An experimental evaluation of fisheries induced evolution and its consequences

In agriculture we ensure that genes from the best animals are taken care of. In fisheries, we do the opposite: by preferentially capturing the biggest individuals, we are also removing the gene variants that help individuals to grow big. Over time this will lead to fish populations that are genetically adapted to start reproducing earlier and grow slower. This can reduce the productivity of the stock and make it less valuable as a resource. Our knowledge about fisheries-induced evolution is primarily based on models and field observations. However, model results suffer from the simplifications that underlie them, and field observations can be difficult to interpret as fish populations are also strongly influenced by the environment. It is also difficult to observe fish in their natural habitats. We overcome these limitations by studying fisheries-induced evolution in the lab. The experiment is based on the guppy, a fish that is easy to maintain and has short generation time. One year in our guppy experiment can correspond to ten years in the wild. We harvested our guppy populations for three years, from autumn 2010 to autumn 2013. We can observe a tendency towards earlier reproduction, but also that the fish are strongly influenced by "environmental" factors such food availability and predation, exactly as happens in the wild, except that the predation in our experiment comes mostly from the larger-sized, cannibalistic conspecifics rather than larger predatory species. In contrast to the wild, we are able to raise the fish also under controlled conditions. These show changes in growth, maturation, behaviour, and subtle changes in morphology and colouration. We can also sequence their genetic material to directly see changes in the inherited traits. Genomic analyses suggest marked genetic changes in the harvest guppy populations related to functions like signal transduction, sensory perception, muscle development, and immune system. The second part of the experiment concerns the potential evolutionary recovery after fishing is stopped. This should usually lead to rapid recovery in population abundance, but the evolutionary recovery is a different story: theoretical models suggest that evolutionary recovery will be much slower than the adaptive evolution during fishing. Results obtained so far suggest that this is true also in our experiment. The project has contributed to one PhD degree (Beatriz Diaz Pauli, November 2012), four master degrees (Ranga Jayawickrama, June 2013; Piero Lopez, December 2014; Geetha Jeyakanth, November 2015; Eihab Idris, June 2016), and one bachelor degree (Joan Sala Coromina, June 2014, University of Barcelona), and lots of practical research experience for local and visiting students. Even though the analysis of our results is still ongoing, the experiment has already been discussed in the media, including an article in the journal "Nature" under the title "A big fight over little fish" (http://www.nature.com/news/ocean-conservation-a-big-fight-over-little-fish-1.12325).

Fisheries have been likened to the greatest life-history experiment ever: fishing amounts to a major source of mortality that favours evolution towards faster life histories, e.g., maturation at an earlier age and smaller size. Evidence for fisheries-indu ced evolution (FIE) is mounting, but many key questions remain open. This project is set up to address questions that have not been adequately dealt with, both fundamental and applied in nature: * Can evolutionary, that is, genetic changes, be reliably de tected using phenotypic data alone? * What is the genetic basis of phenotypic variation in guppies? * What is the genetic fingerprint of FIE? * What is the rate of FIE? * What evolutionary changes fishing may drive, beyond life-history evolution? * What a re consequences of FIE on properties of exploited populations? * Are rates of evolutionary recovery much lower than rates of FIE, as models suggest? We are utilizing an ongoing experiment using guppies as the model organism. Guppies have features similar to commercially exploited fish, apart from their small size and short generation time that make them suited for multi-generation experiments. Replicate guppy populations are exposed to three harvesting treatments involving fishing every 6 weeks. Marking a subset of fish allows age estimation and following of cohort dynamics. Observational data on life histories are collected at 6-week intervals, whereas behavioural and common garden life-history assays are conducted annually. Phenotypic observations are complemented with genetic analyses based on monitoring of candidate genes and deep-sequencing of individuals from the first and last life-history assay. We have a young, dynamic project group with excellent national and international collaborators. The p roject builds on an existing experimental facility that provides a kick-start to the project, contributes to optimal utilization of the facility, and provides very high benefit to cost ratio for additional funding.