504 



80 

 70 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



O 



Q. 

 LlI 

 Q 



60 - 



>- 

 Q 



O 50 



CD 



40 - 



30 - 



(f) 



S 20 



(T 



10 - 



100 



200 

 FORK LENGTH (CM.) 



300 



400 



Figure 5. — Relation of greatest depth of body to fork length. (Measurements by POFI supplemented by measure- 

 ments of the Hawaiian Division of Fish and Game (DFG) on specimens between 150 and 200 centimeter fork length.) 



tlie length of tlie mandible and the length of the 

 snout, measuring the snout from its tip to the 

 anterior edge of the orbit. 



Another method must be used to compare the 

 lengths of the pelvic fins (fig. 6). We find no 

 relation between the length of the pelvic fin and 

 the length of the fish, even in the case of the POFI 

 data on ampla with specimens ranging from 28 to 

 1,002 pounds. Thus, our samples may be com- 

 pared simply bv the mean lengths of the pelvic 

 fin. 



Finally, in a comparison of the length of the 

 20th ray (about the middle) of the first dorsal fin 

 (fig. 7) to the length of the fish there is clear 

 evidence of negative growth. This ray is the 

 longest in small (25-pound) specimens of audax, 

 but it becomes not merely relatively but actually 

 shorter as the fish increases in size. A similar but 

 not so pronounced a trend is evident in ampla. 

 We have compared samples with regard to this 

 character by averaging the length of the 20th 



rays in fish over 200 cm. fork length, since the 

 curves (fig. 7) level off above this size. 



COMPARISON OF DATA 



The type of growth will determine how the data 

 may be compared. In the case both of isometric 

 growth, where we have used ratios, and of charac- 

 ters not related to total length, which can be com- 

 pared on the basis of mean lengths, we shall use 

 the graphical method described by Hubbs and 

 Hubbs (1953). This consists of plotting the 

 mean, one standard deviation on either side of 

 the mean, and the range of the observations. We 

 will not use the additional feature of plotting two 

 standard errors on either side of the mean because 

 we shall not be concerned with tests of significance. 



On the other hand, the characters exhibiting 

 allometric growth will require the use of regres- 

 sion analysis as discussed by Marr (1955). From 

 the regression equations we will compute the mean 

 size of a character for given sizes of fish and the 



