Cefas contract report C3140 Marine Ecosystem Integrity: Development of a Marine Trophic Index for UK waters and recom- mendations for further indicator development for Natural Environment Group, Science Division, Defra (CRO 382) Marine Ecosystem Integrity: Development of a Marine Trophic Index for UK waters and recommendations for further indicator development. Final report for Natural Environment Group, Science Division, Defra Bristol, UK (CRO 382) by John Cotter Stuart Rogers Jim Ellis Steve Mackinson Nick Dulvy John Pinnegar Simon Jennings Simon Greenstreet* Centre for Environment, Fisheries and Aquaculture Science (Cefas) Lowestoft United Kingdom, NR33 0HT email: [email protected] *Fisheries Research Services, Aberdeen, Scotland, AB11 9DB 1 Acknowledgements: The authors are grateful to all those who took part in consultations associated with this project. They are listed below. Their views have been used to assist the writing of this report but they are not responsible for the contents. Chris Pirrie, Natural England Dan Laffoley, Natural England David Connor, JNCC Henrik Sparholt, ICES, Copenhagen Ian Boyd, Sea Mammal Research Unit, St Andrews Jo Myers, Marine biodiversity adviser, Defra, NESD Lucy Oliver, Countryside Council for Wales Mark Stevenson, Defra, NESD Mark Tasker, JNCC Matt Service, Fisheries & Aquatic Ecosystems Branch, AFESD Mike Elliott, IECS, Hull Paul Somerfield, Plymouth Marine Laboratory Phil Kunzlik, FRS Aberdeen Trine Christiansen, European Environment Agency William Cheung, University of British Columbia, Fisheries Centre Yunne Shin, Institut de recherche pour le développement, Sète, France The project steering committee advised on content and direction. It consisted of Jo Myers (Defra), Mark Stevenson (Defra), Mark Tasker (JNCC), Dan Laffoley (NE), and Stephen Hall (Defra). The project was funded by the Natural Environment Science Division of the Department of Environment, Food and Rural Affairs and Natural England under contract CRO 382, Cefas code C3140. 2 Contents Acknowledgements:...................................................................................................2 Executive Summary.......................................................................................................5 1. Introduction..............................................................................................................14 1.1 Project Background............................................................................................14 1.2 Project Aims and Objectives..............................................................................15 1.3 Scope..................................................................................................................16 1.4 Report Structure.................................................................................................16 2. Data and Methods ....................................................................................................18 2.1 Sources of fisheries data, geographical coverage and computations.................18 2.2 Standardised criteria for assessing the suitability of the MTI and alternatives for UK marine waters ....................................................................................................20 2.3 Assessment using scientific expertise................................................................21 3. The marine trophic index (MTI)..............................................................................22 3.1 Introduction and review .....................................................................................22 3.2 Sources of trophic level data for UK marine fish ..............................................24 3.3 Computation of the MTI ....................................................................................26 3.4 MTI results using UK landings data ..................................................................27 3.5 MTI results using UK surveys ...........................................................................32 3.6 MTI results using size-based trophic levels and UK surveys............................36 3.7 Assessment of the MTI options for UK marine waters .....................................39 3.7.1 Availability and future security of data ......................................................39 3.7.2 Representativeness for UK waters..............................................................40 3.7.3 Capacity to provide long term, interpretable trends....................................41 3.7.4 Relevance to marine ecosystem integrity, and validity of thresholds.........42 3.7.5 Power of the indicator to detect change or trends.......................................43 3.7.6 Discussion and further conclusions ............................................................44 4. Length-based indicators (LBI).................................................................................46 4.1 Introduction and review .....................................................................................46 4.2 Computations .....................................................................................................47 4.2.1 OSPAR EcoQO / ICES (2007) length indicator.........................................47 4.2.2 Proportionate length indicator.....................................................................47 4.3 LBI results using UK survey data......................................................................48 4.3.1 English groundfish survey ..........................................................................48 4.3.2 Channel beam trawl survey.........................................................................49 4.3.3 Irish Sea beam trawl survey........................................................................49 4.3.4 Scottish otter trawl survey ..........................................................................54 4.4 Assessment of length-based indicators (LBIs) for UK marine waters ..............55 4.4.1 Availability and future security of data ......................................................55 4.4.2 Representativeness of UK waters ...............................................................56 4.4.3 Capacity to provide long term, interpretable trends....................................56 4.4.4 Relevance to marine ecosystem integrity ...................................................56 4.4.5 Validity to set thresholds ............................................................................57 4.4.6 Power of the indicator to detect trends. ......................................................57 4.4.7 Discussion and further conclusions ............................................................57 5. Threat and occupancy indicators .............................................................................59 5.1 Introduction and review .....................................................................................59 5.2 Method ...............................................................................................................61 5.3 Theory................................................................................................................62 5.4 Results................................................................................................................63 3 5.4.1 English GFS................................................................................................63 5.4.2 Channel BTS...............................................................................................65 5.4.3 Irish Sea BTS ..............................................................................................65 5.5 Assessment of threat and occupancy indicators for UK marine waters.............71 5.5.1 Availability and future security of data ......................................................71 5.5.2 Representativeness of UK waters ...............................................................71 5.5.3 Capacity to provide long term, interpretable trends....................................72 5.5.4 Relevance to marine ecosystem integrity ...................................................72 5.5.5 Validity to set thresholds ............................................................................72 5.5.6 Power of occupancies to detect change and trend. .....................................73 5.5.7 Discussion and further conclusions ............................................................73 6. Non-fish based Indicators for assessing marine ecosystem integrity ......................75 7. Other aspects............................................................................................................77 7.1 Statistical assessment of trends..........................................................................77 7.1.1 Smoothing method......................................................................................77 7.1.2 Estimating 2nd derivatives...........................................................................78 7.1.3 Nonparametric methods..............................................................................78 7.1.4 Quality control methods..............................................................................79 8. Recommendations and conclusions .........................................................................80 8.1 MTI ....................................................................................................................80 8.2 Length-based Indicators.....................................................................................81