Effective fishing effort indicators and their application to spatial management of mixed demersal fisheries

Since the Common Fisheries Policy reform in 2002, there have been various proposals for designing effective input-management tools in the context of demersal multispecies and multimétier fisheries to augment quota management. The relationship between fishing mortality and effort exerted by the English beam trawl fleet is investigated for two stocks of North Sea demersal fish, plaice, Pleuronectes platessa L., and sole, Solea solea (L.). Catchability was adjusted by accounting for targeting by this gear, seasonal and area effects, and individual vessel variation, using results from a generalised linear mixed-effects model (GLMM) that included random effects (in this case, vessel). Descriptors were standardised in relation to distinct submétiers and their impact on both species. Fishing efficiency was calculated as the ratio between relative nominal landings per unit effort derived from the GLMM and survey indices from a standard survey vessel. Fishing efficiency for sole increased (+0.6% annually) and for plaice decreased (−6.2%), likely because of changes in targeting, fuel costs and regulations.