Leave the Sea Lion Out of This, Pal

March 25, 2008 – 6:07 pm

Filed under: Uncategorized — Tags: Bonneville, dam, Oregon, salmon, sea lion — admin @ 6:07 pm

The declines in West Coast salmon populations have made international headlines over the past month, but one proposed solution to the problem is, to put it bluntly, ridiculous. The National Marine Fisheries Service, a federal agency under the US Department of Commerce, is arguing that sea lions living near Oregon’s Bonneville Dam are unfairly eating up salmon that would otherwise swim up the Columbia River to lay their eggs. Following this logic, the agency is getting ready to capture and possibly kill off at least 60 California sea lions for the crime of being too hungry.
The idea that getting rid of 60 sea lions is somehow going to resuscitate the natural habitat of salmon in the Columbia River represents the same anthropocentric thinking that caused salmon populations to plummet to below 10 percent of their historic numbers on the Columbia in the first place.
Let’s step back and take a look at what’s really going on at the Bonneville Dam near Portland, Ore. The feds are arguing that fish ladders installed at the dam are becoming less effective in transporting salmon back to natural spawning grounds because they provide an easy perch for “aggressive” sea lions hunting the migrating salmon. Federal wildlife managers have used rubber bullets, firecrackers and many other non-lethal methods in an attempt to scare away these pesky critters, but all to no avail. So now the feds are taking a page out of Buffalo Bill’s playbook and have declared war on the sea lions for carrying out their natural role in the ecosystem.
But are the sea lions really the biggest threat to salmon at Bonneville Dam? A quick glance at the data suggests a big NO. A 1998 study by Kenyon College’s Environmental Studies Department concludes that dam construction has much more to do with reducing the numbers of naturally spawning salmon in the Columbia River than any other factor. Prior to the beginning of Pacific Northwestern dam construction in 1938 salmon had 260,000 square miles of Columbia River water to swim up, providing plenty of room to dodge predators such as sea lions. Of course quite a few salmon would get caught in the claws of bears and sea lions, but meanwhile hundreds more would go swimming by unbothered. Today, these salmon are squeezed into narrow ladders that circumvent dams, which throughout the entire Columbia only provide about 73,000 square miles of room – a drop of over 60 percent from natural conditions. At Bonneville Dam specifically, each ladder is about 40 feet wide. So of course sea lions that once had to pluck an individual salmon from a run of hundreds leaping up a wide-open river, are now taking advantage of the fact that these salmon are moving up narrow ladders in a relatively orderly fashion (if they can make it up the ladders in the first place, which is another story). As the Kenyon study notes, “Terrestrial animals around the Bonneville Dam become aware of salmon location and routinely feast upon them.”
But that’s not all. The dams also have more subtle effects. Since salmon have adapted to lay their eggs in sandbars and other areas where their posterity will be protected, the destruction of these habitats can create huge declines in salmon populations, as dams destroy these age-old birthing locations. Dr. Franklin Ligon and his colleagues published a study in the BioScience Journal in 1995 that concluded by tweaking the flow of a river, dams often eliminate these sandbars. One can imagine confused salmon looking fruitlessly for the places they’ve been genetically programmed to lay their eggs.
The record of Columbia River salmon catches backs up this analysis. According to data provided by Oregon State University, when the Bonneville Dam was constructed in 1938 the catch of spring run Chinook went from just under 100,000 fish a year to just over 20,000 a year by 1940.
The Northwestern Power and Conservation Council provides similar data. In the 1890s fishermen routinely caught up to 40 million pounds of salmon. By 1993 fishermen were only bringing in one million pounds. The Council also reports that many of the salmon making up the latter figure were raised in hatcheries—artificial “fish farms” that don’t rely on natural salmon spawning habitats.
The factors affecting salmon are many, and natural variations in rainfall and temperature can often have just as big an effect on one year’s population as human activities, such as fishing. And yes, even sea lion predation is a factor that can cause salmon populations to ebb and flow with the passing of time. Yet over the long term, the data seems to support the assertion that dam construction is a major cause for permanent population declines. The sea lions are no doubt killing off many, many salmon, but that’s what they’ve been doing for millennia. If we truly want to solve the salmon population declines, we must take a hard look at the human impact on these fragile rivers.