Population Structuring of the Freshwater Fish, Roach (Rutilus rutilus, L. 1758): Implications for Migration and Management

Steve Crookes

Research output: ThesisDoctoral Thesis

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The roach is a key species component of the economically and culturally significant recreational angling community. It is also a keystone species by which the health of a coarse fishery can be judged. However, despite being commonplace and widely distributed in the British Isles, very little is known about the underlying genetic structuring of this species, which could inform a more inclusive, synergistic management system, thus improving an already billion pound strong industry. This study describes and explains the extent of genetic structuring at hierarchical levels within the putative natural distribution of this species within the British Isles, and to uncover the causes, both historical and contemporaneous, for any non-homogeneous distribution of genetic diversity. Mitochondrial DNA was utilised to account for coarse-grained structuring across catchments to divulge whether any individual catchment or sets of drainages could be considered as individual management units. Low levels of sequence diversity were observed across the UK, consistent with a history of recent post-glacial demographic expansion, although haplotype assemblages within and among river populations differed. The inclusion of microsatellite data allowed a higher resolution analysis of structuring between and within sampled sub-populations of two southeastern rivers: the Thames and the Suffolk Stour. Despite sharing high levels of within-population genetic diversity, significant differentiation was observed among populations within both rivers. Isolation by distance is observed in both rivers, indicating genetic equilibrium had been attained among populations from which estimates of recent migration were obtained. Roach in the Stour embody a source-sink model of equilibrium, explaining its higher levels of inter-population differentiation and rates of migration than the Thames population. The discovery of significant genetic differentiation suggests that one must apply caution in managing this diversity. Stocking from exogenous sources is not recommended unless there exists no other choice.
Original languageEnglish
Awarding Institution
  • Shaw, Paul, Supervisor
Award date1 Aug 2013
Publication statusUnpublished - 2013

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