The evolutionary links between grizzlies and salmon


The evolutionary links between grizzlies and salmon

10 November 2019
The stark images of malnourished grizzly bears on the coast of British Columbia have garnered widespread media attention.

The photographs are difficult to view and strike a chord of deep concern in most people.

Raincoast Conservation Foundation has long advocated for a wildlife welfare ethic when it comes to the conservation and management of large carnivores. This approach becomes even more compelling when the life requisites, in this case wild salmon, of species such as coastal grizzlies are diminished as a result of human activities.

Much of the news coverage associated with the aforementioned situation has been linked to climate change, but this particular salmon-run collapse is likely the result of a suite of influences, not the least of which is the failure to protect wild salmon in B.C. from fishing pressure, habitat degradation, hatchery impacts, fish farms and more.

Wild salmon and grizzly bears have an intertwined relationship, and the choices we make are inextricably linked to their fates. When salmon are plentiful in coastal streams, bears thrive and produce more cubs. Grizzlies also occur at higher densities and grow to larger sizes when salmon are abundant.

Importantly, when salmon are plentiful, bears eat less of each fish, selecting the nutrient-rich brains and eggs and casting aside the remainder. These salmon remains then feed other animals, scavengers, and fertilize the adjacent streamside zone. Thus, abundant salmon boosts the amount and value of food for bears, as well as transfers more nutrients and energy to other wild consumers.

In contrast, when salmon are scarce, grizzlies produce fewer cubs, if any, and eat more of each individual fish. Less discarded salmon enters the surrounding ecosystem with diminished benefits for other wildlife, plants and less-visible organisms such as fungi, algae and insects. Commercial salmon fisheries typically extract 50 per cent or more of the salmon bound for rivers, bears and forests.