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Saving Salmon From Becoming Sea Lion Share: Early Conservation Effort Is Key!

Dec 20, 2016 09:53 AM EST
Sea lion predation on salmon poses a serious wildlife challenge
NOAA Fisheries authorized Oregon, Washington and Idaho wildlife authorities to begin trapping and removing sea lions shown to repeatedly prey on salmon at the dam. The removal program was designed to reduce impacts on protected salmon. (Photo by Justin Sullivan/Getty Images)

California sea lions have begun to feed on Columbia River salmon at Bonneville Dam and scientists have discovered a model to explain this new behavior since this is a major wildlife challenge since the Marine Mammal Protection Act protects the sea lions while the Endangered Species Act protects the salmon they are eating.

Since 2008, NOAA Fisheries have authorized Oregon, Washington, and Idaho wildlife authorities to remove sea lions that preyed on salmon at the dam in hopes of protecting the salmon. Implementation of the policy is expected to continue for the next five years and but the effectiveness of the removal program is currently being reviewed.

By employing epidemiological models to evaluate how the behavior of eating salmon at the dam spread among the sea lions, researchers concluded that the removal program has effectively slowed the transmission of the behavior among sea lions. They also noted that the program would have been more effective had it been implemented earlier.

In their study published in the journal Proceedings of the Royal Society B, Biological Sciences, the researchers emphasized that there was a definite need to act early "from both a conservation and management perspective to prevent the spread of a detrimental behavior and to minimize the total number of animals removed."

"The earlier you start, the more effective you are at slowing the spread, and the fewer animals you have to remove to make a difference," said Zachary Schakner, one of the authors of the study and the Recreational Fisheries Coordinator in NOAA Fisheries' West Coast Region.

Since the program's implementation in 2008, the states had removed 166 California sea lions. Raising protests among animal rights groups was the stipulation that the states were allowed to euthanize sea lions if no permanent holding facility, be it a zoo or aquarium, could be found.

"What was really new was the combination of behavioral ecology with disease ecology to come up with management recommendations that could make the program more effective," said Michael Buhnerkempe, another author of the research and an assistant project scientist at Lloyd-Smith Laboratory at UCLA. It was vital for the researchers to highlight strategies for reducing the number of sea lions to determine which were most effective and which required the removal of the fewest sea lions.

In the same way diseases are easiest to stamp out when they have only affected a few individuals, undesirable wildlife behaviors such as the predation on salmon at Bonneville Dam needed to be addressed at the soonest possible opportunity. "If you can do that, you're beating it before it has a chance to explode into more of an epidemic," Buhnerkempe said. "Otherwise it quickly gets out of control."

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