Factors Influencing the Acoustic Behavior and Nearshore Residence of the Gray Whale (Eschrichtius Robustus) Along Their Migration Route
Abstract
Our long-term goal is to quantify the acoustic behavior of gray whales in the coastal waters of the Northeast Pacific Ocean and to characterize the link between coastal residency patterns of these migratory mammals and the distribution of hyperbenthic swarms of their primary prey (mysids). Several years of observations off the Oregon coast have revealed considerable interannual variability in the residence patterns of gray whales as well as in foraging behavior (Newell and Cowles 2006). For example, during the summer of 2005, the resident gray whale population had 50% fewer individuals than the previous three summers, and those 2005 residents displayed many fewer characteristic feeding behaviors than residents in other summers. This variability in residency and foraging was likely due to changes in the distribution and abundance of swarms of benthic mysids, the gray whale's preferred prey in this region. We have observed that the resident gray whales repeatedly forage on discrete hyperbenthic mysid swarms throughout the spring and summer months (late April-late September). As described in Newell and Cowles (2006), these discrete concentrated swarms can be found along the 10-15 m isobath off the central Oregon coast, and interannual variability in swarm thickness and extent appears to be associated with the timing and intensity of coastal upwelling. In early summer 2005, mysid swarms were less than 1 m thick, approximately 20-30% as thick as in 2003 and 2004, likely limited by the late onset of coastal upwelling and local production (Pierce et al. 2006). These observations strongly support the hypothesis that the ecological link between ocean conditions and mysid swarm dynamics affects the spatial and temporal distribution of both migrating and resident gray whales in the eastern North Pacific.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 2010
- Accession Number
- ADA541678
Entities
People
- David Mellinger
- Kelly Benoit-Bird
- Timothy J. Cowles
Organizations
- Oregon State University