did food limitation cause recent declines of esident killer whales (Orcinus orca) in British Columbia?
Two populations of fish-eating killer whales (Orcinus orca) in British Columbia, known as residents, are listed under the Canadian Species-at-Risk Act due to their small population size and recent unexplained declines in abundance. Threats considered to potentially affect survival and recovery of these populations include environmental pollutants, physical and acoustic disturbance, and reductions in the availability or quality of salmonids, their primary prey. Recent studies have shown that chinook salmon and, to a lesser degree, chum salmon, are important prey for resident killer whales, but other smaller salmonid species are not. In this report, we assess whether food limitation was potentially a significant factor in recent declines of these whale populations. We examined the relationship between trends in killer whale population dynamics based on long-term photo-identification data, and abundance levels of chinook and chum salmon off the British Columbia coast over the past 25 year
