FISHERY BULLETIN: VOL, 77, NO. 4 



PERCENT 



25 50 



MEAN NO PER 1,000m' 

 100 200 300 400 50 100 150 200 



— Gonostomatidae 



Sternoptychidae 



Mycfophidae 



. Other larvae 



Figure 2. — Percent contribution of major families and "other 

 larvae" to the total ichthyoplankton caught within each depth 

 interval of the North Pacific central gyre during summer. 



and Vinciguerria nimbaria (Figure 3b). Maximum 

 diversity occurred at 75-225 m. 



Gonostomatidae 



 Cyclothone alba 



- Vinciguerria nimbaria 



(b) 



Figure 3.— Vertical distributions of larval gonostomatids in the 

 North Pacific central gyre during summer. Concentrations of (a) 

 gonostomatid larvae (12 species combined) and of (bl Cyclothone 

 alba and Vinciguerria nimbaria larvae by depth interval. 



increase in standard length with depth; smaller 

 sizes dominated at 25-50 m, larger lengths at 

 50-75 m, and intermediate sizes at 0-25 m. Al- 

 though median standard length was largest in the 

 75-100 m interval, the cumulative size-frequency 

 curve was not significantly different from that at 

 50-75 m, possibly because of the paucity of larvae 

 captured at 75-100 m. The three largest larvae 

 present in 75-100 m samples (11.6-14.7 mm) were 

 in the prometamorphic (white photophore) stage 

 ( Ahlstrom and Counts 19581 of development. Only 

 three small larvae were caught between 100 and 

 350 m, and 57 metamorphosed individuals were 

 caught at 350-600 m. 



CYCLOTHONE SPP.— Cyclothone alba is a 

 numerous larval fish species in the central gyre 

 throughout the year, ranking second in abun- 

 dance only to Vinciguerria nimbaria (Loeb 

 1979b). It was the most abundant species taken 

 during this cruise (27% of all larvae), and was 

 present in all samples from to 75 m; below 75 m it 

 was rare (Table 2). Eighty-seven percent of the 

 estimated water column abundance was from the 

 upper 50 m, with highest concentrations at 25-50 

 m (Figure 3b). Abundances in replicate tows 

 within the 0-25 m and 25-50 m intervals were not 

 significantly different from each other; they were, 

 however, significantly greater (Mann-Whitney U 

 test, P <0.01) than those in deeper intervals. 



A wide range of larval lengths was found within 

 each depth interval from to 75 m and the cumu- 

 lative size-frequency curves differed significantly 

 (Kolmogorov-Smirnov test, P<0.05) between all 

 three intervals (Figure 4). There was no simple 



100 



UJ 



(J 

 cc 



UJ 

 Cl 



^ 50 



3 

 O 



2 4 6,0 8,0 10.0 12.0 



STANDARD LENGTH (mm) 



14,0 



Figure 4. — Cumulative size-frequency curves for Cyclothone 

 alba larvae by 25 m depth interval (10 samples per interval) 

 within the upper 100 m of the North Pacific central gyre during 

 summer. 



784 



