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Title: Reproductive and molecular ecology of the European lobster : implications for conservation management
Author: Ellis, Charlie Dove
Awarding Body: University of Exeter
Current Institution: University of Exeter
Date of Award: 2016
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The European lobster (Homarus gammarus) is an ecologically important benthic decapod which supports fisheries that are critical to the economic prosperity of coastal communities. However, populations across its range are pressured by rising exploitation, from which management has failed to prevent stock collapses in the recent past. Fisheries management of the species is significantly hindered by deficiencies in our knowledge of fundamental characteristics of population biology, including the connectivity and genetic diversity of stocks. As a result, the effectiveness of strategies designed to conserve recruitment and ensure harvests are sustainable is poorly understood. This thesis focuses on elucidating aspects of reproductive and molecular ecology in H. gammarus which can be used to inform and appraise conservation management initiatives, currently applied via both the regulation of capture and the wild release of hatchery-reared juveniles. The size-specific fecundity of reproducing females was defined around southwestern UK, and spatial variation in clutch size between populations was linked to a longitudinal gradient in oceanic temperature range across Northern Europe. The reconstruction of paternal genotypes show that single males fertilise individual clutches, which hints at demographic stability within a productive Atlantic fishery. Population genetic structure, investigated at a fine spatial scale in the same region, evidenced high connectivity and suggests that the localised interventions of an active hatchery do not lead to juveniles being released beyond areas they might naturally recruit via planktonic dispersal. However, genetic differentiation and isolation-by-distance at a broad geographic scale indicate that direct gene flow between remote populations is limited, so that (i) a failure to maintain spawning stock biomass may negatively affect local recruitment, (ii) the utilisation of non-resident broodstock for hatchery stocking may cause a loss of adaptive potential, and (iii) the recovery of depleted stocks is likely to be problematic. Finally, simulations indicated that genetic parentage assignment will prove accurate in distinguishing cultured individuals from natural stock among admixed populations in the wild, an important development that should facilitate the optimisation of hatchery stocking and lead to rigorous assessments of the conservation value of releasing lobsters reared in captivity.
Supervisor: Hodgson, David Sponsor: European Social Fund ; Fishmonger's Company
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available