Poromitra capito Goode & Bean 1883

Hard, sharp head spines. Scales on body and operculum intact (Ref. 37108).

Adults found mainly below 400 - 500 meters, to 800 - 1,000 meters; juveniles as shallow as 50 - 100 meters (Ref. 51657).

Poromitra capito

This is one of the larger melamphaids, reaching 99 mm. It is limited in distribution mainly to the subtropical North Atlantic, with eastern populations reaching 50°N. In the Ocean Acre it was common in winter, but uncommon in other seasons. A total of 437 specimens was taken during all cruises. During the seasonal paired cruises 333 specimens were taken, 177 of these in discrete-depth samples: 34 during the day, 78 at night, and 65 during crepuscular periods (Table 147).

DEVELOPMENTAL STAGES.—Samples from all cruises included 121 postlarvae, 282 juveniles, 14 subadults and 20 adults. Postlarvae were 5–15 mm, juveniles 13–56 mm, subadults 51–80 mm, and adults 72–99 mm. All specimens larger than 30 mm were sexed. Adult females are larger than adult males (92–99 mm, mean 96.7 mm vs. 72–87 mm, mean 82.7 mm).

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—Poromitra capito probably has a spawning peak in November or December as manifested by the numbers of postlarvae in January and February (Table 157). During other parts of the year postlarvae were rare or absent in our samples. Juveniles also were abundant in January and February, and they predominated at all other times. This may be due to the scarcity of larger sizes or the ability of large specimens to avoid the IKMT. Engel trawls caught 18 of the 34 subadults and adults.

The average size of juveniles increases progressively from 19.4 mm in January to 45.1 mm in September (Table 157). By the end of their first year they probably attain a length of about 50 mm. They appear to reach a length of about 70 mm by the end of their second year, and in their third year they become adults and spawn. There is no evidence to suggest that they live beyond three years.

P. capito was abundant in winter, but uncommon in late spring and late summer (Table 158). Postlarvae and juveniles constitute the vast majority of the catch in discrete-depth samples, and these stages are at peak abundance in winter. The radical decline in catch rate for the other two seasons must be the result of juveniles attaining a size and development that allowed them to avoid the IKMT. The large winter catch in discrete-depth samples was composed almost entirely of specimens smaller than 30 mm SL, and it would seem that avoidance ability becomes increasingly effective at sizes larger than 30 mm.

VERTICAL DISTRIBUTION.—Discrete-depth noncrepuscular sampling by the paired cruises resulted in the capture of 112 specimens: 90 in winter, 12 in late spring, and 10 in late summer. All of the winter specimens were postlarvae and juveniles up to 31 mm SL. During June and September mostly larger sizes (over 30 mm) were taken, but not in abundance. Consequently the vertical distribution picture based on discrete-depth samples is limited mainly to postlarvae and juveniles (Table 159).

In winter 4 postlarvae were caught during the day between 50–150 m and 2 metamorphosing postlarvae at 501 750 m. At night 26 postlarvae were caught between 101–200 m and 2 metamorphosing postlarvae at 551–600 m. Postlarvae inhabiting the 50–200 m stratum do not appear to migrate. Transitional postlarvae and small juveniles (up to 17 mm SL) occur in deeper water, 551–1050 m, where metamorphosis apparently occurs.

Some small juveniles (16–19 mm) were taken at 301–450 m, indicating that some individuals begin to undertake vertical migrations at this size. Juveniles larger than about 20 mm and subadults show a definite vertical migration. They occurred between about 751 m and 1050 or 1100 m during the day (perhaps to 1550 m) and were taken at 251–550 m at night.

The only adult taken in a discrete-depth sample was from 951–1000 m during the day. In open nets, mostly EMT samples in September, adults were caught only below 1000 m during the day, while at night they were taken as shallow as 750 m.

Stage stratification is apparent in winter (Table 159). During daytime, small postlarvae were taken in the upper 150 m, larger ones at 501–800 m; juveniles occurred between 751–1000 m. At night, postlarvae were taken at 101–300 m (some of these apparently were new migrators; a nonmigrator was at 551–600 m); juveniles occurred at 151–450 m, nonmigrators below 550 m.

Size stratification is indicated at other seasons, and the few subadults and adults suggest stage stratification as well. During the day in late spring (Table 159), juveniles occurred at 701–1050 m, subadults and adults only at 901–1050 m. The largest individuals were taken at the latter depth. During the day in late summer, both specimens taken at 901–950 m were smaller than the two taken at 1001–1050 m. At night, size increases with depth in late spring. The late summer data are inconclusive.

The extent of vertical migration appears to decrease with increasing size of fish. Small juveniles migrate from about 700–850 m to 150–250 m (Table 159, winter), larger juveniles from 750–1050 m to 250–400 m (Table 159, late spring and late summer). Subadults migrate from about 951–1000 m only to 501–550 m (Table 159, late spring). Adults, as already indicated, were not taken above 750 m at night in open nets (mostly EMT's).

PATCHINESS.—Patchiness of distribution was indicated only in winter, at which time clumping was shown at 801–850 m during the day and at 101–150 m and 551–600 m at night. The largest specimen at any of these depth intervals was 17 mm SL; thus it appears that, at sizes larger than 17 mm, the distribution is not characterized by patchiness.

NIGHT:DAY CATCH RATIOS.—The ratios of night to day discrete-depth captures, using interpolation in unsampled depth intervals, were 1.3:1 in winter, 0.6:1 in late spring, and 0.5:1 in late summer (Table 160). Postlarvae appear to be almost solely responsible for the winter ratio, at which time those postlarvae at shallow depths appear to avoid the net during daytime. The winter ratio for shallow postlarvae alone is 2.4:1, that for all postlarvae 1.6:1, and that for juveniles 1.2:1. When catch rates are considered without interpolation at unsampled intervals, the winter juveniles (up to 31 mm SL) also show a pronounced night bias (2.6:1). Possibly these smaller juveniles also avoid the net.

It seems highly doubtful that the ratios for late spring and late summer are meaningful, because the actual samples consisted of only 12 and 10 specimens, respectively. Without interpolation, the ratios of the catch rates were 0.8:1 and 1:1, respectively. Furthermore, the probability that all larger sizes avoid the net at all times already has been suggested.

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Poromitra capito Poromitra generoko animalia da. Arrainen barruko Melamphaidae familian sailkatzen da.

大頭犀孔鲷，为輻鰭魚綱奇鯛目大鱗鲷科的其中一種。分布於北大西洋及南太平洋海域，屬深海魚類，棲息深度400-1000公尺，體長可達10公分。

North Atlantic off Flemish Cap and off Bermuda

Found at depths of 600- 1000 m.

nektonic