Abstract. — A ship survey was 

 conducted in summer and fall of 

 1991 to estimate the abundance of 

 cetaceans in California waters be- 

 tween the coast and approximately 

 555 km (300 nmi) offshore. Line- 

 transect methods were used from 

 a 53-m research vessel. Approxi- 

 mately 10,100 km were searched, 

 and 515 groups of cetaceans were 

 seen. The estimated abundances 

 and coefficients of variation (in pa- 

 rentheses) of the most common 

 small cetaceans are the following: 

 226,000 (0.28) short-beaked com- 

 mon dolphins, Delphinus delphis; 

 78,400 (0.35) Dall's porpoises, Pho- 

 coenoides dalli; 19,000 (0.41) 

 striped dolphins, Stenella coeruleo- 

 alba; 12,300 (0.54) Pacific white- 

 sided dolphins, Lagenorhynchus 

 obliquidens; 9,470 (0.68) long- 

 beaked common dolphins, Delphinus 

 capensis; and 9,340 (0.57) northern 

 right whale dolphins, Lissodelphis 

 borealis. The estimated abun- 

 dances (and CV's) of the most com- 

 mon large cetaceans are 2,250 (0.38) 

 blue whales, Balaenoptera musculus; 

 935 (0.63) fin whales, Balaenoptera 

 physalus; 756 (0.49) sperm whales, 

 Physeter macrocephalus; and 626 

 (0.41) humpback whales, Megap- 

 tera novaeangliae. Estimates are 

 also made for other species and for 

 higher-level taxa that could not be 

 identified to species. 



The abundance of cetaceans in 

 California waters. 

 Part I: Ship surveys in summer 

 and fall of 1991 



Jay Barlow 



Southwest Fisheries Science Center 

 National Marine Fisheries Service. NOAA 

 RO. Box 271. La Jolla. California 92038 



Manuscript accepted 31 May 1994. 

 Fishery Bulletin 93:1-14 ( 1995). 



The abundance of cetaceans in Cali- 

 fornia waters is poorly known for 

 the majority of species found there. 

 For small cetaceans, quantitative 

 estimates of abundance with statis- 

 tical confidence limits are available 

 only for common dolphins, Delphi- 

 nus delphis (Dohl et al., 1986) and 

 for harbor porpoise, Phocoena 

 phocoena (Barlow, 1988). For large 

 cetaceans, such estimates are avail- 

 able for gray whales, Eschrichtius 

 robustus (Reilly, 1984; Buckland et 

 al., 1993a); humpback whales, Meg- 

 aptera nov aeangliae (Calambokidis et 

 al., 1990a, 1993 1 ), and blue whales, 

 Balaenoptera musculus. 1 Estimates 

 have been made for some of the 

 other species (Dohl et al. 2,3 ), but 

 these estimates are more than 10 

 years old, and most lack informa- 

 tion on statistical precision. 



Many, and perhaps all, cetaceans 

 in California waters are vulnerable 

 to entanglement and death in 

 gillnet fisheries. A program is now 

 in place to estimate the incidental 

 mortality of cetaceans in the Cali- 

 fornia gillnet fisheries (Lennert et 

 al., in press). It is difficult, however, 

 to assess the impact of gillnet mor- 

 tality on cetacean populations with- 

 out knowing population sizes. Co- 

 ordinated ship and aerial surveys 

 were initiated recently to estimate 

 the abundance of all cetacean spe- 

 cies in the region of California 

 gillnet fisheries. To evaluate the ef- 



fect of seasonality on cetacean abun- 

 dance, surveys were designed to 

 cover both cold-water months (Feb- 

 Apr) and warm-water months ( Jul- 

 Nov). A ship survey was conducted 

 during the warm-water period of 

 1991; an aerial survey was conducted 

 during the cold-water periods of both 

 1991 and 1992. Results from the ship 

 survey are reported here; population 

 estimates from the aerial surveys 

 are reported in a companion paper 

 (Forney et al., this issue). 



Field methods 



A line-transect survey was con- 

 ducted from 28 July to 5 November 

 1991 with the 53-m National Ocean- 

 ographic and Atmospheric Admin- 



1 Calambokidis, J., G. H. Steiger, and J. R. 

 Evenson. 1993. Photographic identification 

 and abundance estimates of humpback 

 and blue whales off California in 1991-92. 

 Final Contract Rep. 50ABNF100137, sub- 

 mitted to the Southwest Fish. Sci. Cent., 

 P.O. Box 271, La Jolla, CA 92038, 40 p. 



2 Dohl, T. P., K. S. Norris, R. C. Guess, J. D. 

 Bryant, and M. W. Honig. 1978. Cetacea 

 of the Southern California Bight. Part II 

 of Summary of marine mammals and sea- 

 bird surveys of the Southern California 

 Bight area, 1975-78. Final Rep. to the Bu- 

 reau of Land Management, 414 p. [NTIS 

 Rep. No. PB81248189.] 



3 Dohl, T. P., R. C. Guess, M. L. Duman, and 

 R. C. Helm. 1983. Cetaceans of central and 

 northern California, 1980-83: status, 

 abundance, and distribution. Final report 

 to the Minerals Management Serv., Con- 

 tract No. 14-12-0001-29090, 284 p. 



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