Little Hawk
Active Member
Howdy,
Here's some food for thought forwarded to me by Fred Hawkshaw.
BREEDING A SALMON DISASTER
British Columbia News: Column
No matter the pond's size, the fish are all small
MARK HUME
mhume@globeandmail.com
2008 CTVglobemedia Publishing Inc. All Rights Reserved.
VANCOUVER -- For decades, fisheries researchers have been watching with concern a disturbing trend in salmon stocks.
The fish have been getting smaller.
On the Pacific Coast, a study of catch data over a 50-year period shows the average weights of sockeye, coho, pinks and chum salmon have all dropped steadily. Depending on the species, the decline has been from half a kilogram to more than one kg, which means that some salmon, such as coho, are now 33 per cent smaller.
Among Pacific salmon, only chinook broke the trend. They did decline in average weight from 1951 to 1990, but then crept upward again. The increase in chinook size coincided with fishing restrictions brought in due to conservation concerns for that species.
Studies around the world, including in Ireland, Norway and Russia, have shown that both Pacific and Atlantic salmon are getting smaller.
For a long time the cause of the incredible shrinking salmon was debated. Some felt a myriad of complex environmental conditions were to blame. But others felt there was a more mundane explanation: the impact of fishing.
In the past year, researchers have concluded there is no longer much doubt. Intensive commercial fishing has had an evolutionary impact on the development of salmon.
Simply put, by relentlessly killing big fish, we have created a breed of smaller ones.
In a paper earlier this year, scientists from eight research centres in Canada, the United States, Britain, Norway and Austria concluded there is strong evidence “that fishing can cause detectable [evolutionary changes] within 10 or fewer generations.”
On the British Columbia coast, salmon have been harvested for a century without any concern for the long-term genetic implications of killing big fish. It is now clear that has been a terrible mistake.
Large salmon are better at surviving long upstream journeys, they carry more eggs than small salmon and their strength allows them to claim the best spawning sites.
They also dig deeper redds, or spawning nests, providing better protection for their eggs.
Simply put, big fish beget big fish. Kill the big fish and you leave the spawning grounds dominated by smaller, weaker specimens. Do that for decades and you breed a smaller race of fish that have a harder time surviving. And in Canada our pursuit of bigger fish has been unrelenting.
Sports anglers have developed a show-off culture in which they kill the big "trophy” fish and throw the small ones back.
In the commercial fishery, mesh sizes in gill nets have been set to entangle the biggest fish. And whoever heard of a seine fisherman releasing big fish, or a native dip netter shaking out the large ones and keeping the small ones?
Commercial hook-and-line trollers call big salmon “smilies,” because the thought of the money they help to put in the bank puts a grin on their faces.
But there is little reason to smile on the West Coast these days, and with the death of each big fish, the future of salmon fishing grows dimmer.
Fishing methods have created a deepening disaster on both of Canada's coasts, where salmon are in a state of decline, growing smaller, weaker and fewer in number.
A farmer would not select the poorest seeds to replant, nor would a rancher breed the weakest bulls while sending the strongest to early slaughter. But the commercial fishing industry has resisted significant change for 100 years.
“Do we know enough about the genetic effects of fishing on salmonids to justify reassessing current approaches to managing them?” a team of researchers, led by Jeffrey Hard of Seattle's Northwest Fisheries Science Center, asked in a paper published earlier this year.
“We believe so,” they concluded, stating that more selective fishing methods are needed.
They don't spell out what those methods should be, but it's obvious that if nets can't be designed to let big fish escape, then nets have to be replaced by methods, such as fish traps, that allow larger salmon to be released alive.
Sports anglers need to be educated and regulated so they let the big fish go.
The Department of Fisheries and Oceans would know this if it had evolutionary biologists helping to plan policy. But it doesn't – which may explain why Canada has bred itself a salmon disaster.
Here's some food for thought forwarded to me by Fred Hawkshaw.
BREEDING A SALMON DISASTER
British Columbia News: Column
No matter the pond's size, the fish are all small
MARK HUME
mhume@globeandmail.com
2008 CTVglobemedia Publishing Inc. All Rights Reserved.
VANCOUVER -- For decades, fisheries researchers have been watching with concern a disturbing trend in salmon stocks.
The fish have been getting smaller.
On the Pacific Coast, a study of catch data over a 50-year period shows the average weights of sockeye, coho, pinks and chum salmon have all dropped steadily. Depending on the species, the decline has been from half a kilogram to more than one kg, which means that some salmon, such as coho, are now 33 per cent smaller.
Among Pacific salmon, only chinook broke the trend. They did decline in average weight from 1951 to 1990, but then crept upward again. The increase in chinook size coincided with fishing restrictions brought in due to conservation concerns for that species.
Studies around the world, including in Ireland, Norway and Russia, have shown that both Pacific and Atlantic salmon are getting smaller.
For a long time the cause of the incredible shrinking salmon was debated. Some felt a myriad of complex environmental conditions were to blame. But others felt there was a more mundane explanation: the impact of fishing.
In the past year, researchers have concluded there is no longer much doubt. Intensive commercial fishing has had an evolutionary impact on the development of salmon.
Simply put, by relentlessly killing big fish, we have created a breed of smaller ones.
In a paper earlier this year, scientists from eight research centres in Canada, the United States, Britain, Norway and Austria concluded there is strong evidence “that fishing can cause detectable [evolutionary changes] within 10 or fewer generations.”
On the British Columbia coast, salmon have been harvested for a century without any concern for the long-term genetic implications of killing big fish. It is now clear that has been a terrible mistake.
Large salmon are better at surviving long upstream journeys, they carry more eggs than small salmon and their strength allows them to claim the best spawning sites.
They also dig deeper redds, or spawning nests, providing better protection for their eggs.
Simply put, big fish beget big fish. Kill the big fish and you leave the spawning grounds dominated by smaller, weaker specimens. Do that for decades and you breed a smaller race of fish that have a harder time surviving. And in Canada our pursuit of bigger fish has been unrelenting.
Sports anglers have developed a show-off culture in which they kill the big "trophy” fish and throw the small ones back.
In the commercial fishery, mesh sizes in gill nets have been set to entangle the biggest fish. And whoever heard of a seine fisherman releasing big fish, or a native dip netter shaking out the large ones and keeping the small ones?
Commercial hook-and-line trollers call big salmon “smilies,” because the thought of the money they help to put in the bank puts a grin on their faces.
But there is little reason to smile on the West Coast these days, and with the death of each big fish, the future of salmon fishing grows dimmer.
Fishing methods have created a deepening disaster on both of Canada's coasts, where salmon are in a state of decline, growing smaller, weaker and fewer in number.
A farmer would not select the poorest seeds to replant, nor would a rancher breed the weakest bulls while sending the strongest to early slaughter. But the commercial fishing industry has resisted significant change for 100 years.
“Do we know enough about the genetic effects of fishing on salmonids to justify reassessing current approaches to managing them?” a team of researchers, led by Jeffrey Hard of Seattle's Northwest Fisheries Science Center, asked in a paper published earlier this year.
“We believe so,” they concluded, stating that more selective fishing methods are needed.
They don't spell out what those methods should be, but it's obvious that if nets can't be designed to let big fish escape, then nets have to be replaced by methods, such as fish traps, that allow larger salmon to be released alive.
Sports anglers need to be educated and regulated so they let the big fish go.
The Department of Fisheries and Oceans would know this if it had evolutionary biologists helping to plan policy. But it doesn't – which may explain why Canada has bred itself a salmon disaster.
