Some Morphometries of Billfishes From the 

 Eastern Pacific Ocean 



PAUL G. WARES' and GARY T. SAKAGAWA^ 



ABSTRACT 



Length-weight and morphometric data collected over 4 yr (1967-70) from sport fisheries at three 

 eastern Pacific locations are presented for striped marlin (Tetraplurui audax), sailfish (Istiophorus 

 platyplerus) , and blue marlin (Makaira nigricans) . The data were gathered from San Diego, California 

 (U.S.A.), Buena Vista, Baja California Sur (Mexico), and Mazatlan, Sinaloa (Mexico). 



Regression of eye-fork length and covariance analysis were used to compare maximum body depth, 

 depth at vent, pectoral fin length, dorsal fin height, maxillary length, snout to mandible and snout to 

 posterior orbit lengths between sexes and areas for each species. Regression equations are given for 

 converting fork length and mandible-fork length to eye-fork length. Based on these conversions our 

 Pacific Ocean data on sailfish are compared with data from the Atlantic Ocean. 



Length-weight regressions using both eye-fork length and fork length are given for each species by 

 sex. 



The eastern Pacific off Mexico and southern 

 California is probably one of the world's most pro- 

 ductive regions for billfishes. Specimens from this 

 region, however, have too often been underrepre- 

 sented in comparative studies on billfish morphol- 

 ogy. It is the purpose of this paper to (1) present 

 some basic data on morphometric and meristic 

 characters of striped marlin (Tetrapturus audax), 

 blue marlin {Makaira nigricans), and sailfish il\- 

 tiophorus plalypterus) from the eastern North 

 Pacific Ocean, and (2) discuss some sources of varia- 

 tion in morphometric characters. 



SAMPLING 

 Source of Data 



The data were gathered by the staff of the Tiburon 

 Fisheries Laboratory during 1967 through 1970. The 

 sole source of data was the sampling of sport land- 

 ings at three locations. These locations were: ( 1 ) the 

 San Diego Marlin Club at San Diego, California; (2) 

 Rancho Buena Vista in the territory of Baja Califor- 



'U.S. Fish and Wildlife Service, Northwest Fisheries Pro- 

 gram, 495 Tyee Dr.. Tumwater, WA 98502. 



-National Marine Fisheries Service, Southwest Fisheries 

 Center, P.O. Box 271, La Jolla, CA 92037. 



nia Sur, Mexico; and (3) the Star Fleet at Mazatlan, 

 Sinaloa, Mexico. Sampling at these locations each 

 year was conducted primarily during the months 

 when billfish catches were highest. The monthly 

 distribution of samples is shown in Table L 



The specimens examined were almost totally fish 

 caught on one-day trips in small boats ranging from 

 about 6 to 12 m in length. For this reason most of the 

 samples at each location represent fishes caught in a 

 radius of less than about 100 km from the landing 

 site. All of the fish were kept fresh, unfrozen, and at 

 San Diego and Buena Vista, usually moist. The bill- 

 fish landed at Mazatlan tended to be in a more 

 dried-out condition. This made full erection of the 

 dorsal fin difficult. Many fish were, therefore, meas- 

 ured when the dorsal fin was only half erect, but we 

 feel that this did not affect the results significantly. 

 The effect of dryness on body measurements is un- 

 known, but we feel that it was not significant. Body 

 length measurements were made with a steel tape. 

 Nearly all of the fish at San Diego and a few of the 

 fish at Mazatlan were measured while hanging by 

 the tail. Otherwise, measurements were made while 

 fish were lying on their side on a flat surface with 

 heads and tails raised to horizontal. We tested the 

 effect of hanging on eye-fork lengths of 10 fish at 

 San Diego by measuring each one while hanging 



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