Conservation Challenges: Salmon, Pinnipeds, and the Impact of Human Activities

By Christopher Moon, Oceanography ‘25

Image Credit: Marine Mammal Center

Image Credit: LE Baskow

Hunters and fishermen widely hunted seals and sea lions from the 1800s to the early 1900s for the fur trade. After the Marine Mammal Protection Act of 1972, all killing of marine mammals was banned, except with a permit from the National Oceanic and Atmospheric Administration (NOAA). However, pinnipeds (e.g. seals and sea lions) are still common victims of certain fishing practices that entangle them and can eventually kill them. California sea lion numbers increased exponentially since 1972, reaching a peak of around 300,000 in 2012. Since 2012 however, populations have declined slightly.

In 2008, NOAA authorized Washington and Oregon to legally cull California sea lions and Steller sea lions at the base of the Bonneville Dam, where they have been congregating in increasing numbers since 2001. This was adjusted in 2018 in response to greater predation. Even as pinnipeds show up more at the bases of dams to eat salmonids, their impact is less than perceived. Most pinnipeds have extremely diverse diets, and salmonids are not a large percentage of their diet. However, salmonids may highly contribute to the diet of certain individuals. A study done at the Bonneville Dam in 2022 using scat analysis and visual observation suggested that sea lions took a fairly insignificant proportion of the salmonid runs. Another study done in the Umpqua River indicated that harbor seals have varying foraging methods and diverse diets. Most of these diets do not include salmonids, and the majority of predation can be pointed towards a few individuals.

Although commercial and recreational salmon fisheries have a large impact upon salmon runs, other human impacts extend far beyond. Habitat loss due to dam blockage, development of riparian areas, and culverts significantly harm salmonid recovery, drastically outweighing the impacts of pinnipeds. Furthermore, dams create physical bottlenecks for the fish, making them perfect hunting grounds for seals and sea lions who can easily take advantage of the situation. The protection of pinnipeds under the Marine Mammal Protection Act and the protection of Steelhead and Chinook salmon under the Endangered Species Act creates a challenging legal landscape. Understanding and respecting this complex interplay of laws is crucial for finding a balanced solution.

Restoring habitats where salmon fry and parr can thrive and improving fish passage are essential for their recovery. Focusing on long-term solutions to salmon recovery, rather than short-term measures such as culling, is essential for achieving sustainable and effective outcomes. Addressing these major threats will demand substantial efforts and resources. Fortunately, significant funding has been allocated to dam removal in the Pacific Northwest, signaling positive progress. By focusing on these critical areas and enhancing habitat restoration, we can better support salmon recovery and foster a more balanced ecosystem for all species, including pinnipeds.