Ridgehead

Head with a sharp angle I the frontal margin. Scales mostly pockets (Ref. 37108).

Dorsal spines (total): 3; Dorsal soft rays (total): 14 - 15; Analspines: 1; Analsoft rays: 14 - 16

Adults found at depths below 500 - 600 meters; juveniles below 50 meters (Ref. 51657).

Melamphaes typhlops

This species is uncommon in the Ocean Acre. It inhabits the Atlantic between 30°S and 45°N. It is one of the few large Melamphaes species (reaching 100 mm SL elsewhere, 73 mm in the Ocean Acre) that seems to occur in relatively sterile as well as productive waters. A total of 135 specimens was taken: 23 postlarvae, 75 juveniles, 19 subadults, and 18 adults. Of these, 51 were taken in discrete-depth samples, 41 of the 51 in noncrepuscular samples from the paired cruises (Table 147).

DEVELOPMENTAL STAGES.—Postlarvae, with light pigmentation on certain parts of the body (Ebeling, 1962), were 5–13 mm, the largest beginning to acquire adult coloration. Juveniles were 12–40 mm. The juvenile-subadult transition occurs at about 35–40 mm, and the subadult-adult transition at approximately 45–54 mm. Subadults in Ocean Acre samples were 35–54 mm, adults 46–73 mm.

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—Captures of postlarvae from January to September (Table 153) indicate that M. typhlops breeds during most of the year. No obvious peak spawning period can be discerned. This species probably spawns for the first time when it is 45–50 mm. Specimens as large as 70 mm suggest that M. typhlops lives as long as two years and probably spawns more than once. Two March specimens 53–54 mm (Table 153), called subadults, were of adult size but had immature gonads. Probably they were adults which already had spawned once.

M. typhlops was most abundant in winter and decreased in numbers through late spring and late summer (Table 154). The specimens that comprise the catch on which these figures are based are almost entirely postlarvae and juveniles. Most of the subadults and adults were caught by the EMT in late August; their absence in an adjacent IKMT cruise in early September suggests that older specimens could have been present at other times but were not taken.

VERTICAL DISTRIBUTION.—Discrete-depth samples (Table 155) captured 3 postlarvae at 51–100 m during the day, and 6 at 1–100 m at night. All were 5–11 mm, and none were metamorphosing; presumably they do not migrate vertically. One 8-mm postlarva was caught at night at 701–750 m. Probably it is a contaminant. Two metamorphosing postlarvae (both 12 mm SL), were caught at 551–750 m during the day, indicating that metamorphosis occurs at depth. At night, several specimens arbitrarily called juveniles (13–15 mm), but still metamorphosing, were caught at 150–200 m, suggesting that vertical migration begins before metamorphosis is completed.

All stages from juvenile to adult apparently undertake diel vertical migrations. Twelve juveniles were taken between 551 and 1000 m during the day and 12 between 151 and 1000 m at night, most of them above 500 m. The only subadult was taken during the day at 1001–1050 m. Two adults were taken during the day at 1001–1150 m, and two at night at 551–600 m.

Ten of 13 adults taken at night by the EMT were caught at maximum depths between 725 and 1000 m; the remaining three were from maximum depths of 450 m and 575 m. Although the EMT sampled to 1000 m during the day, it caught no adults, suggesting that adults inhabit depths below 1000 m during this time. This is also indicated by the IKMT data. Juveniles and subadults were taken below 700 m during the day and as shallow as 200 m at night in EMT and other open-net samples. Both the discrete-depth data (Table 155) and open-net data indicate that larger specimens tend to occupy greater depths both day and night.

NIGHT:DAY CATCH RATIOS.—The ratios of night to day discrete-depth captures, using interpolation for unsampled depth intervals, were 1.2:1 in winter, 1.6:1 in late spring, and 3.7:1 in late summer (Table 156). These data suggest daytime avoidance, but the numbers of specimens involved, especially in late summer, are so small that such a conclusion is uncertain. The higher night ratio is attributable mainly to juveniles in winter and late summer, and to postlarvae in late spring. The day and night vertical ranges of juveniles were similar (250–300 m breadth) in winter and late spring, no compression of range at night being indicated (no juveniles were taken in discrete-depth samples during the day in late summer).

North Atlantic: between 45° and 10°N, including 8 specimens recorded within 28° and 14°N and 27° and 16° W in the eastern Atlantic and 2 records (one dubious) from further south in equatorial eastern Atlantic

Found at depths of 500- 1000 m.

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