Applying a Bayesian model incorporating discards in the assessment of four-spot megrim (Lepidorhombus boscii) Southern stock

Since 2003 when the DCF started at European level by countries, discards data are available for many stocks. Four-spot megrim is traditionally assessed with XSA (extended survivor analysis) which does not include discards. For this species, discards in number are very important, being around the 60% of total catch. A Bayesian model incorporating discards was realized for the hake stock in ICES Divisions VIIIc and IXa by Fernández et al. (2010). This model was also designed to produce a complete time-series of discard estimates. Final run of the model is compared with results from XSA performed in the working group of 2010, showing that mayor differences are in the fishing mortality for younger ages, being higher incorporating discards data

Eledone cirrhosa and SPICT or why it is not easy to assess a short lived cephalopod species

Poster.-- Iberian Symposium on Modeling and Assessment of Fishery Resources, 19-22 October, Vigo, SpainAlthough some cephalopods have had always commercial value and others started to increase in value in recent years, unlike European Atlantic stocks of many commercially important finfish and crustaceans, they are not routinely assessed and no specific management measures are applied to fleets catching cephalopods, with the exception of some regional harvest control rules for artisanal fleets. Among the species that has been gaining importance in landings is the horned octopus Eledone cirrhosa. This octopus represents an important bycatch for several North Spanish otter trawl fisheries, appearing in landings but also in discards. Like other cephalopods, E. cirrhosa is a short-lived and fast growing species, and previous studies showed that its abundance varies in relation to physical and environmental conditions. As a first step towards its possible future inclusion in the ICES annual assessment system, a simple assessment model has been tested in the ICES Working Group on Cephalopod Fisheries and Life History (WGCEPH). The chosen model was SPICT (Surplus Production model in Continuous Time). Using landings and two abundance indices (from a commercial fleet and a scientific bottom trawl survey), preliminary results have been obtained. Overall, although the model converged and all the diagnostics were acceptable, the estimated parameters obtained very wide confidence intervals, suggesting that improvements in the model are needed. Further work, including testing other assessment models or selecting other tuning indices, will help in the assessment process for this speciesN