SHNDARD LENGTH MINUS SNOUT LENGTH 



Figure 2. — Relation between eye diameter divided by 

 snout length expressed in percent and standard length 

 minus snout length in mm for istiophorid young. Blue 

 marlin indicated by open circles, unknown species by 

 closed circles. 



chromatophore on the midline of the gular mem- 

 brane. None of the 10 had any pigment on the bran- 

 chiostegal membrane. Lower jaw pigment was con- 

 fined to the tip or never extended back further than 

 Vi the length of the ramus. Eight of the 10 specimens 

 had the tip of the snout below a plane drawn along 

 the body axis through the eye; two had the tip level 

 with the eye (the 12.1-mm Miami specimen and a 

 9.9-mm specimen from the Gulf of Mexico). The 

 nature of the pterotic spine was variable — five 

 specimens had nearly level spines, two had their 

 spines projecting sharply upwards, and three had 

 their spines directed upwards at a slight angle. The 

 anterior edge of the orbit projected anteriad but no 

 more so than many of the long-snouted specimens. 



The three blue marlin identified by Ueyanagi, 

 which were smaller than 9 mm in standard length, are 

 also shown in Figure 2. They are very similar to the 

 other blue marlin specimens. They all lacked gular 

 pigment, had pigment confined only to the tip of the 

 lower jaw, lacked branchiostegal pigment, and had 

 the tip of the snout below the level of the eye. Two of 

 the specimens had sharply angled upward pterotic 

 spines, while one had this spine slightly angled up- 

 ward. 



All of the remaining specimens were grouped ac- 

 cording to their pigment patterns. These groups are: 



Group 1 — distinct row of pigment on gular mem- 

 brane midline; no branchiostegal pigment. 



Group 2 — distinct row of pigment on gular mem- 

 brane midline; branchiostegal pigment present. 



Group 3 — two or three pigment cells on bran- 

 chiostegal membrane; no branchiostegal pigment. 



Group 4 — two or three pigment cells on gular 

 membrane midline; branchiostegal pigment present. 



Group 5 — one pigment cell on gular membrane 

 midline; no branchiostegal pigment. 



Group 6 — one pigment cell on gular membrane 

 midline; branchiostegal pigment present. 



Group 7 — no pigment on gular membrane mid- 

 line; no branchiostegal pigment present. 



Group 8 — no pigment on gular membrane midline; 

 branchiostegal pigment present. 



The numbers of specimens in each of these 

 groups, their size range, and frequency occurrence 

 of the other characters studied are shown in Table 4, 

 along with the data on the 1 3 blue marlin specimens. 

 As one can see, there does not seem to be any 

 relation between any particular set of characters one 

 may choose. Those five specimens shown in Figure 

 2 with eye/snout percentages greater than 120 per- 

 cent (very short snout) occur in Groups 7(1), 1 (2), 5 

 (1), and 6 (1). Categorizing the blue marlin speci- 

 mens in a like manner, 1 1 would be included in 

 Group 7 and 2 included in Group 5. If there is valid- 

 ity to these groups then two of these five small 

 specimens could be considered to be blue marlin 

 since they occur in Groups 5 and 7. 



I have presented this evidence to illustrate the 

 variability of the characters used to identify larvae. 

 Table 4 demonstrates that one can choose any par- 

 ticular character and separate larvae into groups, but 

 it is difficult to substantiate any particular character 

 with other characters. Since my material comes from 

 a relatively small area, I may not have young of all 

 the species which occur here. But whatever is the 

 case, it appears that there is a great deal of variation 

 in the characters. Ueyanagi's studies have been 

 based on Pacific material so, perhaps, the variability 

 that I find is confined to Atlantic specimens. 



CONCLUSIONS 



It is evident that a great deal of work is necessary 

 to resolve the identity of young istiophorids. Primar- 

 ily, it is necessary to collect a great deal of material 

 from different areas and at different times of the 

 year. Information from gonad maturation studies of 

 all the species would be helpful to predict where and 



69 



