Benthodesmus tenuis

Body extremely elongated. Depth 25 to 31 in st andard length. Head 7.3 to 7.8 in stan- dard length, upper profile smooth, gently rising from tip of snout to dorsal-fin origin, interorbital space and nape flattened, without sagittal crest. Eye 5.9 to 7.5 in st andard length, situated near dorsal contour. Dorsal fin with 40 to 42 spines and 83 to 87 soft rays (tot ally 125 to 129 fin elements), partly divided by deep notch, base of spinous part about twice shorter than soft part. Anal fin with 2 free close-set spines detached from the rest of fin, the second spine delicate, cardi form, and 72 to 75 soft rays, all of them external. Caudal fin forked. Pelvic fins diminutive, inserted well be fore or below pectoral-fin base. Vertebrae 129 to 131. Col- our: body silvery, jaws and opercle blackish.

Body shape: eel-like. Body silvery, jaws and opercle blackish. The inside of the mouth and gill cavities black. Striking features: striking shape of body.

In the western Atlantic off Cape Hatteras, the Gulf of Mexico, off Suriname and sou thern Brazil. Also reported from the eastern Atlantic, Indian, and Pacific oceans. Note: It is possible that B. tenuis may represent a group of closely related spicies. Meristics and proportions given in this account based only on the western Atlantic specimens. Perci formes: Scombroidei: Trichiuridae 1833 Evoxymetopon taeniatus Gill, 1863 Frequent synonyms / misidentifications: None / None. FAO names: En - Channel scabbardfish; Fr - Poisson sabre canal; Sp - Tajalí de canal. Diagnostic characters: Body elongate and remarkably compressed. Depth 11.5 to 12.5 in st andard length. Head 7.5 to 8.0 in st andard length, with upper profile convex, steeply rising from tip of snout to dorsal-fin origin. Interorbital space and nape convex, with sagittal crest strongly elevated. Eye about 5.0 to 5.5 in head, situated later ally. Dorsal fin with a few weak anterior spines hardly differing from soft rays (tot ally 81 to 88 fin elements). Anal fin with a dimunitive, free scale-like spine, and with a few external soft rays, confined to posterior portion of fin. Caudal fin sm all, forked. Pelvic fin reduced to a scale-like spine. Colour: body silvery white with slight red brownish tint on dorsal part; several longitudinal pale yellow stripes on body; anterior part of dorsal fin blackish. Size: Maximum 2 m st andard length. Habitat, biology, and fisheries: Benthopelagic on continental slope, and sometimes on shelf. Very r are. Of no importance to fisheries. Distri bution: In the western Atlantic Ocean known from off Bermuda and Bahamas, the Ca- ribbean Sea, and off sou thern Brazil. Reported also from the western North Pacific. Lepidopus altifrons Parin and Collette, 1993 Frequent synonyms / misidentifications: None / Evoxymetopon taeniatus Gill, 1863. FAO names: En - Crested scabbardfish; Fr - Poisson sabre crénelé; Sp - Pez c into encrestado. Diagnostic characters: Body elongate and compressed. Depth 10.9 to 13.0 in st andard length. Head 5.9 to 6.5 in st andard length, with upper profile almost straight, gently rising from snout to dorsal-fin origin. Interorbital space and nape convex, with sagittal crest elevated. Eye 4.9 to 5.1 in head, situated later ally. Dorsal fin with a few weak anterior spines hardly differing from soft rays (tot ally 90 to 96 fin-elements). Anal fin with 2 close-set spines well-detached from rest of fin, the second spine flat, triangular, and with 52 to 58 soft rays. Caudal fin forked. Pelvic fins reduced, scale-like. Colour: body silvery to brownish, darker along lateral line. Size: Maximum about 70 cm st andard length. Habitat, biology, and fisheries: Benthopelagic from 200 to 500 m; juveniles pelagic. Of no impor- tance to fisheries. Distri bution: The western Atlantic Ocean from 47°N off the Scotian Shelf to 35°S off sou thern Brazil, including the Gulf of Mexico and the Carib- bean Sea. Perci formes: Scombroidei: Trichiuridae 1835 Trichiurus lepturus Linnaeus, 1758 LHT Frequent synonyms: misidentifications: None / None. FAO names: En - Largehead hairtail (AFS: Atlantic cutlassfish); Fr - Poisson sabre commun; Sp - Pez sable. Diagnostic characters: Body elongate and strongly compressed, ribbon-like, tapering to a point (tip of- ten broken). Depth about 15 to 18 in total length. Head about 6 to 8 in total length, with upper profile slightly concave, gently rising from snout to dorsal-fin origin. Interorbital space and nape convex, with sagittal crest el- evated. Eye 5 to 7 in head, nearly touching upper profile. Dorsal fin moderately high, very long, with 3 spines and 130 to 135 rays, not divided by notch. Anal fin reduced to about 100 to 105 minute spinules, usu ally em- bedded in skin or slightly breaking through. No caudal fin. Pectoral fins directed upward, with 1 spine and 11 to 13 rays. Pelvic fins absent. Colour: fresh specimens steel blue with silvery reflection, pectoral fins semitransp arent, o ther fins sometimes tinged with pale yellow; the colour becomes uni form silvery grey after death. Size: Maximum 1.2 m total length, common 50 to 100 cm. Habitat, biology, and fisheries: Benthopelagic on continental shelf to 100 m depth, usu ally in sh allow coastal waters over muddy bottoms, occasion ally at surface at night. Young and immature specimens feed on crusta- ceans and sm all fishes; adults more piscivorous. Matures at about 2 years. Eggs pelagic. Com- mercial species. Caught mainly with bottom trawls and beach seines, also trammel nets, purse seines, and h andlines. Marketed fresh, frozen, and salted. Distri bution: Throughout tropical and temper- ate waters of the world. Moderately abundant in the Gulf of Mexico and the Caribbean Sea, along the Atlantic coast extending from nor thern Vir- ginia (exception ally Cape Cod) to nor thern Ar- gentina. SCOMBRIDAE Mackerels and tunas by B. B. Collette, National Marine Fisheries Service, National Museum of Natural History, Washington D. C., USA Diagnostic characters: Medium to large-sized (to 3 m) with elongate and fusi form body, moderately com- pressed in some genera. Snout pointed; adipose eyelid sometimes present (Scomber); premaxillae beak-like, free from nasal bones which are separated by ethmoid bone; mouth moderately large; teeth in jaws strong, moderate, or weak; no true canines; palate and tongue may have teeth. Two dorsal fins; anterior fin usu- ally short and separated from posterior fin; 5 to 10 finlets present behind dorsal and anal fins; caudal fin deeply forked with supporting caudal rays completely c overing hypural plate; pectoral fins placed high; pelvic fins moderate or sm all. At least 2 sm all keels on each side of caudal peduncle, a larger keel in between in many species. Lateral line simple. Vertebrae 31 to 66. Body ei ther uni formly c overed with sm all to moderate scales (e.g. Scomber, Scomberomorus) or a corselet developed (area behind head and around pectoral fins c overed with moderately large, thick scales) and rest of body naked (Auxis, Euthynnus, Katsuwonus), or cov- ered with sm all scales (Thunnus). Colour: Scomber species are usu ally bluish or greenish above with a pat- tern of wavy b ands on upper sides and silvery below; Scomberomorus and Acanthocybium are blue-grey above and silvery below with dark vertical bars or spots on sides. Sarda has 5 to 11 stripes on back; Euthynnus has a striped pattern on back and several dark spots between pectoral and pelvic fins; Katsuwonus has 4 to 6 conspicuous longitudinal stripes on belly; Auxis and Thunnus are deep blue-black above; most species of Thunnus have bright yellow finlets with black borders. spinous 1st 2nd dorsal fin dorsal fin (soft rays) adipose dorsal eyelid finlets caudal keels sometimes present anal finlets corselet Habitat, biology, and fisheries: A diverse group of pelagic fishes. Some sm aller species inhabit coastal wa- ters while the larger ones, especi ally Thunnus maccoyii, T. obesus, T. alalunga, and T. tonggol carry out wide, transoceanic migrations. All scombrids are excellent foodfishes and may of them are of signifi cant importance in coastal pelagic or oceanic commercial and sports fisheries. Perci formes: Scombroidei: Scombridae 1837 Similar families occurring in the area Carangidae: dorsal-fin spines 3 to 8 (9 to 27 in Scombridae); scutes frequently developed along posterior part of lateral line and usu ally no well-developed finlets are present (except in Oligoplites with a series of dorsal and anal finlets; Elagatis and Decapterus with 1 dorsal and 1 anal finlet); carangids also have 2 detached spines in front of anal fin (except in Elagatis). Gempylidae: back usu ally brown, r arely blue-brown; never distinct markings on body; no keels on caudal peduncle, except in Lepidocybium. no distinct markings no well-developed finlets scutes Carangidae Gempylidae (Lepidocybium) Key to the species of Scombridae occurring in the area 1a. Two sm all keels on ei ther side of caudal peduncle (Fig. 1a); 5 dorsal and 5 anal finlets; adi- pose eyelids c over front and rear of eye . . . . . . . . . . . . . . . . . . . . . Scomber colias 1b. Two sm all keels and a large median keel between them on ei ther side of caudal peduncle (Fig. 1b); 7 to 10 dorsal and 7 to 10 anal finlets; adipose eyelids absent . . . . . . . . . . . .(cid:1) 2 2 sm all keels 2 sm all keels large median keel a) Scomber b) Auxis Fig. 1 caudal keels 2a. Teeth in jaws strong, compressed, almost triangular or knife-like; corselet of scales ob- scure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .(cid:1) 3 2b. Teeth in jaws slender, conical, hardly compressed; corselet of scales well developed . . . . . .(cid:1) 7 3a. Snout as long as rest of head (Fig. 2a); no gill rakers; 23 to 27 spines in first dorsal fin; pos- terior end of maxilla concealed under preorbital bone. . . . . . . . . . . Acanthocybium sol andri 3b. Snout much shorter than rest of head (Fig. 2b); at least 6 gill rakers on first gill arch; 14 to 19 spines in first dorsal fin; posterior end of maxilla exposed . . . . . . . . . .(Scomberomorus) (cid:1) 4 a) Acanthocybium b) Scomberomorus Fig. 2 lateral view of head 4a. Lateral line with a deep dip below second dorsal fin; total gill rakers on first arch 7 to 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scomberomorus cav alla 4b. Lateral line straight or descending gradu ally, without a deep dip below second dorsal fin; total gill rakers on first arch 12 to 18 . . . . . . . . . . . . . . . . . . . . . . . . . . .(cid:1) 5 5a. One long stripe on sides with spots or interrupted lines above and below the stripe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scomberomorus regalis 5b. Sides with sm all round spots, orange in life, without any lines or stripes . . . . . . . . . . . .(cid:1) 6 6a. Second dorsal-fin rays 17 to 20, usu ally 18 or more; total vertebrae 51 to 53 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scomberomorus maculatus 6b. Second dorsal-fin rays 15 to 19, usu ally 18 or fewer; total vertebrae 46 to 49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scomberomorus brasiliensis 7a. Upper surface of tongue without cartilaginous lon- gitudinal ridges (Fig. 3a); 5 no ridges to 10 narrow, longitudinal stripes on upper part of body; 20 to 23 spines in first dorsal fin . . . . . . Sarda sarda 2 ridges on tongue 7b. Upper surface of tongue with 2 longitudinal ridges (Fig. 3b); 9 to 16 spines in a) Sarda sarda b) Katsuwonus pelamis first dorsal fin . . . . . . . . . .(cid:1) 8 Fig. 3 anterior view of head 8a. First and second dorsal fins widely separated, the space between them equal to the length of first dorsal-fin base (Fig. 4); 9 to 11 spines in first dorsal fin; interpelvic process single and long, at least as long as longest pelvic fin ray (Fig. 6) . . . . . . . . . . . . . .(Auxis) (cid:1) 9 8b. First and second dorsal fins b arely separated, at most by eye diameter; 12 to 16 spines in first dorsal fin (Fig. 5); interpelvic process bifid and short, much shorter than pelvic fin rays (Fig. 7). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .(cid:1) 10 dorsal fins widely dorsal fins b arely separated separated Fig. 4 Auxis Fig. 5 Katsuwonus pelamis pelvic fin pelvic fin single, large bifid, short Fig. 6 interpelvic process Fig. 7 interpelvic process Perci formes: Scombroidei: Scombridae 1839 9a. Posterior extension of corselet narrow, only 1 to 5 scales wide under origin of second dor- sal fin (Fig. 8); pectoral fin extends posteriorly beyond a vertical with the anterior margin of the dorsal scaleless area . . . . . . . . . . . . . . . . . . . . . . . . Auxis thazard thazard 9b. Posterior extension of corselet much wider, usu ally 10 to 15 scales wide under origin of second dorsal fin (Fig. 9); pectoral fin does not extend posteriorly as far as a vertical with anterior margin of dorsal scaleless area. . . . . . . . . . . . . . . . . . . Auxis rochei rochei corselet narrow, 1-5 scales wide corselet wide, 10-15 scales wide under 2nd dorsal-fin origin under 2nd dorsal-fin origin Fig. 8 Auxis thazard thazard Fig. 9 Auxis rochei rochei 10a. Three to 5 prominent dark longitudinal stripes on belly (Fig. 5); gill rakers 53 to 63 on first arch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Katsuwonus pelamis 10b. No dark longitudinal stripes on belly; gill rakers 19 to 45 on first arch. . . . . . . . . . . . .(cid:1) 11 11a. Body naked behind corselet of enlarged and thickened scales; black spots usu ally present between pectoral- and pelvic-fin bases (Fig. 10); 26 or 27 pectoral-fin rays . . Euthynnus alletteratus 11b. Body c overed with very sm all scales behind corselet; no black spots on body (Fig. 11); 30 to 36 pectoral-fin rays . . . . . . . . . . . . . . . . . . . . . . . . . . . .(Thunnus) (cid:1) 12 spots no black spots Fig. 10 Euthynnus alletteratus Fig. 11 Thunnus thynnus 12a. Ventral surface of liver c overed with prominent striations; central lobe of liver equal to or longer than left and right lobes (Fig. 12) . . . . . . . . . . . . . . . . . . . . . . . . .(cid:1) 13 12b. Ventral surface of liver without striations; right lobe of liver much longer than left or central lobes (Fig. 13) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .(cid:1) 14 Fig. 12 Thunnus alalunga (liver) Fig. 13 Thunnus albac ares (liver) 13a. Total gill rakers on first arch 31 to 43; pectoral fins short, less than 80% of head length, 16.8 to 21.7% of fork length (Fig. 11) . . . . . . . . . . . . . . . . . . . . . . . Thunnus thynnus 13b. Total gill rakers on first arch 23 to 31; pectoral fins moderate to long, more than 80% of head length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .(cid:1) 15 14a. Total gill rakers on first arch 26 to 34, usu ally 27 or more; second dorsal and anal fins of larger individuals (120 cm fork length and longer) elongate, more than 20% of fork length (Fig. 14) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thunnus albac ares 14b. Total gill rakers on first arch 19 to 28, usu ally 26 or fewer; second dorsal and anal fins never greatly elongate, less than 20% of fork length at all sizes (Fig. 15) . . . . . . . Thunnus atlanticus elongate fin rays Fig. 14 Thunnus albac ares Fig. 15 Thunnus atlanticus 15a. Caudal fin with a narrow white posterior border (Fig. 16); pectoral fins very long, reaching well past end of second dorsal-fin base; greatest body depth at or slightly be fore level of second dorsal fin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thunnus alalunga 15b. Caudal fin without white posterior border (Fig. 17); pectoral fins short or moderate in length, reaching end of second dorsal-fin base (except in sm all individuals); greatest body depth about middle of body, near middle of first dorsal fin. . . . . . . . . . . . . Thunnus obesus white border Fig. 16 Thunnus alalunga Fig. 17 Thunnus obesus Perci formes: Scombroidei: Scombridae 1841 List of spec(cid:1)ies occurring in the area T(cid:1)he symbol is given when species accounts are included. (cid:1) Acanthocybium sol andri (Cuvier, 1832). (cid:1) Auxis rochei rochei (Risso, 1810). (cid:1) Auxis thazard thazard (Lacepède, 1800). (cid:1) Euthynnus alletteratus (Rafinesque, 1810). (cid:1) Katsuwonus pelamis (Linnaeus, 1758). (cid:1) Sarda sarda (Bloch, 1793). (cid:1) Scomber colias Gmelin, 1789. (cid:1) Scomberomorus brasiliensis Collette, Russo and Zavala-Camin, 1978. (cid:1) Scomberomorus cav alla (Cuvier, 1829). (cid:1) Scomberomorus maculatus (Mitchill, 1815). (cid:1) Scomberomorus regalis (Bloch, 1793). (cid:1) Thunnus alalunga (Bonnaterre, 1788). (cid:1) Thunnus albac ares (Bonnaterre, 1788). (cid:1) Thunnus atlanticus (Lesson, 1831). (cid:1) Thunnus obesus (Lowe, 1839). Thunnus thynnus (Linnaeus, 1758).

Benthopelagic at 200 to 850 m; juveniles mesopelagic.

Maximum 70 cm st andard length.

Mainly found over the continental slope (Ref. 27121). Juveniles mesopelagic (Ref. 6181, 58302).

Reproductive mode: dioecism; fertilization: external; nonguarders (open water/substratum egg scatterers); parental care: none.

IUCN Red List Status: Least Concern (LC), assessed 2013-05-21. Resilience: Low (Assuming tmax>10).