Pinks vs. sockeyes at sea
November 10, 2015
This is Fish Radio. I’m Laine Welch – Are swarms of North Pacific pinks causing sockeye salmon declines? First of a two parter after this –
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Growing numbers of pink salmon are out competing sockeyes for food in the ocean, causing the reds to grow slower and smaller. That’s the claim of a new study by Seattle and British Columbia researchers, who say the race for food ultimately affects sockeye abundance and survival.
“The important part of the study is there are multiple lines of study to support that. Our data sets extend up to 55 years each. In terms of looking at productivity or survival of salmon, they’ve included 36 sockeye populations.”
Greg Ruggerone is a senior scientist at Natural Resources Consultants in Seattle and study co-author. He says it was aimed originally at finding causes for declining sockeye runs at British Columbia’s Fraser River in 2009.
“For Fraser populations, we looked at declining growth at sea in relation to pinks over a 55 year time period and age at maturation. All three factors are consistent in pointing to competition with pink salmon for food in the ocean. We know they share a common diet in the ocean.”
Ruggerone also has published similar food competition studies for Bristol Bay. He calls the odd/even pattern of pink salmon abundance a natural experimental control that links sockeye growth and age to the alternating pink cycle. So how does he account for back to back big runs to the Bay?
“For Bristol Bay sockeye, we think that early marine life, before they encounter large numbers of pinks, because there are relatively few pinks in western Alaska compared to Russia, so they most likely encountered favorable conditions that support these large runs. But that doesn’t mean the pinks don’t have an adverse effect on them during the second or third year at sea. It’s just overshadowed by very favorable conditions during early marine life.”
The report recommends an ocean-wide, Pacific Rim approach to managing limited salmon resources, and more immediately, capping hatchery production which affects fish thousands of miles away.
“Hatcheries in Alaska and Russia have continued to increase production of salmon, primarily chums and pinks. There are more hatchery pinks and chums than any of the other species. Up to about 5 billion hatchery salmon are released into the Pacific Ocean each year.”
Hatchery operators at Southeast Alaska and Kodiak respond tomorrow.
Fish Radio is also brought to you by Ocean Beauty Seafoods. Ocean Beauty has contributed over 10 million meals to the U.S. Food Bank network, and is committed to ending hunger in America. www.oceanbeauty.com In Kodiak, I’m Laine Welch.