Project Code: MB5201 National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Authors: J. R. Ellis, V. A. Bendall, S. J. Hetherington, J. F. Silva and S. R. McCully Phillips. Issue date: 15-Jan-2016 Cefas Document Control Title: National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Project Code: MB5201 Submitted to: Defra Date submitted: 15-Jan-2016 Project Manager: Jim Ellis Project Sponsor: Wendy Dawson Report compiled by: Jim Ellis, Vicky Bendall, Stuart Hetherington, Joana Silva and Sophy McCully Phillips Quality control by: David Righton Approved by & date: Version: V1.4 Ellis, J. R., Bendall, V. A., Hetherington, S. J., Silva, J. F. and McCully Suggested citation Phillips, S. R. (2015). National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE). Project Report (Cefas), x + 105 pp. Version Control History Author Date Comment Version Ellis et al. 25 Feb 2015 Initial draft V1.0 Ellis et al. 26 Feb 2015 Edits made by JE and SM V1.1 Ellis et al. 04 Mar 2015 QA by DR, further edits by JE/SM V1.2 Ellis et al. 24 Jul 2015 Following comments from PSG V1.3 Ellis et al. 15 Jan 2016 Final version after external review V1.4 National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page i National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page ii Project Code: MB5201 National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Authors: J. R. Ellis, V. A. Bendall, S. Hetherington, J. F. Silva and S. R. McCully Phillips Issue date: 15-Jan-2016 Head office Centre for Environment, Fisheries & Aquaculture Science Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK Tel +44 (0) 1502 56 2244 Fax +44 (0) 1502 51 3865 www.cefas.defra.gov.uk Cefas is an executive agency of Defra National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page iii National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page iv Table of contents Informing policy .................................................................................................................................... 1 1 Introduction ................................................................................................................................... 3 1.1 Background ............................................................................................................................. 3 1.2 Project background ................................................................................................................. 4 1.3 Format of the report ............................................................................................................... 5 2 Elasmobranchs of the British Isles and prioritisation of species of interest ......................... 7 Summary ............................................................................................................................................. 7 2.1 Elasmobranchs of the British Isles .......................................................................................... 8 2.2 Prioritising elasmobranchs and holocephalans of interest .................................................. 13 2.3 Productivity Susceptibility Analyses ..................................................................................... 17 3 Elasmobranch bycatch in the Celtic Sea .................................................................................. 25 Summary ........................................................................................................................................... 25 3.1 Introduction .......................................................................................................................... 26 3.2 Stakeholder engagement ...................................................................................................... 26 3.3 Approach and data collection ............................................................................................... 27 3.4 Catches of spurdog, common skate and porbeagle ............................................................. 31 3.5 Tagging studies and biological information .......................................................................... 40 3.6 At-vessel mortality ................................................................................................................ 42 3.7 Best practice in handling elasmobranchs and developing a ‘Code of conduct’ ................... 44 3.8 Lessons learnt: Advantages and limitations of fisher-collected data ................................... 47 4 Biological investigations of elasmobranchs ............................................................................ 49 Summary ........................................................................................................................................... 49 4.1 Introduction .......................................................................................................................... 50 4.2 Starry smooth-hound Mustelus asterias .............................................................................. 53 4.3 Spurdog Squalus acanthias ................................................................................................... 61 4.4 Porbeagle Lamna nasus ........................................................................................................ 69 4.5 Other biological investigations ............................................................................................. 73 National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page v 5 Concluding remarks ................................................................................................................... 77 6 Acknowledgments ...................................................................................................................... 81 7 References ................................................................................................................................... 82 8 Annexes ....................................................................................................................................... 87 8.1 List of acronyms .................................................................................................................... 87 8.2 Outputs from project and associated work .......................................................................... 88 8.3 Taxonomic list of chondrichthyans of the British Isles and adjacent waters ........................ 91 National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page vi Figures Figure 1. Diversity of the elasmobranch fauna of the British Isles, showing (a) spurdog, (b) angel shark, (c) porbeagle, (d) blue shark, (e) tope, (f) starry smooth-hound, (g) lesser-spotted dogfish, (h) greater-spotted dogfish, (i) common stingray and (j) electric ray .......................................................... 9 Figure 2. Diversity of the elasmobranch fauna of the British Isles, showing (a) starry ray, (b) blue skate, (c) sandy ray, (d) shagreen ray, (e) cuckoo ray, (f) blonde ray, (g) thornback ray, (h) small-eyed ray, (i) spotted ray and (j) undulate ray. ............................................................................................... 10 Figure 3: PSA plot indicating vulnerabilities of Celtic Sea elasmobranchs in the demersal gillnet fishery. Species codes given in Table 9. ................................................................................................ 24 Figure 4: PSA plot indicating vulnerabilities of Celtic Sea elasmobranchs in the demersal otter trawl fishery. Species codes given in Table 9. ................................................................................................ 24 Figure 5: Disentangling a common skate from fishing gear ................................................................. 28 Figure 6. Main fishing grounds of Vessel A when setting gillnets. ....................................................... 32 Figure 7. Main fishing grounds of Vessel A when setting tangle nets. ................................................. 33 Figure 8. Main fishing grounds of Vessel B when setting gillnets. ........................................................ 34 Figure 9. Main fishing grounds of Vessel C when setting gillnets. ........................................................ 36 Figure 10. Main fishing grounds of Vessel C when setting tangle nets. ............................................... 37 Figure 11. Spatial distribution of spurdog bycatch observed by ICES rectangle .................................. 38 Figure 12. Spatial distribution of porbeagle bycatch observed by ICES rectangle ............................... 39 Figure 13. Spatial distribution of common skate bycatch observed by ICES rectangle ........................ 39 Figure 14. Length frequency of Dipturus spp. tagged and released, showing those identified as Dipturus batis (BSKT), Dipturus cf. intermedia (FSKT) and Dipturus batis-complex (SKT) .................... 41 Figure 15. Relationship between disc width and total length in Dipturus batis ................................... 41 Figure 16. Length frequency of spurdog Squalus acanthias tagged and released ............................... 42 Figure 17. Length frequency of undulate ray Raja undulata tagged and released .............................. 42 Figure