Nearly all the herring roe now used to make the Japanese new-year delicacy kazunoko comes from North America's west coast. The ocean-living herring go there in huge numbers to spawn in March, and are met by ranks of predators, including cormorants, terns and gulls, bald eagles, ospreys, dogfish sharks, salmon, seals, sea lions and, not least, fishermen.

As herring-roe prices tend to be extremely high, competition among fishermen can become fierce. However, there is not only competition between one boat crew and another, but also between fishermen and predators — especially sea lions.

In March 1995, Canadian newspapers carried screaming headlines: "Slaughter at Sea!"; "Slaughter on the Beaches!"; "Good Riddance to Fishermen!" These outpourings were a reaction to the discovery of a number of enormous sea lion carcasses along the beaches of Denman Island, which lies adjacent to the herring spawning and fishing grounds. Witnesses reported many sightings of herring fishermen gunning down the huge marine mammals with high-powered hunting rifles.