Satellite tagging of fin whales off California and Washington in 2010 to identify movement patterns, habitat use, and possible stock boundaries

Citation

Schorr, G.S., E.A. Falcone, J. Calambokidis, and R.D. Andrews. 2010. Satellite tagging of fin whales off California and Washington in 2010 to identify movement patterns, habitat use, and possible stock boundaries. Report prepared under Order No. JG133F09SE4477 from the Southewest Fisheries Science Center.

Introduction

Though fin whales from the California/Oregon/Washington stock are listed as endangered under the ESA and ‘depleted’ under the MMPA, little is known about their movement patterns, habitat preferences, or stock structure within the region. A large number of fin whales were estimated to have been taken in the eastern north Pacific by whaling activities leading to a substantial decline in population estimates (Ohsumi and Wada 1974). The current population estimate for the California/Oregon/Washington stock is 3,454 whales (Carreta et al. 2007) and the population is thought to be increasing, but the observed trends are not significant (Barlow 1994, 1997). Possible threats to this species from anthropogenic sources include ship strikes (e.g. Douglas et al. 2008), fisheries interactions, and interactions with naval training exercises (i.e. sonar, ship strikes, and live fire exercises). A better understanding of fin whale movements, habitat use, and population structure is necessary to more accurately assess the status of this stock and develop management plans to encourage its recovery.
Cascadia Research Collective (CRC) has a long history of small boat-based photo-identification and biopsy sampling of numerous cetacean species, and maintains long term catalogs of blue, humpback, gray whales from the US west coast and Canada. Fin whales have been documented year-round along the US west coast both visually and acoustically (e.g. Moore et al. 1998, Carreta et al. 2007), and have been encountered by researchers at CRC sporadically in most months at points from Washington to northern Baja California, Mexico. While most CRC fin whale sightings were from California between July and October, fin whales have been encountered during surveys off the Washington coast in December and January, suggesting their seasonal movement patterns may not follow those typically seen in other large baleen whales (see Mizroch et al. 2009).
In 2008 three Andrews-style Low Impact Minimally Percutaneous External-electronic (LIMPET) tags were deployed on fin whales off San Clemente Island in conjunction with ongoing cetacean studies at the Southern California Offshore Range (Schorr et al., unpublished data). While all three whales moved extensively throughout the Southern California Bight, with two individuals moving south into Mexico (one over 400km from tagging location) before returning to the southern Channel Islands area (Fig. 1), none of these individuals moved north of Point Conception, CA. Recent evidence from mitochondrial DNA analysis (Archer et al unpublished data) has also suggested a genetic boundary exists within this population near Point Conception.
Deployment of additional satellite tags on fin whales from the California/Oregon/Washington stock can provide baseline movement data for whales in this population to help define this and other boundaries which may exist. Satellite tags can also provide an indication of habitat preference, and will allow for analyses of percent time spent in shipping channels and naval training areas. Several recent fin whale ship strikes by both commercial and naval vessels have highlighted the potential risk these impacts may pose to their recovery.

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