Having Confidence in Productivity Susceptibility Analyses: A method for Underpinning Scientific Advice on Skate Stocks?

tNational and European shark conservation plans aim to manage elasmobranch stocks sustainably. How-ever uncertainties and deficiencies with available data hamper traditional, quantitative assessmentmethods of stock status to inform those plans, and thus effective management. The International Councilfor the Exploration of the Sea (ICES) Expert Groups have explored a range of data deficient assessmentmethods that may be used to support management advice, including Productivity Susceptibility Analysis(PSA). This method was applied to the demersal elasmobranch fauna (21 species) of the Celtic Sea toexplore how such approaches could inform the management of skates (Rajidae). This species complex isan important catch component for demersal trawl and gillnet fisheries and is currently managed undera mixed species total allowable catch (TAC). PSAs were conducted on both of these fisheries, by fourexperts from three countries to introduce independence, and to quantify the range in perceptions of eachstock. Confidence scoring of attributes was incorporated and probability distributions generated to modeluncertainty in the expert responses to susceptibility attributes. Results showed that three shark species(tope, Galeorhinus galeus; angel shark, Squatina squatina and spurdog, Squalus acanthias) were the mostvulnerable species in both fisheries (a consequence of their life history strategy and large size), followedby two skates (otter trawl) and three skates (gillnet). All of these species have some form of restrictivemanagement and, apart from tope, are either currently listed as prohibited species or have a zero TAC inthe area. Blonde ray, Raja brachyura was ranked as the next most vulnerable member of the commerciallyexploited skate complex. This adaptation of the PSA approach enabled skate species of higher and lowerrisk to be ranked and thus inform where management efforts should be focussed, whilst giving a novelconsideration to uncertainty through canvassing expert opinion.

MCCULLY Sophy R.;  SCOTT Finlay;  ELLIS Jim R.; 

2015-09-30

ELSEVIER SCIENCE BV

JRC89752

0165-7836,   

http://www.sciencedirect.com/science/article/pii/S016578361500017X,    https://publications.jrc.ec.europa.eu/repository/handle/JRC89752,   

10.1016/j.fishres.2015.01.005,