Even if your arguments are accepted all they do is make the case for fishing at somewhat less than maximum sustainable yield - not proving the case for marine parks. This lower fishing pressure is often termed as optimal sustainable yield. Ray Hilborn wrote a paper advocating this - he didn't say marine parks were the best way of achieving it (quite the contrary actually).

freediver wrote on May 21^st, 2009 at 10:28pm:


Marine parks make fisheries management robust. All of the failures of traditional management tools can be resolved by simply using the same rules or strategies but reducing the fishing pressure or total catch. Of course, you soon get to the stage where you are better off just recognising the benefit of marine parks as a fisheries management tool and taking home more fish, rather than tolerating an inferior management policy that gives you more freedom to fish wherever you want, but less fish to actually eat.

Just magical thinking FD. No wonder people are starting to call this sort of rubbish 'zombie science' or 'faith based fisheries' - no matter how much you knock it down it just rises up again.

Even the worst fisheries management tools can be made to work if you make them strict enough, but this is not an advantage. You are giving too much credit to traditional tools on the basis that they are what you feel comfortable with, rather than any inherent advantage. The whole point of marine parks is that they change the assumptions around maximum sustainable yield, resulting in an increase in what can be caught sustainably when you take a realistic appraisal of risks associated with unknowable or unmeasurable factors etc into account.
That is, when it comes to practical measures, you end up with mroe fish.

Not proven at all. Actually if you apply this line of reason to marine parks (ie excessive use of the precautionary principle) then they fail the test too! For instance marine parks have been showed to provide negative effects such as displaced fishing pressure leading to local depletions, changes in species assemblages and predator/ prey relationships. It is also quite clear that a marine park strategy will lead to a lower sustainable yield and other adverse ecological effects. The lost ground will never be made up by the so called spill over effect. To maintain the same yield you will have to step up the fishing pressure in the open areas and the use of more destructive methods such as trawling. Of course I have pointed all this out before and you just keep rising up like a zombie.

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But it does prove the case for marine parks PJ. Your argument has withered away to little more than acknowlwedging that marine parks are better, but claiming that it doesn't matter anyway because other options are magically 'better' because you are useed to them.

Have have said no such thing. Stop making stuff up. PS where is the evidence of better fishing on the GBR as a result of the marine park. How about NSW? We have had marine parks here for quite a while too.

Your post appears to recognise this, and accept that this particular defense of traditional management tools such as minimum sizes is fatally flawed. That is, "all they do" is point out the inferiority of traditional management techniques, and the bandaid solutions that are falsely claimed as benefits. Given that this is pretty much the extent of the role fisheries management tools, you seem highly dismissive of failures in this key role. It's like saying that the only thing that arguments against traditional drug policies do is show that tradition drug policies do not work.

What failures? The evidence is that our inshore stocks of NSW (my area of concern) have a lot of natural resilience to fishing pressure (hence no need for excessive and heavy handed use of the precautionary principle) and none are seriously overfished.

I would genuinely appreciate any feedback on the original issues, ie whether minimum sizes lower fishery productivity (as apparently aknowledged by pj), and that this is due not only due to selective pressures for slow growing fish, but also due to short term impacts like the effect of the various natural causes of mortality on population cohort biomass.

Its a strawman argument. Minimum sizes are only a small part of the traditional management mix. All I have acknowledged (and you seem to be so obtuse about), is that I might be a good idea to fish them at a level somewhat less than the MSY. This has nothing to do with minimum sizes.  

Can you verify that maximum biomass tends to coincide with the onset of sexual maturity, and that this is not a result of anthropogenic influences such as the release of undersize fish? That is, would we increase maximum sustainable yields by making less use of minimum sizes and more use of better management techniques? The point of this thread is to counter an apparent technical flaw in the benefits of marine parks, so it is a bit disingenuous to revert to arguing that it doesn't matter anyway whether you can take home more fish. IF you don't understand the technical arguments, you should not make them, or copy and paste them from questionable sources, in the first place.

Whats more questionable - papers from senior fisheries scientists (including Professors of Fisheries), or the half baked theories of a totally unqualified political activist?

PJ, the 'original' link for your article:

http://www.esm.ucsb.edu/academics/courses/595PB/Readings/Parrish_Reserves_CALCOFI.pdf

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I'm just trying to verify his claims, that's all. So far they seem logically flawed and misleading. I have looked, and can't find anything to support his claims. Can you?

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The selective pressures created by minimum sizes that reduce the growth rate of fish. Plus the short term effects of minimum sizes that leads to a reduction in yields. That's what this thread is about remember? One the one hand, you post a claim that this reduction does not exist so there is no problem, but when asked to back up this claim, you switch to arguing that it doesn't really matter anyway because minimum sizes are only a small part of the current management regime. Can you explain why you constantly switch to this line of argument if you don't even recognise the problems associated with minimum sizes in the first place? Surely if you honestly believed that the problems with minimum sizes don't exist you would argue that they don't exist, instead of constantly making up excuses for them.

I posted responses to some of your other points here:

http://www.ozpolitic.com/forum/YaBB.pl?num=1192441509/346#346

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Can you give an example?

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Can you explain the reasoning behind this claim?

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The number of fish that make it well past legal size is greatly reduced compared to natural levels.

Can you link me to that EIS and quote the relevant bit please?

The salmon and kingfish example is not evidence that minimum sizes do not impact fishery productivty. It is evidence that they are naturally fast growing fish, and that the failure of the management regime was detected and corrected before it turned into a complete disaster. The fact that some fish grow faster than others does not give any useful insight into the actual extent of the impact of minimum sizes on fishery productivity, though it does give some insight into the potential. In other words, you do not know how much it contributed to the collapse or slowed the recovery, or reduced the current catch rate. As far as I know, minimum sizes have only be used in Australia for a relatively short time, and these particular species would have had less heavy exposure to them, given the traditional harvest method.

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Why would it be limited to overfished stock? All you need is a selective advantage for the change to be inevitable.

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Are you suggesting that the theory of natural selection must be proven in every situation before it can be used to make a prediction? I am not demanding proof of anything. You are.

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Almost everything is reversible. That doesn't make it a good idea. The lost opportunities from past mismanagement however cannot be regained. All that lost income, food, and recreational value were simply lost to us because some stubborn soul kept demanding absolute proof of the bleeding obvious before we allowed common sense to take it's course.