The molecular mechanisms and reversibility of fisheries-induced evolution - an experimental approach

Many of the world’s exploited fish stocks have recently collapsed and evidence is accumulating rapidly that various phenotypic traits and population-level properties have been altered in these stocks. Although fisheriesinduced evolution consistently arises as the most parsimonious explanation for the observed life-history changes in exploited stocks, empirical evidence that size-selective fishing can cause genetic changes is largely lacking. I will use genomic approaches to study wild-origin zebrafish from my long-term artificial selection experiment, in which I have harvested fish size selectively (large-size selected, small-size selected, randomly selected) for five generations and halted the selection for another five generations. Preliminary results indicate significant phenotypic changes in response to size-selective harvesting, but the molecular changes remain unknown. I will study experimentally 1) Whether size-selective harvesting can induce rapid genetic changes; 2) What the molecular mechanisms behind the potential genetic changes are and 3) Whether these changes are reversible.
I will sequence the expressed proportion of the genome, the transcriptome, of the experimental fish before and after selection using RNAseq to detect potential molecular signals of size-selective harvesting (1). RNAseq allows the survey of both sequence and expression level variation, thus increases our understanding of the biomolecular mechanisms of evolution (2). To confirm the results of RNAseq, follow-up studies will investigate the identified sequence and expression level differences in large numbers of individuals and in each generation.
Finally, I will look at the potential reversibility of the genetic changes by comparing the transcriptomic data before and after halting the selection (3).
The results will have considerable scientific importance as they contribute to the understanding of the mechanisms of evolution and societal importance as little is currently known about thegenetic effects of size-selective fishing despite the heavy exploitation of numerous fish stocks. Addressing questions concerning the extent of evolutionary changes, the reversibility of such changes and their consequences for sustainable harvesting, population recovery and species persistence is a vital step towards sustainable fisheries management.

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