Contrary to popular opinion, minimum sizes lower fishery productivity. This is not just the long term effect of the selective pressure for runts and slow growing fish. Even in the short term, catching the smaller fish will increase the total catch on a weight basis. Basically, throwing them back, or not catching them in the first place, does not mean you catch them when they get bigger. Most of them do not survive to a larger size.

PJ argued that this is not the case because minimum sizes tend to coincide with the onset of sexual maturity and maximum biomass of a population cohort.


pjb05 wrote on Mar 15^th, 2009 at 7:01am:

Here's an interesting article which contradicts many of FD's assertions: http://72.14.235.132/search?q=cache:KQfI9YH2qfIJ:www.esm.ucsb.edu/academics/courses/595PB/Readings/Parrish_Reserves_CALCOFI.pdf +virgin+spawning+biomass&cd=9&hl=en&ct=clnk&gl=au Growth overfishing is most likely to occur in species with low growth and natural mortality rates as well as delayed sexual maturity. It is therefore likely to occur in fisheries for rockfishes and other slow-growing groundfish species. Generally, the term refers to fishing a stock beyond the maximum yield per recruit, and this generally occurs when a species is exploited before the age that an individual cohort achieves its natural maxi- mum biomass. Growth overfishing is generally avoided by delaying, or at least reducing, fishing mortality on fish that have not yet reached the size or age of sexual maturity; this is often near the age that a year class reaches its maxi- mum biomass.

However there are several problems with this argument. I have not been able to find any independent verification that maximum biomass tends to coincide with the onset of sexual maturity. This argument may have the causation backwards. Minimum sizes will create an artifical age of maximum biomass. For many species these were set arbitrarily at the age of sexual maturity, which is perhaps the worst age for creating selective pressure for slow growing fish. Furthermore the age of maximum biomass in a natural setting, to which you could argue fish would adapt their first breeding cycle, and which in turn would be would be caused by or reinforced by breeding effort, would have little correlation to the age of maximum biomass of a fished stock. That is, fishing would change it all anyway. Furthermore, if you were to try to target minimum sizes to maximise catch weight, you would not target the age of maximum biomass of a single cohort (generation). Rather, you would target the age that maximises total growth rate when you take things like intergenerational competition into account. You get the wrong answer when you only consider a single cohort in isolation. The age of maximum biomass becomes almost meaningless when you talk about harvesting based on it, as the harvest itself would have a strong impact on the age of maximum biomass.

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).

Quote:

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.

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. 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.


Quote:

not proving the case for marine parks

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.

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.

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.

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.

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

Quote: 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. 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. [quote]not proving the case for marine parks

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?

So why can't you back it up? It looks to me like Parrish just made it up as he went along. Why were you so quick to concede such an important point and go back to to your vague waffle and slogans?


Quote:

It is also quite clear that a marine park strategy will lead to a lower sustainable yield

Can you back this up?


Quote:

Actually if you apply this line of reason to marine parks (ie excessive use of the precautionary principle) then they fail the test too!

Go ahead and apply it for us then. It would be interesting to see you try to reason it through.


Quote:

changes in species assemblages and predator/ prey relationships

Is this a bad thing?


Quote:

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.

Can you explain the logic behind your claim about more destructive fishing methods?


Quote:

Of course I have pointed all this out before and you just keep rising up like a zombie.

Yes you have made the claim, but when it comes to backing it up, you always fall short.


Quote:

and none are seriously overfished

What, only moderately overfished?


Quote:

Its a strawman argument. Minimum sizes are only a small part of the traditional management mix.

The extent to which they are used does not affect whether it is a good idea to use them. If you reduce the harm by not using minimum sizes exclusively, why not eliminate the harm or minimise it to the extent possible? The fact that other tools are also used does not mean thqat inferior tools magically become a good idea.

PJ, the 'original' link for your article:

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

So why can't you back it up? It looks to me like Parrish just made it up as he went along. Why were you so quick to concede such an important point and go back to to your vague waffle and slogans?

'Looks to me like Parrish just made it up as he went along' - what a brilliant analysis! Why don't you try to get that published FD?

PS what have I conceded?


Quote:

It is also quite clear that a marine park strategy will lead to a lower sustainable yield

Can you back this up?

Yes and I have already. I have put up several papers that make this case (Parrish, Shipton, Hilborn, Buxton). You then stuck your head in the sand by ignoring their arguments and/ or calling the authors names.

Even marine parks advocates in their more honest moments say that fishermen are unlikely to benifit. They justify them on preservationist grounds. Ie they don't like what we do and want a 'look but don't touch' world.


Quote:

Actually if you apply this line of reason to marine parks (ie excessive use of the precautionary principle) then they fail the test too!

Go ahead and apply it for us then. It would be interesting to see you try to reason it through.

I just did. I can expand on them if you like.


Quote:

changes in species assemblages and predator/ prey relationships

Is this a bad thing?

The point is that they can upset the natural balance, eg if the predator is more mobile it will respond less to area closures  than less mobile species. Reduction in the prey nos means less biodiversity and could have commercial implications if the prey is a valuable species.


Quote:

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.

Can you explain the logic behind your claim about more destructive fishing methods?

Some species don't lend themselves to being caught by methods other than trawling. To make up for the lost grounds you would have to step up trawling to maintain the yield. More trawling in a smaller area means more ecological damage (Parrish).


Quote:

Of course I have pointed all this out before and you just keep rising up like a zombie.

Yes you have made the claim, but when it comes to backing it up, you always fall short.

You just ignore what is inconvenient to your mantra.


Quote:

and none are seriously overfished

What, only moderately overfished?

A few are considered growth overfished. This is not a biological problem. These few remaining problems of overfishing can and are being adressed my methods less proscriptive than marine parks.


Quote:

Its a strawman argument. Minimum sizes are only a small part of the traditional management mix.

The extent to which they are used does not affect whether it is a good idea to use them. If you reduce the harm by not using minimum sizes exclusively, why not eliminate the harm or minimise it to the extent possible? The fact that other tools are also used does not mean thqat inferior tools magically become a good idea.

What 'harm' are you talking about? Any substantial fishery has an impact on fish stocks. What are you saying - that you want the World's only fishery that only harvests the tiddlers?

Quote:

'Looks to me like Parrish just made it up as he went along' - what a brilliant analysis! Why don't you try to get that published FD?

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?


Quote:

What 'harm' are you talking about?

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

Quote:

'Looks to me like Parrish just made it up as he went along' - what a brilliant analysis! Why don't you try to get that published FD?

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?

There backed up by real world data from actual fisheries.


Quote:

What 'harm' are you talking about?

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'm just putting your theories in a real world context - if you don't like that, well too bad. Selective pressure for slow growth rates is a phenomenon with scant evidence in real fisheries. It is also only likely to ever be apparent if the fishing pressure is very high (ie few fish get much past legal size) - and I am not arguing for that. Furthermore this selective pressure argument does not prove the case for marine parks. All it does is make the case for a fishing effort not overly heavy or somewhat lighter than the maximum sustainable yield.    

I posted responses to some of your other points here:

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

Quote:

There backed up by real world data from actual fisheries.

Can you give an example?


Quote:

It is also only likely to ever be apparent if the fishing pressure is very high

Can you explain the reasoning behind this claim?


Quote:

(ie few fish get much past legal size) - and I am not arguing for that

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

freediver wrote on May 26^th, 2009 at 9:44pm:

Quote: There backed up by real world data from actual fisheries. Can you give an example? [quote]It is also only likely to ever be apparent if the fishing pressure is very high

Can you explain the reasoning behind this claim?


Quote:

(ie few fish get much past legal size) - and I am not arguing for that

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

The EIS into NSW fisheries states that they do not regard growth overfishing as a biological problem. Also look a how quckly overfished stocks have recovered eg salmon and kingfish in NSW. This is hardly a sign that they have been genetically damaged.

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.

freediver wrote on Jun 8^th, 2009 at 6:59pm:

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.

Well if you can't find the evidence of selective pressures and detrimetal genetic changes in an overfished stock, when are you going to find it? Also you apply a burden of proof to the status quo but treat your own theories as a proven fact and not requiring the same standards of proof. If you look at examples like these it goes to show that a lot of our inshore fish stocks have a high natural resistance to fishing pressure (yes a lot of them are fast growing) and that overfishing is reversible.

Quote:

Well if you can't find the evidence of selective pressures and detrimetal genetic changes in an overfished stock

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


Quote:

Also you apply a burden of proof to the status quo but treat your own theories as a proven fact

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.


Quote:

If you look at examples like these it goes to show that a lot of our inshore fish stocks have a high natural resistance to fishing pressure (yes a lot of them are fast growing) and that overfishing is reversible.

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.

Quote:

Well if you can't find the evidence of selective pressures and detrimetal genetic changes in an overfished stock

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

Duh, the selective pressure is greater in an overfished stock. If there is no sign of permanent harm (ie overfished stocks recover quickly) then it can't be very significant in an sustainably fished stock.


Quote:

Also you apply a burden of proof to the status quo but treat your own theories as a proven fact

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.

I'm not talking about predictions - I'm talking about observations from actual fisheries.


Quote:

If you look at examples like these it goes to show that a lot of our inshore fish stocks have a high natural resistance to fishing pressure (yes a lot of them are fast growing) and that overfishing is reversible.

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.

Uneccessary marine parks mean a permanent loss of productivity, income, food and recreational value because they lock up productive ares for ever. Your faith based mantra is flawed. Just because there have been some fisheries failures in the past or overseas does not mean marine parks are the best way forward.

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

tallowood wrote on Jun 13^th, 2009 at 7:33pm:

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

They are probably farmed fish - for which legal sizes do not apply.

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

tallowood wrote on Jun 13th, 2009 at 7:33pm: Coles stores habitually sell undersized fish and nothing is done about it. They are probably farmed fish - for which legal sizes do not apply.

Trout is but not flathead or snapper.

tallowood wrote on Jun 13^th, 2009 at 8:01pm:

pjb05 wrote on Jun 13th, 2009 at 7:49pm: tallowood wrote on Jun 13th, 2009 at 7:33pm: Coles stores habitually sell undersized fish and nothing is done about it. They are probably farmed fish - for which legal sizes do not apply. Trout is but not flathead or snapper.

Snapper are farmed. Also there are different species of flathead with different legal sizes, you might have misidentified the ones you saw.

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

tallowood wrote on Jun 13th, 2009 at 8:01pm: pjb05 wrote on Jun 13th, 2009 at 7:49pm: tallowood wrote on Jun 13th, 2009 at 7:33pm: Coles stores habitually sell undersized fish and nothing is done about it. They are probably farmed fish - for which legal sizes do not apply. Trout is but not flathead or snapper. Snapper are farmed. Also there are different species of flathead with different legal sizes, you might have misidentified the ones you saw.

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

Tallow, I think that outside state waters, in federal fisheries, they can catch them at a smaller size.


Quote:

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

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.

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.

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:

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

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.

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


Quote:

Any substantial fishing pressure will have an impact (marine parks or not) and yet you talk about wanting zero harm or impact.

 

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.


Quote:

So do you want zero impact?

No. What on earth makes you think that?


Quote:

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

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] 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.


Quote:

Any substantial fishing pressure will have an impact (marine parks or not) and yet you talk about wanting zero harm or impact.

 

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".


Quote:

So do you want zero impact?

No. What on earth makes you think that?

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



Quote:

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

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.  

Quote:

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

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.


Quote:

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".

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".


Quote:

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

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.


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.

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.


Quote:

Plus you again make a huge leap of faith that marine parks are the cure-all for this theoretical problem.

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


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.

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:

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

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.  


Quote:

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".

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.  


Quote:

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

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.  


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.

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!


Quote:

Plus you again make a huge leap of faith that marine parks are the cure-all for this theoretical problem.

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.


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.

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.  

Quote:

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.

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?


Quote:

I think it is a very subtle and subjective difference.

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


Quote:

Don't you know you can measure selective pressure by looking for changes in the age which fish become sexually mature?

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.


Quote:

PS: all your harping about selective pressure does not make the case for marine parks

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


Quote:

just easing for up on the fish stocks somewhat below maximun sustainable yield

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?

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


Quote:

But then you want to eliminate underfishing!

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


Quote:

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

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.

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.


Quote:

I have done and also refered to them several times

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.

Quote:

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.

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?


Quote:

I think it is a very subtle and subjective difference.

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.


Quote:

Don't you know you can measure selective pressure by looking for changes in the age which fish become sexually mature?

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?


Quote:

PS: all your harping about selective pressure does not make the case for marine parks

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


Quote:

just easing for up on the fish stocks somewhat below maximun sustainable yield

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.


Quote:

But then you want to eliminate underfishing!

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


Quote:

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

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.


Quote:

I have done and also refered to them several times

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.  

Quote:

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

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


Quote:

If the recovery was fast (2-3years) then wouldn't it have less credence?

Again, no.

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


Quote:

PS Prof Hilborn used the fast growth under fishing pressure argument.

Where? What did he actually say?


Quote:

Do you think he knows nothing about fisheries?

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


Quote:

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.

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.


Quote:

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.

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


Quote:

They pointed out the problems with marine parks and how they unlikely to beneifit fisheries productivity.

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


Quote:

Just because they didn't explicity tease out your pet theory from their data and analysis does not invalidate their claims.

 

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.

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?


Quote:

If the recovery was fast (2-3years) then wouldn't it have less credence?

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.


Quote:

PS Prof Hilborn used the fast growth under fishing pressure argument.

Where? What did he actually say?

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



Quote:

Do you think he knows nothing about fisheries?

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.


Quote:

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.

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.


Quote:

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.

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.


Quote:

They pointed out the problems with marine parks and how they unlikely to beneifit fisheries productivity.

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


Quote:

Just because they didn't explicity tease out your pet theory from their data and analysis does not invalidate their claims.

 

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.

Quote:

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.

You keep missing the point PJ. It is a matter of logic, not flat denial. That is why my simple questions leave you so stumped.


Quote:

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

And to measure that extent, you would have to be able to say what the recovery rate would have been if the harm was present. You cannot. You pulled a number - 10 years - out of your arse. So please explain where you got that from, and why the recovery rate we saw indicates no harm done. You cannot do this, because your argument makes no sense.


Quote:

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

I am not trying to wiggle out of real world observations. I am trying to state, as clearly as possible, that your observations do not back up your argument. They are meaningless. You are misinterpretting them. You are slipping up on some very basic matters of logic. You see, but you don;t understand, which is why you can't explain yourself.


Quote:

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

I need evidence that there is no contradiction? Again PJ, you are not making any sense.


Quote:

No it doesn't, because they looked at real world data

Again PJ you are missing the point. You claimed they said something about the negative impact of minimum sizes on fishery productivty, but they did not. They avoided the issue altogether. All the real world data in the world won't help you if it is measuring the wrong thing. Evidence, references, etc are not an alternative to thinking for yourself. You still have to figure out what it means. You took an inappropriate generalisation about marine parks and took it to be a specific statement about the impact of minimum sizes - an issue the paper didn't even touch on.


Quote:

including observations from existing marine parks

This is about minimum sizes remember. Whatever you think they observed or said about marine parks, it has nothing to do with minimum sizes and you were just plain wrong to claim they did.


Quote:

so any selective pressure from fishing and advantage of marine parks in this respect would be taken into account

This is getting rediculous PJ. You are assuming that because they didn't even mention the issue, they took it into account. How naive is that?


Quote:

Also they did mention minimum sizes when they said that adjustments to legal sizes

So you did look for it, and that is the best you could come up with - a statement that does not even mention the negative impact of selective pressures on growth rate. Do you honestly think this justifies your claim?


Quote:

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.

Please quote him.


Quote:

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

I thought we had cleared this up PJ. Remember what I said about saying something specific, not waffling on about impact, harm, pressure etc?

[/quote]
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. [/quote]

You keep missing the point PJ. It is a matter of logic, not flat denial. That is why my simple questions leave you so stumped.


Quote:

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

And to measure that extent, you would have to be able to say what the recovery rate would have been if the harm was present. You cannot. You pulled a number - 10 years - out of your arse. So please explain where you got that from, and why the recovery rate we saw indicates no harm done. You cannot do this, because your argument makes no sense.

Try not be be so obtuse FD - ten years was a way of illustrating the point. The dynamics of fish populations and growth rates under fishing pressure are fairly well understood. I knnow pesky real world observations are inconvenient for you, but fast recoveries count against the genetic damage theory - as Prof Hilborn pointed out.  I have yet to see a fisheries scientist make a big deal out of this theory that you do. If you think you know better than Hilborn, Parrish, Buxton or Kearney why don't you email them a critique of their papers? Of course you will have to read them first.


Quote:

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

I am not trying to wiggle out of real world observations. I am trying to state, as clearly as possible, that your observations do not back up your argument. They are meaningless. You are misinterpretting them. You are slipping up on some very basic matters of logic. You see, but you don;t understand, which is why you can't explain yourself.

It must be wonderful to have reached a state of enlightenment of 'just knowing everything' - which is what you are really saying. PS there not just my observations, I have quoted some very senior fisheries scientists and you have no scientific training!


Quote:

No it doesn't, because they looked at real world data

Again PJ you are missing the point. You claimed they said something about the negative impact of minimum sizes on fishery productivty, but they did not. They avoided the issue altogether. All the real world data in the world won't help you if it is measuring the wrong thing. Evidence, references, etc are not an alternative to thinking for yourself. You still have to figure out what it means. You took an inappropriate generalisation about marine parks and took it to be a specific statement about the impact of minimum sizes - an issue the paper didn't even touch on.


Quote:

including observations from existing marine parks

This is about minimum sizes remember. Whatever you think they observed or said about marine parks, it has nothing to do with minimum sizes and you were just plain wrong to claim they did.

Yes and they said adjusting minimum sizes to correspond with growth rate would be a better way forward than marine parks!


Quote:

so any selective pressure from fishing and advantage of marine parks in this respect would be taken into account

This is getting rediculous PJ. You are assuming that because they didn't even mention the issue, they took it into account. How naive is that?

Who's naive? Your the one with no scientific training. And they are looking at real fisheries - not doing games with 'logic' sitting at home.


Quote:

Also they did mention minimum sizes when they said that adjustments to legal sizes

So you did look for it, and that is the best you could come up with - a statement that does not even mention the negative impact of selective pressures on growth rate. Do you honestly think this justifies your claim?

Yep. And I didn't have to go looking for it, remember I have already put that quote up. Once again if you think they have missed somthing why don't you contact them with your theories?


Quote:

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.

Please quote him.

I just did pretty much. If you want to enquire further you will have to get hold of the paper he cited.


Quote:

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

I thought we had cleared this up PJ. Remember what I said about saying something specific, not waffling on about impact, harm, pressure etc?

Well your comments aren't logically consistent. You say we can't be sure of zero harm or impact from fishing pressure but then you say your not a preservationist and want to maximise yields!

Quote:

Try not be be so obtuse FD - ten years was a way of illustrating the point. The dynamics of fish populations and growth rates under fishing pressure are fairly well understood. I knnow pesky real world observations are inconvenient for you, but fast recoveries count against the genetic damage theory

No they don't PJ, which is why you are unable to explain how. The only point your 'ten years' example illustrates is that you are unable to come up with the actual time frame. You can only complete your argument by making up numbers.


Quote:

I have yet to see a fisheries scientist make a big deal out of this theory that you do.

So you haven't looked at the work of Dieckman and Heino yet? Would you like me to provide another link?


Quote:

If you think you know better than Hilborn, Parrish, Buxton or Kearney why don't you email them a critique of their papers?

I am saying I know better than you, because you can't comprehend the issue.


Quote:

It must be wonderful to have reached a state of enlightenment of 'just knowing everything' - which is what you are really saying.

No it isn't. I explained it to you. It is a matter of logic, not evidence. You have to be able to udnerstand what the evidence means. That is where your argument fails.


Quote:

Yes and they said adjusting minimum sizes to correspond with growth rate would be a better way forward than marine parks!

You seem to have forgotten the topic PJ. Either that, or you never figured out what is in the beginning.


Quote:

I just did pretty much.

In other words, you did not quote him. You substituted your own deeply flawed interpretation.

[]
Quote:

Try not be be so obtuse FD - ten years was a way of illustrating the point. The dynamics of fish populations and growth rates under fishing pressure are fairly well understood. I knnow pesky real world observations are inconvenient for you, but fast recoveries count against the genetic damage theory

No they don't PJ, which is why you are unable to explain how. The only point your 'ten years' example illustrates is that you are unable to come up with the actual time frame. You can only complete your argument by making up numbers.

Well it's not hard for Prof Keaney and Hilborn to see the point.


Quote:

I have yet to see a fisheries scientist make a big deal out of this theory that you do.

So you haven't looked at the work of Dieckman and Heino yet? Would you like me to provide another link?

You don't need my permission to put up a link. What did they conclude with regards to practical fisheries management?


Quote:

If you think you know better than Hilborn, Parrish, Buxton or Kearney why don't you email them a critique of their papers?

I am saying I know better than you, because you can't comprehend the issue.

Duh that's very mature - 'I'm right your wrong'! Why don't you contact the authors?


Quote:

It must be wonderful to have reached a state of enlightenment of 'just knowing everything' - which is what you are really saying.

No it isn't. I explained it to you. It is a matter of logic, not evidence. You have to be able to udnerstand what the evidence means. That is where your argument fails.

Why would someone with no scientific training have a better comprehension of the issues? You don't even seem to be all that bright.


Quote:

Yes and they said adjusting minimum sizes to correspond with growth rate would be a better way forward than marine parks!

You seem to have forgotten the topic PJ. Either that, or you never figured out what is in the beginning.

The topic is the merit of marine parks for fisheries management isn't it?


Quote:

I just did pretty much.

In other words, you did not quote him. You substituted your own deeply flawed interpretation.[/quote]

Are you really that thick? I said the actual quote is in one of the recent threads. Why don't you look it up before making such claims?

Quote:

Well it's not hard for Prof Keaney and Hilborn to see the point.

Like I said, you need to think for yourself. References are meant to back up your argument, not act as a substitute for a logical argument.


Quote:

Duh that's very mature - 'I'm right your wrong'! Why don't you contact the authors?

Because they're articles are not about this topic PJ. I have explained why you are wrong plenty of times already.


Quote:

The topic is the merit of marine parks for fisheries management isn't it?

No it isn't. Read the thread title if you have forgotten. It's about the negative impact of the selective pressure arising from minimum sizes on a fishery.

Also, you did bring up marine parks here:


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.

 

However, the papers do not say the opposite. They do not even touch on this particular problem. You seem to assume that because they are critical of one or two marine parks they can be used to back up any criticism you make of marine parks in general. That does not make sense PJ.


Quote:

Are you really that thick? I said the actual quote is in one of the recent threads.

And what? You want me to go looking for it? That is not how it works PJ.

]
Quote:

Well it's not hard for Prof Keaney and Hilborn to see the point.

Like I said, you need to think for yourself. References are meant to back up your argument, not act as a substitute for a logical argument.

Field evidence of critical importance in a topic like this. You want to treat it like some abstract exercise in logic.


Quote:

Duh that's very mature - 'I'm right your wrong'! Why don't you contact the authors?

Because they're articles are not about this topic PJ. I have explained why you are wrong plenty of times already.

They studied a variety management regimes including marine parks and minimum sizes. Unlike you they are looking a real fisheries where genetic alteration may/ may not be a factor. If this is not enough for you and you still think they missed something why don't you write to the authors?  


Quote:

The topic is the merit of marine parks for fisheries management isn't it?

No it isn't. Read the thread title if you have forgotten. It's about the negative impact of the selective pressure arising from minimum sizes on a fishery.

Yes, and are you using the impact of the selective pressure arising from minimum sizes on a fishery as a justification aren't you? If yes then this is part of the merits of marine parks for fisheries management debate isn't it?.


Also, you did bring up marine parks here:


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.

 

However, the papers do not say the opposite. They do not even touch on this particular problem. You seem to assume that because they are critical of one or two marine parks they can be used to back up any criticism you make of marine parks in general. That does not make sense PJ.

See above - they do cover the so called problem.


Quote:

Are you really that thick? I said the actual quote is in one of the recent threads.

And what? You want me to go looking for it? That is not how it works PJ. [/quote]

So accusing me of misquoting without looking at the quote how it works? Is making arguments over nothing how it works? I really don't see the need to keep putiing quotes up again and again. You are perfectly capable of looking them up.

Catch limits, maximum sizes and resilience

http://www.ozpolitic.com/forum/YaBB.pl?num=1244944049/0

The effect has been empirically measured by these scientists:

'Darwinian Debt' May Explain Why Fish Stocks Don't Recover

http://www.sciencedaily.com/releases/2006/01/060112040047.htm

ScienceDaily (Jan. 12, 2006) — Why does it take so long for fish stocks to recover from over-fishing? This problem has been worrying both scientists and fishery managers who expect stocks to quickly rebound when fishing stops.

Now a research team from Stony Brook University believes they have an answer: continually harvesting the largest and oldest fish (as fishing regulations typically require) alters not only size but also numerous other genetic characteristics that are harmful to the overall population.

As reported in Ecology Letters, the researchers experimentally harvested captive groups of a marine fish named the Atlantic silverside. Removing the largest fish over several generations gradually caused a "Darwinian debt": the fish that remained in these populations became progressively smaller but surprisingly many other traits also changed including fewer and smaller eggs with lower survival and growth.

Even behavioural traits like foraging and feeding rate declined. Collectively these changes hamper population recovery and because they are genetic, they don't immediately go away when fishing ceases. How long it would take to undo the debt is now being studied by the research team.

'Undesirable' Evolution Can Be Reversed In Fish, By Letting The Big Ones Go

http://www.sciencedaily.com/releases/2009/03/090303193950.htm

ScienceDaily (Mar. 4, 2009) —  "Undesirable" evolution in fish – which makes their bodies grow smaller and fishery catches dwindle -- can actually be reversed in a few decades' time by changing our "take-the-biggest-fish" approach to commercial fishing, according to groundbreaking new research published by Stony Brook University scientists.

Intensive harvesting of the largest fish over many decades, while leaving the small fish behind, may have unintentionally genetically reprogrammed many species to grow smaller, said lead author Dr. David O. Conover, Professor and Dean of the Stony Brook University School of Marine and Atmospheric Sciences in Long Island, New York.

Although Charles Darwin showed 150 years ago that evolution equips life forms to be better adapted to prosper in their environment, unnatural evolution caused by man's size-selective fishing is causing fish to be smaller, less fertile, and competitively disadvantaged. This has also been a loss for commercial fishers who seek big fish for their livelihoods, recreational anglers in pursuit of trophy fish, and seafood consumers who desire large portions on their plates.

This study demonstrates for the first time ever that detrimental evolution in fish can be reversed, and pokes a gaping hole in theoretical models suggesting that genetic changes are impossible to "undo." It is the result of 10 years of research largely supported by a generous grant from the Institute for Ocean Conservation Science at Stony Brook University.

"This is good news for fisheries, but it also shows that reversal is a slow process," Dr. Conover said. "Over time, fish can return back to their normal size but the reversal process occurs much more slowly than the changes caused by fishing. So the best strategy is still to avoid harmful evolutionary changes in the first place".

Current fishery management plans are generally based upon assessment methods which do not incorporate long-term evolutionary dynamics. It could take years before evolutionary change is incorporated into such plans, since the concept remains quite controversial among scientists.

"It took scientists a long time to reach a consensus on climate change, and acceptance of this phenomenon might require a long time, too," Dr. Conover said.

Dr. Ellen Pikitch, Executive Director of the Institute for Ocean Conservation Science, said, "We now have proof that the negative ramifications of common fishing practices can linger for decades, leaving future generations to grapple with a legacy of diminished ocean productivity. It is essential that fishing be transformed to minimize its evolutionary and broader ecological consequences." Evolutionary dynamics are a fundamental principle of ecosystem-based fishery management (EBFM), a holistic approach that considers the connectedness of different species and the links between species and environmental influences, rather than managing each species in isolation. Dr. Pikitch was among the earliest proponents of EBFM, and lead author of a seminal 2004 article in Science on the concept.

"We have interfered extensively with the natural course of things, and while it is very encouraging that the harmful effects of size-selective fishing may be reversible, the length of the recovery period is sobering," said Dr. Pikitch, who is also a Professor of Marine Science at Stony Brook University. "Restoration of ocean fisheries requires prompt and widespread adoption of an ecosystem-based approach to fisheries management."

Want Sustainable Fishing? Keep Only Small Fish, And Let The Big Ones Go

http://www.sciencedaily.com/releases/2008/11/081130210013.htm

ScienceDaily (Dec. 1, 2008) — Scientists at the University of Toronto analysed Canadian fisheries data to determine the effect of the "keep the large ones" policy that is typical of fisheries. What they found is that the effect of this policy is an unsustainable fishery.

In fact, the opposite policy (keep the small young ones and throw back the large old ones) would result in a more sustainable fishery. In short -- a big fish in the water is worth two in the net.

Put simply, a fish population will produce more young -- and therefore sustain more fishing -- if it is made up of big, old fish.

The team of scientists, led by Paul Venturelli, a graduate student in the Department of Ecology and Evolutionary Biology, used a simple population model, as well as evaluating data from 25 marine fish species. They also tailored their methods to allow for other possible causes for the results, such as the effect of climate.

Finding ways to replenish fishery stocks and improve management provides both ecological and financial benefits.

The research is published in the Proceedings of the Royal Society B.