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Research Profiles : Angling for evolutionary answers :

Protecting genetic variation

So what's a conservationist (or fisherman, for that matter) to do? The first step, according to David, is selecting a management strategy that accounts for - and even expects - evolution: "There are ways to be more Darwinian in our perspective on how we manage things." The main idea is to protect genetic variation, especially the genes that are related to large body size. Two possibilities hold promise:
  • Marine preserves
    By establishing large areas where fishing of any sort is banned, we could create refuges in which genes for large size are not selected against. In these preserves, body size would be allowed to evolve according to normal selection pressures — and not the selection rules inadvertently enforced by the fishing industry. Such preserves would ensure that more genetic variation remains in the population. However, David admits, "It's a tough sell. A lot of the commercial industry resists the idea that there should be places where they're not allowed to fish."

    no fishing

  • New catch criteria
    Another option would change fishing regulations so that they preserve genetic variation in fish populations. Currently, we preferentially select the largest fish out of the population — which reduces genetic variation and favors fish with genes for small size. You might think that we could reverse the trend by harvesting the smaller fish — but that practice alone would also reduce genetic variation. However, David proposes a middle ground: selecting out only medium-size fish would preserve genes for both large size and small size in the population. So instead of keeping the large fish, fishermen would be only be allowed to keep the medium-sized fish. Evolutionary theory predicts that this would allow both large fish and small fish the chance to reproduce and might actually help increase genetic variation in the population.

    Harvesting only the smallest fish reduces genetic variation, while harvesting only the medium-sized fish preserves genetic variation.

Evolutionary answers
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