Gulf of Alaska | Mammals
Declines in survival and fecundity of fish-eating killer whales indicate abrupt and prolonged impacts of a marine heatwave in the Gulf of Alaska Presenter: John Durban , john.durban@oregonstate.edu, Oregon State University Since the 1980s we have used photo-identification to document long-term increases in the abundance of fish-eating Resident killer whale ( Orcinus orca ) pods in the Gulf of Alaska, although AB pod has not yet recovered following exposure to the Exxon Valdez oil spill. In recent years the occurrence of Residents has declined in our coastal study areas in Prince William Sound and the Kenai Fjords, apparently responding to an intense marine heatwave in 2014-2016. To assess the impacts of the heatwave at the population level, we fit a Bayesian latent state mark-recapture model to individual photo-identification records to estimate annual departures from the survival rates expected based on age and sex composition for 2009-2021, spanning five years on each side of the heatwave. We also modelled departures in fecundity from the expectation given female ages, and investigated covariance in survival and fecundity in the same hierarchical Bayesian model. Three of eight pods showed significant declines in survival concurrently at the end of the heatwave, including the most abundant AJ pod and the strategically important AB pod. Furthermore, 6/8 pods showed reductions in fecundity that persisted for as many as five years due to disruption to the whales’ slow reproductive schedules. These data demonstrate that the impacts of environmental variation can permeate to the top of the food chain in the Gulf of Alaska, and have both abrupt and prolonged effects on these long-lived top predators. Notably, the impact of the marine heatwave on the abundance of AB pod was similar in magnitude to the decline following exposure to the Exxon Valdez oil spill. As such, these results increase our understanding of how environmental variation has and will affect recovery potential.
Alaska Marine Science Symposium 2023 240
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