species taken occasionally, included sandbar 

 shark, C. milberti; oceanic white tip, C lon- 

 gimanus; and porbeagle, Lamna nasus; bluefin 

 tuna, Thunnus thynnus; white marlin, Tetrap- 

 turus alhidus; sailfish, Istiophorus platypterus; 

 dolphin, Coryphaena hippurus; and lancetfish, 

 Alepisaurus sp. 



All longline sets resulting in catches of bigeye 

 threshers were made between 0000 and 0300 

 with gear retrieval beginning after 0700. The 

 depth at which the gear was fished ranged from 

 near surface to a maximum of 65 m and was 

 controlled by float lines of varying length. Tem- 

 perature-depth profiles obtained from bathyther- 

 mograph casts were routinely used to determine 

 the optimum depth for the gear. The best catches 

 of bigeye threshers were made in areas where the 

 water regime ranged from 16° to 25°C at the sur- 

 face to a minimum of 14°C at 75 m. 



A total of 65 A. superciliosus were hooked at 11 

 longline stations (Figure 1); of these, 7 broke free 

 as they were being held alongside the vessel, 23 

 were tagged and released, and 35 ( 15 females and 

 20 males) were brought aboard for examination. 

 Length measurements and internal examination 

 of stomachs and reproductive organs were made 

 on all sharks brought aboard. Total lengths (TL) 



for the 15 females ranged from 233 to 399 cm {x — 

 312 cm); the 20 males ranged from 155 to 352 cm 

 (x = 307 cm). 



Morphometric measurements from eight males 

 and four females, summarized in Table 1 as per- 

 cents of fork length, were collected following the 

 methods of Bigelow and Schroeder (1948). Fork 

 length (FL) measurements were used as a pri- 

 mary growth parameter in the morphometric re- 

 lationships in order to discern more accurately 

 any changes occurring in body proportions with 

 increasing size. The same accuracy could not be 

 expected if total lengths were used because of the 

 difficulty in obtaining precise length measure- 

 ments due to the extreme size and shape of the 

 caudal fin. 



Proportional data from Table 1 shows that al- 

 lometric growth is reflected in several characters. 

 The most obvious change associated with increas- 

 ing fork length is a proportionately shorter head 

 length resulting in a decrease in the ratios of 

 snout to: eye, nostrils, mouth, first gill, and pec- 

 toral fin. The relative size of the eye and mouth 

 also decrease as the body lengthens. Characters 

 that increase allometrically with growth include 

 height of first dorsal, length of claspers in males, 

 and interspaces between fins except in females 



Table l. — Proportional dimensions of body parts in percent of fork length for 12 Alopias superciliosus. 



'Orbit. 



223 



