Chale Island South Reef

This was a seaward fringing reef ranging in depth from approximately 10 - 15m. Pocillopora, Porites, Favia and Echinopora were observed. Algae and soft coral were the dominant cover, withiljae co~erirtg-40% bf tfiereef slope. Table 3A. Distribution of reef building corals at the intensive study sites.

Galu Kinodo C hale Mwach;:ma Neotune 0 S V 0 S V 0 S V 0 S V 0 S V

Order Scleractinia Family Pocilloporidae

Stylophora pistillata 0 0 Pocillopora verrucosa 0 0 0 0 0 0 0 0 0 0 0 0 P. eyedouxi 0 0 0 - Seriatopora hystrix 0 0 0 0

Family Acropoidae •

Acropora sp. 0 0 0 0 0 0 0 0 0 0 0 0 A.clathrata 0 0 0 A.palifera 0 0 0 A.hyacinthus 0 0 A.secale 0 0 0 A.nana 0 A.tenuis 0 0 0 0 0 n. 0 A.millepora 0 0 0 Astreopora sp. 0 0 0 0 0 0 0 0 0 0 .. A. myriophthalama 0 0 Montipora sp. 0 0 0 0 0

Suborder FungiiDa . Family Agariciidae " ..... , Leptoseris sp. 0 Pachyseris speciosa 0 0 0 ~ j Family Fungiidae j

Fungia sp. 0 0 0 0 0 F.scutaria 0 _1 F.repanda 0 0 Herpolitha sp. 0 0 0 Polyphyllia sp. -cJ Family Poritidae . Goniopora sp. 0 0 0 0 0 0 1 Porites sp. 0 0 0 P.lobata 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 P.lutea 0 0 0 0 P.nigrescens 0 0 0 0 0 J P.cylindrica 0 0 Alveopora sp. 0 0 0 0 l

_JI Suborder FaviiDa . Family Faviidae Favia sp. I 0 0 0 0 0 0 0 0 0 0 0 _J F.speciosa 0 0 0 0 0 . F. palida 0 0 ) F.maxima 0 J , , ~entune , (1~h Kinodo Chale Mwachema 0 S V 0 S V 0 S V 0 S V 0 S V

Favites sp. a a 0 a a a a a a a a F. flexuosa a OulQphyllia sp. a a Goniastrea sp. a a a Platygyra sp. a a a a a a a a a Hydnophora micrococus a a a Cyphastrea sp. a C. serailia a Echinopora sp. a a a a a a a a a - E.lamellosa a a Montastrea sp. a a a

Family Oculinldae

Galaxea clavus a a a a a a a a a a G. astreata a

FamilyMusstdae Lobophyllia sp. a a a a a a L.hemprichi a .... n "1'. -

c"" Family Pectinifdae .. Mycedium elephantotus 0 Order Stolonifera Family Tubiporldae

Tubipora musica a a

SuborderCaryophyWda FamilyCaryopbyWdae

Eupyllia crista a

Order Milleporina . Family Mllieporldae Millepora sp. a .. a Total 11 11 22 11 12 16 21 23 19 10 13 10 11 8 13 Table 3Ai

Distribution of reef building corals at non-intensive study sites.

Chale Island

" South Tradewinds Leopard

Family Pocillophoridae Pocillopora sp. 0 0 Stylophora sp. 0 0

Family Acroporidae Acropora sp. 0 0 Astreopora sp. 0

Suborder Fungiidae Fungia sp. 0 0 Herpolitha sp. 0 Pachysaris sp. 0

. Family Poritidae Porites sp. 0 0 0 Goniopora sp. 0

.. Family Fayiidae Favia sp. 0 Goniastrea sp. 0 Platygyra sp. 0 Echinopora sp. 0 0 Ouphilia sp. 0

Family Oculinidae Galaxea sp. 0 0

Family Hussidae Acanthastrea sp. 0

Total 14 7 2 G.... LU REEF

Reei rock wilh allae Om Sofl toral dominam 2S ~ hard toral mainly arborestem Acropora and massive Porires

sari toral clominam SShard toral mainly Porir~s

SOrl c:oral willi algae: lOme massive coral

Sand rock and rubble

Sand

.... SOm

SOm KINODO REEF

Reef rock willi Om toraline allac AI ae, rock. IOfl toral and slul'lledltcropora Algae, sorl coral and ISS bard c:oral, mainly A.cropora, Porires 4UId Faviru. .... II&C. dominam IOfl.c:orall and 25 S hard corals, mainly pocillopora. Poriles, Favia and Favilu.

Allac, IOfl corals and lorlonialu

Sand wilh solilary torals

...... 50m J

F" SOm

'littLE lSI AND' REEF

Larle VUicl)' of hard corals .... Iaac. rock, IOrl coral and 20S hard Om toral (large Lobophyllia colonies and 1 arborescenl and plale A.cropora) j

Roc:It, Iiale and elltnlslina corals ) ! .J

Sand and rubble

1 , .J 51

3.3 OUTER REEF PROFILES

All the intensive study sites with the exclusion of Mwachema had similar outer reef profiles and coral zonation. The reef crests at each site are subject to high energy wave action especially during the monsoon seasons and are often exposed at low tides. The reef crest was found to be a platform of reef rock with numerous rock pools present in which algae may be found. The reef edge also a high energy region was found to have a large % cover of algae with small Porites and Acropora colonies present. On the upper reef slope the largest variety of scleractinia are to be found in massive, plate-like and branching forms. Soft corals were found to dominate the substrate cover with a large amount of algae covered rock also present in this area. On the lower reef slope some encrusting, massive and plate-like corals were present with a few gorgonian fans and whips. Soft coral was again found to cover most of the substratum with a significant amount of algae present. Below this point the only corals found were small and solitary positioned in the sandy sea bed.

A cross-section of the reef profiles are shown opposite, the vertical axis shows the depth below the mean low water spring level.

3.3.1 Site Description

Site 1 - Galu

This outer'reef has a reef edge of algae covered rock. The upper reef slope was carpeted with 35% soft corals, plus areas of rubble, sand and algae cover. The hard corals covered 25% of the section observed in this area, Acropora, Porites. Pocillopora, Hydnophora and Favites were observed most frequently. On the lower slope 40% cover of soft corals were observed with 10% hard corals present including Porites, Platygyra, Echinopora. Favia. Lobophyllia and some free living Fungia. At 30m depth gorgonians were observed, below this was sand.

Site 2 - Kinodo

This reef has the typical algae covered rock at the reef crest. The reef edge was observed to have 50% algal cover, 25% soft coral 'and 15% hard coral cover mostly consisting of small Acropora and Pocillopora colonies. The upper reef slope has a similar % cover of algae and soft coral cover to the reef edge, with 15% hard coral mainly Acropora, Pocillopora, Porites. Favia and Astreopora. The lower reef slope has 40% soft coral and 25% hard coral cover, mainly Porites. Favia. Favites and Astreopora. At the base of the reef (25 - 30m) gorgonians are present in amongst 80% algal rock, rubble and sand and 2% ,soft coral. Below 30m depth the substratum is sand. MWCHEMA REEF

50(1 coral. algae and large Rubble, algae Porites and Acropora colonies Om and seagrass Rubble, algae and seagrass Rock. rubble, sof! coral and small har.d coral

Sand. soliwy coral and gorgoniaru

sOm

SOm NEPTUNE REEF

Om Rock with algae and some Acropora Rock with algae and S" hard coral Algae. SO(I coral and 10" hard cotal mainly POf/les, 'Acropora and Aslreopora Rock, rubble. algae and 3" hard coral mainly Echiflopora

Rock wilh algae

Sand

..... - SOm - SOm

• THE CRAB REEF

Rock. rubble and algae 2" hard coral Rubble, dead coraJ and algae Om 50(1 coral, sand, rubble and 10" hard coral J .J

1 i Sand and rubble .J

Sand

.... SOm .. ... 52

Site 3 - Chale Island

Here the reef edge is comprised of algae covered rock, the upper reef was found to have 50% of algal and 30% soft coral cover with 20% hard corals mainly Platygyra. Favia. Acropora. Astreopora and some Cyloseris. The lower slope had 60% algal cover, 10% soft coral and 10% hard corals, including large colonies of Lobophyllia. Echinopora. Porites and Acropora. At the bottom of the slope there was a 90% algal cover with rubble and sand plus a few gorgonians. Below 25m the substrate was sand.

Site 4 - Mwachema

This reef has a complex structure, the reef rises from a 25m deep channel to form a leeward reef. Large tabular and plate-like Acropora colonies have developed here, Astreopora Porites. Favites and Echinopora are all found in large colonies producing 20% cover. A large quantity of algae was observed on the rock and rubble substratum and some sea grass was also found here. The reef descends into another shallower channel ".to rl.se to the wl.ndward reef, here--5"%-covel was of small colonies of Acropora and Pocillopora with 75% soft coral cover on the upper reef slope. The lower slope consisted of 50% rubble, 29% rock 20% algae and 1% hard coral. Gorgonians were observed at approximately 30m depth, below this the substrate was sand.

Site 7 - Neptune

This has a gently sloping outer reef with an algae cove~ed rock reef edge. The upper reef slope has 65% algae, 15% soft coral cover and small amounts of bare rock and sand. Up to 10% hard coral is present on the upper reef slope, mainly Acropora. Astreopora and Porites. The lower slope was mainly bare or algae covered rock with 3% hard coral, Echinopora was the predominant genera found. Below 25m in depth only sand was observed.

Site 9 - The Crab

The reef edge had 50% algal and only 1% hard coral cover. The upper slope consisted mainly of rock, rubble and dead coral. On the lower reef slope 10% hard coral cover was found amongst sand and rock substratum. Below this only sand was observed.

3.3.2 Substratum Cover

The average percentage cover of the different reef substrates are shown in Table 3B. During each horizontal transect twenty five 1m 2 quadrates were assessed for their substratum cov~r, these results were then combined to give an average percentage cover for each horizontal transect. The substrates are classified as hard coral, soft coral, algae (macroalgae), rubble rock, (recently) dead coral and sand. GALU LAGOON (REEF FL1T) PROFILES

....~ . 4m

KINODO ~ ..' : . : "'1.' -......

CHA~E ISLAND m T.ciliaJum t H. univtrviJ T.htmprichii ~ (""\ Hard Coral 1""'\ (Massive)

~ (Branching) c::? Algae 8m Rock ~ 100m Sand

, ; t.._,--,~ .... L ~.,,--'"._...... "'._..,--",. .. _I.. ,-it! l= 53

Scleractinian corals were found to have maximum average cover on Chale Island reef of 13·6% and Neptune reef had the smallest with 2·3% cover. The soft corals seemed to dominate the substrate cover on most reefs in a matting form competing for space with the hard corals.

A large amount of macroalgae was found growing on rock and rubble both on the reef edge, the upper and lower reef slopes. The algae included filamentous and calcareous algae both encrusting and upright such as Halimeda were common. Red, brown and green macroalgae were all present in varying degrees.

Rubble was observed mainly in the deeper parts of the lower reef slope with some uncolonised bare rock being present on all the reefs. Very little recently dead coral was found, though old stands of coral, now algae covered could be found at the base of the reef slope having been broken off from higher up the slope. Some sand was found in the upper reef though this was only in small amounts, whilst below 25m rubble and sand were predominant.

3.4 LAGOON PROFILES

Diani's fringing reefs are separated from land by a lagoon. Th~se lagoons are generally up to lKrn wide and less then 10m deep. The lagoon is a quiet and sheltered area protected from wave damage by the outer reef. The lagoon is used extensively by the local population for octopus hunting, fish trapping and shell collecting it is also used intensively by tourists for recreation purposes.

3.4.1 Site Description

Site 1 - Galu

Here the lagoon gently slopes down to 3m, before rising to the reef crest. Three species of seagrass were observed as seen on the profile opposite, H.univervis and T.ciliatum shared the majority of cover. Porites, Favia and Acropora were observed in the deeper section of the lagoon.

Site 2 Kinodo

Close to the shore the seagrass cover was 50:50 T.ciliatum and H.univervis. Nearer the reef T.ciliatum became dominant. Some massive Porites colonised were noted in the mid section of the lagoon and rubble was observed just behind the reef crest.

Site 3 - Chale Island

The transect was situated south of the island and was observed to have a deeper profile and more variable topography. The transect was from a large sand bank adjacent to the mainland shore. Algae was the dominant cover close to the sand bank, with approximately 20% T.ciliatum cover present. Ridges in LAGOON (REEF FLAT) PR~FILES MWACHEMA

.' ~ -.' .'.

4m .

NEPTUNE

... " .-...

THE CRAB KEY

T.clliatum

~ H.univt",is T.htmprichii • Hard Coral A (Massive) (Branching) ~ c;r Algae Rock

4m , ~ . , Sand 1'r\,r\,m -- L ...<._--- ,-_.1 I . Ii 54

a north and south direction were noted and T.ciliatum was observed growing on the top of these sandy ridges. A few hard c6rals were found growing on the slope of the 8m deep channel though again the substratum was dominated by sand and T.ciliatum. The lagoon becomes shallower to 4m in depth before sloping to the outer reef.

Site 4 - Mwachema

The lagoon here slopes gradually down to a 25m deep channel. Seagrass, sand and rock are present with T.ciliatum being the most common seagrass species.

Site 7 - Neptune

This has a typical lagoonal profile with seagrasses observed near the shore leading to small patch reefs with Acropora. Porites. Pocillopora, Galaxea. Platygyra and Astreopora colonisation. Seagrass cover was greater nearer the outer reef with algae present on rubble and rock behind the reef crest.

Site 9 - The Crab

This site was surveyed as it is an area of great activity a II d so bj e c::-r-----rcy i Iii pac t sat low tid e due tot0 Ulist s V±S±rt-+i'1'nMg:J------ the more accessible parts of the reef for boating, snorkelling and windsurfing. Both T.ciliatum and H.univervis are found growing near the ~hore, although not on the raised bank of reef rock shown on the profile which is exposed at low tide. The lagoon deepens again and hard corals were recorded in isolated patches. Porites. Galaxea. Platygyra and Acropora colonies were all observed, a number of which showed minor damage caused by boat keels or propellers at low tide. Below the reef crest rubble, dead coral and sand was observed. 55

4. DISCUSSION

The fringing reef at Diani represents the extreme of exposure to wave action, being part of a straight reef 20Km long directly facing the ocean. The main coral genera found on the reefs were Acropora. Porites and Pocillopora which agrees with those listed in the IUCN report, Coral Reefs of the World (Wells 1988) for Kenya. Hamilton and Brakel (1984) found exposed reefs off the East African coast to have acroporid and pocilloporid fauna on the upper slope with massive and branching Porites on the lower slope. The Diani fringing reef has a similar zonation except that small colonies of helmet-shaped Porites were commonly found on the upper reef slope, a high energy area. However, large sized colonies were present but only observed in the more sheltered waters of the lower slope or on leeward reefs. All the hard corals in the upper reef slope were small colonies, the small size is probably due to the severe conditions encountered on the upper slope during the monsoon season.

The soft corals were found to dominate the reef cover, pr~bably due to its ability to grow and regenerate relatively fast in comparison to hard corals, a great benefit in a high energy destructive zone. The extensive collection of gastropods (some of which feed on soft corals) for the tourist trade may also be an important factor in the large presence of soft corals. Algae was also present in large amounts on the reef rock, possibly due to overfishing of grazers.

The outer reef profiles of Galu, Kinodo, Neptune and the Crab are broadly similar. Chale Island reef has a similar gentle sloping reef but appears to sustain the largest amount and variety of hard corals in the survey. Mwachema was observed to support large coral colonies on the leeward reef due to its protection from strong wave action by the presence of the outer reef. The leeward reef was the most productive area due to this shelter and the strong currents also present.

Quite a wide variety of hard coral genera were also observed colonising the lagoon. In areas of frequent boat movement, mainly at breaks in the reef, hard corals were found to be quite heavily impacted showing signs of propeller damage especially in the area around Galu.

The substratum cover in the lagoon is dominated principally by seagrasses which appear to be sustaining growth well. The data from lagoon survey may not have encompassed all the possible species of seagrass present in the lagoon due to the large size of the area covered and the limited time available. •

j •

CORAL INDEX •

CORAL INDEX

The following figure (5.1) shows the Coral Index value derived from the completed Reefwatch forms.

Coral Index

hard/soft coral cover score (1-5) hard/soft coral variety/diversity score (1-5)

Where 1 reflects the highest/best grade and 5 the lowest/worst grade. Thus the score for each site can vary from a minimum of 2 to a maximum of 10.' See the Reefwatch form (section 2) for the basis of these values.

The Coral Index is listed in order of decreasing grade (Increasing Coral Index number). • 3 - 5 HIGH GRADE • 6 7 • 8 - 9 • 9 - 10 LOW GRADE

1 J

I ~ ,I .~J

. I ,I I

..,JI

1 I I ,J ..

1 J CORAL INDEX FIG. 5.1

Mwachema River

Diani

Chale Island o 1 2 KM . }J. I I • REEF QUALITY INDEX j

I• I

'" REEF QUALITY INDEX

The. following figure shows the Reef Quality Index values derived from completed Reefwatch forms.

Reef Quality Index

reef typical score (1-5) attractiveness score (1-5) dive site rating score (1-5) hard/soft coral cover score (1-5) hard/soft coral variety/diversity score (1-5) reef fish numbers score (1-5) reef fish variety score (1-5) ~ pelagic fish numbers score (1-5)

Where _1 reflects the highest best grade and 5 the lowest/worst grade. Thus the score for each site can vary from a minimum of 8 to a maximum of 40. See the Reefwatch form (section 2) for the basis of these values.

l'heReef ~uality Index is listed in order of deereasins g-r-r1'l8cf1d'-f'e!------ (increasing Reef Quality Index number) •

• 10 - 15 HIGH GRADE 16 - 20

21 - 25 • ..j 26 - 30 J • 31 - 35 LOW GRADE REEF QUALITY INDEX FIG. 5.2

Mwachema River

Diani

Chale Island

o 1 2 ICH' I I' REEF QUALITY SCORES AND IMPACTS RATINGS FOR ALL SITES

REF. LOCATION REEF INDEX IMPACTS IMPACTS QUALITY SCORE 1 Galu Village 29 Poor 22 Some

1 ... I., • ~ ., ...... , ,., ..,'" ,.., I.. .., ..,~ ...... ~o- ""-.:L ... -..,~ - ,J 3 Chale Island Site 1 23 Good 21 Some .. 4 Mwechema River 25 Good 23 Severe .

5 Leopard~Beach Hotel 29 Poor 19 Some 1 I j 6 Trade WindsH~~:lh 32 V.Poor 19 Some 7 Neptune Hotel 27 Poor 18 Some -1 8 Chale Island South 23 Good 21 Some Site 2 9 The Crab 28 Poor 25 Severe J -,J

.. 1 J, ..1 I .J

1 j

JI 56

BIBLIOGRAPHY

Hamilton H.G.H and Brakel W.H (1984) Structure and coral fauna of ~ast African Reefs. Bulletin of Marine Science, 34(2) 248 26~. - Samoilys M (1988) A survey of the coral reef fish communities on the Kenyan coast. Technical report prepared for the Ministry of Tourism and Wildlife, WWF Project 3797.

Samoilys M (1991) Swara East African Wildlife Soc. Vol 14(4) 15.

Talbot F.R. (1965) A description of the coral structure of Tutia Reef (Tanganyika Territory, East Africa) and its fish fauna. Proceedings of the Zoological Society of London. 145 431-470.

Veron JEN (1986) Corals of Australia and the Indo-Pacific.

Wells S.M. (1988) Coral Reefs of the World prepared by IUCN 153-157. 57

SECTION 6

F ISH E S 58

FISHES

1. INTRODUCTION

Of all the marine life forms represented in our survey area fish are the group that are of greatest direct significance to man. Many species are edible and commercially important as a major component of man's diet, and underwater, fish are the most obvious life form of interest to recreational divers.

2. THE DIANI FISHERY

The fishery in the waters surrounding Diani is, although small by international standards, an important segment of the Kenyan fishery as a whole. The annual catch of demersal species has been estimated at the 1991/92 season levels to have produced 343,486 kilos of scale fish. This low figure possibly relates to the typically low productivity of shallow tropical ocean areas where the formation of a permanent thermocline prevents the mixing of surface and deeper water. This prevents supply from deeper water to the illuminated surface zone of nutrients (nitrates and phosphates) essential for photosynthetic activity. Other studies (Norad - Kenya Seminar 1984) appear to confirm that this situation applies along the East African coast and as a result there are no indications of any remarkably pelagic resources such as sardine and tuna irisurioundirig deeper wafer. It follows therefore that the resources from which efforts should best be aimed are those associated with the coral reef and with shallow water lagoon areas, namely demersal and semi-pelagic scale fish, the spiny lobster and edible shellfish.

The catch of demersal and semi-pelagic species although never likely to be large is nevertheless of considerable national importance contributing significantly to the country's economy. Optimum success is inhibited to a large extent however, because of logistics. Commercial netting of fish is not possible due to a lack of sizeable fish aggregations and the rough sea bed topography. The fishery is therefore based mainly upon traditional fishing methods, predominantly handlines and traps, employed by artisanal and subsistence fishermen. Commercial fishermen are not attracted to these methods due to the relative lack of rewards taking account of the effort required and that the catch is very low priced.

A detailed review of the Diani Fishery is beyond the scope of this report and the intention has been to compliment rather than duplicate the work of the Fisheries Department. The economy of the Diani area is, however, largely dependent on tourism which shares the resources used by the fishery for recreational tourist pursuits. Essential components of any future management of the marine resources must therefore include finding means of maintaining the natural environment of the coast on a sustainable basis both for fisheries and tourism and avoidance, where possible, of any conflicts in the use of these resources. We have therefore attempted to investigate and record any obvious signs of environmental degradation or pollution 59

that could have a detrimental effect on commercial fishing and to recommend means of managing the resource on a sustainable basis for optimum long-term use of both fishery and tourism.

As the main emphasis at Diani is more towards using coastal shallow water areas for leisure and recreational sports including snorkell~ng and diving where the variety of species and clarity of water will be more important than high productivity. The commercial prospects of further development in tourism and recreation in the study area is likely to be substantial and it is with this in mind that a number of the key fish species were chosen for study that are not of commercial food value.

3. ROLE OF THE FISH IN THE ECOSYSTEM

In addition to the direct importance of fish commercially for food and sport there is a further essential role played by fish in the ecology of most sublittoral habitats. Smaller species feature in the organisation of food chains leading to the larger commercial fish and most species which man eats are predators and feed on smaller fish species (see Hiatt and S t r a s b U 1" 8 , 1960 j RaDd a ] ]. 196 Zi . HQ . 1974 • In sea r ass ~nd soft bottom communities fish are principally grazers and predators and transform such areas into highly productive habitats. Fish also play an important role in maintaining 1 the typical balance of many sublittoral habitats particularly j the coral reef community influencing the coral assemblage and reef building process both directly and indirectly. (See Randall, 1974j Ogden and Lobell, 1978j Sammarco, 1980j Wellington, 1982). Herbivorous species are the major grazers of macroalgae and algal lawn and may influence the survival and growth of corals in that intensive grazing can inhibit the ~ settlement of new coral growths and damage adult corals whilst J increased algal growth, such as might follow a reduction in herbivore grazing pressure, can reduce coral cover and reef structural complexity due to overgrowth and smothering of the live coral (Sammarco, 1980j Crossland, 1981). 1

The structural complexity of the reef is in turn mainly 1 responsible for the maintenance of high fish di~ersity (see _J Risk, 1972j Glazin, 1981). Without the shelter provided by the reef in the form of retreats that allow fish to escape from predators the population levels of many smaller species would be reduced to extinction, and a decrease in the types of shelter J provided will lead to a decrease in diversity of the fish community (Goldman and Talbot, 1976). It is often necessary 1 therefore when planning in terms of conservation of the diversity J of species to also consider the maintaining of necessary reef habitats.

.. }I

4. EAST AFRICAN FISH SPECIES or The fish species representative of the shallow water habitats 1 of the East African coast have been studied quite· intensively ...J over the past 20 years (Allan/Bock/Samoilys) the first major i study occurring as early as 1972. I I I .1 60

In more recent times perhaps the most important contributions have been made by Ken Bock with his book "A Guide to Common Reef Fishes of the Western Indian Ocean", published first in 1978 and Melita Samoilys report "A Survey of the Coral Reef Fish Communities on the Kenyan Coast" (1988).

The purpose of our survey was not to compile a list of all the fish species observed in the waters of the Diani area as it would not of course have been practical to devote sufficient resources and time to adequately research and record such information. Observations did indicate however that fish species diversity was equal to the best recorded in other parts of the Indian Ocean and that there are opportunities afforded to view some of the most spectacular of the Western Indian Ocean species.

5. SURVEY METHODS, TYPES OF QUANTITATIVE OBSERVATIONS

The principal objectives of our fish surveys were to record information regarding abundance and distribution of fish species in shallow water (15m) reef environments and the means we used were as follows:

(1) To establish a quantitative characterisation of the f1sh community present on the reefs of the survey area.

(2) To assess the zoogeographic distribution within the survey area of selected species and record the associated changes in the fish assemblage.

(3) To indicate the extent of differences in species diversity and abundance between different sites.

Such data serves to assist in developing a strategy for conservation of different sectors of the coast in identifying candidate sites for protected areas and in providing exact information to allow a better understanding of ecological interactions that may be of importance in maintaining the reef ecosystem. In addition the data, especially that collected at Detailed Study Sites, is of importance in providing base line information in order that these sites may be used to monitor conditions along different parts of the coast on a further ~ continuous basis.

As it was not possible to estimate populations of all fish species at all sites visited, for most purposes survey work was restricted to three important fish groups:

(1) Chaetodonditae, (all species recorded) and Pomacanthidae, used for a comparison of diversity between the two sites and as an indicator of coral health (Reese, 1981). Zanclus canescens (family Zanclidae) was included to avoid confusion with Heniochus butterflyfish. 61

(2) Triggerfish, large Wrasse and Pufferfish, the large invertebrate predators.

(3) Emperors, Snappers and Groupers, the dominant commercial species.

The species were chosen to be easily identified by inexperienced divers and compatible with previous work by Samoilys (1988) on the Kenya coast, and Gaudian, Medley and Ormond (in press) on an artisanal fishery at Zanzibar, Tanzania. A brief description of the fish, their diet and distribution is given below. In the case of the snapper most common at Diani, it was not possible to accurately distinguish between L.ehrenbergi and L.fulviflamma due to the large numbers present, although L.fulviflamma appeared to be the most dominant. It was finally decided that these two species should be grouped together.

The species within these groups represent well over half of the common shallow water species of the East African Coast. These families were selected both on ecological grounds, to include the species most important in the transfer of energy

The addition as noted by Brock (1982) visual census techniques are most accurate when restricted to diurnally-active non-cryptic species and the fish in the above families meet such criteria. Some of the fish species or families are also useful in monitoring reef communities. Reese (1977, 1981) has suggested that certain species of butterflyfish (Chaetodontidae) which are obligatory coral feeders might be useful as indicators of the abundance of their food (i.e. coral) and similarly angel fish (Pomacanthidae) are principally sponge feeders. J Estimates of population of species within the selected families followed the strategy outlines in the methods (section - j i (1» of assessing the distribution of species in the study area .~ by using at different sites at two levels of intensity. (i) At each of the five Detailed Study Sites, two . ) transect lines 250m in length were laid, one at approximately 5m depth and the other, parallel to the first, at 10m, or the base of the coral if that was_ 1 shallower. The team of ten divers swam in pairs at .J a constant speed (10m per minute) along the transect lines, and surveyed fish within 5m either side of the line. Care was taken to stagger the counts so"as to minimise disturbance of the fish. All counts were J undertaken between 08.30am and 14.00pm, because sea conditions deteriorated in the afternoon. This should also have avoided any diurnal change over of species (Teodulo et al 1988). , i I 62

(ii) At the remaining three Reefwatch sites data was recorded on a semi quantitative basis using timed counts over a 25 minute period at each site. Pairs of divers finned in a set direction at 10m then returned at 5m recording fish in the same format as for detailed study sites.

(iii) Counts were recorded on waterproof forms (examples in appendix 1). For the commercial species, size was estimated, using the following categories (cm):

20 20-29 30-49 50-74 75-99 100-130 130

Divers specialised in one or two groups of fish to reduce variability in the data. Details of the census technique differed for different species groups. Divers counting cryptic species actively looked for them under overhangs etc, whereas divers counting snappers and emperors looked further ahead along the transect. For each species group a minimum of three counts were usually obtained at each intensive survey site.

A potential source of error was mis-identification. A number of the divers were not familiar with the fishes of the region,and there was little timQ fortraining.--- In the analysis, data that was known to be unreliable or non standard (for example where the diver had been concentrating on training another diver, or had had to cut short a dive) were excluded.

(iv) The census sites, both Detailed and Reefwatch, were not always ideally placed in terms of experimental design, as they were unavoidably constrained by the need to collect other information for the expedition as a whole. Reefwatch sites outside the Detailed Study area were intended as controls, however, only three sites were surveyed due to time copstraints.

The results of these studies will be discussed on a family by family basis combined with a brief summary of the biology of each family. The actual data is presented as a series of maps showing estimated population numbers and distribution by location. Where times counts have been made we give mean values for each station or site, expressed as a value index based upon a superabundant, abundant, numerous, limited or absent classification. Actual numbers appertaining to each classification vary dependent upon family and species and details of individual family base data are included within the family by family section.

5.1. BRIEF DESCRIPTION OF THE ECOLOGY AND DISTRIBUTION OF FISH FAMILIES COUNTED .. BUTTERFLYFISH There are about 113 species of butterflyfish globally, with 63

approximately 65 species in the Indian Ocean from 8 genera, 48 of these species being Chaetodons. Butterflyfish have a maximum length usually less than 25cm, and are characterised by a compressed body with stout dorsal and anal spines. They usually .inhabit depths of 10 to 10m and occupy a home range. C.trifascialis is known to be particularly territorial. Butterflyfish often form male/female pairs that may be permanent. They are generally diurnal, and their diet may include hard and soft coral. For this reason they have been suggested as a possible indicator species of reef health (Reese 1981). Other prey items are benthic invertebrates and occasionally zooplankton, for example in the diet of Chaetodon kleinii, and Hemitaurichthys zoster, the latter of which sometimes feeds upon zooplankton in large schools. A list of coral feeding butterflyfish found in the Shimoni area (taken from Samoilys 1988) is given below:

Chaetodon falcula Chaetodon lineolatus Chaetodon melannotus Chaetodon meyeri Chaetodon trifascialis Chaetodon tr:l.fasC::iatus j Chaetodon vagabondus

Randall includes: • Chaetodon auriga Chaetodon bennetti Chaetodon unimaculatus

MOORISH IDOL

In a family of its own (Zanclidae) but closely related to 1 the surgeon fish (Acanthuridae), the Moorish Idol, Zanclus cornutus, is an omnivore found in the Indian Ocean, Indo Pacific and the Eastern Pacific. J

ANGEL FISH A ! Angel fish are from the family Pomacanthidae, closely related J to the butterflyfish. They differ in having a stout backward projecting spine on the lower edge of the cheek. This is the preopercular bone. There are 31 species in the Indian Ocean, in 6 genera. Most species live in water shallower than 30 metres, and in many species the juveniles differ significantly in morphology from the adults. Angel fish are generally diurnal. Pomacanthus, Holocanthus and Pygoplites feed mainly on sponges as adults. Centropye graze algae and detritus.

TRIGGER FISH , Trigger fish are in the order Tetraodontiformes and the family Balistidae closely related to the file fish, Monacanthidae. .. 1 There are about 20 species of trigger fish and 39 of file fish in the Indian Ocean.

""",I 64

Trigger fish have relatively deep compressed bodies and long snouts, small mouths and few teeth; their eyes are set high on their heads. Their demersal eggs are guarded by the male. They have two dorsal fins, the first of which can be locked into an upright position with the small secondary spine. It is this that has given them their name. They swim by undulating the second dorsal and anal fins, using their tails only when they need to move fast. They sleep in holes at night and often hide in them by day when disturbed. They are generally solitary, but Odanus may form aggregations.

Most are less than 30cm in length, but Pseudobalistes may reach 60cm, B.viridescens has been reported to 75cm, and O.niger can be up to 50cm. Trigger fish are usually carnivorous, feeding on urchins, starfish, crabs, shrimps and molluscs. B.undulatus eats the tips of Acropora coral and benthic algae (often red corraline algae). O.niger feeds mainly on zooplankton and S.bursa is an omnivore, feeding on a wide diversity of small benthic invertebrates.

PUFFERS

PuffelsuhavelloupeivicfiIlS and no spiny fin rays. They can inflate their bodies to several times their normal size when disturbed. They are fairly slow moving, and 'row' themselves through the water with their pectoral fins. Puffer .. fish can contain the toxin tetrodontoxin, especially in the ovaries and liver, and are therefore not a commercial important species. They are omnivores, feeding upon algae, crustacea, polychaetes, sponges, hard and soft corals, tunicates, starfishes, sea urchins and hard shelled molluscs. There are about 40 species of puffer fish in the Indian Ocean, only about half of which are found on reefs. Most reef puffers belong to the Arothron or Canthigaster genera. Included under the general name of puffers are porcupine fish, Diodontidae, of which there are approximately 10 species in the Indian Ocean, characterised by a covering of hard spines over most of the body. They are nocturnal, feeding on invertebrates.

GROUPERS

Groupers are in the order Perciformes, and the family Serranidae. They are a large family of carnivores, taking fish and crustaceans. Groupers are often important commercial species. In the Indian Ocean there are approximately 130 140 species in more than 30 genera. There are about 45·- 50 Epinephelus species, 12 - 15 Cephalopholis and 3 Plectropoma.

Most are benthic predators, and many have the ability to change colour rapidly to match their background. Some have distinct colour phases. 65

EMPERORS

Emperors aTe in the family Lethrinidae. There are 15 - 20 species of emperor in the Indian Ocean, generally preferring open sandy areas to the reef, although Monotaxis grandoculis is usually found on the reef. These fish feed mainly at night, eating molluscs, urchins and hard shelled invertebrates. They are sought after as a commercial species.

SNAPPERS

About 42 species of snapper inhabit the Indian Ocean, 25 of which are from the genus Lutjanus, and are abundant on reefs. Snappers often shoal during the day, and break up to hunt during the night. All are carnivorous, and most are bottom dwelling. Their diet includes crustaceans and small fish, and are themselves an important food species, often caught with handlines. L.ehrenbergii, L.argentimaculatus, and L.fulvus ~re known to live 1n mangrove stands as Juven11es.

6. OBSERVATIONS AND RESULTS

6.1 Introduction

The following sections outline the work undertaken by the divers concerned with the fish counts. The aims were to identify target fish species and in certain cases estimate their size. 1

6.2 Study area. Outer reef sites 1 Fish counts were undertaken at all of the 8 sites surveyed, at 5 of which on a detailed quantitative • 1\ basis, these were:- j

1) Mwachema River • 1 2) Galu Reef 3) Neptune l 4) Kinondo 5) Chale Island North

The remaining 3 sites were classed as control sites, these were:

1) Leopard beach 2) Tradewinds 3) Chale Island South

j 68

Butterflyfish were chosen as a target species for this survey because they act as an indicator of coral health and whilst the numbers present on this site compare favourably with those on the other survey sites, their diversity is lower. Diversity and numbers . wera greatest on the shallow survey site due to the higher coral cover.

Angelfish, species, diversity and numbers were surprisingly low. Pomacanthus semicirculatus was the most common species observed.

The Mwechema site in terms of suitability as a habitat for reef fish species appears to be ideal. It is a shallow reef area with a 30° slope into deeper water (26m). The upper reef is a mixed terrain of soft and hard coral, with soft coral species predominant. There are also areas of extensive algal growth, present as a thick lawn l'Scm in length. This form of habitat is sited predominantly on the top of the reef in approx. S mts. The reef was classed, using Reefwatch study parameters, as a typical reef for the area and assessed as moderately attractive for diving tourism.

The Mwechema reef is used regularly as a tourist dive site, although not to the same extent as other tourist sites surveyed. It would relieve pressure on other tourist diving areas if this psx ticalsx sitecualdbe Inure·· utilised. Coral 'Variety was moderate to good with between 10-20+ genera represented. Fish numbers were numerous, although in places, over algal rock, were conspicuous by their absence. This consequently gave the site a lower rating than it possibly deserved. The variety of fish was moderate with up to 40 species present and pelagic numbers although small in size, were assessed as numerous.

The upper reef area is rich in coral cover, however, along the reef base the walls dropped away to reveal a sparse cover on a sandy, silt covered, sea bed. At the northern head of the survey site, a deep water channel runs parallel, allowing clean oceanic water to flow close to the reef. Consequently, this area is rich in fish diversity and the numbers of fish abundant and of a larger size than observed on other parts of the reef. Large shoals of both herbivores and predator fish were recorded.

This reef is also used intensively by local fishermen and considerable numbers of fishing boats were observed including the large "Pemba" style craft. The absence of any large aggregations of commercial species or large specimens on the upper reefs supports conclusions drawn from the survey that this area is seriously over-fished. The shallow upper reef area is fished by line, net and trap and is also accessible to spear fishermen who were observed on a number of occasions in the water or outside the reef waiting for tourist divers and the survey team to leave the'area.

Large coral heads were found lying overturned along the deeper slopes which would indicate the large scale use of nets over this reef. The size of many of these broken coral heads was greater than could result from diver damage and would seem to be due to the action of a snagged net. 69 Galu

The Lutjanids observed on this site were found in small compact aggregations scattered across the reef. Only one large aggregation was observed and this was on the deep survey. The size ranges on both the shallow and deep transects covered only the lower size classes, indicating that there are no more than 3 year classes present. As would be normally expected there is a decrease in numbers as the size class increases and breeding size specimens form only a small proportion of the total recorded. This progressive reduction with increase in size is not abnormal and is a direct result of natural mortality and fishing effort. However, the numbers in the upper size range are very low and this can be linked directly to over-fishing. Lutianus kasmira was observed as the dominant Lutjanid species on the reef.

Larger numbers of Emperors were observed on the shallow survey, but as with the Lutjanids, whilst the smaller size classes are all present there is a marked decrease and lack of abundance at the top of the size range. The site is intensively fished and consequently as with the Lutjanids fishing "effort must be lfnkedwith decrease in Ilumbersof the upper size classes. No specific species was noted as dominant across the reef.

There is an almost total absence of grouper on the upper reef area. During the shallow reef survey only 3 (20cm specimens were observed. The deeper survey showed an improvement where 21 specimens in total were recorded. 2 specimens were noted to be in the SO-7Scm size range and the remainder were much smaller, 11 of (20cm in length.

As with the other commercially important species on the reef, 1 over-fishing is believed to be responsible for such low grouper numbers, either directly by over-intensive fishing of members of this family group or indirectly by the removal of the smaller fish on which they prey. However, there is no clear evidence to support an indirect cause in this case and lack of abundance is more likely to be due to direct fishing pressure.

The numbers of triggerfish on the reef were also low. The greatest abundance and diversity was recorded on the deep survey, coinciding with the distribution of target prey invertebrate populations, which were concentrated around the base of the reef.

No large wrasse were observed on the shallow survey, however, 2 Chelinus indulatus (Humphead wrasse) were recorded on the deeper transect. i J Abundance levels of large pufferfish were poor on this site, and only one member of the species (Arothron stellatus) was recorded on the shallow survey. Distribution was. better on the deep survey where four specimens of three different species, Arothron hispidus (1) A.stellatus (2) and A.citrinellus (1) were recorded. 70

The abundance of Butterflyfish by comparison to other detail study sites was moderately poor, however, the diversity showed an increase over the control Reefwatch sites.

It is possible that the butterflyfish numbers recorded on this site are lower than those actually present. This would be due to the popularity of the reef for diving tourism. On all occasions, whilst the surveys were being carried out, non survey divers had been or were in the vicinity. This could easily deter timid species such as butterflyfishes, forcing them away, temporarily, from the survey area.

~ The Angelfish numbers recorded were low but not lacking in diversity. Members of four species were observed with only Pygoplytes diacanthus recorded as absent.

The reef at Galu offers a good variety of habitats likely to encourage large reef fish populations. Located on the seaward side of the fringing reef, the upper reef area reaches within 8 meters approximately of the surface. The reef slope terminates at 16 meters changing to a matrix of algal rock on a sandy, silty bottom with sparse patches of broken coral rock, and very little live coral cover. The reef slope is comprised mainly of hard and soft coral, with over 50% of the cover confined

to soft cOIalspecies. n ealal divelsity -ismadelatewith species of between 10-20 genera represented whilst towards the reef crest and shoreline the coral gives way to an extensive thick lawn of algae, l·Scm long. This is a typical reef profile for the Diani fringing reef and the site is rated as moderately attractive for diving tourism purposes on Reefwatch assessment.

The abundance of fish within the family groups surveyed was not high and Quite limited in certain areas, especially along the deeper edges of the reef adjacent to algal rock. Fish diversity was also somewhat limited with only between 15-29 species recorded. Numbers and diversity of pelagic species similarly were poor and overall the site attained a poor rating.

This reef is noticeably impacted both from the intense fishing effort in the area and high tourist diving activity. Tourist diving is particularly popular at this location with up to 100 divers visiting each day. There was clear evidence of diver impacts such as broken and overturned coral heads especially close to tourist diver buoy anchorage points. The main reason for the popularity of this site is undoubtedly the convenience of close proximity to the major tourist diving schools of the large hotels.

The lack of large individual fish numbers in the. commercially important species groups and the low abundance of these species also indicates that the intense fishing pressure is also particularly damaging. Fortunately there was no evidence of the use of inappropriate fishing methods such as spearfishing taking place. However, due to the depth of the site, any spearfishing would naturally be confined to the upper shallow region of the reef. 71

Neptune

Lutjanus fuluiflamma and Lutjanus kasmira are the dominant Lutjanid species on this site. On both the shallow and deep surveys they_ overwhelmingly outnumbered other members of the genus. Abundance was greatest on the deeper survey transect as would be expected as Lutjanids are predominantly nocturnal feeders which congregate in deeper water during daylight hours. A noticeable feature was that all fish observed were of a small size, (20cm, and it appears that only one age class is • represented on this site.

As with the Lutjanid species, the Lethrinids were predominantly of a small size range and the greatest numbers were found on the deep transect. However, no substantial numbers of any specific year class were observed. The Big Eye (Monotaxis grandoculis) was noted as being the dominant species.

Very low numbers of Groupers were recorded, the majority of which on both transects (deep and shallow) appeared to be of a small size, (20cm, although a few specimens of up to sOcm in ~Qn8th wers 9bsSFV&doathe deepeTtrsnseet.

Triggerfish numbers compared favourably with those recorded for other detailed study sites and were deemed to be low. The Blue Throated Triggerfish (Sufflamen chrysopterus) was the dominant species on both the shallow and deep surveys.

Pufferfish abundance and diversity was also low and at similar levels for both shallow and deep surveys. J No large Chelinus species were observed. 1 The most dominant species of butterflyfish on this site were Chaetoden kleinii, C.madagascariensis and C.guttatissimus. Zanclus canescens was also observed in large numbers. A small number of individuals of other species were also noted. This J site, in comparison to other intensive sites, has an abundance of Angelfish, with Pomacanthus imperator and Pomacanthus semicirculatus dominant.

The greatest abundance of both angelfishes and butterflyfishes was recorded on the deeper survey transect. .1

This site has reasonably good coral cover, approximately 50% soft coral with a low proportion of hard coral species. There are approximately 10-20 genera of hard coral represented J and the Reefwatch rating for the site is moderately attractive. There is little evidence of broken and dead coral and an extensive thick lawn of algae grows to more than l·scm in length J on the algal rock in the shallow sections of the reef. 1 The reef fish numbers were rated as numerous, although the j numbers of pelagic species were very limited. Reef fish diversity was moderately good with between 30-44 species observed. _. J I 72

Whilst the site is not subject to diver impacts, the effects of fishing are considerable. Fish traps (malema, uzio) were numerous on this site. The lack of year classes and the observed low numbers of commercial species indicates an intensive fishing effort in this area. This site is close to the Galu detailed study site and diving tourists area and if correctly managed could act admirably as an alternative diving tourism location relieving the mass diver impact pressure on Galu.

Kinondo

Large numbers of both Lutjanus fulviflamma and Lutjanus ¥ kasmira were observed in dense aggregations on both the shallow and deep surveys. falling mainly into the 20cm class, there were also, however, large aggregations of larger sized fish. This was the only site surveyed with a number of reasonably strong year classes represented.

A similar pattern is confirmed with the Lethrinids. There is a high abundance in upper size class and also intermediate and small size ranges represented. The Big Eye (Monotaxis grandoculis) was the dominant Lethrinid species on this reef.

Relatively high numbers and good diversity of grouper species ---;wHe'""'I'p.·p>e-a-}--s.o--ohser,ed on this site, with specimens of all size classes present. The greatest abundance was, however, within the smaller size classes. The number of larger specimens represented, nevertheless indicates that the fishing pressure is not as great at this site as is found on the surrounding reefs.

Cephalopholis argus is without doubt the dominant species, though Epinephelus chlorostigma. Epinephelus fuscoguttatus and Variola louti were all evident in reasonable abundance.

The numbers of triggerfish were high by comparison to the other detailed study sites surveyed. On the shallow line, Sufflamen bursa. Sufflamen chrysopterus and Balistapus undulatus were the dominant species, whilst on the deeper survey Balistapus undulatus and Odonus niger were most evident. The large aggregations of Odonus niger which were observed on the deep survey, increased the numbers recorded dramatically and is the major difference in accounting abundance pattern between shallow and deep surveys.

All Key species of pufferfish were represented on this site, with the addition of Arothron citrinellus. Abundance was approximately 50% greater on the deeper transect by comparison with the shallow counts.

Small numbers of Chelinus undulatus were observed on this site, both along the shallow and deep lines.

From the data collected, it can be observed that this is an excellent reef for both the diversity and abundance of butterfly species. Almost all of the Key species of this group 73 are represented including two additional species i.e. Chaetodon leucopleura (Somali Butterflyfish) and Hemitaurichthys zoster (the Black Pyramid Butterflyfish). The deeper survey provided the greatest abundance and diversity of butterflyfishes, although only marginally so than the shallow census.

The numbers of Angelfish present were, surprisingly, only moderately higher than observed on other sites, possibly due to the lower algae cover, a principle part of their diet.

This reef has a very high level of coral cover, mainly soft ... coral species but also featured good diversity, (between 20 30 genera) and reasonable abundance of hard corals also. The reef achieved a high attractiveness rating in Reefwatch terms, and was considered to be rather better than the other reefs in the area. The algal growth was less abundant forming patches of extensive lawn, approximately lcm long.

The reef fish numbers were classed as abundant and pelagic species numerous. Reef fish variety was the greatest recorded with up to 50 species represented.

Whilst there is definitely some fishing on the reef and possibly a small amount of spearfishing, this is much less than recorded on other sites in the area. The amount of tourist diving on the other hand is considerable as this is a popular site with the dive boats sited along the Diani coastline. There is some evidence of broken and dead coral, although very small.

If the measures recommended later for managing this reef are enforced swiftly, within a short time scale, the populations of commercial species will increase and the site would act as a buffer zone replenishing the commercial fish stocks in adjacent fishing areas.

Chale Island (North)

Low numbers of Lutjanid species were recorded at this site and all were within the lower size range, 20cm. There appears . 1 to be only a single year class represented on this particular J reef. The dominant species observed were Lutjanus gibbus and

Lutjanus fulviflamma. ~ I As with the Lutianids, low numbers of Lethrinids were J observed, all under 20cm in length. Again, this confirms that only a single year class is present on this reef. No particular ] species was observed in great numbers. .1

A similar pattern applied with groupers as for the other Key commercial species and very low numbers were recorded and those that were observed were generally small, 20cm. There were a small number of specimens in the larger size classes, but well below normally anticipated levels for a reef of this ! class. The greatest numbers of specimens in the higher size J classes were found along the deeper survey line. Cephalopolis argus being the dominant species. J 74

Triggerfish diversity was not high but abundance was greater than recorded on other sites. There was no marked difference between the shallow and deep lines and Sufflamen bursa and Sufflamen chrysopterus were observed as the dominant species.

Pufferfish diversity and abundance were only average for the area, with the greater numbers present on the deeper transect.

Only one Chelinus species was observed and located on the deep survey.

The abundance and diversity of butterflyfish species were well above average for this area. Higher numbers were observed on the deeper transect, with Chaetodon kleinii and Chaetodon guttatissimus the dominant species. There were also large numbers of Zanclus canescens present on this reef.

Large numbers of Angelfish were also observed, mainly during the deeper survey, where Pomacanthus chrysurus was present in r~ater numbers than recorded at any other site. Pomacanthus semicirculatus andPomacant uS1mp~ra or wee species at this locatio~.

The site has a high coral cover mainly of soft coral species but with good representation also from hard coral species.

Hard coral diversity is good, with between 20-30 genera represented. The site is higher rated due to its attractiveness and classed as superior to other reefs found in the area.

There are extensive areas of thick algal growth which provide an ideal habitat for the numerous angelfishes found on the reef and must be a strong contributing factor towards their relative abundance.

The reef fish numbers present were rated as numerous, although the counts of pelagic fish were definitely limited. Reef fish diversity was reasonably good with up to 45 different species recorded as present.

The fishing pressure on this reef is considerable and whilst there was no evidence of fish traps (maleama, ozio), netting and handlining was commonly practised. The shallow upper reef areas are ideal for spearfishing and the hand removal of shells and this was observed during our surveys.

There is some evidence of dead and broken coral, although only slight. As the site is used only occasionally by dive boats from the major dive stations, this damage could be as a result of the damaging effects of fishing the area. 75

6.4.1 Discussion on the Detailed Survey Sites (outer reef)

The sites included in the detailed survey featured a wide variety of reef fish species and, for an inshore reef, including relatively high levels of abundance for other than genera containing commercial species where diversity and abundance was poor. It was noticeable, also, that at all sites the numbers of pelagic fish species were similarly low. As previously discussed the presence of a permanent thermocline in the shallow waters along the East African coast is a major cause of the relatively low productivity in terms of inshore fish populations but fishing pressure on these limited fish stocks including visiting pelagic species must, in the Diani area, also be a principal contributing factor.

Whilst the populations of non-commercial species exhibit a wide diversity, and a reasonable high abundance, commercial species are below levels which are likely to allow the fishery to remain sustainable. Abundance levels of commercial species are well below those, for example, of protected reefs such as the Kisite Marine National Park and the absence of numerous size ranges and therefore year classes indicates non-sustainable Eishing pressure QR all-Qf the sites surve)!ed withthepassih1e exception of the reefs at Kinondo. Even ~aking account of possible errors of sampling all counts of commercial species were low and a continuing trend of reducing numbers could very quickly remove many of these species permanently from the reef.

The five detailed study sites where our studies were undertaken could partly assist in reversing this trend. These are small areas but a very important part of the Diani reef system in terms of fish populations. If these sites, which are also critically important for diving tourism, were to be designated as Marine National Parks not only would they be safeguarded from the existing conflicts between fishery interests and tourism due to over-fishing but would also act as excellent buffer-zones and assist in replenishing fish stocks over the whole Diani reef system. J

6.4.2 The Diani Fishery .J

The D1ani fishery is a typical example of an artisanal fishery. From information obtained (Fisheries department, Diani ~--j sub-station Annual Report 1992) we find that in that year there were 341 men employed as fishermen using traditional fishing methods, predominantly handlines and traps (malema, uzio). There are a small number of fishermen using gill nets and set J nets and also in evidence were crews using seine nets. During the year of operation there were 162 boats in operation, exclusively of two types, non motorised dug-out canoes (dau) and outrigger canoes (ngalawa). In addition to the fishermen J using boats, there were also 118 men actively employed in fishing, working from the shore without boats. The methods of fishing used by these men are spears or local harpoons. J These fishermen fish solely in the lagoonal area, as do the J 76

majority of the boat fishermen. However, when the weather is suitable boat fishermen w1ll move out beyond the fringing reef and fish outer reef locations.

During the high tourist season, some fishermen abandon fishing and use their outrigger boats (ngalawa) to take tourists on cruises within the shallow water of the lagoon. These part time fishermen return to full time fishing during the tourist low season. From the division's own estimates there were 200 men employed in this fashion using 160 outrigger boats (ngalawa) in the 1992 season.

The Diani coastline between the Mwechema river and Chale Island supports 3 main fisheries divisions. These are Tiwi, Diani and Galu/Kinondo. The fish production for the whole of this area, January to December 1992, was assessed as 343,486 kgs. (Fisheries dept., Diani sub-station Annual Report 1992).

Along the "Diani" coast there are 23 hotels, which are sited directly on the beach front. During the tourist season other forms of fishing take place inshore as large numbers of foreign tourists attracted to this area engage in recreational sports f ishing. There are apprQximatelYnlQ spartsfj shi ng boat s .. ill u operation along this stretch of coastline.- These are mostly owned by the beach hotels, although a number are owned by independent operators. Sports-fishing reaches its peak during the high tourist season, and some boats are not operational at all during the low tourist season.

The coral reefs and lagoonal coral gardens along the Diani coast also offer a variety of fish species highly prized by aquarists. There are 4 main areas of collection Mwaepe, Tradewinds, Mwakamba and Chale and collectors from Mombasa and Kikambala employ local people to catch ornamental fish at these locations choosing subjects according to their customers requirements. All ornamental fish which are collected are sold for export to Europe.

6.5 Reefwatch control Survey Sites (Outer reef)

Leopard Beach

The numbers of Lutjanids were assessed as moderately high in comparison to the intensive study sites. Two size classes were in evidence, indicating that more than one year class was present. Lutjanus kasmira was the dominant species, however, Lutjanus fulviflamma and Lutjanus gibbus were present in considerable numbers.

As with the Lutjanids, Lethrinid species were present in more than one size range, evidence of more than one year class. On the deeper survey especially larger numbers of Lethrinids were observed over a number of size ranges.

By comparison, grouper diversity and abundance was assessed as low and no large sized specimens were recorded, not even 77 on the more densely populated deeper survey site. Epinephelus chlorostigma and Cephalopholis argus were the dominant species.

Only two triggerfish species were observed on this site and there was very little difference between the deep and shallow surveys. Both Sufflamen bursa and Sufflamen chrysopterus were present in moderate numbers.

Key pufferfish species were also present, but in moderately low numbers.

Just one Chelinus species was observed on the shallow survey.

There was a marked difference in the distribution of butterflyfish on this site. The shallow survey provided a low species count and moderately lew numbers, Chaetodon klienii was also present in large numbers as was Chaetodon guttatissimus.

By comparison the deeper survey produced both a higher diversity and abundance. Fourteen species of butterflyfish were noted but Chaetodon klienii remaining the most abundant of these. Zanclus canescens was also present in large numbers.

Angelfish diversity and density followed a similar pattern, with Pomacanthus chrysurus being the dominant species.

This site contained a moderate coral covering, composed of over half soft coral species. Coral variety was assessed as moderate to limited with a low percentage covering of hard coral.

The reef could not be classed as a particularly attractive site for tourist diving, although it is typical of this stretch of the reef system. Large areas on the reef slope were given to algal rock which grew as an extensive thick lawn, 1'5 cm in length.

Fishing pressure was rated as considerable, the remains of lost traps were evident on the sea bed as were the broken and dead coral heads, dislodged as a result of snagged nets or lines. 1 I A local fisherman was observed attempting to retrieve a snagged .J net from this reef.

There is also some spearfishing on this system of reefs and more than likely shell collecting, when the opportunity arises.

Tradewinds

No noticeably high numbers of Lutjanids were observed, those that were present were Lutjanus gibbus. all of which were sized below 20 cm.

Only one small aggregation of Lethrinids was observed, these were on the deep survey and were all also below 20 cm in length.

1 j 78

Very few grouper specimens were noted on this site, the deep survey produced the larger count and these numbers were distributed across a wider size class. Cephalopholis argus, Epinephelus miniata and Variola louti were the most abundant species.

Triggerfish counts revealed a definable difference in abundance between shallow and deep surveys. The shallow survey was poor in diversity and only two species were recorded with Sufflamen chrysopterus represented in large numbers. During the deeper survey six species were recorded, however, Sufflamen chrysopterus was the only species present in large numbers.

Pufferfish numbers were low on this site and no Chelinus species were observed.

Butterfly and Angelfish diversity and abundance were assessed as low and only Chaetodon klienii was present in relative high numbers. Observations on the shallow survey recorded the greatest diversity of butterflyfish whilst the greatest diversity of Angelfish species was found on the deeper lines.

The site has a moderate coral cover, about half of which J..~ softcolaispeciesuandhald cOlaidiveIsity is failiylow.· The relative poor quality of the corals resulted in the site being assessed very low"in attractiveness terms. Algae formed as an extensive thick lawn over rocks and coral rubble and resulted also in a poor dive site rating. The reef, however, is probably typical of the system in this area.

Reef fish numbers were limited as was the diversity of species present. Pelagic species similarly were low in diversity and numbers.

The level of fishing pressure and impacts on this reef is difficult to determine. There was some evidence of dead and broken coral and this would suggest that some form of net fishing has occurred. Local fishermen fish the whole outer reef system from the Tradewinds north to Mwachema and the low numbers of reef fish may indicate that an intensive effort has occurred in the past. However, it is possible that these reefs are not very productive and have never been heavily stocked with demersal species therefore only occasionally fished.

Chale Island South

Moderately high numbers of Lutjanids were observed over three size ranges, indicating that more than one year class was present. The deeper survey produced the highest counts and all the target species were present in moderate numbers.

Lethrinid numbers compared favourably with the best detailed study sites. There is very little difference in distribution patterns between shallow and deep surveys and all key species were present in equal concentrations. 79

Grouper numbers and diversity was classed as moderate and individuals were observed belonging to all the lower scale size classes. More specimens were observed on the deeper survey than the shallow. Cephalopholis argus and Epinephelos chlorostigma were present in the greatest numbers with individuals of each species present up to 50 cm in length.

Low numbers of triggerfish species were observed, although the abundance of individual species compared favourably with other sites.

Sufflamen chrysopterus was the most abundant species and was present in large numbers on the deeper section of the site.

Low pufferfish counts were recorded on the shallow survey, however, numbers were higher on the deeper survey section. All Arothron key species were present although Diodon hystrix was absent.

Chelinus undulatus was observed on the deeper line.

The numbers and diversity of the butterflyfish and angelfish . , compaFe~ ievoarahlywitk tke better 4etaile4sY~¥~¥ sites.

This reef site is a continuation of the Chale Island system and almost identical in"appearance. Whilst there were larger areas of algal rock and more patches of sand the coral diversity and cover was very similar. J

Reef fish numbers were assessed as numerous and the diversity of a reasonably high level, with up to 50 species represented. l The abundance of pelagic species was rated numerous and the diversity was noted as moderately varied. j It was assessed that the area suffers considerably from the effects of fishing. Extensive spearfishing occurs and also the collection of shells. The area is used occasionally as J a dive site and there was evidence of broken and dead coral. It was difficult to determine whether this damage is as a result of careless diving practices or as a direct consequence of local fishing methods. 6.5.1 Discussion of Control: Reefwatch sites. . J The areas of the reef system used as control sites (Reefwatch sites) produced varied fish counts. The Leopard beach survey site held reasonable large aggregations of Lutjanids and Lethrinids, however no other species was observed in any abundance.

The Tradewinds survey site was of a poor standard in terms J of fish abundance and diversity. No species from the Key groups were present in large numbers.

The Chale Island South survey site was the exception. This site compared favourably with the detailed study sites. Reef J 80

fish numbers and diversity were reasonably good and pelagic fish abundance and diversity of a similar level. Because this site is at such a good standard recommendations will be included later in the report that this site should be buoyed and managed as a major dive site.

6.6 The Lagoon Survey Site

6.6.1 Introduction

A main objective of the expedition was to determine the general pattern of distribution of various fish species within the study area. It was requested that, additionally, a survey be carried out in the lagoon to determine the biomass of the commercially important species, and the current status of the lagoonal fishery. However, with limited time and resources, the logistics of such a survey made this impractical. It was, therefore, only possible to survey a reduced area. The section of the lagoon chosen was sited directly opposite the Jardini beach hotel staff quarters (Base camp).

Tbelagoon··at ·tn1s p01ntextertds from the ubeach area across to the inner face of th~ fringing reef, a distance of approximately 1 kilometer.

6.6.2 Method of survey

The survey was accomplished by employing a team of 4 snorkellers, each responsible for observations of Key species within a single genus of commercial species. The snorkellers swam a direct line from the beach to the fringing reef, observing these Key species within a 5 mts. area either side of their course of direction.

Upon reaching the fringing reef, the snorkellers returned to the beach along a course, parallel to their outward survey at a distance of 10 mts. further along the lagoon. Each snorkeller carried out two such surveys, covering an area of approximately 20,000 meters, and providing a total survey area of 80,000 meters covered by all the snorkellers.

6.6.3 Analysis and Results

The results obtained from the survey have been condensed to show numbers of individual species per 22 2 mts. It must be noted that while the lagoon holds a large number of fish species, those deemed as commercially important and therefore, of most interest, were the principle target species of the survey.

The following data was collected and the average size of individual species is depicted in brackets: 82

The following total number of individual species were recorded during the survey of the lagoon. (Commercial species shown in table 6·1 included).

Table 6-2 Lagoonal Survey of all Fish Species

Labridae Wrasse Labroides dimidiatus Stethoju1is axi11aris (Juveniles present) Coris formosa (Juveniles present) o Pomacentridae Damse1fishes Abudefduf annu1atus Abudefduf dicki Abudefduf saxati1is Abudefduf sexfasciatus Abudefduf sparoides Amphiprion ephippium Dascy11us aruanus Dascy11us trimacu1atus Chromis caeru1eus Chromis dimidiatus Pamacentrus pulcberrimis

Lethrinidae Emperors Lethrinus hartak

Lutjanidae Snappers Lutjanus Johni Lutjanus fu1vif1amma Lutjanus gibbus Lutjanus bohar

Siganidae Rabbit fish Siganus oramin

Pempheridae Sweepers Pempheris oua1ensis

Mu11idae Goatfish Pseudopeneus macronema

Gaterinidae Sweet1ips Gaterin gaterinus Gaterin f1avomacu1atus

Acanthuridae Surgeonfish Acanthurus triostegus Acanthurus tennenti Acanthurus mata

Ho1ocentridae : Soldierfishes Ho1ocentrus diadema Holocentrus sammara .. Myripristis murdjan 83

Chaetodontidae Butterflyfishes Chaetodon auriga Chaetodon klienii Chaetodon lunula Chaetodon guttatissimus

Pomacanthidae Angelfish Pomacanthus imperator Pomacanthus semicirculatus

Scorpaeridae Scorpionfish Pterois volitans

Diodontidae Porcupinefish Diodon hystrix -, Tetraodontidae Pufferfish ! Arothron stellatus Arothron meleagris

Ostraciidae Boxfish Ostracion tuberculatus (Juveniles present) . Canthigasteridae Sharp-nosed puffers 1 Canthigaster valentini

Whilst it was not the intention of the survey team to compile a definitive list of all lagoon fish species, it was decided J worthwhile to list also those fish species encountered during the survey of commercial species which were not regarded as food species to give a better indication of the importance the J lagoon plays in terms of the whole fish ecology of the area. These observations confirm that the lagoon supports a wide diversity of reef fishes and compares favourably in diversity terms with the outer reef sites surveyed.

6.6.4 Discussion on the Lagoon Survey Site J

As stated earlier the limited resources and lack of time prevented a comprehensive detailed study of the fishes of the lagoon. The work carried out by the survey team is therefore too superficial to allow any really meaningful conclusions to be formed from what are only limited observations. The lack J of, and unavailability of any published earlier research of the lagoonal system, also prevents any comparisons to be drawn from historic data. J On analysing the results of this survey, indications are that whilst the diversity of reef fishes in the lagoon as a whole is good, the abundance of commercial species is limited. Lethrinus harak and Acanthurus triostegus were observed to be the most abundant of the commercial food species but occurred only in relatively small numbers. There were also, albeit J very small, numbers of all the other commercially important species also observed. 84

There does appear to be a wider range of commercial species size classes in the lagoon by comparison with the outer reefs. This would normally be expected to occur in a lagoon system where the juveniles and immature fish of many species take refuge in the more sheltered waters within lagoonal coral gardens and seagrass beds. Such areas play an important role in the ecology of both the lagoonal and outer reef systems, acting as they do as nursery areas and it is vital that they should be protected where possible from any man made impacts which might harm these processes.

It was also noted that juvenile fish stocks have not remained unnoticed by the fishery during routine visits to all of the fishing depots along the Diani coastline, immature and juvenile fish of all the commercial species were observed being landed. The removal of fish of these year and size classes is very damaging to the fishery and likely to, quickly, totally decimate the stocks of the target commercial species. If the fishery is to continue to progress, then the recommendations following in this report to safeguard juvenile and immature fish stocks must be implemented.

Pi na]] y, . as these obsenz:atioos. ualth.o.ughbaseli .. onl;im1teli information, indicate a possibly serious decline in commercial fish stocks within the lagoon it is recommended that broader and more detailed research be undertaken to extend the boundaries of the present work and obtain a clear understanding of the lagoon, its ecology and role as a fishery.

6.6.5 The lagoonal fishery

The lagoon is formed by a fringing reef, located approximately 500 mts to 1 Kilometre offshore. The lagoon stretches from the river estuary at Mwechema and continues South to Chale Island. There are a number of fishing stations sited along the shores of the lagoon all of which fish the lagoon intensively.

The lagoon is comprised of many different habitats, commencing with a sandy beach and intertidal area which quickly gives way to seagrass meadows. Amongst the seagrass beds are ridges and sandy bars with pockets of coral rubble. These areas support a varied diversity of fish species with the juveniles of many reef species commonly observed. In this shallow in-shore area, Diodon hystrix was observed as the most abundant species.

In deeper water the seagrass gives way in places to large coral heads (Porites) and raised columns of coral rock. These coral formations support a myriad of life, sheltering below their overhanging forms. Invertebrates of many species can be observed as can numerous fish species. Towards the fringing reef, the coral heads become more numerous, coral rubble dislodged during seasonal storms provides large areas of cover for many species of fish, both adults and juveniles. 85

In many areas the lagoon system dries out as the tide ebbs and the lagoon drains into the open sea. Fish species follow the ebbing tide out and move onto the reef systems beyond the fringing reef. They return as the tide turns and begins to flood the lagoon. The juveniles of many reef species are abundant and they remain within the lagoonal system during all states of the 'tide, concentrated in the deeper pockets and submerged coral gardens.

The lagoon provides many opportunities for fishing and a wide range of methods are employed. The shallow waters are ideal for spearfishing and local fishermen employ this method very effectively to capture cephalopods, both octopus and squid. The majority of octopus landed at the stations are caught by spear and taken from within the lagoon. Shell collecting is also practised as a by-product of spearfishing. In the past this has taken place extensively along the outer edges of the lagoon and still occurs although, due to diminishing returns, at a reduced rate.

All of the lagoonal fishery is based entirely on artisanal methods such as spearfishing and effort ~s dictated by season and weather conditions. Fish traps are an~ther principal means adopted and used extensively as ale handlines. Nets axe-also employed in the pursuit-of small pelagic species such as sardines, when in season, and beach seines, which usually provide low yield and, characteristically, a high incidence of non-commercial species caught such as the Spiny Pufferfish (Diodon hystrix) as a by-catch. Beach seining is immensely damaging to the lagoonal ecosystem due to the indiscriminate nature of the method and the impacts on the various habitats.

There are no separate catch figures for the lagoon fishery, the catch total for the 1991-92 season of 343.486 kgs (Diani sub-station, Annual report, 1992, Fisheries dept). also includes fish removed from outside the lagoon. It has been estimated however, that the lagoon yields up to 50% of the total annual catch as for almost eight months of the year fishing outside the lagoon is very restricted due to weather conditions. J

Calculations based upon attributing the whole of the catch in 1 the eight inclem~nt months to the lagoon fishery and \ extrapolating these results to provide a full year yield for J the lagoon calculates as 161,532 Kgs in the 1991/92 season of a total 343,486 Kg. which ap~ears to confirm this.

I .J 86

7. RECOMMENDATIONS FOR MANAGEMENT OF THE DIANI FISHERY

1) The main recommendation would be to manage the whole Diani coast as a National Marine Reserve with provisions for setting aside zones of the lagoon and off-shore reefs temporarily to allow heavily fished areas to recover. In addition the five outer reef sites used for the detailed study should be designated Marine National Parks. These small areas, whilst not deleting too great a catch from the fishermen because of their limited size, would act as buffer zones and assist in replenishing fish stocks over the whole Diani reef system.

2) In order to control and regulate the numbers of fishermen using the fishery it is recommended that a licensing system should be introduced which applies to all individuals and only holders of a valid license will be able to fish in the Diani Fishery area either within the lagoon or on outer reef areas.

3) Minimum size limits should be introduced for all species and mesh sizes of·nets "iobe set at a minJ.mum of SOmm :x:·SOmm to protect juvenile and immature fish stocks.

4) To enforce this practise all fish landed should be logged at depot or landing stations, sized and weighed.

5) Beach seine netting to be totally prohibited to prevent damage to lagoonal habitats and safeguard lagoonal ecology.

6) Allocation of quotas for each depot to restrict cephalopod landings if necessary to protect this fishery.

7) Separate catch statistics to be maintained for the lagoon and outside the fringing reef in order to monitor lagoon and outer reef Fisheries separately.

8) Provide training for fisheries officers in monitoring techniques in order to more effectively manage the fishery. 87 BIBLIOGRAPHY

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Craik, W. (1979) Survey identifies trends in reef fish catches. Aust. Fish. 1979 29-32 88 Craik, G.J.S. (1981) Under water survey of coral trout Plectropomus leopardus (Serranidae) populations in the Capricornia section of the Great Barrier Reef Park. Proc. 4th Int. Coral Reef Symp. Manila l 53-58 Dahl, A.L. & Salvat, B. (1988) Are human impacts either through traditional or contemporary uses, stabilizing or destabilizing to reef community structure? Proc. 6th Int. Coral Reef Symp. Australia l 63-69 Ferry, R.E. & Kohler, C.C. (1987) Effects of trap fishing on fish populations inhabiting a fringing coral reef. N. Am. Fish. Manage. I 580-588 Gaudian, G. Medley, P.A.H. & Ormond, R.F.G. (1993) A study of the size, immigration and spatial distribution of a coral reef fish stock. Coral Reefs in press. Getz, W.M. & Haight, R.G. (1989) Population harvesting. Demographic Models of Fish. Forest and Animal Resources. Princeton: Princeton Univ. Press.

Goeden, G.B~(1979~ !s the GreatBarr~eF Reef ~eiBgeverf4shed2 Aust. Fish. 1979 18-20

Goeden, G.B. (1982) Intensive fishing and a keystone predator species: incredients for community instability Biological Conservation 22 273-281 J

Grigg, R.W., Polvina, J.J., Atkinson, M.J. (1984) Model of a 1 coral reef ecosystem III. resource limitation, community J regulation, fisheries yield and resource management Coral Reefs 1. 23-27 j Hurlbert, S.H. (1984) Pseudoreplication and the design of ecological experiments. Ecol. Monogr. 54 187-211

Johannes, R.E. (1978) The productive strategies of coastal marine J fishes in the tropics. Env. BioI. Fish. 3 65-84 Johannes, R.E. (1982) Traditional conservation methods and J protected marine areas ion Oceania. Ambio 11 258-261 . J Johannes R.E. (1981) Working with fishermen to improve coastal tropical fisheries and resource management. Bull. Mar. Sci. 11. 673-680 I _J Loubens, G. (1980) Biologie de quelques especes de Poissons du lagon neocaledonien. III Croissance Cahiers de l'Indopacificque 1. 101-153 MacArthur, R.H. & Wilson, E.O. (1967) The theory of biogeography Princeton University Press, Princeton.

) J 89

Magurran, A.E. (1988) Ecological diversity and its measurement. Croom Helm, London.

Marshall, (1985) Ecological sustainable yield (fisheries potential) of coral reef areas, as related to physiographic features of coral reef environments. Proc. 5th Int. Coral Reef Congr. 5 525-529

Marten, G.G. & Polvina, J.J. (1981) A comparative study of the fish yields from various tropical ecosystems. In Theory and management of tropical fisheries. Pauly, D. & Murphy, G.L. (eds) ICLARM Conf. Proc. 9 ICLARM, Manila Philippines and Division of Fisheries Research CSIRO, Australia.

McClanahan, T.R. & Muthiga, N.A. (1988) Changes in Kenyan coral reef community structure and function due to exploitation. Hydrobiologia 166 269-276

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-----Me€lanahan, T .. R. & Sh-aftf'--";"-S.H. 099Q) Causes aae·eeasequeftees of sea urchin abundance and diversity of Kenyan coral reef lagoons. Oecologia 83 362-370

Munro, J.L. (ed) (1983) Caribbean Coral Reef Fishery Resources. Manila: ICLARM

Munro, J.L., Parrish, J.D., Talbot, F.H. (1987) The biological effects of intensive fishing upon coral reef communities. In Human impacts on coral reefs: facts and recommendations B. Sal vat (ed.) Antenne Museum E.P.H.E. French Polynesia 41-49

Munro, J.L., & Williams, D. McB (1985) Assessment and management of coral reef fisheries: biological, environmental and socio economic aspects. Proc. 5th Int. Coral Reef Congr. 4 544-578 Tahiti

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Polvina, J.J. (1984) Model of a coral reef ecosystem 1. The ECOPATH model and its application to French Frigate Shoals. Coral Reefs 1 1-11

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Wright, A. & Richards, A.H. (1985) A multispecies fishery associated with coral reefs in the Tigak Islands, Papua New Guinea. Asian Marine Biology 1 69-84. Fig.6.0 Key to the classification of Fish Families based upon a minute count

CLASSIFICATION OF ABUNDANCE VALUE INDEX . LIST OF FISH FAMILIES SUPER ABUNDANT NUMEROUS LIMITED ABSENT ABUNDANT

CHAETODONTIDAE BUTTERFLYFISH 26 11-25 4-10 1-3 0 ZANCLIDAE MOORISH IDOL 26 11-25 4-10 1-3 0 POMACANTHIDAE ANGELFISH 6 4-5 2-3 1 0 3-6 1-2 BALISTIDAE TRIGGERFISH . 10 7-10 0 TETRAODONTIDAE PUFFERFISH 7 5-6 3-4 1-2 0 DIODONTIDAE PORCUPINEFISH 7 5-6 3-4 1-2 0 SERRANIDAE GROUPERS 10 7-9 4-6 1-3 0 LETHRINIDAE EMPERORS 50 40-49 10-39 1-9 0 LUTIJANIDAE SNAPPERS 100 50-99 20-49 1-19 0 • • • o The following Figures 6.1 to 6.59 illustrate the Fish Value Index derived from the completed 'Reefwatch' forms. •

Table 6.1 Butterfly fish mean abundances by specieS

LOCATION

...:l r/.l...:l ...:l r.:I~ ~ ~~ :1 ~ r.:I r.:IP: ~~ 8r.:1 ~Q ~g c.:t:: 5~

r.:I:t:: ~~ ~~

FISH SPECIES o:t:: ~~ 5~ ,~

~Q! !;:If> ~~ ~~ °3

tJ:l ~~ tJ:l ~

F. avissimus F. 10 irostris H. acuminatus 1 Z. canescens 3 H. monoceros 1 C. tri asciatus 2 C. Ruttatissimus 3 C. m eri C. xanthoce halus C. unimaculatus 3 C. falcula

C. mculaRascariensis I I 1 I 1 I 2< I 1 I 2 I 211; 2:i",12 [!::2/i] 2=r:i~'{11 li!:'i::::.":12 L ,4:

I 3 I 1 I 1 I 1 1;;::'1,."I 1 !':'lec. 1 c'>'~"" I 1':,·.,:",;_.-. .,::;"_: .....,,

SPECIES COUNTI 11 I 9 I 7 I 14 I 7 I 4 I 111113 I 9 I 12 I 17 I 19 I 16 I 16 I 10 I 12 Mwachema River

-I

IIIIi \ I l

] J

1 . .1

I j

Chale Island

i J Chaetodon auriga (Threadfin) Fig. 6.1 92

SECTION 7

,i ~ d

4------ l I N V E R T E BRA T E S

.., ! . I

J 93

INVERTEBRATES

7. INTRODUCTION

The aims of this section of this report are to identify and map the main distribution of selected macro invertebrates species of the waters on the Diani coastal region. These invertebrates include members of the classifications porifera, cnidaria, mollusca and echinoderma, but exclude hard corals. Due to the considerable differences in animal size, only species which are larger then 1 cm in length were recorded. As a result of the restriction in the time available, this criterion was necessary to ensure that a large sample from the reef was obtained in the short period and not just a small niche sampled intensively.

7.1 STUDY SITE AREA

The study area is located on the Diani coast and extends from the Mwechema river estuary in the north to the south of Chale Island. The reef is an exposed fringing reef unlike the relatively sheltered reefs found in earlier studies of the waters surrounding the islands of Kisite and Mpunguti. Th1S coastl1ne 1S not protected by any tfarine National Park or Marine National Reserve regulations, however, there are pnoposals to designate the whole area a Marine National Reserve incorporating a number of small areas as Marine National Parks within the boundaries.

The Diani coastal area has been extensively developed as a tourist resort for both international and national travellers, with 23 large hotels and more under construction. Diani is the principal resort on the coast and provides employment for a large number of people from surrounding villages. Coastal villages such as Galu and Kinondo have also developed into major fishing communities which regularly supply fish and decorative shells to the hotels and visiting tourists.

'. ,.' With such demands on reef resources for tourism, a major part of the study was to determine what the effect, if any, was on the composition of invertebrate communities in these waters. In order to measure any degradation comparisons have been made later in the report between this study and Kisite and Mpunguti which are long established protected areas.

7.2 STUDY METHODS

7.2.1 Outer Reef Slope Studies

Eight study sites were surveyed along the outer reef slope using SCUBA diving equipment at depths of 5-18 m. Qualitative recordings were made along a 250m, transact line placed at selected depths (see Section I for details). All recordings were made in situ on matt-surface ridged 94

plastic sheets. There was no collection of specimens from the reef as this was considered against the conservation principals of the expedition and underwater photographic techniques were where necessary substituted. The use of underwater photography as a research tool is well established George (1980), and photographs of living specimens in their natural habitats provided an excellent means of identification of some unknown specimens on the return to the U.K. All photographs were taken with the Nikonos V camera system with a 35 mm lens and extension tubes to provide 1:2, 1:1 and 2:1 magnification ratios on Fuji Velvia slide film.

7.2.2 Lagoon Reef Flats Studies

The tidal variations found in this area are on average between 2-3 m, and during low water, the lagoon reef flats were almost completely drained and could be sampled by snorkelling alone. However, snorkelling these areas during the flood tide was also undertaken to investigate the types of more highly mobile animals which migrate into the lagoon during such periods.

7.2.3 Methodology

The abundance of a particular species was judged by their mode of living, i.e. sessile animals which were colonial were judged by the relative percentage cover and individual counts used for free living animals. A numeric key from 1 to 3 was used where l=present, 2=common and 3=abundant as shown in Table 7.1.

7.3 OBSERVATIONS

7.3.1 PORIFERA

The fringing reefs on the Diani coast is exposed to strong tidal flows, fuelled by the large tidal differences in the region. Colonisation was widespread'by sponge colonies, because large water movements of this nature are favoured and desired by most sponge species to help the animal extract food from the water column. Axinella carteri colonies were very common and were found on all outer reef sites (none were recorded within the lagoon). Around Chale Island, this orange sponge species was fairly common and well developed standing up to 20 cm in height, whereas most A. carteri colonies were comparatively smaller on other sites. A similar species which closely resembled A. carteri was recoTded only on Leopard Beach, Tradewinds and Neptune Beach (unidentified species 1). This species was also of orange in colour and had the same morphological colonial structure as A. carteri but with larger osculums. Colonies of Gelliodes gracilis also showed similar distribution patterns to A. carteri colonies but G. gracilis was not present on the Neptune Beach and Chale Island (south) sites. Gelliodes gracilis were more abundant in shallower depths on the 96 great diversity in form and species and positive identification could only be made by close examination of the octocoral sclerites. Three main forms of Sinularia species were predominant, Sinularia leptoclados with nobular figure like processes, Sinularia polydactyla had more densely lobed colonies with finger like projections and Sinularia gardineri had folds on its dorsal surface frequently radiating from the centre.

The bright sulphurous yellow soft coral Parerythropodium fulvum is another common mass covering colony which was well represented but far less so than was recorded on the Kisite and Mpunguti sites further south. On the Kisite and Mpunguti sites, P. fulvum was observed in certain areas to cover close to 100% of the sea bed, but on the Diani coast P. fulvum was recorded in far lower abundance, usually covering coral rubble, but in an irregular manner. An unidentified soft coral species (unidentified species 2) closely related to P.fulvum was also recorded on the Diani coast, but was less abundant and seemed to favour shallower depths. This unidentified species had larger polyps and was purple in colour with whiter basal structures.

Only two species of tree-like soft coral forms were recorded along the transact lines, Umbellulifera striata was positively identified but one Dendronephthya species was not. Umbellulifera striata has a very dull brown coloration and does not have the conspicuous sclerites frequently observed embedded within the stalks of other species (e.g. Dendronephthya rubeola). The unidentified Dendronephthya species had a bright purple coloration with white sclerites within its stalk. Both species were far less common, than the leather corals (Sarcophyton and Sinularia species), and the distribution of the unidentified Dendronephthya species was restricted to the areas in front of Neptune Beach only.

The distribution of hydrozoans were fairly constant throughout the study sites. Small colonies of Aglaophenia allmani (Nutting) were usually found under rocks and rubble and within crevices, but there was not great abundance of these animals, and non recorded on the extreme north and south sites. The larger, branching black and white Lytocarpus philippinus (Kirchenpauer) was only observed in the deeper waters at Kinondo Village and Chale Island (north). A much more conspicuous hydroid was the sea nettle Aglaophenia cupressina (Lamouroux), a relatively large animal which favours settlement on coral of rock out crops.

Only one specimen of Cassiopeia ornata (Haeckel) was recorded within the lagoon. This jellyfish species was observed settling on seagrass beds or on sandy areas bordering seagrass beds and was very recognisable by its mode of settlement. Cassiopeia ornata rests on its exumbrella (bell), up-side-down with its tentacles facing the sunlight where photosynthesis takes place by symbiotic 95

Kinondo Village and Chale Island sites. but in deeper waters these colonies were more developed.

Size. morphology or coloration of sponges can make certain colonies very distinctive. and the most conspicuous sponges recorded on the Diani coast have a very recognisable "goblet" shape to the colony. and have been identified as belonging to the Tethya genera. Two Tethya species were recorded and both colonies were goblet shaped with the main colonial mass being supported by a thin stalk securely anchored to the sea bed and standing more than 30 cm in height. Tethya species 1. (red) coloration varied from yellow to a deep red. the latter being much more common. and Tethya species 2 (brown) was only observed to have a very dark brown (almost black) coloration. On the dorsal surface of the main body mass. Tethya (red) had multiple openings clustered together whereas Tethya (brown) only had singular openings. These goblet sponge species were very conspicuous because these animals were located in the open and seldom found amongst coral or rock formations of which they are similar in height. Tethya (red) colonies were commonly found mostly on the Tradewinds and Kinondo Village sites and Tethya (brown) was only commonly found on the Kinondo Village site. On Chale Island (south). both goblet sponge species were present but at much lower densities. No obvious distribution was apparent. but sea bed topography may playa critical role in their distribution pattern.

The vase sponge colony forming. Phyllospongia caliciformis. had a more obvious distribution pattern. and was commonly found from the north at the Mwechema river estuary site down to the Trade Winds site. This species was not recorded at the Galu Village and Kinondo Village sites. but was relatively abundant in the shallower waters of Neptune Beach and Chale Island (south). P.caliciformis has a bowl shaped mass and mustard coloration similar to the Caribbean species Cribrochalina vasculum (Lamarck). but has no ridges within its inside surface and very smooth to the touch. Some of these colonies continue to survive when filled with sediment and colonised by the marine algae Halimeda macroloba on the Trade Winds site.

There were several other unidentified sponges. some of which produced very large colonies. One such species was a tubular blue sponge (Unidentified Haliclona species) which resembled a candle stick. and was very conspicuous standing about 20-30 cm in height.

7.3.2 CNIDARIA (EXCLUDING HARD CORALS)

Soft corals are by far the most dominant animal phyla on the coral reefs of the Diani coast and can represent up to 100% of substrate cover (see also section 5). Sarcophyton and Sinularia species were dominant and can cover very large areas with individual colonies growing to a size in excess of 1 m in diameter. Sinularia have 97

algae within the tentacles.

The most common sea anemone found on the Diani coast is the large Heteractis magnifica (Quoy & Gaimard) a species, which is frequently cohabited with Damsel (Dascyllus trimaculatus) and/or Clown fishes (Amphiprion akallopisos or A. bicinctus). Very large specimens could accommodate more then on species of fish as well as a crustacean shrimp or two (Periclimines brevicarpalis). The distribution of H. magnifica was wide spread but non was recorded on Chale Island (south). On Neptune Beach this anemone was observed in clusters of up to seven individuals clumped together, only on a few occasions were they located in isolation from each other. Brilliant colours from deep blues to reds or greens cover the main body of H. magnifica, but the coloration of their tentacles remain uniform between individuals.

Heteractis magnifica is light requiring (photosynthetic), and consequently was always located on the uppermost surfaces of coral rubble or rock making identification easy. The burrowing, or sand anemone Heteractis aurora was not so easily located, and was observed only at the base of the reefs or any other location where pockets of sand could _ be found. This anemone has circular ribbed tentacles and a relatively small oral disc area and cohabited with only small juvenile fish and/or shrimps Stoichactis gigas was not as widely distribute but much larger than H.magnifica and also was coinhabited with fish and/or shrimps within its short stubby tentacles. This species is green in coloration and also photosynthetic requiring positions on the well lit upper surfaces of coral rock in shallow water.

7.3.4 PLATYHELMINTHES

Only two species of platyhelminthes were commonly recorded, these were Pseudoceros zebra and Pseudoceros splendidus. Pseudoceros zebra is very conspicuous with its tiger stripes and coloration of yellow, orange and black. Pseudoceros splendidus is dark purple in colour with a darker border along the edge of its entire body. These animals were recorded browsing in the open, a more intensive examination of the reef may reveal more diversity. A further unidentified species was recorded at the Chale Island south site. This species was very conspicuous having a black body with large orange spots patterned on its dorsal surface, together with a green and blue fringe.

7.3.5 MOLLUSCA

A large number of gastropods (see Figure 7.1) are collected either for their shells or flesh; and certain species for both. This is probably a significant cause for the lack of observations of large commercially important species such as Lamb~s lambis and L. chiragra species on the Diani coastal reefs. These gastropods were Figure 7.1 Quantity of Common Shell Species Collected In the Study Area

SHELL NUMBERS SHELL SPECIES ..., ..., ..., ..., ..., ..., ..., ..., ..., ..., ~ ~ CIl CIl CIl ~ ~ CIl CIl CIl CIl CIl i ..... III :; :; ) t! ~ & :.2 ~ ::E "'1l "'1l ~ i 8 ~

Cyvraecassis rufa 240 30 90 90 460 - 240 40 36 340 525 340 Lambis truncata 340 17 20 30 360 - 174 14 26 660 105 60 Lambislambis 410 20 60 40 380 - 246 30 27 240 315 240 Charonia tritinis 2 3 15 25 7 - 2 1 2 4 7 4 Tridacna maxima 60 40 7 50 30 - 90 16 12 40 8 40 Cypraea tigris 340 90 110 40 700 - 240 45 46 460 ### 460

Source: Fisheries Department. Shimoni

! ~ 98

not well represented here and there was a noticeable lack in numbers in comparison to the Kisite and Mpunguti sites. On the Kisite and Mpunguti sites these gastropods grazed openly on the algae growing on the reef tops, and the size of some specimens were comparatively large. All the L.lambis and L.chiragra gastropods found on Leopard Beach, Tradewinds, Neptune Beach and Chale Island (south) were small.

In the deeper waters on Leopard Beach the Common Egg shell Cowry, Ovula ovum (Linnaeus) was observed frequently in pairs feeding on soft corals (Sarcophyton). These gastropods are highly prized by collectors but presumably the depth placed these out of easy collection range.

Of the three opisthobranchians species noted, Bulla ampulla (Linnaeus) was identified by the empty shells found at the base of the reefs on Galu Village and Kinondo Village sites. The more conspicuous, shelless Chromodoris guadricolor (Ruppel & Leuckart) and Phyllidia varicosa (Lamarck) were more common with an unexpected large number of P.varicosa recorded on Neptune Beach.

Big bivalve clam species such as Tridacna gigas (Linnaeus) and Tr1dacna crocea (Lamarck) were comparatively low in abundance when compared with the results from the Kisite and Mpunguti sites. There was some evidence of the shells from these bivalve species offered for sale on the beaches. Other smaller bivalve species were recorded on massive Porites coral formation, either embedded in the coral itself, or clinging to it. Pedum spondylioideum is a bivalve which embeds itself into such coral structures, and therefore its distribution is dependent on these massive Porites coral formations. The protection offered by such modes of habitat has reduced the shells of P.spondylioideum to a very thin material. The mantle of P.spondylioideum has a distinctive deep purple coloration and can be easily identified by this. The Thorny Oyster, Spondylus aurantius (Lamarck), can also be found attached to the undersurfaces of coral or rock. These bivalves are very well camouflaged with no obvious distribution pattern other than local habitat selection.

The two common Eastern Pacific cephalopod species were well represented and numerous visual sightings of Octopus cyaneus actively moving around on the reefs were recorded. Adult Sepia plangon were not observed, but their egg cases were commonly found attached to reef structures.

7.3.6 ANNELIDA

The more conspicuous fan worms protruding from massive Porites coral formations constituted most of the annelidian numbers. The relatively large Sabellastarte magnifica (Shaw) and the doubled spiralled Sipirobranchus giganteus (Pallas) could frequently be found colonising these massive coral structures, however, small numbers of isolated specimens were located in the tips of broken coral projections. The 99

brilliant coloration of S.giganteus is highly variable but its double crown of tentacles is much smaller than the less colourful, singular crowned ~.magnifica. Due to the lack of suitable coral formations these fan works were absent from some sites.

Reteterebella gueenslandia (Hartman) with white thread like tentacles were recorded during the survey but only at the Leopard Beach and Tradewinds sites where their tentacles (up to l'S m in length) were a feature extending usually from below rocks or boulders.

7.3.7 CRUSTACEA

The distribution of crustaceans over the Diani study sites was poor and similar to the results of the earlier observations at Kisite and Mpunguti. Only the larger more brightly coloured members such as the Painted Reef Lobster, Panulirus versicolor (Latreille) and Mantis Shrimp, Odontodactylus scyllarus were commonly observed. The white antenna of P.versicolor protruding out from under crevices were telltale signs of the lobster's presence. However, the locating of O.scyllarus was not as easy. The apparent acute eyesight of these animals usually alerts them to the presence of any diver within the vicinity, and they were only recorded from the glimpses of bright green and red coloration as the mantis shrimp headed for cover. Several other smaller shrimps species were identified, Periclimines brevicarpalis is small and mostly transparent with large white patches and was found sheltering within the tentacles of the Carpet Sea Anemone Stoichactis gigas. The more colourful shrimp Stenopus hispidus (Olivier) was only located in "stag horn" coral formations on the shallower Kinondo village site. Only one hermit crab species was found on this coast, that of the large, red and hairy Dardanus megistos (Herbst).

7.3.8 BRYOZOA

Bryozoans were common in certain areas but easily overlooked. Three species were identified on these reefs on coral rock. The Purple Lace Bryozoan Iodictyum phoeniceum was easily identified, however, Adeonellopsis sulcata and another Adeonellopsis species could be found in dense clumps. Adeonellopsis sulcata had a light brown coloration whereas the unidentified Adeonel1opsis species was blue. The distribution of these bryozoan species was concentrated on the more northerly sites (Mwechema river estuary and Leopard Beach) with a few specimens located on Neptune Beach and Kinondo Village sites.

7.3.9 ECHINODERMATA

Asteroidean and echinoid species formed the main population numbers which were recorded on these reefs, there was however a noticeable lack of crinoid recordings, similar 100 to observations at the Kisite and Mpunguti sites. A small number of specimens of Comanthus parvicirrus (J. Muller) were located hidden in crevices, under large coral or boulder forms and occasionally in what appears to be plague proportions within the "prongs" of hard corals. Undoubtedly observations at night when these animals feed would allow much higher numbers to be noted.

Of all the asteroidean species, Linkia laevigata (Linnaeus) was the most conspicuous. The distribution of L. laevigata had no obvious pattern with regards to depth, but preferred form of habitat appears to be a flat topography with little or no large coral formations where L. laevigata abundance was relatively higher. Both its bright blue and orange forms were present on most sites and the orange forms of L. laevigata were easily confused with the reddish starfish L.multifora (Lamarck), especially at deeper sites where red-light spectra was poor. Linkia multifora was not tommon (compared to densities of L.laevigata) but nonetheless on close inspection they were present on certain sites.

'Protoreaster lincki (de Blainville) was also very con~picuous especially on gently sloping outer reef sites, and!tw1th1n the lagoon where it was easily located in the

Ophiuroidean species were not easy to identify, however, Ophiocoma erinaceus (Muller and Troschel) and O. pica were recorded lodged within coral or rock formations. On occasions positive identification was not possible without separating limbs from these animals when attempts were made to dislodge them from uheir hiding places.

The most common sea urchin species on the Diani coast was Echinometra mathaei (de Blainville) which was recorded in the lagoon where their density reached on average up 2 to 7 m • Another species of lagoon sea urchin was Tripneustes 101

gratilla (Linnaeus), with a density far less than E. Mathaei. However, T. gratilla is a species which likes to camouflage itself with pieces of debris (usually seagrass leaves) which makes their location more difficult. The distribution of these two sea urchin species in the lagoon was constant but both species preferred the shallower depths away from large sandy areas.

Algae covered coral rubble on the outer reefs was usually colonised by Echinostrephus molaris, a small sea urchin with black or purple spines. These small sea urchins are rock borers and had a similar distribution recorded on the Kisite and Mpunguti sites. They had a definite distribution pattern, which appears to be governed by the availability of coral rubble (or dead coral) which has been encrusted by green algae. Most areas of dead coral with algae cover were usually colonised by these small echinoids.

The distribution of Diadema savignyi (Michelin) and D.setosum (Leske) was very similar to each other with both usually occurring together, but D. savignyi was more common than D.setosum. These two species were recorded in groups or clusters at shallow depths, and were found mainly in arQas where the hard corals were damaged.

Echinothrix diadema (Linnaeus) is a much larger black sea urchin species with short and thick black spines (often sheltering numerous small black fish). At shallow depths E. diadema was also discovered in groups or clusters, however, in sreater depths, this species occurred only as single individuals or as a pair. This behaviour is not clear, but when found in large clusters of more than 15 individuals in one cluster this was usually on a site where the corals were damaged similar to the observations of the groups of D.savignyi and D.setosum.

Due to the difference in reef topography of the Diani and Kisite - Mpunguti reefs, the distribution pattern of certain holothuroid species, such as Thelenota ananas (Jager), was restricted by comparison with these sites. The reefs on the Diani coast rarely have a distinct "base~ ; or border between the main coral formation and the sandy bottom of the sea floor. In the Kisite and Mpunguti sites T. ananas was always recorded on the sand close to the reef. Similar habitats did not occur in the more northerly areas of the Diani coast and only a few individuals were recorded on areas where sand had collected. The reef structure on Chale Island (south) was similar to Kisite and Mpunguti and the distribution of T. ananas was better as expected.

The most common sea cucumber recorded for the Diani coast was Holothuria edulis (Lesson), a black animal with pink coloration on its ventral surface. Stichopus variegatus was also frequently noted feeding on sandy areas sometimes side by side with H.edulis. Stichopus variegatus was comparatively large (30 cm) in length and similar in 102

Diameter. The animal was black with three white "tear drop" shaped patterns on each side of its body. Bodhadshia graeffei (Semper) is a sea cucumber species which lives amongst the corals and not on sand. B.gfraeffei feeds on the mucus of hard corals is frequently observed rearing up to reach the coral heads. The Worm Sea Cucumber, Synapta maculata (Chamisso and Eysenhardt), was noted but only recorded in the lagoon area feeding in the seagrass beds.

7.3.10 ASCIDIACEA

The abundance of ascidians on the Diani coast was less than recorded on the Kisite and Mpunguti sites with most of the numbers recorded occurring on the southern sites around Chale Island. However, Didemnum molle (Herdman) has a wide distribution pattern and occurs in clumps favouring the basal areas of the Sea Nettle, Aglaophenia cupressina.

Polycitor giganteum was positively identified and has a distinctive appearance. This ascidian is a colonial species enclosing itself in a transparent gelatinous test with a brilliant white "collar" around the exhaust openings of each 1nd1v1dual w1th1n the colony. The most commonly recorded ascidian species has not yet, unfortunately, been positively identified. This ascidian is another colonial species with individual animals enclosed in a common gelatinous test. The test of this species was white and opaque with no other coloration.

7.4 CONCLUSION

On the Diani coast, due to the relatively low abundance of fish the pressures from fish predation must be substantially less than those which occur on the reefs around Kisite and Mpunguti. With less fish predation, certain invertebrate communities especially molluscs should increase in density. However, this prediction was not observed to be correct at Diani. Shell collection activities are probably the main cause of depleted gastropods levels in an area in which they should have flourished. Figure 7.1 shows the numbers of the most common shell species collected in the Diani area between December 1992 and November 1993. These levels of collection are very high in many cases and considerably greater than acceptable levels for sustainable yield.

Sea urchins congregate in areas where reef damage has taken place and are therefore a good indicator of the health of a reef. The shallow waters of the Mwechema river estuary and Neptune Beach sites had the highest densities of Echinothrix diadema and also where these numbers occurred, so too was evidence of coral damage. Table 7.2 shows the sea urchin counts recorded along the transact lines. Significantly high numbers are recorded on more northerly sites, however, Echinothrix diadema numbers were highest on Neptune Beach. Table 7.1 Invertebrates Species Found In the Survey Area

MACRO INVERTEBRATE LOCATION SPECIES :c rg ..J :c ~~ ~ ~z r.:lr.:l E r.:l Z r.:l :J 00 zE- 8r.:l r.:l 0 r.:li: cc r.:l- :J~ g ~~ o~ fi :c~ i: zj :i!~ r.:l :i!..J Co:c ~..J :c..J :cO ~a: °~ o..J o~ Co ~§ !> ~~ !O:!!> o~ ~~ 0 ~ ..J 2 ..Jr.:l S cc ~ 10 Site 4 .! .!= Site 1 Site 7 Site 2 Site 3 Site 8 r;j r;j T'\, __..1. (:> T'\ ...... ,...... ,...... ,...... ,. .... I

PHYLUM PORIFERA Axinella carteri 1 2 1 1 1 2 1 1 1 2 1 2 2 1 1 CallvsDOnllia carens I, 1 1 1 1 G1!lliodes I(racilis 1 1 1 1 1 1 2 1 2 1 Haliclona SIJIJ. 1 1 1 1 ') Phakellia aruensis 1 1 1 1 I J Ph.yllosTJOnRia caliciformis 2 2 2 2 3 1 1 1 3 Tethva SIJIJ. (brown) 2 1 Tethya SIJIJ. (red) 2 2 1 VeronRia SIJIJ. 1 1 1 XestosDOnRia muta 1 Unidentified spp. 1 1 1 1 1 Unidentified sPP. 2 .' .' 1 1 2 Unidentified spp. 3 2 1 L 1 .... 1 1 1 2 1 Unidentified spp. 4 8 1 1· >, .;" ;. . ... ':.:

Other demosponge sDecies... I'. ') 1 :2 > '.'.... . Species count 2 5 6 10 3 0 3 3 8 8 5 6 4 5 6 3 MACRO INVERTEBRATE LOCATION SPECIES :t: 0 ..::I :t: ~ roJ Eo ~ < ~Z tiJ tiJ z tiJ tiJ tiJQ ~i: l:Q 00 zb 8 ~ roJ- ::>~ z~ ~~ ~~ i:~ f~ 0 5f5 roJ ~..::I o:j :t:..::I :t: ~ ~§ ~~ ~> o~ o~ ~~ 0 > ..::I ~ l:Q 6! ~ Q ~ 10 c Site 4 ~ .3 . Site 1 Site 7 Site 2 Site 3 Site 8 aJ 1ii Depth SID S D In I Out SID SID SID SiD SID

PHYLUM CNIDARIA

ALCYONACEA (SOFT CORAL ( .... " Dendronephthya spp. 1 1 HeterO%enia !Uscescens 1 1 1 1 1 1 2 1 1 1 1 1 Lithophyton arboreum 1 1 2 1 1 1 1 1 1 1 1 1 Palvthoa caesia 2 1 1 1 1 Parerythropodium fulvum 1 1 1 1 1 1 1 1 1 1 Sarcophyton trocheliophorum 1 1 2 1 1 2 2 1 1 1 2 3 2 Sinularia /lOTdinen 3 3 2 2 3 3 2 1 2 2 1 1 1 1 Sinularia leptoclados 2 1 1 1 3 2 1 1 2 1 3 2 Sinularia polydactyla 3 2 2 1 3 2 1 1 2 1 1 2 1 Umbellulifera striata 1 1 1 1 1 Unidentified spp. 1 1 1 1 Unidentified spp. 2 1 1 1 1

Other softcoral species... 1 2 2 1 1 2 2 2 2

HYDROZOA Aglaophenia allmani 1 1 1 1 1 1 1 1 1 1 Aglaophenia cupressina 1 1 1 3 2 2 1 2 1 1 1 1 Lvtocarpus philippinus 1 I

Other hydrozoan species... 1 1 1

SCYPHOZOA Cassiopeia ornata 1

ANTHOZOA ktinodendron plumosum 1 1 I I Heteracm aurora I 1 1 1 Hetercu:tis magnifica 1 1 1 1 1 1 2 1 1 Heteractis malu 1 Palythoa heiden I Phymanthus crucifer I.·'· Stoichactis JliIlfJ,8 1 ,. \ 1 1

Species count .' PHYLUM PLATYHELMINTHES Pseudoceros splendidus. Pseudoceros zebra

Other pla!)'helminthes species... I I

Species count 6 9 16 12 7 0 12 14 13 13 13 13 11 11 10 6 MACRO INVERTEBRATE LOCATION SPECIES :I: ..:I - ~~ f!S ~Z rz:lrz:l - ~ Z rz:l z~ 8rz:l rz:l~ c:Q 00 ~Q ~~ Q !i 5f3 rz:l ~~ ~~ f~ ~~ :I:j :I: Q ~ rz:lO o~ o~ Q" ~§ 01> ~I> ~~ 0 ~ z:i ..:I E! ~ Q c:Q ~ 00

PHYLUM MOLLUSCA GASTROPODA PROSOBRANCffiA Charonia tritonis Conus consors I I 1 Conus textile I Cypraea tiJZris I Cypraecassis rufa I Harpa amouretta I I I Lambis chiragra I I Lambis crocata I I Lambis lambis I I I I Ovula ovum I 2 I I Vasum ceramicum I

Other prosobranchia species... I I I I

OPISTHOBRANCffiA Bulla ampulla 1 1 Chromodoris quadricolor I I I Phyllidia varicosa I 1 2 I 1

Other opisthobranchia species... I I

" BIVALVIA Pedum spondylioideum ,', ",' I Pinna muricata I Pycnodonta hyotis I ,"" tt·,.)t Spondylus aurantius I I ,,'>' Tridacna crocea I I I Tridacna KiRas Tridacna squamosa

" CEPHALOPODA Octopus cyaneus I I 2 1 3 2 I Sepia planllon I I . I Species count 3 3 9 5 2 0 3 3 4 2 4 6 3 4 3 2 MACRO INVERTEBRATE LOCATION SPECIES = rIJ ..::I i= ~~ 0 ~z "'1~ ~ Z "'1 ~~ 8"'1 CQ 00 "'1i: "'1 z~ ~~ :;;!~ =f3 0 !i ~~ 0..::1 "'1 i=~ fi z..::l =..::1 =0 ~ ~§ Cl!> ~~ !;2!> of!: o~ ~~ 0 ...:I ~ CQ r!2 Ci! ~ 8 IC

PHYLUM ANNELIDA POLYCHAETA Reteterebella Queenslandia 1 1 Sabellastarte magnifica 1 1 1 1 1 Spirobranchus RiRUnteus 1 1 1 1 1 1

2 2 1 0 1 0 ~ Species count 1 2 2 2 0 0 0 0 0 0

PHYLUM ARTHROPODA CRUSTACEA Dardanus meJ(istos 1 1 1 LYBwsQuiUa maculata 1 Odontodactylus scyllarus 1 1 1 1 Panulirus versicolor 1 1 Periclimines brevicarpalis 1 1 Stenopus hispidus 1

Other crustacean species... 1 l' 1 1 1 1

Species count 0 1 1 2 1 0 1 2 2 2 3 0 0 2 1 1 I,·::',···· PHYLUM BRYOZOA ..:.. (. " 1 Adeonellopsis sulcata 1 .' 1 . ,. 1 Adeonellopsis sulcata 1 J .. 1 . 1· ... 1 1 lodictvum phoeniceum ::. I . " ,,' . , Other bryozoa species... L '.: 1 > Species count 1 3 2 1 0 0 0 0 1 1 0 l' 0 1 0 0 MACRO INVERTEBRATE LOCATION SPECIES ::c 0 rn oJ ::c ~ C ~z tz:ltz:l Eo ~~ r:1 Z 00 tz:l zEo- 8tz:l tz:l;:) a:l ~ tz:l~ ;:)~ z~ ~c ~@ 6~ 0 tz:l ::c< ~oJ f~ zoJOoJ ::cj ::cO ~ ~§ Os;: tz:l0 ;;as;: O~ OJ i~ 0 ~ zr:1 ii! ~ is a:l ~ 10 CCl .! .! Site 4 en en Site 1 Site 7 Site 2 Site 3 Site 8 Depth SiD S D In I Out SiD SiD SiD SiD SID

PHYLUM ECHINODERMATA ... CRINOIDEA Comanthus parvicirrus 1 1 1 ./ 1 1

Other crinoid species... 1 1 1 1 1

ASTEROIDEA kanthaster planci 1 1 1 Choriaster Jl1"anulatus 1 1 Culcita schmideliana 1 1 1 1 2 Linckia laeviRata 1 2 1 1 2 1 2 2 1 1 1 1 1 Linckia multi ora 1 1 1 1 1 1 1 1 .... 1 Nardoa rosea 1 1 Protoreaster lincki 3 3 3 2 3 1 - Thromidia catalai 2 1 1 - Other asteroid species... 1·

OPHIUROIDEA Astroboa clavata 1 1 1 1 Oohiocoma erinaceus 1 1 1 1 Ophiocoma pica 1 1 1 1 1 1

ECHINOIDEA Diadema savignyi 1 2 1 2 2 1 Diadema setosum 1 1 2 1 1 1 Echinocardium cordatum 1 Echinometra mathaei 3 Echinostreohus molaris 2 2 1 1· 1 1 1 1 1 1 1 1 1 1 1 1 .- Echinothriz diadema 3 1 2 1 1 3 1 3 3 1 Heterocentrotus mamillata 1 1 Trioneustes Jl1"atilla 3 >

. i • . HOLOTHUROIDEA Bodhadschia ar/lU8 if Bodhadschia graeffei 1 Holothuria edulis 1 1 1 1 2 1 1 1 1 1 Stichoous chloronotus 1 1 Stichopus variegatus 1 1 2 1 1 $ynapta maculata 2 1 Thelenota ananas 1 1 2 ~

Species count 10 11 17 12 10 1 6 4 18 12 7 8 3 4 6 5

__ .1 Table 7.2 Sea Urchin Counts On Study Sites

MACRO INVERTEBRATE LOCATION SPECIES :I: > (,) rI} ...::I :I: Q ~Z r.:l Eo ~.~ < r.:l ::l r.:l~ r.:l Z (,)0 ~b 8r.:l r.:l Q ttl rzJ ::l~ r.:l@ Q !i Z~ ~~ ~Q :I:~ ~...::I ~i 0...::1 5&3 r.:l 0...::1 :t:...::I ~a: ~ (,)~ 5~ c. ~§ > r.:l~ ~> 2~ 0 g Zr.:l ...::I r.:l ttl ~ Ci! ...::I is

IlO Cl:l Site 4 ~ ~ Site 1 Site 7 Site 2 Site 3 Site 8 i:i3 i:i3 Depth SiD S D In lOut SiD SiD SID SiD SiD

Echinothru di.adema Echinostre hus molaris MACRO INVERTEBRATE LOCATION SPECIES :I: 0 ...:l :I: ~ ~ ~Z r.:lr.:l Eo < ~ r.:l Z r.:l 8r.:l Q ~~ ll:l 00 zb r.:l r.:l@ ~ r.:l ~~ ~:I: Z~ 5~ Q :I:~ ~...:l ~~ ~Q r.:l Q,,:I: 0:3 :I: o...:l r.:lO 0_cn 5~ ~ ~ ~~ i~ 0 g E§ z;J ...:l r.:l ll:l f:!a ii! ...:l Q

10 lC Site 4 .3 .3 Site 1 Site 7 Site 2 Site 3 Site 8 i:i3 i:i3 Depth SID S D In lOut SiD SID SID SiD SID

PHYLUM CHORDATA ASCIDIACEA Didemnum moUe 1 1 1 1 1 1 1 1 1 1 Didemnum moseleyi 1 1 1 1 1 1 1 Polyeitor RiRanteum 1 Unidentified spp. 2 1 1 1 2 1 2

Other ascidian species... 1 1 1 1 1 1 1

Species count 0 2 3 0 0 0 3 2 0 0 3 4 2 4 5 4

Total invertebrate count 103

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George, J.D (1980) Photography as a marine biological research tool. In: Price, J.H.; D.E.G. Irvine and W.F. Farnham (eds.) The shore environment Vol 1. Methods. systematics ass. special. 17(a): 45-115.

Haywood, M. and S. Wells (1989) The interpet manual of marine invertebrates. Salamander Books Ltd. London, U.K.

March, L.M. (1977) Coral reef Astreroids of Palau, Caroline Island. Micronesica. 13: 251-281. 104

McClanahan, T.R. (1989) Kenyan coral reef-associated gastropod ~ fauna: a comparison between protected and unprotected reefs. Mar. Ecol. Prog. Ser. 53: 11-20.

McClanahan, T.R. and N.A. Muthiga (1988) Changes in Kenyan coral reef community structure and function due to exploitation. Hydrobiologia. 166: 269-276.

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Pulitzer-Finali, G. (1982) Some new or little-known sponges '.,. from the Great Barrier Reef of Australia. Bolletino dei musei e degli istituti biologic della. 48/49: 87-141.

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Talbot, F. (1984) Reader's digest book of the great barrier reef. Reader's Digest Services Pty Limited, Sydney, Australia.

T~ylor, J.D. (1971) Reef associated molluscan assemblages in the western Indian Ocean. Symp. zool.Soc.Lond. 28: 501-534.

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SECTION 8

CON C L U DIN G REM ARK S

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CONCLUDING REMARKS

This report provides details of the distribution and occurrence of a wide range of marine habitats and species from which it is possible to draw several general conclusions with respect to the whole ecology of the area. In particular, comment can be made concerning the distribution of critical habitats and the nature of biogeographic trends. These general conclusions may be used in association with observations on potential and actual habitat deterioration in the survey area to develop recommendations for the management of the Diani coastal resources and for the establishment of protected areas. These recommendations are presented in detail in the accompanying report (Part II).

CRITICAL HABITAT DISTRIBUTION

Evidently a number and wide variety of habitats contribute towards the high productivity of the coral reefs of the Diani coast. The seagrass beds and mangrove stands provide nutrients and are also critical habitats in the sense that they are vital to the breeding and reproduction of species of economic importance or scientific significance as well as being of primary si.gnificance to many species of molluscs, lobster and reef f1Sh. The channels passing through the islands carry the nutrients from the mangrove stands to the reef and are also vital to the breeding and reproduction of the many reef species using these channels as a nursery area.

Such areas not only export primary food material to the reef but feature in the life cycle of many reef species. The disruption of mangroves or the pollution of channels by land borne pollution docks and marinas can therefore not only affect the productivity of the areas themselves but also threaten the reefs and the natural productivity of the whole region.

The productivity of the reef is variable being highly productive local to the high energy channels through the fringing reef and affected at wider channels by sedimentation from water borne sediment from the mainland. The coral reefs are however the single most productive habitat in the productive neighbouring areas. Fish and invertebrates may migrate to other areas to be taken by predators, and predators such as barracuda and Jacks may visit the reef to feed even though they themselves may be caught by man well out in open water.

The occurrence and distribution of these critical habitats has important implications for the development of a management plan for the natural resources of the region and the degree of inter-dependence between habitats cannot be overlooked.

BIOGEOGRAPHY

The extent of the survey area was small in terms of coral reef biogeographical distribution and it is not surprising that no clearly defined biogeographical sub-zoning was recognised. 107

Major differences and deficiencies in the distribution of fish and other animal species within the area are related to normal distribution corresponding to preferred habitats but there is also clear evidence of major differences when comparing protected areas (Kisite MNP/Mpunguti MNR) with those areas of Diani affected by impacts of commercial and recreational activities.

MANAGEMENT CONSIDERATIONS

This survey has been carried out in order to assist in the development of guide lines for the management of the renewable natural resources of the coastline and inland waters of this part of the Kenya coast. The detailed data on the occurrence of critical habitats and significant species clearly provide key information for their management. It is essential to know how much of each resource is available and where it is.

The essential ingredients of any future management plan for the area are likely to be to maintain and restore the value of the natural resources where there area at present impacts or likely to be impacts in future. It is necessary therefore first to designate the areas to be protected based upon ) ecological and social parameters and then to control the activities with potentially harmful effects withift ~he bOtiftdaries J of the site and those outside but linked by critical status.

The following report, 'Management of the Marine and coastal J resources of Diani and recommendations for managing protected areas', provides a case for such measures in this area and develops recommendations for a coastal zone management plan J and for the establishment of a network of protected areas.

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