Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8343
Title: Long distance migration of prey synchronizes demographic rates of top oceanic predators
Author: E. J. Ward, M. E. Dahlheim, J. Waite, Candice K. Emmons, Kristin N. Marshall, Brandon Chasco, K. C. Balcomb III
Publication Year: 2016
Journal: Ecosphere
Keywords: killer whale,salmon,Chinook,Alaska,SRKW,

 1. Reproductively and geographically isolated predator populations may be synchronized by common responses to external processes, such as climate, density dependence (parasites, disease), or prey. Prey species with greater migrations than the predator populations that eat them also may synchronize isolated populations of predators.

2. The objective of our study was to investigate evidence for correlations of demographic rates between geographically isolated populations of piscivorous killer whales in the Northeast Pacific.

3. Using long-term mark-recapture datasets collected over the last 30+ years, we constructed a hierarchical occupancy model, linking models of survival and fecundity in a single framework. We allowed demographic rates to vary over time and potentially be correlated both within and between populations.

4. We found strong support for differences in demographic rates between Southeast Alaskan and Southern Resident killer whales, which are geographically and reproductively isolated. We found that though these populations are isolated, they experience extremely correlated dynamics – the correlation in fecundity rates between populations exceeds 0.9.

5. The correlation in demographic rates across populations of killer whales in the Northeast Pacific that don’t overlap spatially suggests they are synchronized by a common driver. The long distance coastal migration patterns of prey (in particular Chinook salmon) is even greater than the migration patterns of killer whales. Thus, isolated killer whales be synchronized by consuming prey from the same populations of origin, just at slightly different times. 

Theme: Ecosystem approach to improve management of marine resources
Foci: Characterize ecological interactions (e.g. predation, competition, parasitism, disease, etc.) within and among species.
Assess ecosystem status and trends.