Saturday, September 23, 2006

Killing sea lions to save salmon?

Is it OK to kill marine mammals that are eating endangered salmon? Now that's a tough question.

How about when the seals are so cheeky that they're swimming into fish ladders at Bonneville dam? That's 140 miles upstream from the ocean.

Sea lions have invaded the big Bonneville dam fish ladders on the Columbia River between Oregon and Washington. They wait for fish dinners, right where the salmon have to swim to get upstream and spawn. Outraged fishermen are seeking permission from the US Govt to kill sea lions that they believe are taking away their fish. All manner of screens and loud noises and rubber bullets have not kept the sea lions away, so maybe it's time to bring on something stronger. Never mind that the real problem is the dam and fish ladders, we have a situation here.

Some biologists support killing predators in unusual situations where endangered fish are subject to especially harmful impacts. Is this one of those situations? Sea lions are estimated to take only a few % of the salmon. And...fishermen primarily want the salmon for themselves.

The plot thickens...there's a long tradition of fishermen killing seals and sea lions that are eating "their" fish. Some fishermen in New England want to propose seal kills, based on the idea that seals are harming cod and other species. There are the same cod that have been overfished by humans for at least the last 2 decades in a row, and probably much, much longer.

Certainly the sea lions aren't doing themselves any favors by waving out the window of the fish ladder at people who came to see salmon.


Tracy Rouleau said...

The very characteristics that make the sea lion so appealing to humans, their agility and intelligence, have also put them in conflict with fishermen time and time again.
I first began to study this problem in 1997 when it was a major issue on the California Coast, and NOAA first proposed exemptions to the MMPA for limited legal "takes" of sea lions interfering with commercial salmon fishermen. I wrote my Master's thesis on the conflict, using economics to examine the problem from the sea lions POV (NOAA was concurrently conducting a similar analysis from the fishermens/salmon perspective). I found that the value of the sea lion protection was likely to outweighed the economic benefits of the salmon they were eating (NOAA's analysis on the value lost due to sea lion predation was never completed to my knowledge).
And while there were limitations to my findings, they clearly showed that lethal removals of sea lions would not likely pass a cost benefit analysis.
However, due to destructive human practices such as overfishing, development of coastal streams and rivers, pollution, and dams on spawning streams, the precautionary principle may need to come into play, and for the protection of critical salmon runs (not for human profit or convenience) some lethal takes of pinnipeds may be warranted.

Anonymous said...

I have heard reports of prey capture for sea lions, seals, gulls, and terns, prior to '84, indicating that the primary prey species was Pacific lamprey. Lamprey decline has received very little attention as a limiting factor for salmonid recovery. Severe lamprey decline has greatly reduced marine-derived nutrient fertilization of coastal watersheds. Freshwater restoration effort pays very scant attention to habitat needs of lamprey. Since lamprey are not a commercial sp. they don't seem to rate the time of day with fisheries managers. How many more salmon would survive if the lamprey populations had not declined radically?