We are please to announce a new publication examining the potential conflict
that may be emerging in the northeastern Pacific for southern resident killer
whales (Orcinus orca) and their primary prey, Chinook salmon (Oncorhynchus
tshawytscha).
Williams, R., M. Krkošek, E. Ashe, T.A. Branch, S. Clark, P.S. Hammond, E.
Hoyt, D.P. Noren, D. Rosen and A. Winship. 2011. Competing Conservation
Objectives for Predators and Prey: Estimating Killer Whale Prey Requirements
for Chinook Salmon. PloS one 6: e26738.
The publication is available on-line at:
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0026738
ABSTRACT:
Ecosystem-based management (EBM) of marine resources attempts to conserve
interacting species. In contrast to single-species fisheries management, EBM
aims to identify and resolve conflicting objectives for different species. Such
a conflict may be emerging in the northeastern Pacific for southern resident
killer whales (Orcinus orca) and their primary prey, Chinook salmon
(Oncorhynchus tshawytscha). Both species have at-risk conservation status and
transboundary (Canada–US) ranges. We modeled individual killer whale prey
requirements from feeding and growth records of captive killer whales and
morphometric data from historic live-capture fishery and whaling records
worldwide. The models, combined with caloric value of salmon, and demographic
and diet data for wild killer whales, allow us to predict salmon quantities
needed to maintain and recover this killer whale population, which numbered 87
individuals in 2009. Our analyses provide new information on cost of lactation
and new parameter estimates for other killer whale populations globally. Prey
requirements of southern resident killer whales are difficult to reconcile with
fisheries and conservation objectives for Chinook salmon, because the number of
fish required is large relative to annual returns and fishery catches. For
instance, a U.S. recovery goal (2.3% annual population growth of killer whales
over 28 years) implies a 75% increase in energetic requirements. Reducing
salmon fisheries may serve as a temporary mitigation measure to allow time for
management actions to improve salmon productivity to take effect. As
ecosystem-based fishery management becomes more prevalent, trade-offs between
conservation objectives for predators and prey will become increasingly
necessary. Our approach offers scenarios to compare relative influence of
various sources of uncertainty on the resulting consumption estimates to
prioritise future research efforts, and a general approach for assessing the
extent of conflict between conservation objectives for threatened or protected
wildlife where the interaction between affected species can be quantified.
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