Bigscale

Caudal peduncle moderate in length (Ref. 37108).

Dorsal spines (total): 2; Dorsal soft rays (total): 11; Analspines: 1; Analsoft rays: 8

Juveniles (1-2.9 cm SL) feed on amphipods and adults(3-6.9 cm SL) feed on tunicates, siphonophores and pteropods (Ref. 51328).

Trawled below 300 m (Ref. 4241).

fisheries: of no interest

Scopelogadus mizolepis mizolepis

This species is uncommon in the Ocean Acre. It has a tropical-semisubtropical distribution in the Atlantic, occurring in reduced numbers north of 30°N, in the western North Atlantic. Ebeling and Weed (1973) examined 743 specimens captured north of 10°N, of which only 55 were taken north of about 30°N. A total of 127 specimens was taken in the Ocean Acre, 31 in discrete-depth samples, 23 of these in noncrepuscular samples on the paired cruises.

DEVELOPMENTAL STAGES.—No postlarvae were taken. The 49 juveniles were 9–47 mm. At 9–10 mm they had acquired the large scale pockets and pigmentation characteristic of the larger stages, and at 35–40 mm a small degree of gonad development was evident. Fifty-four subadults were 38–58 mm, and 24 adults 52–66 mm (Table 161). Ebeling and Weed (1963) recorded adults as large as 90 mm but observed that, in unproductive waters such as the Sargasso Sea, S. m. mizolepis does not attain as large a size as in productive waters.

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—The absence of postlarvae indicates that this species probably does not breed as far north as the Ocean Acre area. Older stages presumably stray into the area from the warmer waters of the Southern Sargasso Sea.

The presence of small specimens (9–15 mm SL) in March, June, and September (Table 161) indicates that the breeding season probably extends from late winter to summer.

Scopelogadus m. mizolepis was most abundant in late spring, decreasing in numbers by late summer through winter; total abundances (Table 162) were: late spring 4.0, late summer 2.0, winter 1.1. These figures are based on a total of only 23 discrete-depth captures, but the numbers in Table 161 suggest that the relative abundances probably are correct. More specimens were taken in August-September than in June, but the vast majority were taken by the EMT, whereas June includes only IKMT samples. From November through February, although 91 net hauls were made, only 3 specimens were captured.

The dearth of late fall and winter captures suggest that S. m. mizolepis enters the Ocean Acre area only during the warmer seasons.

VERTICAL DISTRIBUTION.—In discrete-depth noncrepuscular samples from the paired cruises, all 11 specimens taken during the day were from between 651 and 1000 m. At night, 12 were taken between 51 and 400 m and one (17 mm SL) at 851–900 m. Open-net captures support the discrete-depth data: daytime captures were from 650 m or deeper, night captures as shallow as 100 m.

Only the data for late spring are extensive enough to clearly indicate diel migratory behavior for all three stages, and the night data show size-depth stratification. During the day, they occupy depths of 651–1050 m. The 10 specimens taken at night were distributed as follows: 3 specimens, 9–20 mm, at 51–100 m; one specimen 28 mm, at 151–200 m; 6 specimens, 45–58 mm, at 201–250 m.

Ebeling and Weed (1963) calculated that the average daytime depth of capture of postlarvae and young of this species was 533 m, while the average nighttime depth was 268 m; for large young and adults, the average daytime depth was 1150 m, the nighttime average depth 447 m. However, they concluded that much of the difference between the daytime and nighttime averages might be artificial, because a large number of their specimens came from the Dana collections, which comprised mostly shallow nighttime hauls (average depth 150 m) and deep daytime hauls (average depth 717 m). They did conclude that younger individuals occupied shallower depths than older ones.

The Ocean Acre data indicate that members of this species undergo a diel vertical migration, and they support Ebeling and Weed's observations on size-depth stratification.

NIGHT:DAY CATCH RATIOS.—Sums of catch rates for all 50-m depth intervals, using interpolation in unsampled intervals, were greater during the day than at night in late spring (0.8:1) and late summer (0.1:1). The only two winter specimens were taken at night. Without interpolation the late spring catch was higher at night. The data are, thus, equivocal as to the relative effectiveness of day or night sampling.

Atlantic: in tropical waters to 20-30°S. as far north as 43.6°N

Found to depths of 3385 m.

nektonic