Research continues on pinniped predation in Salish Sea

In the Salish Sea, the three most common pinnipeds are Steller sea lions, California sea lions and harbor seals.

The report, which was funded as part of Gov. Jay Inslee’s Southern Resident Orca Whale Task Force Report, found that the “preponderance of evidence” supports the idea that pinnipeds are “likely impeding the recovery of salmon populations in Washington waters.”

The Seattle Times first reported on the issue.

Due to protections under the Marine Mammal Protection Act, pinnipeds are protected from hunting, which has caused populations to boom in the past several decades.

Casey Clark, a state Fish and Wildlife biologist who is researching pinniped predation, said that in the Salish Sea it is known that the population of harbor seals has mostly leveled off.

Pinnipeds’ impact on salmon could also lessen available fish for Southern Resident orcas, which have chinook salmon as a large part of their diet.

The report also states that any attempt at the lethal removal of pinnipeds to help salmon recovery would be a substantial management experiment.

Clark said such an experiment would need to remove enough animals to know that there would be a “measurable effect” on salmon and would have to take place over a long period time, making it a challenging prospect.

In addition, the Marine Mammal Protection Act in its current form would not allow for a large-scale lethal removal.

Clark called the problem “an age-old question of how humans coexist with other predators in the landscape or the seascape.”

Clark works with the Stillaguamish Tribe of Indians to assess pinniped predation on salmon, including studying feces and conducting genetic analysis.

He said preliminary observations are that the impact of harbor seals, the main pinniped on the Stillaguamish River, on chinook salmon is pretty low.

Clark said more research is needed to understand how big a problem pinnipeds are for salmon populations compared to issues such as fish passage and toxic contaminants.

The goal of the group that Clark works with is to identify specific locations where predation is a serious problem and has a big impact on salmon runs.

The group is also trying to understand to what extent predation on salmon comes from specific seals that have a taste for salmon, or whether predation is from a wide range of animals.

“If you think about whether it’s all of the individuals a little bit of the time versus a few of the individuals a lot of the time, that has really big potential management implications into the future for trying to deter those animals,” Clark said.