tangledline
Well-Known Member
- Joined
- Jul 10, 2008
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read this article and it re-affirmed the old age philosophy that if you are not gonna eat the fish you just caught then catch and release the little guy. if the fish was dumb enough to be caught by me i want it to go back and reproduce many more like him/her. 8)
http://www.canada.com/topics/technology ... b3&k=71820
Fish that lunge at lures drain gene pool
Tom Spears , Canwest News Service
Published: Tuesday, February 26, 2008
OTTAWA- Old-timers who insist that fish don't bite like they used to are right, says a new Canadian study that warns we're killing off the aggressive, fast-growing fish in lakes and oceans.
Aggressive fish chase food harder, grow faster and get caught more often. These, unfortunately, are the fish that would have the largest number of offspring if they lived.
That's likely one reason the northern cod isn't coming back faster, the University of Calgary study suggests: fishing killed off the fittest fish.
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Font:****What happens is a reverse of the usual evolution. The timid, slow-growing fish lose the race for food and would normally lose the evolutionary race. But in heavily fished waters they're the ones that survive and pass on their genes. The result: a whole gene pool of slow-growing, passive, timid fish that don't lay very many eggs.
``Fast-growing fish . . . are harvested at three times the rate of the slow- growing genotypes within two replicate lake populations,'' says the study, published today in the Proceedings of the National Academy of Sciences.
Peter Biro and John R. Post of the University of Calgary studied rainbow trout in two small lakes near Merritt, B.C. The idea came from the fact, already well known, that some fish in any population are much bolder than others, Biro said in an e-mail interview from Australia. He is now a postdoctoral fellow at the University of Technology in Sydney, but did the fish research while in Calgary.
``It just made sense that those that tend to be active and bold would also be more likely to bump into and be caught by gill nets . . . Active and bold fish encounter more food, feed more and grow more, but get caught and killed more.''
That theory is what the experiment tested. The young fish tend to carry on the same personality - aggressive or timid - as their parents, he noted. This leads to a population where the aggressive fish are weeded out and replaced by shy ones. Biologists call this ``genetic selection.''
Timid fish, he said, are generally less fit for breeding. ``The problem is that such a population does not yield much to a fishery (remaining fish are harder to catch and smaller, so less profitable) and does not rebound well from overfishing because slow growers tend to be smaller at any age, possess fewer eggs, smaller eggs, and hatch smaller young that are less likely to survive.
``We think this is the reason why the (Atlantic) cod is not rebounding well after closure of the fishery,'' he said. ``The same arguments apply for (sport) angling as for commercial fishing.''
Aggressive fish grow larger, but protecting big fish doesn't help save the aggressive ones, the study found. This is ``because fast-growing fish that are still small (young) are zooming around gathering food at high rates which gets them into trouble.''
The results from both lakes were identical, lending support to the conclusions, the two scientists wrote.
© CanWest News Service 2008
http://www.canada.com/topics/technology ... b3&k=71820
Fish that lunge at lures drain gene pool
Tom Spears , Canwest News Service
Published: Tuesday, February 26, 2008
OTTAWA- Old-timers who insist that fish don't bite like they used to are right, says a new Canadian study that warns we're killing off the aggressive, fast-growing fish in lakes and oceans.
Aggressive fish chase food harder, grow faster and get caught more often. These, unfortunately, are the fish that would have the largest number of offspring if they lived.
That's likely one reason the northern cod isn't coming back faster, the University of Calgary study suggests: fishing killed off the fittest fish.
View Larger Image
Email to a friend
Printer friendly
Font:****What happens is a reverse of the usual evolution. The timid, slow-growing fish lose the race for food and would normally lose the evolutionary race. But in heavily fished waters they're the ones that survive and pass on their genes. The result: a whole gene pool of slow-growing, passive, timid fish that don't lay very many eggs.
``Fast-growing fish . . . are harvested at three times the rate of the slow- growing genotypes within two replicate lake populations,'' says the study, published today in the Proceedings of the National Academy of Sciences.
Peter Biro and John R. Post of the University of Calgary studied rainbow trout in two small lakes near Merritt, B.C. The idea came from the fact, already well known, that some fish in any population are much bolder than others, Biro said in an e-mail interview from Australia. He is now a postdoctoral fellow at the University of Technology in Sydney, but did the fish research while in Calgary.
``It just made sense that those that tend to be active and bold would also be more likely to bump into and be caught by gill nets . . . Active and bold fish encounter more food, feed more and grow more, but get caught and killed more.''
That theory is what the experiment tested. The young fish tend to carry on the same personality - aggressive or timid - as their parents, he noted. This leads to a population where the aggressive fish are weeded out and replaced by shy ones. Biologists call this ``genetic selection.''
Timid fish, he said, are generally less fit for breeding. ``The problem is that such a population does not yield much to a fishery (remaining fish are harder to catch and smaller, so less profitable) and does not rebound well from overfishing because slow growers tend to be smaller at any age, possess fewer eggs, smaller eggs, and hatch smaller young that are less likely to survive.
``We think this is the reason why the (Atlantic) cod is not rebounding well after closure of the fishery,'' he said. ``The same arguments apply for (sport) angling as for commercial fishing.''
Aggressive fish grow larger, but protecting big fish doesn't help save the aggressive ones, the study found. This is ``because fast-growing fish that are still small (young) are zooming around gathering food at high rates which gets them into trouble.''
The results from both lakes were identical, lending support to the conclusions, the two scientists wrote.
© CanWest News Service 2008
