Sunday, May 06, 2007

Climate change justifies overfishing?

In a stunning twist, climate change is a new shield for failed fishery management. Why did cod collapse off New England and Newfoundland? Al Gore did it.

Global warming is blamed for slowing cod growth, so that as fishermen removed cod they were not replaced fast enough. Beware the topsy-turvy thinking that makes fishing an unchangeable baseline and the messy ocean and capricious cod a villian that undermines our economy.

Such reasoning enshrines overfishing as an entitlement, a right. Fishermen were happily catching cod, and they caught way too many until the fishery crashed. But now a new study by Brian Rothschild says the environment failed, cod had too little to eat, and that was the problem. The darn cod just weren't growing fast enough to support the fishing that was happening.

So, if I spend more money than I make, I can just blame the darn economy for failing to provide me with enough income?

The author of the new study has a long history with fishery management, and he testified before Congress in favor of Mr. Pombo's bill weakening US fishery laws to allow managers more leeway to keep overfishing. This is not the mainstream of US fishery science or management.

Mr. Rothschild does agree that fishing matters. He explained that fishing has a "much stronger effect" on the health of cod stocks when there is a negative environmental change happening in the ocean. However, when the environment is in a more positive state, the same level of fishing has a "much lesser effect," he said.

In other words, the environment (and the fish) are responsible for overfishing.

8 comments:

Ihadira said...

That is incredible I cannot believe the logic.

Mark Powell said...

Not the first time for such silliness. The groundfish disaster on the west coast in 2001 was declared because fish didn't reproduce as fast as they were caught. Check blogfish archives here (particularly the next to last comment) for a post and lengthy debate of this example.

Rick MacPherson said...

just to expand on the profound illogic inherent in this argument, consider the japanese argument for "scientific whaling"...

japanese whaling (and now iceland and a few other nations) continues under the heading of "science" since these harvests are an attempt to characterize the overall health of ocean ecosystems and also demonstrate that the real cause of fisheries collapse is HUNGRY OVERPOPULATED WHALES, not destructive commercial fishing...

scientific whaling is about as scientific and legitimate as intelligent design creationism... it's a bunch of disingenuous, self-serving agendas cloaked in white lab coats...

Anonymous said...

I think you missed the point of the article. If you read the very last quote from Dr. Rothschild in the article he states "We need to manage fisheries so we take environmental signals into account."

The section prior to that stated... He explained that fishing has a "much stronger effect" on the health of cod stocks when there is a negative environmental change happening in the ocean. However, when the environment is in a more positive state, the same level of fishing has a "much lesser effect," he said."

My take on that statement is he is saying that, you can get away with a lot of management mistakes when conditions are good, but if you screw up when environmental conditions are not so good it can have a really negative impact on the fish. i.e. if you are a millionaire losing $10000 is nothing, but if you only have $40k then $10000 actually means something.

Combining his two statements, I think he is stating that you can't assume that the baseline conditions are fixed. When you are managing a stock, you have to take into consideration what is happening with the overall environment when you make your decisions. Is it a good year for copepod production? Is the gyre going to keep the larvae on the nursery grounds or push them out to sea? Are the fish larvae going to be able to grow quickly this year or are they going to be slow growers this year?

Right now it seems like managers basically assume that this year and every other year larvae (of a hypothetical species) grow at 0.20 mm/day and suffer a daily mortality rate of 0.3 d^-1. Rothschild is wanting managers to say, this, this and this are happening so lets assume the larvae are going to grow a bit slower, but on the other hand, because of x, y, and z mortality is going to be 0.25 instead of 0.3.

Mark Powell said...

Look deeper for the roots of the overfishing entitlement, and look at Mr. Rothschild's testimony in favor of Mr. Pombo's attempt to weaken US fishery law.

The fundamental problem is that fish were caught faster than they could reproduce. What was the failure? Overly aggressive fishing, pushing the limits of productivity, coupled with resistence to evidence of problems.

Try an analogy. We're careening down a twisty mountain road in the fog. Going 100 mph around sharp curves. If we crash, what was the mistake? Making a curve too sharp for our driving speed? Or reckless driving?

We are much too prone to do risky fishing, and then we wonder why we end up with a crash.

This type of thinking leads to nonsensical conclusions like fish failed to reproduce as fast as they were being caught. I've heard it said, believe it or not.

It is possible to do better. Where overfishing is viewed as an unacceptable mistake, we are much less likely to see fisheries crash. Where fishing is sacred and fishing cutbacks are fought vigorously, then we see the inevitable logic of overfishing: a crash.

Anonymous said...

I've read both Dr. Rothschilds testimony and the article you posted. I think that you are unfairly distorting his comments. He is not blaming the cod for not growing fast enough or not reproducing fast enough. He is saying that the overfishing happened because management did not account for the effects of changing climate on fish growth rates and recruitment.

Remember that the average fish is a dead fish and that 95% of fish mortality generally happens in the first year of life. If you haven't already done so you should take a look at Houde (1987). Small changes in growth and/or mortality rates of larval fish can have order of magnitude effects on fish abundances. This usually happens well before the first attempt is made at catching the fish.

Your analogy of the situation isn't very good. I think a better one would be that you are driving down a long slightly curvey highway and you decide to see how good your wheel alignement is. You take your hands off the steering wheel and let the car drive on it's own. For the first mile or two you stay more or less on the road. When you hit 5 or 6 miles you notice that you are starting to drift to the right (or left your choice). At 10 miles you drift off the road.

The stock wasn't overfished in a year, it happened over a number of years and the cause, as Rothschild sees it, was that managers didn't consider the effects of a changing environment. If they had recognized that the large scale-environmental conditions were important, they likely could have reduced the TAC on the stock and potentially prevented the overfishing.

If you keep distorting other scientists comments you're going to end up being associated with Behe and the Discovery Institute rather than PZ Myers as you desire.

Hilborn and Rothschild have put their claims through the peer review process and published them. If you think they are wrong write your rebuttal paper and get it published. Until then you are just another ranting environmentalist yelling half truths. You need to do a better job of backing up your claims.

Yes old fish might produce better eggs then young fish, but the data isn't clear cut and it may not be true for all species or any species.

Yes fisheries managers want to fish down the large old fish WITHIN A SPECIES, but they do it because they want to free up space for younger, fast growing fish OF THE SAME SPECIES. Young fish produce new fish biomass much quicker than old fish. Take a look at some growth curves.

Anonymous said...

I've read both Dr. Rothschilds testimony and the article you posted. I think that you are unfairly distorting his comments. He is not blaming the cod for not growing fast enough or not reproducing fast enough. He is saying that the overfishing happened because management did not account for the effects of changing climate on fish growth rates and recruitment.

Remember that the average fish is a dead fish and that 95% of fish mortality generally happens in the first year of life. If you haven't already done so you should take a look at Houde (1987). Small changes in growth and/or mortality rates of larval fish can have order of magnitude effects on fish abundances. This usually happens well before the first attempt is made at catching the fish.

Your analogy of the situation isn't very good. I think a better one would be that you are driving down a long slightly curvey highway and you decide to see how good your wheel alignement is. You take your hands off the steering wheel and let the car drive on it's own. For the first mile or two you stay more or less on the road. When you hit 5 or 6 miles you notice that you are starting to drift to the right (or left your choice). At 10 miles you drift off the road.

The stock wasn't overfished in a year, it happened over a number of years and the cause, as Rothschild sees it, was that managers didn't consider the effects of a changing environment. If they had recognized that the large scale-environmental conditions were important, they likely could have reduced the TAC on the stock and potentially prevented the overfishing.

If you keep distorting other scientists comments you're going to end up being associated with Behe and the Discovery Institute rather than PZ Myers as you desire.

Hilborn and Rothschild have put their claims through the peer review process and published them. If you think they are wrong write your rebuttal paper and get it published. Until then you are just another ranting environmentalist yelling half truths. You need to do a better job of backing up your claims.

Yes old fish might produce better eggs then young fish, but the data isn't clear cut and it may not be true for all species.

Yes fisheries managers want to fish down the large old fish WITHIN A SPECIES, but they do it because they want to free up space for younger, fast growing fish OF THE SAME SPECIES. Young fish produce new fish biomass much quicker than old fish. They have less bulk that needs to be maintained. Take a look at some fish growth curves.

Mark Powell said...

Overfishing is a political failure, especially when scientific advice is ignored, as it was for cod in Newfoundland and New England. More on this later.

The roots of this crisis are deep in the assumptions of fishery science, and we’re not getting there in this discussion. I’ll come back with a post directly on this subject. If you, Mr. Anonymous, want to use your name then I invite you to state your case in a guest post adjoining mine. Email me if you’re interested.

Finally, I don’t see the solution in more science since it's a political problem. And besides, if I wanted to spend my life on publications, I’d still be a professor. No thanks on that suggestion.