Crab and lobster fisheries - stock assessments: results 2016 to 2019

Abstract

The Scottish creel fisheries are long established and tend to be mixed species fisheries with brown crab, velvet crab and lobster as the main target species. The importance of each species varies regionally and in relation to season and market demand. The landings of the combined fishery into Scotland in 2020 were 9,000 tonnes with a first-sale value of £31M. This report presents the results of Scottish regional brown crab (Cancer pagurus), velvet crab (Necora puber) and lobster (Homarus gammarus) stock assessments carried out by Marine Scotland Science (MSS) based on length cohort analyses (LCAs) applied to commercial length frequency data for the period 2016-19. The stock assessments presented are conducted on a regional basis for the crab and lobster management areas in Scottish waters, with males and females assessed separately. The methodologies used include length-based methods, size indicators and analysis of survey data, providing stock status for stocks with available data. Analysis of trawl and dredge survey data for brown crab in the east and west coast indicates that abundance and recruitment (the number of young crabs entering the adult population annually) show a general increase from 2008 until the 2013-2016 period and a decline in recent years. The decline in survey catch rates coincides with a period a declining brown crab landings from 2016. There are no survey data available for velvet crab and European lobsters. The stock assessment results in this report for the three species are based on estimates of fishing mortality in relation to a reference point for each stock, to infer whether or not a stock is fished above the level that would in theory result in maximum sustainable yield (in the long term). The results of assessments for the period 2016-19 indicated that in the majority of the assessment areas, brown crab, velvet crab and lobster in Scotland were fished close to or above fishery reference points. To ensure sustainability of these fisheries, it is recommended that effort/fishing mortality should be reduced in those stocks for which fishing mortality is estimated to be above the sustainable fishing mortality (F_MSY).