Pacific White-sided Dolphin 

 Lagmorhynchus ohlnjuidtns Gill, 1865 



The Pacific white-sided dolphin is one of the most widely distribut- 

 ed delphinids in the eastern North Pacific and may be the most 

 abundant delphinid in temperate portions of that region. There are 

 two forms or ecotypes: a smaller form found from about the Califor- 

 nia/Mexican border northward and a larger form found from about 

 Point Conception southward. The two can be differentiated only by 

 skeletal features and body proportions. 



From an extensive review of all data available on the species we 

 concluded that east of longitude 180 W these gregarious dolphins 

 occur from about latitude 20 N ( )ust south of the southern tip of Baja 

 California) to latitude 61 N (Valdez, Alaska). They are found in 

 pelagic waters, over the continental slope and shelf and in some inland 

 marine waters of Washington, British Columbia and Southeast Alaska. 

 They appear to be continuously distributed across the temperate 

 North Pacific. 



Pacific white-sided dolphins sometimes come very close to shore in 

 Monterey Bay, Vizcaino Bay and along the explosed coasts of Southern 

 California. Less frequently, they enter Magdalena Bay and the en- 

 trances to Puget Sound. Queen Charlotte Sound and Southeast 

 Alaska. These dolphins have been seen and photographed recently on 

 Gorda Banks, in the Cerralvo Channel and around Isla Espiritu Santu, 

 all in the Sea of Cortez, though they are apparently not common in 

 those regions. 



In the areas of most intensive observations (latitude 20 N to 54 N 

 on the Pacific coast j the species has been observed mainly shoreward of 

 the outer margin of the California Current, suggesting that it is 

 principally an inhabitant of rich upwelling waters, especially near the 

 heads of deep ocean canyons. There have been a few sightings in water 

 as shallow as 10 fms. especially off San Diego. Santa Monica and Santa 

 Barbara in winter, but the species seems to prefer deeper water. White- 

 sided dolphins are encountered widely in continental shelf continental 

 slope and offshore zones. The species is a common inhabitant of the 

 SCB, where it appears to occur in inshore waters from November 

 through April and farther offshore from May through October. Herds 

 have been reported near Santa Rosa and Santa Cruz islands and around 

 the outer Channel Islands in summer and autumn. We have commonly 

 seen them: at widespread locations in the Santa Barbara Channel, 



Figure 34. Pacific whice-sided dolphins have also been called Pacific striped 

 dolphins, because of the "suspender" stripes on the back. White sided 

 dolphins are eager bow riders. ( Photo ofiFAnacapa Island, 20 January 1985 by 

 S. Leatherwood.) 



1-lt tlRE ? s- White-skicd dolnhm^ .irc .i noi uncommon sight in the CINMS. 

 This herd was encountered near Anacapa Island, seen in the background. 

 (^ Photo by H. Leone courtesy of C. PiUsbury.j 



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