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Fishery Bulletin 88(2). 1990 



The vernacular name for P. sinus tended to vary 

 between communities and individuals. Fishermen in 

 San Felipe referred to P. sinus as "cochito," "cochi- 

 nito," and "vaquita." In contrast, for La Paz fishermen 

 "vaquita" refers to Kogia simus or Phocoena spp., 

 whereas "cochinito" refers to Delphinus delphis, 

 "cochito" to Glohicephala macrorhynchus, and 

 "duende," also meaning P. sinus in some communities 

 (Magatagan et al. 1984), refers to Lagenorhynchus 

 obliquidens (D. Aurioles, pers. commun., June 1987). 



Discussion 



Although surveys were conducted throughout the up- 

 per Gulf, sightings of Phocoeyia sinus were limited 

 almost entirely to the western side. One or a combina- 

 tion of the following features may account for vaquita 

 distribution patterns in the upper Gulf. Relative to the 

 eastern shore, the western boimdary exhibits lower sur- 

 face temperatures (Robinson 1973) resulting partly 

 from northward-bearing upwelled water from the 

 Midriff Island region. With respect to the eastern coast- 



line of the upper Gulf, the western perimeter is char- 

 acterized by stronger north-south tidal currents year- 

 round (Hendrickson 1973) which may contribute to 

 increased mixing on the west coast. 



Vaquita often surfaced near surface slicks, which 

 are caused by tidally induced internal waves (Ewing 

 1950, Shanks 1983) or areas of convergence of different 

 water masses, a common feature of the northern Gulf 

 of California (Hendrickson 1973, Lepley et al. 1975). 

 Surfacing near slicks has been noted in other cetaceans, 

 including Feresa attenuata, Steyio breda.nensis, and 

 Pseudorca crassidens (K.S. Norris, Cent. Mar. Stud., 

 Univ. Calif., Santa Cruz, CA 95064, pers. commun., 

 Aug. 1987). Concentrations of small marine organisms 

 are associated with internal waves (Shanks 1983, 1988; 

 Kingsford and Choat 1986). Vaquita and other ceta- 

 ceans may be drawn to aggregated prey in these 

 features. 



It is believed by some researchers that the entire P. 

 sinus population is limited to the upper Gulf, which 

 represents the smallest range of any marine cetacean 

 (Brownell 1986, Barlow 1986); however, the actual 

 range remains unsubstantiated. Although presently 



