Elasmobranchs in UK seas: prioritising vulnerability and addressing life history data gaps to inform assessment and management

Phillips, Sophy (2020) Elasmobranchs in UK seas: prioritising vulnerability and addressing life history data gaps to inform assessment and management. Doctoral thesis, University of East Anglia.

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Elasmobranchs straddle commercial and biodiversity (conservation) interests. Their biological vulnerability has led to patterns of stock depletions and regional extirpations following commercial exploitation. Proactive management through pragmatic and timely measures are required to promote sustainable exploitation and conserve depleted species - both central tenets of the UK Shark, Skate and Ray Conservation Plan (analogous to a National Plan of Action (NPOA) for Sharks). The current thesis provides a framework for evidence-based decisions to be made under NPOAs, with case-studies providing new biological data to inform assessments and management advice in support of sustainable exploitation.

The UK-NPOA omits a number of elasmobranchs and does not prioritise species or actions. This thesis considers all UK elasmobranchs using data-limited methods to provide an impartial, evidence-based prioritisation of species of interest for subsequent research. Research and management needs are further prioritised using a semi-quantitative Productivity Susceptibility Analysis (PSA) to rank relative vulnerabilities of elasmobranchs that may interact with otter trawl and gillnet fisheries in the Celtic Sea. These approaches will be of wider applicability, particularly for developing countries where data are most limited.

The approaches guide the selection of three commercially exploited species as case studies: starry smooth-hound Mustelus asterias, shagreen ray Leucoraja fullonica and sandy ray Leucoraja circularis. Supplementation of fishery-independent surveys with additional specimens provided a standardised approach to collecting quantitative maturity data, which in turn informs assessment and management advice. Results have already been incorporated into ICES Expert Group assessments and advice. All three species are vulnerable to over-exploitation. A maximum landing length of ca. 100 cm for starry smooth-hound would protect the large, fecund females. Both Leucoraja species are listed as Threatened by IUCN and with the presentation of the first available estimates of maturity which highlight their biological vulnerability, restrictions on landings are recommended.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Chris White
Date Deposited: 20 Dec 2021 14:43
Last Modified: 20 Dec 2021 14:43
URI: https://ueaeprints.uea.ac.uk/id/eprint/82741

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