An interesting article about the massive sockeye run this year

[Coastrider]

By CBC News, cbc.ca, Updated: October 25, 2010 6:11 PM


A volcanic eruption might have helped produce B.C.'s largest sockeye salmon run since 1913.

The 34 million salmon that returned to B.C.'s Fraser River this year were "adolescents" in the Gulf of Alaska when the Kasatochi volcano erupted there in 2008, said Tim Parsons, a research scientist at the Institute of Ocean Sciences in Sidney, B.C.

The ash from that eruption fertilized the ocean, leading to a massive bloom of special phytoplankton called diatoms — an unusually rich source of food for the growing salmon.

"When you have an adolescent of any kind [and] you give them lots of food, they have lots of energy, and they build strong bodies," Parsons said.

"So, we get back, in my hypothesis, 34 million salmon — which was totally unpredicted — instead of the 1.5 million salmon of the previous year, which fed on a diet — which was the normal diet of the Gulf of Alaska — composed of very small plankton."

Parsons said he based his hypothesis on the recent research results reported by Roberta Hamme, an assistant professor at the School of Earth and Ocean Sciences at the University of Victoria.

Hamme, who observed the plankton bloom using satellite imaging, said in a recent paper in Geophysical Research Letters that it was one of the largest such blooms observed in the subarctic North Pacific.

Parsons said the 2009 sockeye run was small because the fish in that run were older, closer to adulthood, and were starting to move out of the Gulf of Alaska at the time the eruption happened.

The link between the plankton bloom and the huge sockeye run of 2010 is consistent with Parsons's own research. In one 1970s experiment, the sockeye run increased seven fold after he fertilized a lake on Vancouver Island. In other studies, he found salmon populations in the Gulf of Alaska depend on the density of phytoplankton.

Parsons suggests that if his hypothesis proves true, it could help fisheries managers make better predictions about salmon populations.

A federal inquiry into the state of B.C.'s wild salmon stocks opened in Vancouver on Monday.

[Troutman Clay]

very interesting article, the run this year was so huge and so out of the blue, something such as this could be something that had something to do with it. I never new the volcano could ever increase a salmon run so dramaticaly, but a good theory

[nthrngrayling]

I was talking to a biologist a short time ago and he also expressed the same thing, that there was an over abundance of phytoplankton called diatoms available. It would be interesting to see what would happen if more lakes were fertilized.

[Steve Zissou]

Yeah, I also heard that diatoms may have had a booming couple of years because of irregularities in the Aleutian low and volcanic ash.

I didn't know that Sockeye would bother with them outside of when they were alevin or smolts. I didn't think that juvenile fish would bother with them because at that age they are still large enough to eat something else with ease.

Perhaps this was a misquote that was meant to say that there was an abundance of food at all stages because larger prey also ate the diatoms? Or maybe I misunderstand what exactly the biologist means by juvenile.