Changing Durations of Southern Resident Killer Whale Discrete Calls

The increase of mean durations of discrete calls demonstrated here indicates that the Southern Residents are making a behavioral adjustment as a result of vessel noise. Because they are adjusting their vocal behavior, we must consider the very real possibility that engine noise is hindering their ability to communicate, and may well impact their efficiency at using acoustics to forage and navigate, as well. The results presented here underscore the importance of future research concerning the impact of vessel noise on Southern Resident killer whales and should be considered in the development of new conservation and management plans.

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Fraser River Chinook Salmon Main SRKW Prey Species

Species and stock identification of prey consumed by endangered southern resident killer whales in their summer range

ABSTRACT: Recovery plans for endangered southern resident killer whales Orcinus orca have identified reduced prey availability as a risk to the population. In order to better assess this risk, we studied prey selection from 2004 to 2008 in 2 regions of the whales’ summer range: San Juan Islands, Washington and the western Strait of Juan de Fuca, British Columbia. Following the whales in a small boat, we collected fish scales and tissue remains from predation events, and feces, using a fine mesh net. Visual fish scale analysis and molecular genetic methods were used to identify the species consumed. Chinook salmon, a relatively rare species, was by far the most frequent prey item, confirming previous studies. For Chinook salmon prey, we used genetic identification methods to estimate the spawning region of origin. Of the Chinook salmon sampled, 80 to 90% were inferred to have originated from the Fraser River, and only 6 to 14% were inferred to have originated from Puget Sound area rivers. Within the Fraser River, the Upper Fraser, Middle Fraser, South Thompson River and Lower Fraser stocks were inferred to currently be sequentially important sources of Chinook salmon prey through the summer. This information will be of significant value in guiding management actions to recover the southern resident killer whale population.

*Email: brad.hanson@noaa.gov