Relative importance of chinook salmon abundance on resident killer whale population growth and viability

Abstract

Two distinct populations of resident killer whales (Orcinus orca) in the north‐eastern Pacific Ocean have been listed in Canada and the USA as being of conservation concern. One of the major threats recognized for these two populations is nutritional stress associated with prey abundance levels and availability. The predominance of chinook salmon (Oncorhynchus tshawytscha) in the summer diets of both killer whale populations has been shown by recent studies, and correlations between indices of chinook salmon abundance and resident killer whale (RKW) vital rates have generated hypotheses about the potential for chinook salmon abundance to limit RKW population dynamics. This study merges statistical inference derived from linkages between RKW vital rates (survival probability and fecundity rates) and chinook salmon abundance with demographic perturbation analysis and population viability analysis to address some of the pressing questions that have recently engaged the efforts of scientists and managers interested in: (1) the role of chinook salmon abundance in the population dynamics of RKW; and (2) how RKW population viability is expected to respond to changes in chinook mortality owing to harvest. Numerous interactions between the abundance of chinook salmon aggregates and RKW vital rates were found and deemed to result from predator–prey dynamics. However, the results of this present analysis also indicated that the effects of these interactions on RKW population growth and viability are relatively small and/or uncertain and in need of further research. Other factors (genetic, environmental and/or anthropogenic) could be at play limiting RKW population growth and possibly masking and confounding the detection of stronger interactions between RKW vital rates and chinook salmon abundance. Given the current state of information, it is highly uncertain whether the allocation of chinook salmon resources for RKW would be an effective management action in RKW recovery plans. © 2014 Her Majesty the Queen in Right of Canada Ecohydrology © 2014 John Wiley & Sons, Ltd.

Approaches to reduce noise from ships operating in important killer whale habitats

“…Periods of low Chinook abundance over the past several decades have been linked with reduced birth rates and lower survival of resident killer whales (Ward et al 2009;Ford et al 2010;Vélez-Espino et al 2014). Both short term disturbance and chronic ocean noise from shipping and small boat traffic have been shown to disrupt foraging behaviour (Williams et al 2006) and may mask both the social calls that killer whales use to coordinate group movements (Williams et al 2013) and the echolocation clicks used to hunt salmon (Holt 2008).…”

Optimizing an eDNA protocol for monitoring endangered Chinook Salmon in the San Francisco Estuary: balancing sensitivity, cost and time

“…We targeted Chinook Salmon in our experiments for a variety of reasons. First, as a widespread species in the North American Pacific Northwest, it has invaluable importance for the stability of the marine ecosystem of the region [10] and at the same time, provides a critical source of income for historic fishing communities [11,12]. In California, the Central Valley Spring-run, Fall-run and Winter-run Chinook salmon are listed as vulnerable while the Sacramento River winter-run and Central Valley late Fall-run are listed as endangered [13].…”

Conservation Risk and Uncertainty in Recovery Prospects for a Collapsed and Culturally Important Salmon Population in a Mixed‐Stock Fishery

“…Pacific salmon are central to the ecosystems, economies, and cultures of the Northeast Pacific. Returning adult salmon transport marine-derived nutrients to coastal marine food webs (Vélez-Espino et al 2015) and terrestrial flora and fauna (Reimchen 2000;Hocking and Reynolds 2011). In coastal communities, salmon support commercial and recreational fisheries, and their abundance indirectly supports tourism and recreation.…”