Coles stores habitually sell undersized fish and nothing is done about it.

pjb05 wrote on Jun 13^th, 2009 at 7:49pm:



Trout is but not flathead or snapper.

pjb05 wrote on Jun 13^th, 2009 at 8:45pm:


Don't know if the snappers are from a farm but the lizards are unmistakeably duskie and sandy and undersized.

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Like I siad, that recovery is not evidence of zero harm. You appear to think that anything other than a total permanent collapse of a fishery is good management.

Don't have me saying things I haven't actually said. You seem to miss the point that a quick recovery means the so called "harm" or impact can't be all that significant. Also do you realise that you are holding on to two opposing ideals at the same time. On one hand you say marine parks will give a greater yeild and on the other you use preservationist arguments about selective pressures and biodiversity. Any substantial fishing pressure will have an impact (marine parks or not) and yet you talk about wanting zero harm or impact.   

If there is no sign of permanent harm (ie overfished stocks recover quickly)

Like I siad, that recover is not evidence of zero harm. You appear to think that anything other than a total permanent collapse of a fishery is good management.

So do you want zero impact?

The Dieckman paper is a good starting point on the harm done by minimum sizes in wild fisheries. It has also been demonstrated in a lab countless times how easy it is to change growth rates with selective pressures.

http://www.ozpolitic.com/fish/marine-parks-fisheries-management-tool.html#links [/quote]

There are countless examples of real world fisheries data showing that fish actually grow faster under heavy fishing pressure.

[/quote] Don't have me saying things I haven't actually said. You seem to miss the point that a quick recovery means the so called "harm" or impact can't be all that significant. [/quote]

But it is PJ, for three reasons. One, there is normally at least a few years of significantly reduced catches.

Of course they nedd a few years to build up numbers even if they are fast growing.

Two, even once the stocks are recovered, the catches must be restricted to more conservative levels to compensate for the problems inherent in the management approach used.

Whats wrong with that? Better biodiversity, higher catch per effort, better recreational fishing and no huge socio economic cost of locking up large areas of ocean for ever. You keep making the huge leap of faith that the relatively minor fisheries problems left in Australia can be overcome in a cost effective way with marine parks. Experienced fisheries biologists like Prof Kearney and Buxton will tell you that you couldn't come up with a less cost effective way than marine parks!

But these first two are more a topic for the other thread. Third, like I said, this apparent recovery is not evidence that no harm has been done via the mechanism of selective pressure reducing growth rate. Nor is it evidence that the harm done is not significant. That's because it is not a useful measure of the extent of the harm. Because of the relatively rapid and interactive changes our fisheries are undergoing, and the highly variable nature of Australia's climate, we have no way of knowing what the catch rates would be without the harm done by minimum sizes. Recovery does not mean that catch rates are equal or close to what they would be without this harm. The examples Dieckman use are extreme because the harm done by minimum sizes actually prevents the recovery of a collapsed stock. But to suggest that anything less than a long term collapse is insignificant is completely absurd. The harm done by minimum sizes will not normally become evident as a collapse of a fishery, or the prevention of the recovery of a collapsed fishery. If anything they will make it appear more resilient, while reducing total catches.

No, your absurd. If the stock can recover in a few years then obviously their growth rates are not significantly affected.

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Please quote where I talk about wanting zero harm or impact. You just finished accusing me with "Don't have me saying things I haven't actually said", though I have no idea what you were actually referring to.

Duh, you said this twice in the last thread: "You appear to think that anything other than a total permanent collapse of a fishery is good management".

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No. What on earth makes you think that?

Numerous statements like this: "Like I siad, that recover is not evidence of zero harm".


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No doubt they do, due to reduced competition etc. I hope you are not suggesting that this somehow contradicts the theory of natural selection. Are you? It is not fishing pressure that reduces a fisheries productivity via this mechanism, but a specific management tool. I am not criticising fishing pressure for reducing the growth rate of fish. I am criticising minimum sizes. Don't let the confounding factors confound you. [/quote]

If natural selection is so easily overidden by such confounding factors then that is evidence that natural selection it not that significant a factor. Plus you again make a huge leap of faith that marine parks are the cure-all for this theoretical problem. I have put up papers which say quite the opposite. All I have from you is your own unqualified musings.   

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That is not obvious PJ. This is a simple matter of logic. In order to judge whether something had significantly affected their growth rate, you would need something to compare it to. You don't have that. That is why your conclusion is totally unfounded.

Yes I do realise we don't have a parallel universe to conduct experiments. So we have to take not of natural observations. A few years to recover goes contrary to the theory of significant genetic alteration. 

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Well, that is how it appeared. Even now you still claim this is an example of good management, despite the fact that the stock collapsed. You claim it is evidence that no harm was done, even though you have no 'unharmed' state to compare it to. If this to you is good management, it is no wonder you have trouble understanding the benefits of marine parks over inferior management tools. It's like you are arguing that the exception proves the rule. "Look at these examples of traditional managment tools failing, isn't this great proof that they are better than marine parks".

I just pulled you up about misquoted and you do it again! Just goes to show how weak your case is. If you recall we were talking about selective pressure and damage to growth rates. Hence I used the examples of recovery from overfishing. A no time did I say this was an example of good management, just that the worst cases haven't usually been that bad.   

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But PJ, that was in response to claims by you that no permanent harm was done. This was not an outof-the-blue statment that I wanted zero harm. Also, you appear to be confusing zero harm with zero impact.

Well that's why I asked if you want zero harm or impact. PS what am I confused about? What difference is there between harm or impact in your eyes? I think it is a very subtle and subjective difference. 

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No it isn't PJ. It doesn't mean that natural selection is over-ridden, it means that you cannot measure the impact easily. Also, the impact could be massive and still be over-ridden by the increase in growth rate due to the decrease in competition.

Don't you know you can measure selective pressure by looking for changes in the age which fish become sexually mature? PS: all your harping about selective pressure does not make the case for marine parks, just easing for up on the fish stocks somewhat below maximun sustainable yield. But then you want to eliminate underfishing!

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A cure-all for a single problem? Is that supposed to make sense?

Stop playing with yourself - it's a turn of phrase and you know very well what I mean.

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You obviously thought they do, and for some reason still think they do, but as I pointed out the first time, they don't. They do not even mention the negative impact of minimum sizes on fishery productivty. But then again, you do have an unusual habit of interpretting an ambiguity (or in this case even silence) as direct support for your postion. Perhaps you would like to quote one of those papers explaining how marine parks will make the negative impact of minimum sizes on fishery productivity even worse.... [/quote]

I have done and also refered to them several times - unlike your unsupported and unqualified flat assertions. Recall Parrish said that to get the same yield with a system of marine parks you would have to sstep up ecologically damaging practices like trawling. Buxton said they could hasten the collapse of overfished stocks and they would be the equivalent of a TAC increase in the open areas. 

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No it doesn't PJ. It tells us nothing at all about it. Or perhaps you would like to explain how the theory of natural selection predicts a different outcome for the case? You don't need a parallel universe to make a comparison. Or is this your magical thinking argument in a different guise?

You are in the habit of projecting your own weaknesses/ faults back on to me. It's not magical thinking. If the stock was slow to recover (say 10 years) then the genetic alteration argument would have more credence would it not? If the recovery was fast (2-3years) then wouldn't it have less credence?

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Well then perhaps you should ask a more specific question about the harm/impact. Or better yet, just move on.

Well you raised the point about 'harm' I tried to expand on it. You just haven't been able to respond in a sensible way.

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Well done PJ. That makes a lot more sense than proclaiming that a recovery in X years is somehow proof that the harm is not significant. Though it would still not get you around all those other confounding factors. But it is a good start nonetheless. I can tell you have been thinking about this now.

I have known about that measure for a long time - it doesn't appear that you have. PS Prof Hilborn used the fast growth under fishing pressure argument. Do you think he knows nothing about fisheries?

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I never intended it to make the case for marine parks on it's own.

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You mean, underfishing? Because of the flaws in traditional managment tools? The flaws you insist are not significant? Are you trying to help me argue in favour of marine parks now?

No, and you are contradicting your own arguments about biodiversity, resilience, improved yields, better recreational fishing and so on. All these will be better if the stocks are fish at somewhat less than the MSY. The question is which is the best way of achieving this locking up a large part of the ocean and fishing what's left harder - or prtecting the whole ocean with quotas and input reductions.  

BTW, can you explain how easing up on fishing pressure would eliminate this problem?

Duh, the lower the fishing pressure then the lower the selective pressure. If you want to 'eliminate' the so called problem then have no significant fishing pressure - ie the preservationist argument.

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I want to increase catches. Among other things of course.

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Yes I have heard the phrase before. Though I must admit I have never heard the phrase 'cure all' applied to a single problem. That's why it threw me a bit.

Stll playing with yourself. There is more than a 'single' fishery or fish species.

BTW, I often have great difficulty figuring out what you mean. That's why I ask you to reference/link/quote people so often. It is so much easier to go to the original claim than work from your interpretation of it.

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Actually no you haven't. You have made several claims about them, but this is the first time you have claimed that the papers show that marine parks will make the harm done by minimum sizes worse. In any case, if there is such a claim somewhere, I'm sure you'd like to bring it up right now. This thread would be the perfect place for it after all. I remember noting that prof. Buxton's paper ignored the issue, though I don't think I bothered mentioning it at the time, as there were more significant problems with your interpretation of his paper.

They pointed out the problems with marine parks and how they unlikely to beneifit fisheries productivity. Just because they didn't explicity tease out your pet theory from their data and analysis does not invalidate their claims.  

If the stock was slow to recover (say 10 years) then the genetic alteration argument would have more credence would it not? [/quote]

No it wouldn't PJ. Why do you think it would?

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Again, no.

You flat denials aren't very convincing. The extrordinary resilience and fast recoveries shown by NSW fisheries to heavy commercial pressure contradict the genetic damage theory. You just cling to this theory like a drowning man to justify marine parks. 

Like I asked already, please explain how the theory of natural selection predicts a different outcome for the case?

Theories only go so far - what matters is the extent and magnitude of the effect.

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Where? What did he actually say?

His 'Faith Based Fisheries' and we have been over it several times.


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Most often it is a case of you misinterpretting what they write.

No it's often a case of you using sophist arguments to wiggle out of real world observations which contradict your mantra.

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There is no contradiction PJ. You can improve on more than one measure at the same time with marine parks. That's what makes them such great fisheries management tools.

Simply asserting they are does not make it so. You need justifications and evidence - which you are very short on.

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Wouldn't it make more sense to use marine parks?

No, because the costs outway the benefits. The benefits are largely hypothetical and not proven as well.

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Are you admitting they made no such claim about the impact of selective pressure on minimum sizes?

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True, but it does prove you wrong. It demonstrates yet again your tendency to interpret an ambiguous statement, or no statement at all, as a statement in support of your position. After all, no scientists is seriously going to deny the impact of natural selection.

No it doesn't, because they looked at real world data, including observations from existing marine parks, so any selective pressure from fishing and advantage of marine parks in this respect would be taken into account. We are not talking about an 'ambiguous statement' either. The Buxton report is several hundred pages long and demonstrates considerable rigour. Also they did mention minimum sizes when they said that adjustments to legal sizes with repect to what is known about growth rates of the fished species would be a better way forward than marine parks.

Also Prof Kearney refered to a paper which pointed to a moderate level of disturbance from fishing actually increasing biodiversity. Genetic variability is part of biodiversty.

And once again if you want no impact have no signifcant fishing pressure and don't pretent you trying to benefit fishermen.