CLARKE: ECOLOGY OF LANTERNFISHES 



Litnipiinyctus steinbecki 



All postlarval L. steinbecki appeared to 

 migrate regularly. Within the night and day 

 depth ranges, the size-frequency curves were 

 usually displaced to the right with increasing 

 depth (Figure 9). The differences were signifi- 

 cant only in September and December when 

 several size classes were present in abundance. 

 In these cases the differences were due to 

 changes in absolute numbers of both small and 

 large individuals, the shallower samples being 

 composed almost entirely of juveniles and the 

 deeper ones of adults only. Consistent, signifi- 

 cant differences in size-frequency curves of day 

 samples indicated that adults (>40 mm) 

 occurred mostly below 850-900 m and few 

 smaller fishes occurred at these depths. 



The percentages of females among mature 

 fish tended to decrease with depth in the March 

 1971 night samples. The values for samples 

 from 95, 120, 135, 175, and 265 m were 82, 

 63, 64, 55, and 44% , respectively. The only 

 significant differences were between the highest 



20 



30 



40 



50 



100 1 



20 30 40 50 

 STANDARD LENGTH (mm) 



Figure 9. — Top: Cumulative size-frequency curves for 

 samples of Lampanxctus steinbecki collected at night 

 during new moon, September 1971, at depths of 80 m, 

 58 individuals (A); 100 m, 59 (B, solid line); 125 m, 

 46 (B, dashed line); 145 m, 49 (C, dashed line); and 

 165 m, 28 (C, solid line). Bottom: Cumulative size- 

 frequency curves for L. steinbecki calculated from samples 

 taken throughout the water column in September 1970 

 (A); December 1970 (B); March 1971 (C); and June 

 1971 (D). 



value and the two lowest ones. There were some 

 significant differences among the June 1971 

 night samples, but no trend with depth was 

 evident. 



The calculated totals were higher for the day 

 series in all cases. The day totals were 

 relatively highest for the September and De- 

 cember 1970 series (2 x and 1.6 x night totals, 

 respectively) and were probably in part a result 

 of poor timing of the night samples with 

 respect to moon phase. For March and June 

 1971 the day totals were about 1.5 x higher 

 than night. Except for December 1970 the 

 calculated size-frequency curves for day and 

 night series were quite similar. Thus all sizes 

 appear to avoid the IK better at night. 



The individual CT tows caught from 0.7 to 

 4.5 X their paired IK tows, and there was no 

 obvious trend in differences of the size-frequency 

 curves. The calculated curve for the CT was 

 displaced slightly to the right of both night and 

 day IK curves for March 1971, but the calculated 

 CT total was only 3.4 X the night IK total. 

 Apparently L. steinbecki avoids the CT more 

 than the IK. 



During new moon in September 1971 the 

 peak depths were at 80 and 100 m, and at full 

 moon none were caught above 120 m. The 

 catches at 170 and 190 m at full moon both 

 exceeded the peak catches at new moon. The 

 water column totals were nearly equal, but the 

 full moon calculated curve and the individual 

 curves were displaced far to the left of new 

 moon curves indicating substantially greater 

 numbers of 20- to 40-mm individuals. The new 

 moon tows seemed to miss substantial numbers 

 of juveniles; and if large numbers of larger 

 fish occur below 190 m at full moon (there was 

 some evidence for this from full moon tows in 

 other series), it is possible that full moon tows 

 may also sample the larger fish better. The 

 increase in night depth with full moon, about 

 100 m for the juveniles, was about twice that 

 observed for other species. 



Both day and night calculated totals indicated 

 that L. steinbecki was least abundant in March 

 1971 and present in comparable numbers during 

 the rest of the seasons. The calculated size- 

 frequency curves (Figure 9) indicated that 80% 

 of the individuals were immature in September 



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