Are the Orcas Finding Enough Salmon in Winter? By Richard Osborne, Ph.D., and Tracie Hornung, The Whale Museum The Southern Resident Community of orcas has a strong preference for salmon as its main food resource. Although findings on the diet of resident orcas in Washington and British Columbia show that they eat a large variety of fish and marine mammals as occasional prey, up to 90% of their diet is likely salmon. Each of the Southern Residents needs to eat an average of 25 salmon every day, all year round. For the current population of approximately 80 orcas, that's about 62,000 salmon a month, or 750,000 per year. During the summer when the inland waters are full of returning adult salmon, the needs of the orcas can easily be met. The big question among orca biologists is whether the whales are finding enough salmon in winter. J Pod used to be the only pod of the three that remained feeding in the inland waters during winter. But since 1999 K and L pods have stayed in the inland waters through December, and during 2001-2002 they stayed until February, adding even more pressure on the local winter salmon stocks. Washington state fisheries data show that almost all species of salmon are abundant in the summertime when the whole Southern Resident Community is feeding here almost every day. During winter, salmon resources drop significantly, except for chinook and coho. (Many chinook salmon, and some coho, remain in the coastal and inland waters to mature instead of going out to sea as other salmon do.) However, among the salmon stocks that are now extinct are some traditional winter runs of chinook and coho. The wild runs of chinook and coho that remain in Puget Sound have recently been listed under the Endangered Species Act. Reduction of the traditional salmon resources favored by the resident orcas may affect their nutrition in winter, making them more vulnerable to toxic chemicals stored in their bodies and causing them to change their traditional patterns of movement to search for food. Complicating things further, recent scientific studies show that approximately 70% of the salmon in Puget Sound are actually hatchery-raised fish that will potentially compete with endangered stocks. Also, hatcheries have been practicing late-release of the chinook and coho they have raised, in the hope that those stocks will stay in inland waters and be more available to local anglers. These late-release salmon that stay in coastal waters are also supporting our local orcas. Ironically, hatchery fish may now be the most important winter food resource for the Southern Resident orcas, and if hatchery fish are phased out to protect wild stocks, a severe impact on the whales' food may result. Yet, the range of potential prey for orcas as a species is vast, making it hard to conceive of a situation where free-roving orcas would starve to death-even the Southern Resident Community with their apparent "addiction" to salmon. Nevertheless, under present conditions of regional salmon habitat loss and over-fishing, an addiction to salmon is a habit the orcas are probably finding harder to sustain. If salmon depletion is stressing the orca population or requiring them to shift to different prey, we should continue to see a change in their seasonal movements. We need to continue focusing our efforts on the protection of salmon and their habitats. Perhaps more than any other species in the Salish Sea, salmon are a barometer of the health of the ecosystem. If we can save the salmon, then all wildlife will benefit, especially the resident orcas. For more info visit http://www.whalemuseum.org/