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Work Package 8 - Genetics


  • Dr. Illaria Coscia (Aberystwyth University)
  • Dr. Joe Ironside (Aberystwyth University)
  • Dr. Jo Porter (Heriot-Watt University)
  • Miss Hayley Watson (Aberystwyth University)

The aim of the GENEFISH work package is to assess genetic diversity and gene flow in the common cockle (Cerastoderma edule) and the edible crab (Cancer pagurus), two of the Irish Sea‘ s most commercially important shell fish species. Both species produce planktotrophic larvae and so gene flow depends upon the extent of larval dispersal as well as upon migrations of adults, in the case of the edible crab. We will sample cockles and crabs from multiple sites on both sides of the Irish Sea, including the most heavily exploited populations and those known to have suffered mass mortality. These samples will be analysed using a panel of microsatellite DNA markers to assess genetic diversity and gene flow. The results will be used to test the predictions of our models of larval dispersal and to infer losses of genetic diversity due to overexploitation and/or mass mortality events. These results will enhance the management of crab and cockle populations by indicating the extent to which they comprise discrete, self-recruiting stocks.

Population Genetics of Edible Crab in the Irish Sea

  • Miss Hayley Watson

Edible crab (Cancer pagurus) is of high economic value to the UK and Ireland and is being exploited with increasing intensity due to the decline of fin-fisheries. As part of SUSFISH to inform sustainable development of Irish Sea shellfisheries for the next 50-100 years, we aim to determine the effective population size and genetic structure of C. pagurus populations in this area and to establish the extent to which they are self-recruiting. Knowing such details is essential for the sustainable exploitation of this commercial species.

It has been assumed that C. pagurus form a single, panmictic population around the British coast due to having planktotrophic larvae and mobile adults. However, research using microsatellite markers indicates very restricted gene flow between local C. pagurus populations around Britain.

Current research includes the analysis of C. pagurus from 11 locations within the Irish Sea; seven off the coast of Wales (north, mid and south) and four off the coast of Ireland (north, mid and south) (Figs 1&2). Their genetic diversity and population structure are being investigated by analysing DNA extracted from the haemolymph of living crabs using 12 species-specific microsatellite markers. 

Findings could have important management implications since isolated populations cannot recover through migration from local declines caused by overexploitation or disease.

Ireland Sampling                       
Figure 1. Sampling C. pagurus  in Ireland                                                       Figure 2. Bleeding haemolymph from C. pagurus for DNA analysis