Interspecific problem of non-native Oregon fish spells

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According to a recent study By scientists at OSU, ODFW, and the US Forest Service’s Pacific Northwest research station in Corvallis, the biggest consumers of endangered salmon in Oregon are non-native warmwater fish species.

The study found that non-native warm-water fish species like walleye, bass and crappie consume more baby salmon than native fish per individual.

These findings will hopefully help Oregon’s fisheries managers identify the best ways to organize and plan, said Christina Murphy, lead author of the study and postdoctoral researcher at OSU.

“We provide the science to help managers identify the trade-offs to make the best management decisions for each individual location,” said Murphy.

In part as a result of this research, management action is being taken to remove fishing restrictions on non-native warmwater fish species that are prized by many anglers. In particular, these restrictions are removed in areas where non-native fish overlap with sensitive native species, such as salmon.

The study also found that the dams in the Willamette River and other areas formed a largely unnatural overlap between native and non-native fish species in the reservoirs. This has resulted in non-native species having a significant predatory impact on salmon populations, including spring chinook.

Additionally, according to a lawsuit filed against the US Army Corps of Engineers earlier this year, these dams have also blocked spawning grounds for threatened chinook salmon and rainbow trout, contributing to the rapid decline in populations. Federal Judge Marco Hernandez ruled in favor of the three environmental organizations that sued the Corps, claiming it had failed for years to maintain adequate passage for these species in the dams it operates along the Willamette Basin – and ordering them to make immediate changes. Interestingly, in a separate OSU study, genetic analyzes have revealed that hatchery-born coho salmon can also negatively impact wild coho salmon and their ability to reproduce.

By combining isotope analysis and examining the stomach contents of non-native fish, the researchers were able to shed light on one of the biggest questions in the Oregon fishing world: who eats all the salmon?

While we know that sea ​​lions have a big impact on adult salmon populations, it was not known exactly what the adolescent salmon and baby salmon ate. The guilty ? Walleye, with between 15.8 and 18.5% of all walleye examined having salmon in the stomach.

Largemouth bass, white crappie and native pike had trace amounts of salmon detected in their stomachs, with black crappie, cutthroat trout, rainbow trout and yellow bullhead having no salmon. present in their stomachs during the study.

A co-author of the article, Ivan Arismendi, assistant professor in the Department of Fisheries, Wildlife and Conservation Sciences at OSU, had more to add.

“Our results support this integrated management strategy, highlighting that the capture of popular non-native warmwater species such as walleye can be encouraged in areas that overlap with salmon conservation priorities,” said Arismendi.


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