Zoology (Reports)

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    North Eastern Atlantic cephalopods stock assessment in a data limited framework Surplus Production in a Continuous Time (SPiCT): Annex1to WP.4.2deliverable
    (Cephs and Chefs (Interreg Atlantic Area Community Engagement Publications), 2021) Larivain, Angela; Petroni, Michael; Iriondo, Ane; Abad, Esther; Valeiras, Julio; Moreno, Ana; Dinis, David; Rocha, Alberto; Laptikovsky, Vladimir; Robin, Jean-Paul; Power, Anne Marie; European Regional Development Fund
    The lack of management leaves fishery resources vulnerable to increases in fishing pressure.Although some cephalopods are of commercial importance, most of Northeast Atlantic stocks are non-quota species(no catch or effort limits in large-scale fisheries and only some harvest control rules at the local scale in inshore fisheries). Cephalopods are short-lived, fast growing species, with highly plastic lifehistory characteristics and wide year to year variation in abundance linked to environmental variation. This had contributedto prevent the use of classical stock assessments methods and monitoringsuch species is also data-demanding with some of the largest EU cephalopod fisheriesbeing not includein fishery data collection protocols.These factors have led the cephalopods to be classified under the ICES category 3 data limited stocks.Severalstock assessment exercises were already carried out in European cephalopods but the wide variety of models tested to tackle distinctive features of different species makes it difficult to compare results. The progress on assessment methods for short-lived data limited stocks that are cephalopods and estimation of biological and MSY proxy reference points, focused on the application of the model SPiCT for stochastic production in continuous time (Pedersen and Berg, 2017).This model allowed the abundance time series for several Northeast Atlantic cephalopod stocksto be fit, including cuttlefish and squids(Loliginidae and Ommastrephidae) and octopuses (Octopodidae). The different assessed stocks were distributedfrom Scottish to Spanish and Portuguese fishing grounds. All models have beenfitted with the R package SPiCT, the homogeneous protocol allowingcomparisons between outputs. In the presentedcases, the model converged and the exercise provided useful preliminary diagnostics, allowing long-term trends in productivity to be considered reasonable(only the Rockall6.b exercise for Loligospp.showed unreliable outputs). Results for the cuttlefish indicated a rather good condition of the stock since 2008, relative fishing mortality interestingly following the fishing efforts trends on the available time-series. For several Loliginidstocks, results allowed statements to be made about whether biomass and fishing effort were above or below MSY reference values. However, especiallyforOmmastrephidaeand Octopodidae, confidence intervals were still huge and it was generally not possible to be sure whether biomass and fishing effort were above or below reference levels.Also the convergence was sometimes obtained after a set of input parametrization on the priors.The possible causes for this uncertaintyare discussed andwill have to be further exploredeven if some refinements to the approach taken arealreadyproposed for future work.