Conservation of diversity in an exploited species: spatiotemporal variation in the genetics of herring in the North Sea and adjasent areas (HERGEN)


Project leader


Funding source

EU Fifth Framework Programme - Quality of Life and management of living resources


Project Details

Start date: 01/01/2002
End date: 31/12/2004
Funding: 1553000 EUR


Description

The misidentification of population structure within stock complexes can lead to overexploitation by depleting spawning components, affecting intraspecific genetic diversity. This problem is exacerbated in stock complexes with demographically diverse components that intermingle seasonally, as is the case with Atlantic herring, the target species of the present study. Our project has 6 objectives: (1) to estimate the population genetic structure of herring spawning aggregations in the North Sea, Skagerrak/Kattegat, and western Baltic and west of Scotland. (2) To assess short term (among cohorts) and long term (generations) temporal variation in this population structure. (3) To quantify the composition of mixed aggregations generally targeted by the fisheries in these areas. (4) To assess temporal variability in these contributions. (5) To incorporate findings into the management of herring stocks. (6) To disseminate our results. Previous efforts to examine genetic structure in herring using allozymes an mitochondrial DNA have shown little or no heterogeneity among populations. These results could reflect unsuitable sampling from lack of attention to ecological and life history detail, rather than genuine genetic homogeneity among populations. The use of markers with relatively low polymorphism may also have hindered the detection of genetic divergence. We plan to achieve our objectives through consideration of: Sampling, Genetics, Otolith structure, Data analysis. (1) Sampling: We will target ripe-and-running fish from aggregations on spawning grounds, on locations selected taking into account oceanographic processes. Mixed aggregations on feeding grounds will also be sampled. Sampling will be done by institutions in 5 countries using research and fishing vessels, but will be co-ordinated by a single HERGEN partner to ensure representative geographic coverage and standardised protocols. (2) Genetics: our main genetic tool will be microsatellites. Allozymes and mtDNA will be examined in some samples to assess temporal variability by comparison with previous results over a 20 yr period. Genes of the Major Histocompatibility Complex (MHC), known to be under selection, will be used to examine selective differentiation among populations. (3) Life history and otoliths: Fish will be described with respect to length, weight, sex, gonadal stage. Otolith structure will be used to determine season the fish hatched. (4) Data analysis: We will use both, traditional and marker specific statistical techniques. Maximum likelihood methods will be used to estimate proportions of individuals of different sources in a mixed sample (mixed stock analysis) or the population of most likely origin for individuals (assignment tests). We will disseminate information in 3 ways: (1) Reports to the EU. (2) Refereed scientific papers and conference presentations. (3) Contributions to ICES meetings.


External Partners


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