Charles Darwin studied the relationships among species and speculated on how acclimatisation could affect them. His view of acclimatisation is clearly illustrated in the Pacific Northwest where Atlantic Salmon have been introduced. Atlantic Salmon farms are in direct competition with wild Sockeye Salmon stocks, and they are introducing disease and parasites into the salmon migration routes. Due to their extensive range and the ability of salmon to acclimatise between fresh and saltwater, peripheral species are affected by low spawning numbers. The American Black Bear is particularly dependent on the Sockeye. In The Three Bears, only a trace of the bears remain.