514 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



10 12 14 16 18 20 22 



HEIGHT FIRST DORSAL AS PERCENT OF FORK LENGTH 

 Figure 17. — Mean, standard deviation, and range of the ratio of height of anterior lobe of first dorsal to fork length. 



good one for distinguishing audax from eacli of 

 the other two species, because with a dividing 

 point of 8 cm. only 1 out of 35 audax had a sliorter 

 20th ray and only 5 out of 62 ampla had a longer 

 20th ra.y. None of the 13 marlina had a 20th ray 

 longer than 8 cm. 



Caudal spread 



When plotted, the caudal spread showed no 

 evidence of allometric growth and, hence, has 

 been compared on the basis of its ratio to fork 

 length (fig. 21). It may be seen that audax tends 

 to have the slightly smallest tail, marlina inter- 

 mediate, and ampla the largest, but tliere is so 

 much overlap that the character is useless for 

 distinguishing the species. 



There is a persistent tendency for the speci- 

 mens measured by POFI in each species to have 

 slightly broader caudals than those measured by 

 Gregory and Conrad (1939) and Conrad and 

 LaMonte (1937). All of the POFI measure- 

 ments, except the one largest ampla, were ob- 

 tained on board ship at sea from fish that had 

 never been lifted by the tail. Consequently, the 

 fin rays had not been compressed and the measure- 



ment of the spread might be expected to be slightly 

 greater than if the fish had been handled or hung 

 up by the tail. We suspect that some or all of 

 the fish measured by the authors cited miglit have 

 been lifted by the tail; consequently, we attach no 

 significance to the slight differences. 

 Lateral line 



Nakamura (1949) has pointed out that audax 

 and marlina have simple lateral hues, whereas 

 ampla has a complex lateral line. We concur in 

 the presence of a complex lateral line in a pre- 

 served specimen (specimen No. 1 in appendix 

 table 1-E, p. 545) of ampla in which the lateral 

 line is conspicuous. In all fresli material we have 

 examined at sea and in tlie Honolulu market, we 

 iiave found the lateral line extremely difficult to 

 locate and to determine whether or not it is com- 

 plex. We question the usefulness of this charac- 

 ter in the field. 

 Flexibility of the pectoral fin 



Many people who liave seen marlina have re- 

 ported that the pectoral fin cannot be folded back 

 against the body. Those who have not examined 

 the fisli quite naturally have wondered if this 



