Some Biological Observations of Billfishes Taken in the 

 Eastern Pacific Ocean, 1967-1970 



MAXWELL B. ELDRIDGE and PAUL G. WARES 1 



ABSTRACT 



From 1967 through 1970 sport -caught billfishes were sampled at Mazatlan, Sinaloa; and Buena Vista, 

 Baja California, and at San Diego, California. Lengths, weights, morphometries, meristics, and gonad 

 data were gathered on a total of 2,056 striped marlin, 821 sailfish, 61 blue marlin, and 1 black marlin. This 

 paper presents information on reproduction, average length and condition factor, food habits for 1970, and 

 notes on parasites. 



Developing gonads were found only in the Mexican fish. Our data on reproduction indicated that both 

 striped marlin and sailfish spawn once per year with peak spawning activity probably in June and July. 

 There is also the possibility that sailfish spawn in other months. First maturity in striped marlin and sailfish 

 occurred in the 155-165 cm eye-fork length class. Fecundity estimates ranged from 2 to 5 million eggs for 

 four sailfish and from 11 to 29 million eggs for three striped marlin. It appears mat striped marlin move 

 offshore from the Mexican coastline to spawn while sailfish remain closer to shore. 



Much of the interest in billfishes in the eastern 

 Pacific Ocean stems from their popularity among 

 sport fishermen. Commercial fishermen have also 

 been interested in the billfish resources as indicated 

 by their extensive and continuous operation in this 

 area since 1956 (Suda and Schaefer, 1965). Since 

 1963 this fishery has concentrated off Mexico where 

 it is directed primarily at striped marlin (Tetrapturus 

 audax) and sailfish ( I stiophorus platypterus) (Kume 

 and Schaefer, 1966; Kume and Joseph, 1969a). 

 Throughout the history of the billfish fishery in the 

 eastern Pacific no attempt has been made to manage 

 these resources; this is partly due to the lack of 

 information on the life history and population 

 dynamics of these fishes. This report provides data 

 gathered from billfishes landed at sportfishing sites 

 in southern California and Mexico from 1967 to 

 1970. Specimens were examined at San Diego, 

 California; Buena Vista, Baja California; and 

 Mazatlan, Sinaloa, Mexico (Fig. 1). A total of 2,056 

 striped marlin, 821 sailfish, 61 blue marlin (Makaira 

 nigricans) and 1 black marlin (M. indica) 

 were sampled. This paper is one of a series of publi- 

 cations describing the results of these studies. Evans 



and Wares (1972) published information of the food 

 habits of fish collected in 1967-1969, and another 

 paper (Wares and Sakagawa, 1973) has been pre- 

 pared to present meristic and morphometric 

 analyses. 

 The purpose of this paper is primarily to present 



'NOAA, National Marine Fisheries Service, Tiburon 

 Fisheries Laboratory, Tiburon CA 94920. 



Figure 1. — Location of the three billfish sampling sites. 



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