Herring populations have previously been distinguished by stocks based on tag returns, differences in spawning times and other life history characters. The characteristics of different stocks suggest a complex population structure, but most previous genetic studies have failed to reveal significant differences among populations. This could reflect on the use of markers with relatively low polymorphism and unsuitable sampling due to a lack of attention to ecological and life history detail, rather than genuine genetic homogeneity among populations. The objective of this study is to apply high-resolution microsatellite DNA analysis in order to estimate the genetic structure of herring spawning populations in the North Sea, the Skagerrak, Kattegat, the western Baltic and the west of Scotland. In addition, the aim is to estimate the proportions that these spawning populations contribute to feeding aggregations of mixed origin targeted by commercial fisheries. This will be achieved by integrating genetic data with knowledge of the ecology and demography of herring, regional and temporal differences in spawning and migration, and oceanography.
The project's overall goal is to provide guidelines for the conservation and management of biodiversity of Atlantic herring in the North Sea and adjoining waters by identifying its genetic population structure, and by quantifying relative stock contributions to the fishery. Within the project the six major objectives are:
1) to estimate genetic differentiation amongst spawning aggregations
2) to determine temporal stability of population differentiation
3) to determine the composition of mixed feeding aggregations
4) to determine temporal (seasonal and annual) variability in contributions to mixed aggregations, by comparing contribution estimates from repeat samples in two regions
5) to prepare a proposal for the incorporation of findings in management of herring stocks
6) to disseminate the results and guidelines.
Progress to Date
Sampling of spawning aggregations: The first year of sampling is complete.
Pilot modelling and sampling design: A computer program package is being developed that estimates, through simulation, the statistical power for detecting genetic heterogeneity among sampled populations when using genetic markers with a large number of alleles.
Microsatellite calibration: The first year has focused on the choice of microsatellite loci to be used, the subsequent optimisation of the laboratory procedures and the standardisation of scoring.
MtDNA calibration: Since the whole calibration/standardisation phase proved complex and time consuming, it was agreed that the mtDNA-RFLP work would be conducted entirely in Hull.
Genetic structure among North Skagerrak populations: During 2002, the Goeteborg University partners received samples of nine herring spawning aggregations and genotyping work at ten microsatellite loci began during 2002.
Genetic structure among populations east of the UK and west of Scotland: Genotyping at ten microsatellite loci is currently in progress.
Genetic structure among populations in Danish waters, Skagerrak/Kattegat, and western Baltic areas: The work, during 2002, concentrated on the calibration among partners of the DNA extraction procedure, on the choice of microsatellite DNA loci, and on the calibration of their scoring and interpretation.
Allozyme population structure: During 2002, 920 herring tissue samples became available for allozyme analysis, and approximately half of them have been genotyped.
MHC population structure: Messenger RNA has been isolated from a single herring individual. The mRNA was used to construct a cDNA library and this library was amplified and stored for further use. A microsatellite (TG) in intron 3 of the MHC class II alpha gene has been identified. Primers will be designed flanking the repeat sequence and the polymorphism of this microsatellite has been evaluated using a number of herring individuals. The locus was shown to be polymorphic.
Mixed stock aggregations: Biological measurements (length, weight, age from otoliths, etc.) were taken from the majority of sampled individuals. Analysis of microsatellite DNA polymorphism in these samples has been initiated.
Phenotypic and otolith characterisation: The work to characterise individuals according to the season they were spawned is ongoing using otolith type.
Data analysis: This package is at the core of the HERGEN project. It concerns the analysis and interpretation of the molecular, phenotypic and meristic data produced.
As data are only beginning to be produced and will not be available until later in the project, no robust or meaningful analysis has yet been undertaken.
FISHERIES AND AQUACULTURE
Scientist responsible for the project
Dr DORTE BEKKEVOLD
DK 8600 Silkeborg
Denmark - DK
Phone: +45 89213100
Fax: +45 89213150
||Danish Institute for Fisheries Research
||01 January 2002
||2 170 409 €
|Total EC contribution
||1 553 000 €
|Web address of the project