Atlantic Silver Hatchetfish

View data on Catalog of Fishes here.

Dorsal-fin rays 9; anal-fin rays 12; pectoral-fin rays 10–11; total gill rakers 15–17; vertebrae 34–36. Large species, often exceeding 70 mm SL; body very deep, depth at end of dorsal less than 1.4 into SL: dorsal spine quite high, its height about equal to its length; post-temporal spines present; dorsal surface of post-temporal with distinct serrations: postabdominal spines well developed, the posterior much larger than anterior; ventral keel extends well below body margin near postabdominal spines; preopercle spines short, both pointing ventrally; jaws large, teeth long, recurved, with two enlarged canines in lower jaw; spines present below and in front of subcaudal photophores; gill rakers medium to short, with dentate inner surfaces; pigment diffuse on trunk, no marked pigment on midline, pigment concentration above subcaudals present, pigmentless bar anterior to caudal peduncle in young.

Supra-abdominal, preanal, anal, and subcaudal photophores not in a continuous straight line; subcaudal photophore group in a single glandular cluster, no appreciable gap between each photophore; two separate hypural elements in lower caudal lobe. Two separate postabdominal spines; anal subcaudal gap fewer than 2.0 times anal-preanal gap; dorsal-fin rays 9. Posterior postabdominal spine directed posterioventrally and markedly larger than the anterior; anterior margin of posteriormost abdominal keel scale slants markedly forward; standard length fewer than 3.4 times body depth; pair of enlarged canine teeth present in lower jaw; subcaudal spines present.

Taken in the Caribbean and Gulf of Mexico; in the North Atlantic to about 40°N and 35°W; occurs in the northeastern Atlantic south of about 35°N along the North African coast associated islands; essentially absent from the tropical Atlantic; small to moderate catches in the southwestern Atlantic represent this species; taken in the central Indian Ocean from about 10°S to 40°S reported off the eastern South African coast; a few records scattered along the western Pacific from north of New Guinae to Japan in the Pacific; a number of moderate catches indicate its presence in the north central Pacific; also off eastern Australia, Chile.

Occurs 200–600 m by day with the greatest concentrations from 350-450 m; marked diurnal movement with major concentrations at 80–200 m at night.

Baird RC. 1971. The Systematics, Distribution, and Zoogeography of the Marine Hatchetfishes (family Sternoptychidae). Bulletin of the Museum of Comparative Zooology 142(1):1–128.

Baird RC. 1971. The Systematics, Distribution, and Zoogeography of the Marine Hatchetfishes (family Sternoptychidae). Bulletin of the Museum of Comparative Zooology 142(1):1–128.

Often exceeding 70 mm SL.

Azores, Portugal, eastern Atlantic.

Holotype: MNHN 0000-1817.

An oceanic and mesopelagic species concentrated at 300-600 m by day and 100-300 by night (Refs. 4462, 4739). A selective dusk-time feeder mainly on conchoecid ostracods, to lesser extent on copepods, decapod larvae, fish larvae, etc (Ref. 4739). Adult photophore developing at about 15 mm SL (Ref. 4739).

Deep body, lower opercular spine straight downward and curved outward. Upper opercular spine short, pointing outward (Ref. 37473).

Dorsal spines (total): 0; Dorsal soft rays (total): 9; Analspines: 0; Analsoft rays: 12

An oceanic and mesopelagic species concentrated at 300-600 m by day and 100-300 by night (Refs. 4462, 4739). A selective dusk-time feeder mainly on conchoecid ostracods, to lesser extent on copepods, decapod larvae, fish larvae, etc (Ref. 4739). Adult photophore developing at about 15 mm SL (Ref. 4739). Also Ref. 58302.

fisheries: of no interest

Argyropelecus aculeatus

Argyropelecus aculeatus is broadly distributed in the Atlantic, Pacific, and Indian oceans. It is particularly abundant in the Caribbean Sea, the Gulf of Mexico, the western North Atlantic, and the eastern North Atlantic along the North African coast (Baird, 1971). These areas of abundance correspond to the Gulf of Mexico, North Atlantic subtropical, and Mauritanian Upwelling faunal regions proposed by Backus et al. (1977).

This is a large sternoptychid, ranging from 6–83 mm SL in the Ocean Acre area. Our largest specimens are among the largest recorded. Argyropelecus aculeatus was the third most abundant sternoptychid in the Ocean Acre area in all seasons (Table 5). A total of 857 specimens was captured in the 14 cruises; 420 were taken during the seasonally paired cruises, including 246 in discrete-depth samples, with 207 of these from noncrepuscular tows (Table 4).

DEVELOPMENTAL STAGES.—Sex and/or developmental stage were determined for 841 specimens of A. aculeatus. Postlarvae were 6–11 mm (mean = 7.5 mm) and juveniles 7–21 mm (mean =11.4 mm). It was not possible to determine sex in these two stages. Subadult females were 14–43 mm (mean = 20.5 mm) and adult females 52–75 mm (mean = 60.1 mm). As with other sternoptychid species, males were difficult to stage due to gradual and subtle changes in the testes with maturation. On the basis of microscopic examination and sizes of subadult and adult females, an arbitrary demarcation between subadult and adult males was made between 35 and 36 mm SL. On this basis, subadult males were 14–35 mm (mean = 22.3 mm) and adults from 36–60 mm (mean = 48.7 mm). Although the mean length of all males from the seasonally paired cruises (30.5 mm) was greater than the mean length of all females (25.1 mm), the largest females were about 20 mm longer than the largest males. This suggests a sexual dimorphism, with some females growing to a larger size.

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—The reproductive cycle and seasonal abundance of subadults and adults were difficult to estimate due to the few large specimens taken with the IKMT. On two late summer cruises (7 and 12), much larger Engel trawls were employed. While these nets effectively sampled larger specimens, the seasonal coverage was limited. Despite this limitation, a proposed reproductive cycle can be formulated based upon the seasonal abundance of the early life-history stages.

The presence of some postlarvae and ripe adults in all seasons (Table 14) indicates that A. aculeatus breeds continuously throughout the year. An extended peak in spawning from June or July through late fall is indicated by the relative abundance of small individuals in late summer and winter. This species has at least a two-year life cycle, reaching approximately 20–40 mm SL at the end of the first year. At this time a small portion of the year class may become sexually mature. This is indicated by a 34 mm female that was in breeding condition in August. The majority of specimens, however, probably do not reach sexual maturity until the end of their second year, when most spawn and die. Based on IKMT data, overall abundance was highest in winter, intermediate in late summer, and lowest in late spring (Table 14).

In late summer postlarvae accounted for 34% of the catch and juveniles for 47%. The small size of these individuals (mean length less than 11 mm) indicates that they were spawned over the summer months. The relative abundance of these small individuals (Table 14), particularly postlarvae, clearly indicates that spawning is heavy at this time. Subadults were also relatively abundant, accounting for 12% of the IKMT catch and 17% of the EMT catch. In the IKMT samples subadults averaged 22.4 mm, while in the EMT samples the average length was 39 mm. In the EMT samples, 7 females (57–71 mm) were classified as subadults based on the condition of their ovaries. Their relatively large size, however, suggests that these were actually adults in postspawning condition that were approaching a second spawning. It is postulated that subadults captured in late summer were about one year old, having been spawned the preceeding summer or fall. Presumably these would constitute the major portion of the breeding population the following year. Adults accounted for 7% of the IKMT catch and 74% of the EMT catch in late summer. Mean lengths using these two types of gear were 59.3 and 56.0 mm, respectively. The relative abundance of ripe adults captured at this time indicates that spawning is heavy and that it will probably continue for some period of time.

In winter, seasonal abundance reached its highest level (Table 14). The great majority of specimens at this time were juveniles (81%), with a mean length of 10.9 mm. The abundance of these small individuals is a clear indication that spawning had been heavy during the preceding fall months. Subadults were at their lowest seasonal abundance, accounting for only 5% of the catch. Based on IKMT catches, adults were at their peak seasonal abundance. Their presence, along with some postlarvae (Table 14), indicates that some spawning is occurring at this time.

Seasonal abundance was lowest in late spring (Table 14). At this time the catch was dominated by juveniles (75%) and subadults (19%), but the presence of some postlarvae and adults indicates that some spawning was occurring. The juveniles averaged 12.5 mm and probably were produced during the late fall or winter months near the end of the extended peak spawning season. Subadults averaged 22.2 mm. These probably were spawned the preceding summer, and would have matured the following year.

To summarize, the life-history of A. aculeatus appears to last for about two years. The majority of adults, which are probably two years old, spawn in the summer or fall months. Following spawning most of these individuals die, but some may live to spawn a second time. Postlarvae produced during these months develop into juveniles by the following winter, and into subadults by the following late summer or fall. At this time some may reproduce, but most spend a second year as subadults, maturing to adults and spawning near the end of their second year.

SEX RATIOS.—No significant difference between total numbers of males and females was indicated at any of the three seasons (Table 15). In actual numbers, more males than females were captured in winter (14:5) and late spring (34:27), and more females than males in late summer (20:10). The only significant difference in sex ratio was seen among late summer subadults, where females outnumbered males 17 to 4. Because of the small number of specimens considered here, little credence is given to this significant difference; sex ratios probably are not different than 1:1.

VERTICAL DISTRIBUTION.—In the seasonally paired cruises, A. aculeatus was caught from <50–1100 m during the day and from 51–1250 m at night (Table 16). Of the 92 discrete-depth specimens captured during the day in these cruises, 79 (86%) were caught from 301–500 m. Of the remaining 13, only one, a winter juvenile, was taken shallower than 301 m. This specimen is considered a contaminant from the previous tow. Ten of the remaining 12 specimens were taken from 501–850 m. These included late spring juveniles and subadults and late summer postlarvae, juveniles, subadults, and adults. These are thought to represent some scattering of the species toward greater depths. Two specimens, a juvenile and an adult, were caught at 1001–1050 m in winter. These were considered contaminants, since in each case the previous tow had fished at the preferred depths of A. aculeatus.

Of the 113 discrete-depth specimens captured at night, 103 (91%) were caught from 201–500 m (Table 16). Nine of the remaining 10 specimens were taken shallower than 200 m. These specimens, which included winter juveniles and subadults and a late summer adult, may represent some upward straying of A. aculeatus at night. The remaining individual, a late spring juvenile taken at 1201–1250 m, is certainly a contaminant.

The vertical distribution of A. aculeatus in the Ocean Acre area is similar to other localities. Badcock (1970) indicates that near the Canary Islands the species is concentrated from 410–450 m during the day and 350–410 m at night. Baird (1971), reporting on a variety of locations, states that daytime depths are from 200–550 m with a concentration from 350–450 m, and that the species is concentrated from 80–200 m at night. Similarly, Badcock and Merrett (1976), working in the eastern North Atlantic, found that daytime depths were 300–500 m, and that nighttime depths were 100–500 m, with peak concentrations at 200–300 m.

Since all life-history stages occupy the same range of daytime depths in all seasons (Table 16), no daytime stage stratification is indicated. In late summer, when postlarvae were most abundant, they were found from 301–700 m, but were concentrated from 351–500 m. The few postlarvae caught during the day in winter and late spring were taken within the same depth range. In winter, when juveniles were most abundant, they were found from 301–450 m and were relatively abundant from 301–400 m. Although the range of daytime depths occupied by juveniles was broader in late spring (301–700 m) and late summer (301–850 m), the depths of abundance were similar to those of winter. The few subadults caught during the day were taken from 351–450 m in winter, 401–700 m in late spring, and 451–700 m in late summer. Too few specimens were taken to accurately describe their preferred depths. This is also true of adults, which ranged from 351–450 m in both winter and late spring, and from 351–700 m in late summer.

Although the nighttime depth distributions of the different life-history stages overlap broadly in all seasons, there is an indication of some stage stratification, with older and larger individuals occurring slightly shallower. Late summer postlarvae were found from 301–500 m at night, with most from 351–400 m. The few caught in winter were taken from 351–400 m. Juveniles tended to occupy a shallower nighttime range of depths. In winter they ranged from 151–500 m, were very abundant from 301–350 m, and were quite abundant from 251–300 m. In late spring juveniles were captured from 251–500 m and were abundant from 251–400 m. A somewhat shallower range (201–500 m) was occupied in late summer, with the greatest catch per unit effort from 301–450 m. Subadults ranged from 251–350 m in late spring and from 201–350 m in late summer. In each of these seasons they were most abundant at 251–300 m. In winter, subadults were captured from 151–200 m at night. Nighttime captures of adults occurred only in late summer and winter. In late summer a single adult was taken from 51–100 m, while others were taken from 251–350 m. In winter, the range of depths for adults was 251–400 m, with most caught from 301–350 m.

All life-history stages of A. aculeatus appear to undergo a diel vertical migration (Table 16). In late summer, postlarvae occupied a wide range of depths during the day (301–700 m). The nighttime narrowing of this range to 301–500 m indicates that at least some postlarvae migrate upward at night. A similar situation is seen among juveniles in which the nighttime range of depths is typically 50–100 m shallower than the daytime range. Athough the depths of maximum abundance were similar from day to night in each season, shallower strata, which contained few or no juveniles during the day, had an abundance of juveniles at night. In winter, for example, juveniles were absent from 251–300 m during the day, but were abundant at this depth at night. Similar diel changes in other seasons (Table 16) indicate that juveniles migrate upward 50–100 m at night. The daytime depth range of subadults (approximately 351–700 m) is considerably compressed and shallower at night. In winter, they were found from 151–200 m at night, while in late spring and late summer they occupied depths from 251–300 m. It is apparent then, that subadults migrate upward at night, perhaps as much as 200–400 m. The same compression of depth range and shallower nighttime distribution is seen in adults. The paucity of specimens prohibits an accurate estimate of the magnitude of upward migration, but it is probably about 100 m, which is a shorter migration than that of the subadults.

PATCHINESS.—There is some indication that small specimens of A. aculeatus may be patchily distributed during the day. Two significant daytime CD values were found; one in winter at 301–350 m and one in late summer at 351–400 m. The winter depth interval was composed entirely of juveniles, ranging in length from 7–15 mm SL. The late summer interval contained one adult (74 mm SL), but was heavily dominated by postlarvae and juveniles 7–13 mm SL. Each of these intervals was within the preferred daytime depth distribution of this species. No patchiness was indicated at night.

NIGHT:DAY CATCH RATIOS.—The ratio of total night to day catch rates was different from 1:1 in each season (Table 17), with slightly more fish per unit effort being caught at night. This trend was reversed only in postlarvae caught in late summer, where the daytime catch rate exceeded the nighttime rate. This may have been due to these small individuals aggregating during the day. In all other life-history stages the nighttime catch rates equaled or exceeded the daytime catch rates in all seasons. The greatest differences were seen among late summer subadults and among winter and late summer adults. Since no clumping was indicated at night, these observed differences probably were due to increased net avoidance during the day. The larger differences in catch ratios among these larger individuals suggests that net avoidance may be enhanced with increased size.

分布於三大洋，包括東大西洋：葡萄牙到塞內加爾，那米比亞有記錄；西大西洋： 40 ° N-10 ° N 與 15 °S-35 °S，圭亞那外海有標本；西北大西洋：加拿大；印度洋：0 °-35 ° S；西太平洋：35 ° N-35 ° S；東南太平洋：30 °S-35 ° S。臺灣主要分布於東部、東南部、西南部及南中國海等。

一般以底拖網捕獲，不具食用經濟價值，通常做為下雜魚用。

頭與軀幹相當高，體甚側扁，尾部逐漸變細。兩頜齒細小且為錐狀犬齒。眼睛比例大。鰓孔寬大，鰓耙發達。D 9；P 6；V 9-11；A 10-13；GR 14-16；脊椎骨34-36。具一由7個背鰭上神經骨特化而成的大型背刀，背刀上棘具許多突起，且連接的薄膜背側有鋸齒狀邊緣，高度約等於寬度。腹部發光器鱗片延長形成腹稜脊，其上有小棘，黑色色素分布在發光器周圍，並且延伸佈滿第5-7個的發光器鱗片的腹緣；臀前發光器鱗片腹緣有棘；尾下發光器每個發光器上有2-3個小棘，尾下發光器前，有似發光器的部份亦有許多小棘分布。後顳骨棘1，粗短；後腹棘2，兩棘幾乎相等，左側棘往外並往前腹側延伸，右側棘往外並往後腹側延伸；前鰓蓋骨棘2。前頜骨、上頜骨、齒骨皆有向內彎之犬齒，左右前頜骨及齒骨各有一特別較大向內彎之犬齒。體表為銀色，體側黑色素分布在身體的背側邊緣、尾柄邊緣及各發光器周圍，另背刀下方有一寬圓凸黑色塊。

大洋性中層魚類，具明顯的日夜垂直迴游行為，白天位於200m~550m之間，最高密度在350~450m，夜晚在80~200m。以橈腳類、端足類、介形蟲、磷蝦和小魚等為食。

Argyropelecus aculeatus, the lovely hatchetfish or Atlantic silver hatchetfish, is a species of fish in the family Sternoptychidae. It may exceed 70 millimetres (2.8 in) standard length (SL). It lives in the mesopelagic zone of all oceans and performs diel vertical migration. A. aculeatus feeds on a large range of prey items; in the Gulf of Mexico ostracods and copepods dominated the diet of small individuals (

Feeds on ostracods, copepods, decapod larvae and fish larvae

Grand Banks to the Caribbean

An oceanic and mesopelagic species concentrated at 300-600 m by day and 100-300 m by night.

nektonic

Known from seamounts and knolls