WiLD Blog

Anadromous fish are those whose habitat includes both the ocean and rivers.  Of these, salmon is perhaps the best known. In the Sacramento River, Chinook salmon are suffering from both excessive river diversions and global warming. The fall 2007 run was just 10% of the high reached a few years ago, and the coming May run is likely to be so low that the $150 million fishery will be canceled by the authorities. While the cause of the decline is not known with certainty, scientists point to two likely causes. 

One of the probable causes is a lack of food in 2005 and 2006 due to unusually warm ocean conditions. Global warming has disrupted the timing of the upwells and cold currents that provide the fish with prey such as rockfish and krill. Climate models now “predict unpredictability” instead of the alternation of cold and warm years that has prevailed until recently. Consequently, food may come to the salmon’s oceanic range too late, too early, or not at all, and the fish can only travel so far to find it. As Elizabeth Kolbert describes in Field Notes From a Catastrophe: Man, Nature and Climate Change (Bloomsbury, 2006), all species that are around today have already survived catastrophic climate change, namely, the most recent glaciation, often by migrating to a location with a more suitable climate. However, habitat destruction has restricted some species’ mobility, hindering their ability to adapt. A 2004 study attempted to estimate the number of extinctions that global warming would cause. Looking at eleven hundred species of animals and plants from sample regions, and using a moderate projection of temperature rise, the authors concluded that, assuming the species were “highly mobile”, 15 percent would be “committed to extinction” by mid-century.

The other probable cause of the poor Chinook run is the functional equivalent of habitat loss– excessive diversion of water from the river to agricultural and residential users.  In 2005, for example, 55% of the flow was diverted before reaching San Francisco Bay. A network of nonprofits has threatened to sue the state if diversions are not reduced. Given that water use in California is a complex issue, what can be done on the grassroots level to improve the health of rivers such as the Sacramento? By using less water, people can reduce the amount of water that needs to be diverted.

In Washington and Oregon officials have obtained permission from a federal agency to kill up to 85 sea lions- a dubious amendment in the Marine Mammals Protection Act allows this - in order to protect endangered salmon and steelhead, the ocean-going variety of the rainbow trout. The sea lions have cleverly found their way into areas around the Bonneville Dam designed so that the beleaguered fishes can pass unimpeded around the dam, thus making an easy meal of the them. The Humane Society of the US argues, and we agree, that the sea lions have become a scapegoat for deeper problems, such as pollution and overfishing, that are more difficult to tackle than knocking off a few dozen helpless animals. Another problem, the damming of wild rivers, is more controversial, as dams provide many benefits, including cheap and clean power. However, more environmentally friendly energy sources exist. The dam is what provides the sea lions easy access to these endangered species in the first place. 

-Thomas Holder