Sternoptychidae

Family Sternoptychidae

Sternoptyx diaphana Hermann, 1781 —Diaphanous hatchetfish (Fig. 9)

One specimen of 4 cm TL was caught at a depth of 771 m. Habitat and Distribution: bathypelagic, oceanodromous at depth range 400–3,676 m, usually 500– 800 m. Mainly in tropical regions of Atlantic, Pacific and Indian oceans. Scattered records southwest of Ireland and also from Spain to Angola in the eastern Atlantic. Vulnerability: DD (IUCN), LV (FishBase).

Argyropelecus hemigymnus Cocco, 1829 —Half-naked hatchetfish

23 specimens were caught at depths between 765 and 1,460 m. Length data were available for 22 specimens ranging from 2 to 4 cm TL. Habitat and Distribution: oceanic and mesopelagic, from 100 to 4,054 m depth, mainly at 250– 650 m. Worldwide distribution in tropical and subtropical waters of all oceans. Vulnerability: LC (IUCN), LV (FishBase).

Argyropelecus olfersii (Cuvier, 1829) —No common name

5 specimens were caught at depths between 771 and 1,674 m. Length data were available for 4 specimens ranging from 9 to 11 cm TL. Habitat and Distribution: oceanic, mesopelagic with adults and juveniles at 200–800 m during daylight and from 100 (sometimes shallower) to 600 m at night. Restricted in the northeastern Atlantic Ocean between 35°N and 65°N, probably with a bipolar distribution, and in the southern Pacific Ocean between 30˚ S and 50˚S from Chile to New Zealand. Vulnerability: DD (IUCN), LV (FishBase).

Argyropelecus aculeatus Valenciennes, 1850 —Lovely hatchetfish

1 specimen of 8 cm TL was caught at a depth of 791m. Habitat and Distribution: oceanic and mesopelagic species at 100–600 m depth, concentrated at 300–600 m during daylight and 100–300 m at night. Atlantic Ocean, essentially absent from the tropical Atlantic; Pacific from north of New Guinea to Japan and off eastern Australia and Chile and central Indian Ocean from about 10°S to 40°S. Vulnerability: DD (IUCN), LMV (FishBase).

Argyropelecus gigas Norman, 1930 —Hatchetfish

124 specimens between 6–11 cm TL were caught by bottom trawl during the 1998 surveys. They were identified as A. gigas, but we consider this identification, at least in part, as dubious. The size of the specimens, which is larger in A gigas, was used in the first surveys as one important criterion to differentiate Argyropelecus species. However, in posterior surveys, we found a similar size range in A. olfersii. Habitat and Distribution: bathypelagic at depth range 300–1,000 m, usually 400– 600 m. Circumglobal, except northeastern Pacific Ocean. Vulnerability: DD (IUCN), LMV (FishBase).

Maurolicus muelleri (Gmelin, 1789) —Pearlsides

1 specimen of 5 cm TL was caught at a depth of 1,094 m. Habitat and Distribution: mesopelagic, abundant near continental shelf-slope breaks and seamounts, rare in the open ocean. Found to depths of at least 1,524 m, migrating in the water column at depths of 150–250 m during daylight and to about 50 m at night. Tropical, subtropical, sub-Arctic, and sub-Antarctic waters of the Pacific and Atlantic oceans, and the Mediterranean Sea. In the eastern Atlantic it occurs from Iceland and Norway to Senegal and also from Democratic Republic of the Congo to Namibia. Vulnerability: DD (IUCN), LV (FishBase).

Valenciennellus tripunctulatus (Esmark, 1871) —Constellationfish (Fig. 10)

1 specimen was caught at 790 m depth. Biometry and meristic: 34 mm TL, 29 mm SL. Photophores: VAV: 5; PV: 15; OA: 4; AC: 3+3+3+2+4; IP: 3+4. Habitat and Distribution: oceanic and mesopelagic, between 100 and 700 m depth, with marked stratification of size with depth. Worldwide in tropical and temperate waters. Scattered records from the eastern Atlantic, Iceland, Ireland, from Portugal to Namibia, and in the Mediterranean Sea. Vulnerability: DD (IUCN), LV (FishBase).