CLARKE and WAGNER: VERTICAL DISTRIBUTION OF MESOPELAGIC FISHES 



980 m (94 mm). The 12 large (77-126 mm) in- 

 dividuals taken during the day were from 

 750-1,150 m. 



Among the 18 fish sexed, there were 12 males 

 (80-109 mm) and 6 females (78-126 mm). None 

 appeared mature. The collection of so many small 

 individuals in one of the seasonal series indicates 

 that A. cornuta has a rather short spawning 

 season. 



Stylephoridae 



Stylephorus chordatus Shaw ( 19; ca. 60-31 5 mm) 



Seven S. chordatus (ca. 60-315 mm) were taken 

 at night between 300 and 600 m. Eleven (63-282 

 mm) were taken between 625 and 800 m during the 

 day, and one at dusk at 500 m. Thus S. chordatus 

 appear to migrate about 200-300 m upward at 

 night. 



Two females (282 and 315 mm) appeared ma- 

 ture; the next largest female was 147 mm. The four 

 largest males were 235-243 mm. 



Gempylidae 



Gempylus serpens Cuvier (29; 7-148 mm) 



All but two G. serpens were taken at night in the 

 upper 250 m; 19 were from 30-100 m. During the 

 day, a 60-mm specimen was taken at 450 m and a 

 30-mm one at 800 m. It seems likely that the latter 

 or both of the day catches were made in transit 

 and that G. serpens migrates downward only a 

 short distance, if at all, during the day. None were 

 near maturity. 



Nealotus tripes Johnson (95; 7-173 mm) 



Most A'', tripes were small (9-41 mm) taken at 

 50-200 m at night. Seventy-three were taken in 

 December-58 in three tows at 170-200 m and 12 in 

 a tow at 250 m. The CT collected four large 

 specimens at night, three (75, 168, 173 mm) at 100 

 m and one (68 mm) at 250 m, while only one (49 mm 

 at 150 m) was taken by the IK. No small fish and 

 only three large ones were taken during the day. 

 The CT captured a 49-mm individual at ca. 350 m, 

 and the IK took two (63, 105 mm) in separate tows 

 at ca. 750 m. The small N. tripes apparently stay in 

 the upper layers both day and night. Since the 

 larger fish were obviously inadequately sampled 

 by the IK and there were no deep day tows made 



with the CT, it is not clear whether adults descend 

 or not. The two deep day catches by the IK may 

 well have been coincidentally taken in transit by 

 tows which fished the same depth. 



Diplospinus multistriatus Maul (224; 8-239 mm) 



Most of the D. multistriatus were small in- 

 dividuals caught at night at two depth zones and at 

 two separate seasons. Of the 100 specimens taken 

 in December, 78 (8-30 mm) were taken in three 

 tows at 170-200 m. In July, 62 specimens were 

 taken; 31 (7-18 mm) were from four tows at 100-110 

 m. Other small fish taken at night were mostly 

 from the upper 200 m with a few, probably cap- 

 tured in transit, taken in deeper tows. Of the 18 

 larger (35-239 mm) specimens taken at night, 13 

 were taken in the upper 130 m, 4 at 200-300 m, and 

 1 probably captured in transit, at 500 m. 



Only 37 were taken in day tows, all but 2 

 between 500 and 1,000 m. Only one of these (11 

 mm) was in the size range which dominated the 

 night catches. Three specimens were slightly 

 larger (36-42 mm) and the remainder 68-221 mm. 

 Most less than 140 mm were taken above 800 m, 

 and most over 140 mm were taken below 700 m. 



The near absence of small D. multistriatus in 

 the day samples suggests that they either remain 

 in the upper layers during the day (and were not 

 sampled by our tows) or occur deeper and avoid the 

 net during the day. The latter seems improbable 

 for such small fish. Assuming the former is true 

 and considering the data on larger fish, it appears 

 that D. multistriatus occurs in the upper 100-200 

 m at night and that the larger sizes migrate to 

 progressively greater depths by day. 



Of the 46 specimens sexed, 12 were males (93-207 

 mm) and 34 females (75-239 mm). Eight females 

 (163-239 mm) were mature. 



DISCUSSION 



Vertical Distribution and Migration 



The diverse group of fishes considered here, as 

 might be expected, exhibit a greater array of ver- 

 tical distribution patterns than the myctophids 

 and stomiatoids which occur in the study area. 

 Most species of the latter two groups undertake 

 substantial diel vertical migrations. The remain- 

 ing species do not vertically migrate at all. Among 

 the species considered here, migrators and non- 

 migrators are about equally represented, and 



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