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PACIFIC WHITE-SIDED DOLPHIN (Lagenorhynchus obliquidens): California/Oregon/Washington, Northern and Southern Stocks
| Content Provider | Semantic Scholar |
|---|---|
| Copyright Year | 2001 |
| Abstract | STOCK DEFINITION AND GEOGRAPHIC RANGE Pacific white-sided dolphins are endemic to temperate waters of the North Pacific Ocean, and are common both on the high seas and along the continental margins. Off the U.S. west coast, Pacific white-sided dolphins have been seen primarily in shelf and slope waters (Figure 1). Sighting patterns from recent aerial and shipboard surveys conducted in California, Oregon and Washington at different times of the year (Green et al. 1992; 1993; Barlow 1995; Forney et al. 1995) suggest seasonal northsouth movements, with animals found primarily off California during the colder water months and shifting northward into Oregon and Washington as water temperatures increase in late spring and summer (Green et al. 1992; Forney 1994). Stock structure throughout the North Pacific is poorly understood, but based on morphological evidence, two forms are known to occur off the California coast (Walker et al. 1986; Chivers et al. 1993). Specimens belonging to the northern form were collected from north of about 33N, (Southern California to Alaska), and southern specimens were obtained from about 36N southward along the coasts of California and Baja California. Samples of both forms have been collected in the Southern California Bight, but it is unclear whether this indicates sympatry in this region or whether they may occur there at different times Figure 1. Pacific white-sided dolphin sightings (seasonally or interannually). Recent genetic analyses have based on aerial and shipboard surveys off confirmed the distinctness of animals found off Baja California California, Oregon and Washington, 1991-96 (see from animals occurring in U.S. waters north of Point Conception, Appendix 2, Figures 1-5, for data sources and California and in the high seas of the North Pacific (Lux et al. information on timing and location of survey 1997). Based on these genetic data, a boundary or area of mixing effort). Dashed line represents the U.S. EEZ, between the two forms appears to be located off Southern thick line indicates the outer boundary of all California (Lux et al. 1997). surveys combined. Although there is clear evidence that two forms of Pacific white-sided dolphins occur along the U.S. west coast, there are no known differences in color pattern, and it is not currently possible to distinguish animals without genetic or morphometric analyses. Geographic stock boundaries appear dynamic and are poorly understood, and therefore cannot be used to differentiate the two forms. Until means of differentiating the two forms for abundance and mortality estimation are developed, these two stocks must be managed as a single unit; however, this is an undesirable management situation. Furthermore, Pacific white-sided dolphins are not restricted to U.S. territorial waters, but cooperative management agreements with Mexico exist only for the tuna purse seine fishery and not for other fisheries which may take this species (e.g. gillnet fisheries). Additional means of differentiating the two types must be found, and cooperative management with Mexico is particularly important for this species, given the apparently dynamic nature of geographical stock boundaries. Until these goals are accomplished, the management stock includes animals of both forms. For the Marine Mammal Protection Act (MMPA) stock assessment reports, Pacific white-sided dolphins within the Pacific U.S. Exclusive Economic Zone are divided into two discrete, non-contiguous areas: 1) waters off California, Oregon and Washington (this report), and 2) Alaskan waters. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.nmfs.noaa.gov/pr/sars/pdf/stocks/pacific/2016/po2016_pwd-cow.pdf |
| Alternate Webpage(s) | http://www.nmfs.noaa.gov/pr/pdfs/sars/po2000dopw-cow.pdf |
| Alternate Webpage(s) | http://www.nmfs.noaa.gov/pr/sars/2013/po2013_pacwhitesideddolphin-caorwans.pdf |
| Alternate Webpage(s) | http://www.nmfs.noaa.gov/pr/pdfs/sars/po2010dopw-cow.pdf |
| Alternate Webpage(s) | https://storestuff.s3.amazonaws.com/13200_103400534_1?AWSAccessKeyId=AKIAJBNEEVWEAALCCECQ&Expires=1583264210&Signature=8JZst4RNaQ7Oa%2BYOULd1sH%2BB4/M%3D&response-content-disposition=attachment%3B+filename%3D%22po2000dopw-cow-508.pdf%22%3B+filename*%3DUTF-8''po2000dopw-cow-508.pdf |
| Alternate Webpage(s) | http://www.nmfs.noaa.gov/pr/pdfs/sars/po2003dopw-cow.pdf |
| Alternate Webpage(s) | http://www.nmfs.noaa.gov/pr/pdfs/sars/po2007dopw-cow.pdf |
| Alternate Webpage(s) | https://storestuff.s3.amazonaws.com/13200_103400560_1?AWSAccessKeyId=AKIAJBNEEVWEAALCCECQ&Expires=1583256027&Signature=YuVzYPvBPHtUVNN9BVuFPnizpCc%3D&response-content-disposition=attachment%3B+filename%3D%22po2007dopw-cow-508.pdf%22%3B+filename*%3DUTF-8''po2007dopw-cow-508.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
