Outdoor Alaska: How small streams help Bristol Bay's productivity

Published: Aug. 8, 2019 at 5:57 PM AKDT
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Bristol Bay is unrivaled in its production of sockeye salmon.

This year's run topped out at more than 56 million reds. While it didn't reach last year's all time record, it's still more than 15 million fish greater than the Department of Fish and Game's preseason forecast.

The University of Washington has been documenting data on everything ranging from environmental conditions to daily counts of fish in numerous streams in the Bristol Bay watershed.

Nerka Lake in Southwest Alaska.

Through long term monitoring, researchers with UW have been able learn a lot about what drives Bristol Bay's production. One key factor - diversity.

"You can see its only five or six feet wide, but this little stream over the course of the about a half mile to a mile of stream looks like it will support this year maybe five or six thousand fish," Daniel Schindler, professor at the UW School of Aquatic and Fishery Sciences said.

Schindler has spend summers on the Wood River system in the Western Bristol Bay watershed since 1997.

"If you came here in a month you would see very little evidence that salmon were ever here. And you'd look at this tiny stream, and it's not deep enough for holding things like trout in it, and it would be very easy to underestimate how very important it is for supporting, in this case, sockeye salmon," Schindler said. "They are very effective at using little tiny pieces of habitat like this that are only a few feet wide to the river that we just came up that is in some places 200 meters wide, to spawning on the beaches of lakes where the lakes are maybe 10 miles across.

Although the overall fishery in Bristol Bay has been highly productive overall, Schindler says individual streams where salmon spawn are highly variable.

"The big surprise we often see is that the population of fish that we see at any given location is anything but stable. Some years you'll see a couple hundred fish in a stream like this, and some years you'll come back and there will be 5,000 fish that have returned to spawn in this location," Schindler said. "And it's not as if those were fish that took a wrong turn. Those are fish that we know were born in this little stream."

Schindler says although individual streams and rivers go through boom years and bust years, the overall system is stable because not all the booms and not all the busts line up.

"That's one of the mysteries that we'd like to figure out, is why certain streams do well and other streams do well in other years," Schindler said.

Small streams aren't just important to the overall health of the fish stock. They're also important for wildlife.

"This is the first opportunity to get salmon when they come back to the watershed during the summer. Bears are very effective at killing fish in a stream like this and they can eat this while they're still relatively fresh," Schindler said. "Things like bears and eagles actively exploit this diversity on the landscape. They're start feeding on places like this in July and by September they'll be feeding on the big rivers where those populations spawn."

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