Why can large numbers of sea otters compete with shellfish fisheries?

Large numbers of sea otters can compete with shellfish fisheries because they are voracious predators that rely on these same marine resources for their diet. Sea otters feed primarily on sea urchins, crabs, clams, and abalones.12

When sea otter populations are high, their intense predation can significantly deplete the populations of these shellfish. Because commercial fisheries also target these same species for harvest, the otters' natural foraging behavior creates direct competition for the available supply. While this predation is ecologically vital—as it prevents urchins from overgrazing kelp forests and helps maintain eelgrass meadows—it inevitably reduces the density of shellfish stocks that humans seek to exploit.123