GENetic adaptations underlying population Structure IN herring, Clupea harengus

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2016

End date

12/31/2021

Budget

1,019,055 EUR

Fundings

Abstract

Atlantic herring is an important species in the pelagic fisheries with average annual harvest rates exceeding a million tons in the North-eastern Atlantic. Herring display a remarkable variability in phenotypes, e.g., size-at-age and timing of spawning, but at the same time a low genetic divergence between herring populations. The observed genetic difference between populations has however been suggested to be of adaptive relevance. Recent advances in genomics can now be used to document variability in genes with potentially high adaptive significance. During the project period we have for the first time produced viable second-generation offspring of herring from parents that have been raised their entire life under controlled experimental conditions. The studies have shown that the parental adaptation to salinity conditions during maturation subsequently influenced offspring fertilization success at different salinity conditions. Ongoing genetic analyses will reveal if specific genes are over-represented (selected) in the surviving offspring. Studies of mutations rates in herring from our experimental populations have shown that it is among the lowest documented so far in vertebrates. This may be a contributing factor to the relatively low genetic variability typically observed between different herring populations. An example of a mutation with adaptive significance is found in the genes coding for rhodopsin, where the Baltic herring has a variant commonly found in freshwater fishes, while the Atlantic herring has a variant commonly found in marine fishes. The efforts on collecting samples and undertaking genetic analyses from different natural herring populations have shown clear regional differences, and genetic assays have been developed that easily will clarify genetic origin of sampled material. As an example, genetic markers to distinguish spring- and autumn spawning herring have been developed, and international sampling programs are ongoing to document the utility of these genetic markers for herring stock management in collaboration with the International Council for the Exploration of the Seas (ICES). A new experiment has been initiated where herring from different populations have been crossed and raised at different temperature and seasonal light regimes. The work is two years on the way and has generated data on phenotypic variability generated by seasonal light and temperature differences. Genetic markers have been developed to identify individuals to specific parental genotypes. The rearing and genotyping of sampled material will continue until expected maturation at age three years (in 2022). The data will be part of an additional project co-funded PhD (2020-2024).