The Fish and the Bear
Only the foolhardy would snatch a meal from the jaws of a hungry, 1,200-pound (540-kilogram) 10-foot-tall (3-meter-tall), snarling, brown bear (Ursus arctos). But in a roundabout way that is exactly what many people do. How? It can be explained by the case of the salmon and the bear.
Every year millions upon millions of salmon swim up the rivers of the Kamchatka Peninsula in the Russian far east to spawn and then, well, die. With its nearly 2,000 rivers offering over 26,000 miles (42,000 kilometers) of water, Kamchatka attracts the world's greatest concentration and diversity of salmon, a quarter of the entire Pacific population. Mother Nature being what she is, this mass congregation of fins and gills could not go unexploited. The salmon sustain dozens of marine and terrestrial mammals including sea otters, giant Steller's sea eagles, brown bears, and humans. In addition, when the salmon die and decay, marine-derived nutrients are transferred to the terrestrial ecosystem via riparian invertebrates and vegetation. The salmon are a keystone species to this ecosystem.
Kamchatka's harsh climate allows a very short growing season. When hibernating bears wake up for the summer, they have two objectives: eat and mate, fast! They want to pile on the pounds to build reserves to survive the winter. Eating salmon offers about ten times more calories than eating berries. Scientists have observed some adult males eating a salmon every 20 minutes. It is no surprise that the largest brown bears in the world are also found where their primary food is salmon.
Female reproductive success is directly related to the number of calories she eats. However, some females will choose not to feed on salmon. Why? Bears will only tolerate another bear fishing nearby if the density of salmon in the river is high. More salmon, more bears. Fewer salmon, more fights between bears. Thus a female will choose to stay away from salmon and eat berries, sacrificing calories for safety.
The bears' heavy dependence on salmon links their fate to that of the fish. And there are many threats to the salmon of Kamchatka. Its waters account for more than 60 percent of the fisheries resources of Russia, with more than two million tons of fish legally landed annually, and about the same amount again fished illegally. In addition, every year a massive number of salmon are killed by poachers for their caviar. At what point will the harvest of salmon start to impact the bears that depend upon them? In this unique aquatic-terrestrial dependency, Kamchatka's bears could be fished out of existence.
—David A. O'Connor