When salmon are plentiful in coastal streams, bears won't eat as much of an individual fish, preferring the nutrient-rich brains and eggs and casting aside the remainder to feed other animals and fertilize the land. In contrast, when salmon are scarce, bears eat more of a fish. Less discarded salmon enters the surrounding ecosystem to enrich downstream life, and a richer stream life means a better environment for salmon.
In four out of the six study systems, allowing more salmon to spawn will not only help bears and the terrestrial landscape but would also lead to more salmon in the ocean. More salmon in the ocean means larger harvests, which in turn benefits fishers. However, in two of the systems, helping bears would hurt fisheries. In these cases, the researchers estimated the potential financial costthey looked at two salmon runs on the Fraser River, B.C., and predicted an economic cost of about $500,000 to $700,000 annually. This cost to the human economy could help support locally threatened grizzly bear populations, they argue.
While these fisheries are certified as sustainable by the Marine Stewardship Council (MSC), the researchers suggest that the MSC principle that fisheries have minimal ecosystem impact might not be satisfied if the fishery is contributing to grizzly bear conservation problems.
The researchers believe the same analysis can be used to evaluate fisheries around the world and help managers make more informed decisions to balance economic and ecological outcomes.
|Contact: Bryan Ghosh|
Public Library of Science