Abundance and Spatial Distribution of Brown Crab (Cancer pagurus) from Fishery-Independent Dredge and Trawl surveys in the North Sea

Carlos Mesquita* (Corresponding Author), Helen Dobby, Graham J. Pierce, Catherine S. Jones, Paul G. Fernandes

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Spatial information is important to understand the distribution, population structure and dynamics of commercially important marine species. Brown crab (Cancer pagurus) is a crustacean that supports important commercial fisheries along the British coastline. There have been no specific studies based on fishery-independent surveys documenting the habitat preferences of brown crab around Scotland. This paper provides an analysis of dredge and trawl fisheries surveys in the North Sea (2008-2018) with the aim of describing the spatial distribution of brown crab and developing abundance and recruitment indices for the species. The distribution of brown crab is investigated using geostatistical methods, and generalized additive models (GAMs) are used to model crab catch rates in relation to a number of explanatory variables (depth, distance to coast, sediment type and year). Brown crab catch rates were higher in coastal areas. The male and female crab distribution was relatively similar and juvenile crabs (<100 mm) showed a very clear inshore distribution along the shoreline up to 20 km from the coast. The total abundance as estimated from the dredge survey varied between years, from 34 to 86 million crabs from the dredge survey. The annual trawl catch rate, which provides an index of relative abundance, ranged between 16 and 65 animals/km2. The dredge and trawl indices were correlated, showing a similar trend of increasing catch rates in the early years of the time series up to 2016, and a subsequent reduction. A recruitment index was also estimated, showing a gradual increase in captured juvenile crabs up to 2014, followed by a steep decrease with the lowest estimated value being reached in 2018. The advantages and limitations of using active fishing methods rather than passive gears such as traps for obtaining standardized catch rates are discussed. The results obtained provide baseline information on abundance, distribution and habitat for a widely distributed species and could be used in future stock assessments, informing the management of this important species.
Original languageEnglish
JournalICES Journal of Marine Science
Publication statusAccepted/In press - 26 May 2020

Keywords

  • brown crab
  • geostatistics
  • survey
  • fishery-independent data
  • dredge
  • trawl
  • spatial distribution
  • creel fisheries
  • Scotland

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