Doctoral dissertation (article) (G5)

Population dynamics and evolutionary genetics of life history variation in Atlantic salmon




List of AuthorsCzorlich Yann

PublisherUniversity of Turku

PlaceTurku

Publication year2019

ISBN978-951-29-7687-4

eISBN978-951-29-7688-1

URLhttp://urn.fi/URN:ISBN:978-951-29-7688-1

Self-archived copy’s web addresshttp://urn.fi/URN:ISBN:978-951-29-7688-1


Abstract

Knowledge about variation in abundance and life-history traits is necessary to manage exploited populations. Atlantic salmon, Salmo salar, has high cultural, ecological and economic importance, supporting subsistence, leisure and commercial fishing. This species has been exposed to numerous threats (e.g. introgression, climate change, overexploitation) leading to a global decrease in Atlantic salmon production and changes in life history traits. Historical collection of data and biological material coupled with modelling and recent advances in genetics may help in describing those changes and identifying potential causes. In this thesis, we used data and biological material collected from 1975 to 2014 in the northern European Teno river, which hosts a highly structured salmon population and yields one of the largest riverine salmon catches in Europe. We quantified a total of 120 different life history combinations in the Teno river, including variation in smolt age (2-8 years), age at maturity (1-5 years) and several forms of repeat (37) and alternate spawners (54). Life history traits varied both spatially and temporally, particularly the age at maturity with an important decline in the proportion of large salmon, maturing after three years at sea. We demonstrated adaptive evolution of age at maturity over 40 years in the main population of the Teno river by observing an 18% decrease in vgll3 late maturation allele frequency, a genetic marker strongly associated with this trait. Changes in vgll3 allele and genotype frequencies were likely to have been driven by direct and indirect effects of fishing, by intensively exploiting a salmon prey (capelin) and using selective fishing gears in the river. Only males clearly responded to genetic changes at the phenotypic level, with a strong decline in age at maturity. The consequences of changes in genotype frequencies on mean age at maturity may differ between sexes because of sex-dependent variation in vgll3 additive and dominance effects. Furthermore, this sex-specific genetic architecture differed in a second population with contrasting age structure, likely affecting selection patterns. We finally developed a Bayesian life cycle model for salmon in Utsjoki, the largest tributary of the Teno river, which could later be extended to data-poor stocks using hierarchical structures. Such a model, including various sources of information (e.g. video counting, expert knowledge and literature) and accounting for different kind of uncertainty (e.g. observation and process errors), may be useful to provide reference points for management and evaluate attainment of objectives. The combined use of ecological and genetic data in this thesis improved our knowledge about the diversity and variation of life history traits in Teno river Atlantic salmon, along with potential factors affecting them. A further development would be to integrate both types of data in eco-evolutionary models to improve our understanding of the interaction between ecology and evolution and its consequences for population viability.


Last updated on 2021-24-06 at 11:47