Science Questions

Could we 'restock' the oceans by releasing captive bred fish

Sat, 29th May 2010

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Question

Stacey Rollings asked:

We have been encouraged to eat more fish, yet many wild fish stocks are endangered or decreasing, and fish farming can be detrimental to the environment.† Would we lessen these problems if we were to "stock" the oceans by breeding large numbers of fish in captivity and then releasing the young fish into the wild?

Answer

Helen -  Itís a very nice idea in some ways, but first of all, you have to think about the scale of what you're trying to do here.  The oceans are absolutely enormous.  The numbers of fish weíre catching are absolutely enormous, and I just don't think we have the technology, if we even wanted to go about this if we thought it was a good idea.

We are doing some smaller scale things.  Some European eels for example are being ďre-stockedĒ and I'm saying that in inverted commas because they arenít actually being bred in captivity, they're just being moved around the place because in some areas, they're doing very, very badly, so tiny baby eels are being moved to try and restock rivers, to allow people to carry on fishing. 

There are things like genetic issues you might need to consider as well.  What sort of species?  Where are they coming from to restock them?  And I think we mustnít forget that the oceans have an incredible ability to restock themselves.  We just have to give them a chance.

When we take away fishing pressure from certain areas, we do see an extraordinary recovery.  So we really have to focus on oceans healing themselves.  I think stepping in and doing it ourselves is not the approach.  Itís a case of letting the oceans do it themselves and giving them a chance.

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Stacey Rollings asked the Naked Scientists: We have been encouraged to eat more fish, yet many wild fish stocks are endangered or decreasing, and fish farming can be detrimental to the environment.† Would we lessen these problems if we were to "stock" the oceans by breeding large numbers of fish in captivity and then releasing the young fish into the wild? What do you think? srollings, Sat, 24th Apr 2010

I read recently that one of the reasons why fish stocks are decreasing is that the temperature of the oceans have risen by 1oc. This doesn't seem much of a rise but it changes the density of the sea water. Fish that feed on plankton track them by tracing a sort of density footprint which they leave as they swim. The changed density of the hotter water is enough for this footprint to fade much more quickly. This means the fish find it harder to find food. The food is there for them in abundance but it has just become more difficult to track.
I guess what I'm saying is that even if you did try to repopulate the seas with fish, you would be condemning them to starve to death. Maybe evolution will catch up with this problem but maybe it won't. It is not all about over fishing sadly. Make it Lady, Tue, 4th May 2010

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