Bigeye Sand Tiger

fieldmarks: A large, bulky shark with a long bulbously conical snout, eyes very large without nictitating eyelids, mouth long and extending behind eyes, teeth moderately large with prominent narrow cusps and a single pair of lateral cusplets, upper anterior teeth separated from lateral teeth by one or two rows of small intermediate teeth, anal fin and second dorsal fin smaller than first dorsal fin but broad-based, first dorsal fin on back and closer to pectoral fins than to pelvic fins, upper precaudal pit present but lateral keels absent from caudal peduncle, caudal fin asymmetrical but with a strong ventral lobe, colour uniform blackish, dark chocolate brown or reddish brown, without spots, first dorsal fin with a light apical blotch. One row (occasionally two rows) of small intermediate teeth between upper anterior and lateral tooth rows; a pair of rows or a single row of upper symphysial teeth present, but sometimes absent; usually 2 to 4 pairs of lower symphysial tooth rows present; tooth rows 34 to 43/37 to 46 (71 to 83 total); root lobes moderately arched and broad; anterolateral teeth with a single pair of lateral cusplets. Pectoral fin rounded. First dorsal-fin apex broadly rounded in adult. Anal fin with height 2.4 to 4.5% of total length. Anal fin with straight posterior margin. Caudal fin with ventral caudal lobe hardly developed. Background colour of surface black, chocolate brown or dark reddish brown dorsally and ventrally, without dark spots on sides of body; fins black, first dorsal fin often with a white blotch at tip.

Possibly circumglobal in all warm seas but as presently known sporadically distributed with very few records in the Atlantic and Central Pacific.Western North Atlantic: USA (Texas, Gulf of Mexico). Central Atlantic off Mid-Atlantic Ridge just north of the Equator.Western South Atlantic: Southern Brazil. Eastern North Atlantic: Madeira. ?Western Indian Ocean: possibly Seychelles. Pacific: South of Hawaiian Islands, USA; off Marshall Islands, possibly South China Sea.

Maximum at least 3.6 m; males possibly adolescent at 217 cm, three males adult at 326 to 342 cm long; a female immature at 321 cm and another adult at about 326 cm.

Apparently an inhabitant of the continental and insular slopes near the bottom.At 600 to 1 000 or more metres and well off it near the surface at 100m in water 640m deep, and in the epipelagic and mesopelagic zone of the open ocean at 60 to 450 m in water 4 500 to 5 300 m deep. Its uniform dark coloration, similar to many deepwater oceanic teleosts, suggests a mesopelagic rather than epipelagic habitat, and it could be primarily an oceanic shark rather than a primarily slope-dwelling epibenthic species. This is a poorly known deepwater shark.One was caught at night near the Marshall Islands at 75 m with a longline set over water between 4 500 and 5 300 m deep, suggesting that it may migrate vertically to the epipelagic zone at night and descend in the daytime but this cannot be confirmed at present. It may also be migratory and seasonal in distribution, as Brazilian catches were made only during the springtime. Reproduction unknown. Feeding habits little known; one specimen had squid beaks and fish otoliths in its stomach.One caught near Hawaii writhed and snapped vigorously when captured.

Incidental and apparently rare bycatch of pelagic longliners but little-utilized. The holotype was taken on a vertical longline set by fishermen for black scabbardfish (Aphanopus carbo). Presumably taken occasionally by deepwater fisheries with line and net gear, including pelagic gill nets, purse seines and deep-set longlines. It may live mostly below the depths normally fished by horizontal pelagic longlines and purse seines, and is possibly too large to be a regular bottom or pelagic trawl catch. Conservation Status : Conservation status unknown.