Then, after a few years in the ocean environment, using cues we still poorly understand, the adult salmon find (with remarkable fidelity) their native stream and return to the freshwater environment where they were born. Here the adults release their eggs and sperm and, shortly after spawning, die. As such, their freshwater nursery environment is both their cradle and grave. Of course, many salmon do not make it back to their native stream or lake but are intercepted by human fishers as well as a host of other animals, foremost among them being black and grizzly bears.
There are various estimates, but in some areas over 50 per cent of the diet of female grizzly bears comes from returning salmon. But this is only part of the story – the bears often do not eat the entire salmon and leave part of the carcasses on land, providing food for eagles and a host of other animals. Moreover, the bears and other animals then defecate this marine-derived food (i.e. the salmon) in the woods and thereby fertilize the forests, to the point that about 25 per cent of the nitrogen in some plants is derived from this salmon-bear linkage. Now, if the salmon are gone (as they are or are disappearing throughout much of the west coast) so does much of the “neighbourhood”. Just like the seabirds are playing a critical role in fertilizing some land areas, the salmon are providing marine-derived nutrients to terrestrial ecosystems. Connections are everywhere.