CLARKE: ECOLOGY OF STOMIATOID FISHES 



tended to occur shallower during both periods. 

 During the day those over 70 mm long were mostly 

 below 525 m and those over 120 mm were below 

 575 m. At night none over 90 mm were caught 

 shallower than 50 m and none over 120 mm were 

 above 75 m. 



Smaller D. taenia (< 70 mm) were more fre- 

 quently taken in June, July and September, and 

 larger fish appeared most abundant in March. 

 This suggests that spawning is seasonal, but the 

 season cannot be estimated since the age of 35-to 

 70-mm individuals is not known. Size at maturity 

 was about 140 mm. It was not possible to deter- 

 mine the spawning season from gonad state of 

 females since very few mature females were 

 taken. The data from the March 1971 series indi- 

 cated that individuals 100-140 mm long avoided 

 the IK better than the CT, but that neither trawl 

 sampled larger individuals adequately. 



Vinciguerria nimbaria (2,927; 8-49 mm) 



For most series, the data indicated that V. nim- 

 baria occurred at 400-560 m during the day and 

 migrated to 20-125 m at night. In December 1970, 

 two night tows in the day depth range caught 

 substantial numbers of V. nimbaria — more than 

 expected on the basis of short oblique tows and 

 other night tows below 150 m. The size composi- 

 tion of these catches was within the range of that 

 of the shallow night catches and close to those of 

 day catches at similar depths. The number of ma- 

 ture fish in the deep night catches was low, but 

 there was no obvious difference in sex ratio or 

 gonad state between these and those of other tows. 

 Thus it appears that a fraction, roughly 607c, of 

 the population did not migrate in December. 



The larvae ofVinciguerria are restricted to the 

 surface layers and do not apparently undertake 

 substantial migrations until metamorphosis 

 ( Ahlstrom and Counts, 1958). Those collected dur- 

 ing this study (8-14 mm) were taken mostly at 

 15-50 m at night. (No day tows were taken above 

 250 m.) 



Consistent and frequently significant differ- 

 ences in size-frequency curves indicated that 

 smaller V. nimbaria occurred shallower in the 

 water column both day and night (Figure 1). Few 

 fish over 25 mm were captured shallower than 75 

 m at night and few less than 20 mm were captured 

 below this depth. In the day, the small fish occur- 

 red mostly above 500 m and the large individuals 

 were taken almost exclusively below 500 m. 



15 20 25 30 35 



STANDARD LENGTH (mm) 



Figure 1. — Cumulative size-frequency curves for Vinciguerria 

 nimbaria taken at 60 m (A, 35 individuals), 80 m (B, 96), 100 m 

 (C dashed line, 44), and 125 m (C, solid line, 12) at night in 

 September 1971. All pairs were significantly different (P<0.05) 

 from each other except 100 m vs. 125 m. 



The full-new moon series of night tows in the 

 upper layers during September-October 1971, in- 

 dicated substantial differences in depth distribu- 

 tion related to phase of the moon (Figure 2A), but 

 the picture was complicated by the presence of 

 many more larvae and recently transformed 

 juveniles during the October (full moon) series. 

 Calculated (see Clarke, 1973) total numbers in the 



NUMBER/TOW 



60 90 120 



I 

 H 

 O. 

 LlT 

 Q 



Figure 2. — Catches of Vinciguerria nimbaria per tow (l'/2 h 

 each) at several depths at night at new moon (solid circles and 

 lines) and full moon (open circles, dashed lines) during 

 September-October 1971. Left: total catches including larvae 

 and recently transformed juveniles. Right: catches offish larger 

 than 15 mm. 



339 



