Investigating the inter-cohort genetic structure of Welsh populations of Cerastoderma edule in relation to ongoing Mass Mortality Events within the Burry Inlet

  • Thomas Waymouth

Student thesis: Doctoral ThesisDoctor of Philosophy


Cerastoderma edule is an edible bivalve species with a high commercial value and wide geographic distribution across Europe. The Burry Inlet population in the Carmarthen Bay has been undergoing recurring mass mortality events after spawning every year since 2002, resulting in a stock predominantly consisting of small cockles with significantly lower value. This thesis therefore investigated the inter-cohort genetic structure of this location in conjunction with fisheries situated at Three Rivers, and Dee Estuary to examine fine-scale differentiation and how the mass mortality events may be affecting it. Initial examination using microsatellite markers indicated a chaotic genetic patchiness with cohorts appearing relatively distinct from one another indicating the possibility for these populations living in sweepstakes reproductive success, however longitudinal study of these populations refuted this by showing no increased similarity between the same cohorts over subsequent sampling and the allelic diversity of a cohort being approximate to that of the whole population. Investigation into the inter-cohort genetic differentiation over a temporal scale at Burry Inlet also showed a consistent schism between pre- and post-mortality cohorts, indicating a correlation between the genetic structure of this location, and these mass mortality events. Finally, genotyping by sequencing was employed to develop a large dataset of single nucleotide polymorphisms, supporting previous results showing increased temporal differentiation at both Three Rivers and Burry Inlet, indicating these sites undergo chaotic genetic patchiness however the cause for this pattern could not be determined. Isolating markers acting under selection resulted in one single nucleotide polymorphism which had a higher ratio of minor alleles present in the pre-mortality Burry Inlet in comparison to post-mortality Burry or the Three Rivers cohorts, with a sequence search showing a predicted gene coding for the beta-subunit succinate--CoA ligase enzyme, part of the pathway for anaerobic metabolism.
Date of Award2023
Original languageEnglish
Awarding Institution
  • Aberystwyth University
SupervisorJoe Ironside (Supervisor) & Sarah Dalesman (Supervisor)

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