Sunday, August 23, 2009

Wild salmon declines--possible causes

Salmon are in trouble in British Columbia and elsewhere. Is it salmon farming? Pollock trawling? Or what?

I'm not up on all the data, but there are signs of salmon problems from California to Alaska. Not just near salmon farms, and not just where trawlers catch pollock.

The problem has hit sockeye from the Fraser River. But it's also hit salmon from British Columbia all the way to California. Salmon farming has been blamed, but there aren't salmon farms to cause problems all the way to California.

The kings are in trouble in the Yukon River, and pollock trawlers have gotten some heat, but there are disease problems linked to warmer temperatures also causing problems for these fish.

Oh...and there are seabird problems in some of the same areas, British Columbia and the US west coast.

Not sure what to think about all this, but I'm going to focus my worrying on the larger scale issues like ocean warming, either cyclical or CO2 driven.


Anonymous said...

You're right Mark, there are many possible issues and they all combine for very serious pressures. One that can't be overlooked is the 25 year cycle where the food sources for salmon move from Alaska waters to oceans further West (there's a fancy name for it which now escapes me). We, apparently, are in the middle of the time when the food source is over Russia - and they have experienced good returns of salmon for the past few years.
By the way, the sockeye have not returned to SE Alaska either(aside from Bristol Bay). So you can combine Caly to Alaska in the salmon downturn.

Anonymous said...

Its funny, pink salmon are doing very well in all parts of British Columbia. Remember, just a few years ago the environmentalists were sounding off alarms stating that pink salmon were going to go extinct at the hands of salmon farmers. Well, it looks like that isn't the case - rivers in Campbell River, Port Hardy, Nanaimo and the Broughton ARchipelago are all having very high returns.

So, now they've switched to sockeye.

Basically, whatever species wherever that doesn't do as well as the year previously (by the way, there will ALWAYS be that river somewhere!) is blamed on salmon farming.

I'm glad some people are starting to poke holes in their stories....

Anonymous said...

Hmmmm...Alaska has caught about 10% more sockeye than they expected and everyone to the south of them has not seen them return to their rivers?

Wonder where the sockeye went huh??