Seite - 8 - in options, Band summer 2016

science into policy 8 options + summer 2016 www.iiasa.ac.at iiasa research Fine tuning fishing Preventing damaging impacts on fish populations’  gene pools I ncreasingly intense fishing around the world has driven some fish populations to the point of collapse. However, heavy fishing not only reduces the size of fish populations, it can also alter their basic  genetics. “Always taking the largest fish, as commercial fisheries do, means that those that remain smaller, and reproduce at an earlier age are more likely to pass on their genes to the next generation,” says IIASA Evolution and Ecology Program Director Ulf Dieckmann. In this way, the fished population becomes dominated by fish with genes for early maturation, small size, or both. This “fisheries‑induced evolution” can affect a stock’s productivity, stability against collapse, and recovery potential. What’s more, it affects the whole gene pool and is very hard to reverse, even if fishing ceases. Can such damaging impacts be avoided? IIASA researchers have contributed a substantial body of work, not only investigating fisheries‑induced evolution itself but also taking into account its socioeconomic impacts and providing practical advice for decision makers. The evolutionary impact assessment framework, developed by IIASA scientists and collaborators working under the International Council for the Exploration of the Sea, enables managers to estimate the vulnerability of different fish populations to fisheries‑induced evolution and to identify strategies that best achieve evolutionarily sustainable fisheries. Researchers have recently applied the framework to the case of North Sea plaice, the most commonly fished flatfish in Europe. They found that centering fishing effort on intermediate sizes—still letting the small go, but also sparing the largest to some extent—would be best for plaice. “This work allows fisheries managers to fine‑tune the fishery to reduce the risks of fisheries‑induced evolution,” says Dieckmann. “We basically know the answer to the question how much should we fish? It’s almost always ‘less.’ But we go beyond this to the question of how  should we fish?” There are several options available: changing the fishing gear used, the types of nets for instance, can control the sizes taken to a certain degree. Fishing at different times of year might also help. Finally, altering the fishing location can make a big difference, and this is likely to be particularly effective in the case of the plaice stock, because for this species larger fish tend to gather in distinct areas. Developing sound management advice for different species, stocks, and fisheries takes considerable investment of time and effort for scientists and fisheries managers  alike. To streamline this process, researchers in the Evolution and Ecology Program are now developing a library of computer tools that can be applied to standard fisheries data to assess how vulnerable a stock is to fisheries‑induced evolution. “At the moment we are doing this for about 40  stocks,” says Dieckmann. “We hope to be able to give managers the tools they need to create thriving, sustainable fisheries.” DB Further info Mollet FM, Poos JJ, Dieckmann U, Rijnsdorp AD (2016). Evolutionary impact assessment of the North Sea plaice fishery. Canadian  Journal of Fisheries and Aquatic Sciences [doi:10.1139/cjfas-2014-0568]. Ulf Dieckmann dieckmann@iiasa.ac.at