Big Fish Catches Mean Smaller Fish

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Scientists have warned that a fishing rethink is needed after finding that catches of big fish trigger a rapid change in the gene pool of fish stocks.


Researchers at Bangor University say they found that over-harvesting larger fish leads to a population of smaller fish that are less fertile.

The research suggest that the change happens within a few generations.

The scientists say the findings could have a massive impact for the future of global fishing policies.

"Our findings have major implications for the sustainability of harvested populations," said Prof Gary Carvalho, of Bangor University's School of Biological Sciences.

He said a "shift in the genetic make-up of harvested fish to smaller less fertile individuals" would be "serious global consequences for the environment and for global fishing industry".

"We would urge the scientific community, policy makers and managers to consider the capacity of harvested stocks to adapt to, and recover from, harvesting and predation."

Written By: BBC News
continue to source article at bbc.co.uk

17 COMMENTS

    • In reply to #3 by Virgin Mary:

      Blame the Spaniards, Chinese, and Japanese for this. They’re morally vacuous and have a blatant disregard for the welfare of the animal kingdom.

      Sure. Because white people have never over fished or over hunted anything have they?

  1. The outcome of such aggressive fishing industry practice is far more serious than a shortage of seafood to the ever hungry human primates.This kind of carelessness has the potential to severely threaten the entire marine ecosystem and the impact on our environment would be considerably less favorable than we dare to think.

    • In reply to #4 by kamel:

      The outcome of such aggressive fishing industry practice is far more serious than a shortage of seafood to the ever hungry human primates.This kind of carelessness has the potential to severely threaten the entire marine ecosystem and the impact on our environment would be considerably less favorable than we dare to think.

      Indeed kamel, There are regions of ocean in Asia that have become so denuded of any fish that the waters are now being overrun with jellyfish and squid. The small jellies and squid used to feed small and large fish but with nearly no fish left by local fishermen they have a much larger survival rate. The squid and jellies then dominate the ocean and resist the return of fish quite well. They have even become navigation hazards, damaging engines clogging water pipes and actually reducing ship speeds due to the pure mass of their bodies. It is unfortunate that in most cases the Jellies and some of the squid are inedible to humans.

  2. I had read a similar article about lake sport fishing. Most states impose size limits on what you can keep for each species. All the big fish are being culled from the gene pool, while the little fish have to be released.

  3. IOW, overfishing of the larger fish is interfering with natural selection and deteriorating the overall gene pool. The larger specimen who would have been more likely to reproduce are being removed from the population and therefore unable to replicate their genes.

    I often find it depressing to see how much damage we do as a species, both to ourselves and the rest of the planet. Almost makes me wish we never colonize other planets since we’d probably end up destroying those as well.

  4. Reminds me of the story (not sure whether it’s true) that elephant tusks are getting smaller because poachers go for the biggest tusked animals. The smaller tuskers are more likely to survive and breed more small tuskers.

    • In reply to #13 by paulmcuk:

      Reminds me of the story (not sure whether it’s true) that elephant tusks are getting smaller because poachers go for the biggest tusked animals. The smaller tuskers are more likely to survive and breed more small tuskers.

      Reminds me of trophy hunters going after the biggest (american) elk antlers. Weakens the herd’s gene pool.

      • In reply to #15 by bluebird:

        In reply to #13 by paulmcuk:

        Reminds me of the story (not sure whether it’s true) that elephant tusks are getting smaller because poachers go for the biggest tusked animals. The smaller tuskers are more likely to survive and breed more small tuskers.

        Reminds me of trophy hunters going after the biggest (american) elk antlers. Weakens the herd’s gene pool.

        I actually have a question here to go along with several statements. Is it true that the impressive antlers that are hunted for actually drop off the target animals about a month after the end of hunting season and can then be simply found and hung on walls without a need to actually kill the hunted animal? Would it not be more sensible to go hunting with a camera and a marker of some sort and end up with a nice Photograph and set of Antlers. It has been told to me that the actual meat from rutting males is barely edible.

        As to animals being selection pressured into smaller forms I was fairly certain that this has been known of for quite a long period.

        One of the primary reasons for farming fish is to get uniform large sizes as the wild populations have been pushed massively to smaller body forms. This is particularly the case where major net fishing has been in place for a while. There has even been a need to reduce the ‘weave’ of the nets due to the smaller fish escaping. This has generally led to reduced average fish size in many heavily fished species that then forces the industries to farming for size.

        It is obvious that once the human take becomes the major predation method on a species and that take is affected by human desires then a target species would be pushed away from the human desire. Of course with many species of fish we just take everything and the failures become pet food and fertilizer. But with other animals that have become scarce over longer historic times and have special rules in place regarding size, gender and other traits there has been major population shifts away from these limitations.

        • In reply to #16 by ozkrenske:

          Is it true that the impressive antlers that are hunted for actually drop off the target animals about a month after the end of hunting season and can then be simply found and hung on walls without a need to actually kill the hunted animal? Would it not be more sensible to go hunting with a camera and a marker of some sort and end up with a nice Photograph and set of Antlers. It has been told to me that the actual meat from rutting males is barely edible.

          “Take only photos, leave only footprints”

          It is the thrill of the hunt (rifle, bow, muzzleloader) – whole mounted heads is s.o.p. Hunters will certainly bring home any antlers found on the ground as a matter of course.

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