in fish less than 10 pounds in weight, with one 

 mode at 2 pounds (46 cm.) and a second ranging 

 from 5 to 8 pounds (64 to 76 cm. ). Only a few 

 specimens larger than 10 pounds were taken 

 over the period. 



WEIGHT-LENGTH RELATIONS 



Weight-length relations were calculated for 

 each of the four most abundant species accord- 

 ing to the usual formula relating weight, W (in 

 pounds), with length, L (in centimeters): 



W 



aL 



log W = log a + b log L 



The constants log a and b as determined by 

 least squares are given in table 8, along with 

 other pertinent data. Although the numbers of 

 fish are small, the calculations are included 

 because samples of small fish are usually 

 unavailable from commercial catches. 



With the dolphin, unlike the tunas, there 

 was an indication of sexual dimorphism in the 

 weight-length relation. Beyond 6 pounds (68 cm.) 

 the males tended to be heavier for a given length 

 than the females (fig. 9). This is probably re- 

 lated to a well-known sexual dimorphism in the 

 shape of the head, the males having a much 

 higher forehead than the females (Schuck 1951). 



Skipjack 



Of 34 7 troll- and pole-and-line-caught 

 skipjack, 3 had gonads so undeveloped that the 

 sex could not be determined. The remainder 

 comprised 61.0 percent males and 39.0 percent 

 females. The departure from a 1:1 ratio was 

 statistically significant a s determined by the 

 chi-square test. 



Brock (1954) points out that, in his samples 

 from the commercial catch, males were signi- 

 ficantly more abundant than females in the fall 

 of the year (September to December) but not in 

 spring (March to May) nor in the summer (June 

 to August). When our data are arranged accord- 

 ing to season (table 10) there is a significant 

 preponderance of males in the summer. At 

 present we can offer no satisfactory explanation 

 of these differences in sex ratio. 



Of the 344 fish which could be sexed, 12 

 were recorded as "immature" (gonad stage 1) 

 and 4 were "spent" (stage 5). Some of the fish 

 recorded as "immature" may have been spent, 

 for they ranged in weight from 3 to 17 pounds. 

 The four fish classed as "spent" ranged from 5 

 to 7 pounds. Despite the apparent confusion in 

 separating these two stages, it is evident (table 

 9) that the majority of the fish were "maturing" 

 or "nearly mature" and that a few may have 

 spawned. Considering their size and assumed 

 age, it seems safe to conclude with Brock that 

 skipjack may mature in 1 year. 



SEX AND MATURITY 



Little Tunny 



Summary data on sex and gonad maturity of 

 six species of fish are given in table 9. The 

 numbers of fish do not agree with those of pre- 

 vious tables as many of the fish, particularly 

 little tunny, yellowfin, and dolphin, were trans- 

 ferred alive to holding ponds and consequently 

 were not examined in respect to sex or stage of 

 maturity. 



It was impossible to determine the sex of 8 

 small (1 to 2 pounds) little tunny. Of the re- 

 maining 93 fish, males were slightly but not 

 significantly less numerous than females, 

 forming 48.4 percent of the catch. 



The gonads of most of the fish were in the 

 "maturing" condition (stages 2 and 3). The 7 



Table 8. --Number of fish, size range, and constants in the weight-length relations 

 (log W = log a +b log L) for four species of troll-caught fish 



14 



