Science Questions

How resilient are the oceans to over-fishing?

Sun, 14th Mar 2010

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Question

Burt Johnson asked:

Are the oceans resilient enough that fish populations will recover if only given a very few years without commercial fishing?† If so, would it be possible (barring political roadblocks) to establish rotating portions of the ocean that are blocked from fishing for maybe 10 years or so, which would result in oceans replenishing themselves?

 

Answer

Helen -   Itís a great question and itís something thatís being talked about more and more in the news as we hear about the emptying oceans and fish stocks being depleted.  In fact, I had a look at this question and our listener comes up with a nice idea, in fact a brilliant idea of ďcouldnít we just give the oceans a rest?  If we perhaps blocked off bits of the ocean from fishing for say, 10 years or so, we could rotate around and the oceans would replenish themselves.  Could they?Ē 

Yes, they could indeed.  In fact, what you're talking about are marine protected areas or marine reserves this is the sort of tool for ocean management thatís being talked about by governments and by conservation groups. Because we know that if you leave a piece of sea alone from the impacts of us people catching so many fish, it will very quickly recover.  Itís extraordinary how resilient the oceans can be and it does offer us some hope.  The question is, can we actually get this done?  I love the idea of blocking off and rotating parts of the ocean that we can have as these protected areas, if only it could happen.  At the moment, less than 1% of the oceans are protected from human activities and there are various estimates as to how much we should protect in order to have a resilient ocean that keeps itself going: thatís up to as much as 30% or a third of the oceans.  If we could do that, then we would have much better chance of ensuring that fish stocks and all sorts of other marine creatures will still be around in years to come.  So, letís hope we can do that and we can achieve resilience in the ocean because I think it will fight back but we need to give it a helping hand.

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Burt Johnson asked the Naked Scientists: This story was in many newspapers today, circulated by AP: ††† http://www.mercurynews.com/california/ci_14163385 Basically, they say: "There is a lot of fish now, there is plenty of fish. There is more fish than people can actually use because the international fishermen have been scared away by the pirates," The pirates are a relatively new phenomenon, going back a few years.† You have talked several times about the overfishing of the oceans and how badly the fish populations have plummeted.† This story makes me wonder... Are the oceans resilient enough that fish populations will recover if only given a very few years without commercial fishing?† If so, would it be possible (barring political roadblocks) to establish rotating portions of the ocean that are blocked from fishing for maybe 10 years or so, which would result in oceans replenishing themselves? What do you think? Burt Johnson , Wed, 13th Jan 2010

Burt

Some fisheries have been over-fished, and thus become commercially unproductive. However, the populations do not always recover as expected when the commercial industry moves on to other species. Thats because other species have been given an advantage.

Well, anyway, much of the world has discovered how to manage their fisheries for maximum harvest without depleting the base population. This is certainly true in the North Pacific. I am unaware that wild salmon, crabs, or whitefish are in any danger. Oddly, this also seems to be the case with lobsters off North America.

The general productivity of the oceans is largely the product of species that are not commercially valuable such as plankton and crill. Accordingly, the base structure continues to provide bio mass generation regardless of which creature higher on the food chain gets nailed by fishing.

As for the pirates? I am of the opinion one shot one kill is a good calculation for pirate harvest sustainability. I think Navy Seals harvested three pirates recently, without depleting the species. litespeed, Sat, 16th Jan 2010

Overfishing is one of the most serious problems we face today. On the other hand we have others too, just as serious as global warming, deforestation etc.

The fishes are dying not only because of overfishing but also due to the rising acidity of the oceans, in its turn due to manmade CO2 increasing, loss of oxygen creating oxygen free waters, heat forcing them to migrate and overfishing, Probably I've missed some other problems here already :)

According to overfishing.org "over 25% of all the world's fish stocks are either overexploited or depleted. Another 52% is fully exploited, these are in imminent danger of overexploitation (maximum sustainable production level) and collapse. Thus a total of almost 80% of the world's fisheries are fully- to over-exploited, depleted, or in a state of collapse. Worldwide about 90% of the stocks of large predatory fish stocks are already gone."

Their sources are the UN Food and Agriculture Organization. The FAO Fish and Aquaculture organisation - with a two yearly report from The State of World Fisheries and Aquaculture(SOFIA) on the state of the world's fisheries and aquaculture. "Figures on this page are taken from the 2006 version of the report. The report is generally rather conservative regarding the acknowledging of problems but does show the main issues.In general it can be stated that the SOFIA report is a number of years behind time of the real situation."

So yes, it is very serious. Outside Japan they now have an invasion of jellyfish instead of the species of fish they traditionally have fished there. And there are 'pirates' everywhere fishing on national waters where the states have a weak protection.
yor_on, Thu, 28th Jan 2010

yor_on

I clicked on the overfishing URL you provided. It displays only a simple home page. I then clicked on which seemed the logical choice, but was directed to the .

Please provide end links for your various stats. I just can't find any of them... litespeed, Fri, 29th Jan 2010

It's working for me? They seem to want javascript on but I have it of :)
Overfishing

And here are the sources they've used. If you read the quote it seems like they've used the 2006 version of the report (SOFIA)
Sofia

"In the first chapter we discussed already that globally fishing fleets are at least two to three times as large as needed to take present day catches of fish and other marine species. To explain why overfishing is a problem we first have to get an idea on the scale of the problem. This is best done by looking at some figures published by the UN Food and Agriculture Organization. The FAO Fish and Aquaculture organisation - http://www.fao.org/fi/default.asp The FAO scientists publish a two yearly report (SOFIA) on the state of the world's fisheries and aquaculture. The State of World Fisheries and Aquaculture (SOFIA) can be found on http://www.fao.org/sof/sofia/index_en.htm. Figures on this page are taken from the 2006 version of the report. The report is generally rather conservative regarding the acknowledging of problems but does show the main issues. In general it can be stated that the SOFIA report is a number of years behind time of the real situation."

Hope this help?

As for Jellyfish you can check
Jellyfish

And this PDF discuss the reasons behind it 
The jellyfish joyride
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The jellyfish joyride: causes,consequences and management responses to a more gelatinous future By Anthony J. Richardson1,2,3, Andrew Bakun4, Graeme C. Hays5 and Mark J. Gibbons6

1 Climate Adaptation Flagship, CSIRO Marine and Atmospheric Research, Cleveland, QLD 4163, Australia
2 School of Mathematics and Physics, The University of Queensland, St Lucia, QLD 4072, Australia
3 The Ecology Centre, The University of Queensland, St Lucia, QLD 4072, Australia
4 Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, FL 33149, USA
5 Institute of Environmental Sustainability, Swansea University, Singleton Park, Swansea SA2 8PP, UK
6 Department of Biodiversity and Conservation Biology, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa

It's good reading btw.
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And the fishing boats invading territorial waters :)
Just Google on 'fishing boats invading territorial waters' and you will see it happening all over the world. yor_on, Fri, 29th Jan 2010

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