Research Technical Report

Preliminary results of cetacean and ecosystem surveys along the U.S. west coast and within four National Marine Sanctuaries during 2005

Forney, K., C.E. Bowlby, J. Roletto, L.T. Ballance, J.V. Redfern, P.C. Fiedler, J. de Marignac, A. DeVogelaere, and D. Howard (March 2007)

Poster presentation at the 2007 Sanctuary Currents Symposium, Seaside, CA

ABSTRACT

The abundance of cetaceans along the U.S. West Coast was estimated from a shipboard line-transect survey conducted during 2005. Ecosystem data collected concurrently with cetacean data provided indicators of variation in physical habitat, mid-trophics, and seabirds. The surveys were designed to uniformly cover waters off California, Oregon and Washington from the coast to 300 nmi (556 km) offshore, and to provide fine-scale coverage within four of the five West Coast National Marine Sanctuaries (NMS).

Preliminary abundance estimates for 19 species were calculated using a geographically stratified, multiple-covariate line-transect analysis. As in past years, the most abundant species coastwide was the short-beaked common dolphin (Delphinus delphis), and the most abundant whale was the fin whale (Balaenoptera physalus). Off Oregon and Washington, Dall's porpoise (Phocoenoides dalli) was the most abundant species. Within the NMS, humpback whales (Megaptera novaeangliae) were the most common whale species and Pacific white-sided dolphins (Lagenorhynchus obliquidens) were the most common delphinid. Abundance estimates for most species during 2005 were comparable to estimates from a similar coast-wide survey in 2001. Blue whales have been less abundant along the U.S. West Coast in 2001 and 2005 than during the 1990s, whereas estimated humpback whale abundance is greater than during all previous assessments through 2002. The ecosytem data provide an additional context for the 2005 observations relative to past coast-wide surveys during 1991-2001. The additional fine-scale survey coverage within the NMS allowed an evaluation of the significance of these regions to cetaceans and seabirds, and NMS waters clearly represent important habitat for many species.