https://redlib.catsarch.com/r/stupidpol/comments/1ssxoou/rep_perez_dwa_these_big_boys_sea_lions_are/

Hey I’m a fish biologist. Almost all of the entire west coasts fisheries issues are actually due to over allocation of water to the agricultural industry. This has modified a lot of the habitat and made it easier for predators to hunt and harder for salmon to live. A lot of the narratives such as this one are created by the agricultural industry itself to keep any sort of scrutiny of them out of public discourse. The sea lions do actually sit at the dam on the Columbia river and eat a shit load of Salmon but not in a way that is more meaningful from poor water management.

Specifically on the Columbia river, there are a series of dams that Salmon have to migrate through and survival analysis has shown that survival decreases dependent on each dam that the salmon have to traverse. Over allocation of water leads to poor flows and increased temperature which makes the water oxygen poor. This combined with poor ocean conditions have been the major contributing factors to population declines.

The sea lions are mostly a red herring. There is evidence their predation has an impact but their ability to be predators is heavily influenced man made bottle necks in habitat (right below Bonneville dam for example) and an unwillingness to take the difficult measures to actually increase the salmon populations.