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I. Open Water Swimmers


Open Water Swimmers Roundscale spearfish (= Round-scaled marlin) Tetrapturus georgii Lowe, 1841 - Istiophoridae

A rare species from warm temperate waters. (1) Bill long and thin. (2) Nape rising smoothly. (3) First dorsal fin with anterior lobe rounded (a little deeper than body), then rather low. Pectoral fins long (longer than body depth). Back blue-black, sides silvery white. Size: 1.5-2 m. Depth: 0-200 m. From Madeira to southern Portugal and Sicily (Mediterranean).

Longbill spearfish

Tetrapturus pfluegeri Robins & de Sylva, 1963 - Istiophoridae An offshore tropical species. (1) Bill long and thin. (2) Nape rather sloping. (3) First dorsal fin with high angular (but not pointed) anterior lobe, a little deeper than body, and then of constant height. Pectoral fins long (longer than body depth), pelvic fins even longer. Back blue-black, sides silvery white. Size: 2-2.6 m. Depth: 0-200 m. tropical Africa up to Madeira.

Some very peculiar fish

All the fish in these pages (pp 98-101) are open sea dwellers and fast swimmers. Most are quite solitary and highly migratory. It is thought that their sword or bill allows them to kill or hurt their preys, but can also be used for defence.The shape of their first dorsal fin is often a good criterion to distinguish the species; other useful visual criteria are summed up here.


pectoral fins

pelvic fins


1st anal fin

Xiphias gladius Swordfish

very long flattened sword




Istiophorus albicans Atlantic sailfish

long (round in cross section)

fairly long

very long


Makaira nigricans Blue marlin

fairly long (round)

fairly long

± like pectoral fins

distinctly pointed

Istiompax indica Black marlin

not very long but robust

fairly long and rigid, erect

shorter than pectoral fins

distinctly pointed

Kajikia albida White marlin

long (round)


± like pectoral fins

just before 1st anal fin

rounded (fairly high)

Tetrapturus belone Mediterranean spearfish

short (round)


much longer than pectoral fins

well before 1st anal fin


Tetrapturus georgii Roundscale spearfish

long and slender (round)


± like pectoral fins

slightly before 1st anal fin

rounded (with a long base)

Tetrapturus pfuegeri Longbill spearfish

fairly long and slender (round)


slightly longer than pectoral fins

slightly before 1st anal fin rounded (fairly high)


Odd shapes White marlin (= Atlantic white marlin) Kajikia albida (Poey, 1860) (= Tetrapturus albidus) Istiophoridae Primarily a subtropical species. (1) Forehead rather deep. (2) Dorsal fin with rounded anterior lobe (as deep as body), then regularly tapering. Bill long. Pectoral fins long (longer than body depth). Back blue-green to greyish-blue, sides silvery white. Size: 2-3 m. Depth: 0-150 m. From tropical Africa to south of Western Mediterranean. A White marlin jumping out of the water (Western Atlantic, North Carolina, SHD).

Blue marlin (= Atlantic blue marlin) Makaira nigricans Lacépède, 1801 - Istiophoridae Southern, only in the Atlantic Ocean. (1) Nape steep, almost humped. (2) First dorsal fin with anterior lobe pointed (less deep than body), then very low. Bill fairly long. Pectoral fins rather long (about equal to body depth). Body quite thick. Back blue to grey-blue, sides lighter and belly white; may be entirely dark. Size: 3-5 m. Depth: 0-200 m. From tropical Africa to north of Spain.

Black marlin

Istiompax indica (Cuvier, 1832) (= Makaira indica) - Istiophoridae Only seldom straying into our regions. Very similar to Blue marlin, but: (1) Falcate and rigid erect pectoral fins (that cannot be folded against side of body). Bill somewhat shorter and stouter. Nape steeper, more elevated. Back blue-grey to brown, sides greyish, belly lighter. Size: 3-4.7 m. Depth: 0-900 m. Individuals coming from the Indian Ocean may stray into subtropical Atlantic; one record in the Mediterranean (Ligurian Sea).

Long snouted lancetfish

Alepisaurus ferox Lowe, 1833 - Alepisauridae A rare species, often in deep water. (1) Dorsal fin deep. (2) Adipose fin present. Body elongate, subcylindrical. Mouth large with a few strong sharp teeth. Overall colour pattern pale to dark with iridescent sheen, back darker. Size: 1.5-2.15 m. Depth: 1-1 000 m. Sometimes near coasts. From Iceland to subtropical Africa, Western Mediterranean.

Often caught quite deep, Long-snouted lancetfish are rarely landed in a good condition (SHA/NOAA).


Open Water Swimmers The Silver scabbarfish is a pelagic species, sometimes caught in open water by anglers (BAN). It may occasionally be encountered by divers during the night on soft bottoms, sometimes even in groups ( & French Riviera, VIP). The distinctive mouth features pointed jaws and impressive teeth (French Riviera, JUE).

Dorab wolf-herring

Chirocentrus dorab (Forssk책l, 1775) Chirocentridae A rare Red Sea immigrant. (1) Large mouth oriented upwards, with dagger-like teeth. (2) Dorsal fin short, set backwards, with blackish upper part. Anal fin twice as long as dorsal. Size: 0.6-1.1 m. Depth: 1-120 m. A coastal open water swimmer. Eastern Mediterranean; rare (up to now, only larvae of this species have been identified in Turkey). A Wolf-herring stranded on the beach (Kuwait, LOP). It could be here a very similar species, Chirocentrus nudus.


Odd shapes Silver scabbardfish

Lepidopus caudatus (Euphrasen, 1788) Trichiuridae

Size 1.5-2.1 m

Depth 40-300 m (10-620 m)

Identification criteria: (1) Long, continuous dorsal fin. (2) Tail forked. (3) Anal fin present. Supplementary description: Body elongated, ribbon-like. Large mouth, snout and lower jaw tips pointed. Robust sharp teeth, especially developed on upper jaw. Pelvic fins vestigial. Body silvery-white, back somewhat darker; a blackish area on dorsal fin origin. Habitat and behaviour: This fish usually lives in open water more than 100 m deep, above sandy or muddy bottoms. It occasionally rises close to the surface, and may even approach the shore during the night, sometimes lying on the sand to sleep. The species is still not well known however, and your observations are welcome (cf. p. 17)! Possible misidentification: With Black scabbardfish and Hairtails (this page). A related species, Benthodesmus elongatus (Clarke, 1879), only lives in deep water.

Lepidopus caudatus

Black scabbardfish (Espada) Aphanopus carbo Lowe, 1839 Trichiuridae A deep-water species, occasionally caught. Similar to Silver scabbardfish, but: (1) Colour copperyblack. (2) Dorsal fin with a clear notch. No pelvic fins in adults. Size: 0.9-1.1 (1.45) m. Depth: 200-1 700 m. Swim in open water, young not as deep as adults. Atlantic from Denmark to tropical Africa; not in the Mediterranean.

Black scabbardfish at a fishmonger stall (TRM).

Hairtail (= Largehead hairtail) Trichiurus lepturus Linnaeus, 1758 Trichiuridae Sometimes in shallow water at night. (1) Long dorsal fin of uniform height. (2) No caudal fin (pointed tail). (3) No visible anal fin. Body very elongate, ribbon-shaped. Mouth large with strong sharp teeth. No pelvic fins. Overall colour pattern silvery. Size: 1.2-1.5 (2.34) m. Depth: 100-350 (0-600) m. Sometimes in relatively shallow waters or near coasts. From Norway to tropical Africa; Mediterranean. The Largehead hairtail is a worldwide species, which may be caught in large numbers in some areas (WIKI).


Open Water Swimmers Spinous pipefish (= Pelagic pipefish) Syngnathus phlegon Risso, 1827 Syngnathidae A Mediterranean species, usually offshore. (1) Tubular snout long and slender, almost cylindrical, widened at mouth level. (2) Prominent body rings, often with spinous points. No pelvic fins, reduced anal fin. Caudal part (behind dorsal fin) well longer than half the body length. Back blue, light belly; sometimes a few wide dark rings. Size: 15-20 cm. Depth: 0-50 m (?). Mediterranean (mostly Western) and close Atlantic. A Spinous pelagic pipefish caught off Tuscany (Ligurian Sea, Italy, SEF/ARPAT). Although it is the most common fish of the family Molidae, the Sunfish is only seldom encountered by divers ( Toulon, Provence, RUX; L’Estartit, Catalonia, ROE).

Sharptail mola

Masturus lanceolatus (Liénard, 1840) Molidae A subtropical cousin of the common Ocean sunfish. Can be distinguished by: (1) Pointed pseudocaudal part. Brown to silvery-blue, often with large dark spots on sides and pale spots on fin bases; back and fins darker. Size: 1.5-3.3 m. Depth: 0-670 m. Tropical Atlantic to Azores and Madeira. A Sharptail mola observed in the tropical Atlantic (NOAA).


Odd shapes Schmidt’s pipefish (= Black Sea pelagic pipefish) Syngnathus schmidti Popov, 1927 - Syngnathidae

A Black Sea pelagic pipefish. Similar to Spinous pipefish, but: (1) Snout longer and more slender. (2) Caudal part (behind dorsal fin) well shorter than half the total length of body. Colours of live fish not well known. Size: 8-11 cm. Depth: 0-10 (100) m. Black Sea and Sea of Azov. Note: Numerous other Pipefishes live on the sea bed (pp. 434-445), but their juveniles may be encountered in open water up to a relatively large size.

A preserved specimen of Schmidt’s pipefish (Russian Black Sea coast, PAA).

Ocean sunfish

Mola mola (Linnaeus, 1758)4 Molidae

Mola mola

Size 1.5-2 m (3 m)

Depth 0-30 m (360 m)

Identification criteria: (1) Dorsal and anal fins paddle-shaped, set backward and opposed. (2) No tail but body ending abruptly in a thickened pseudo-caudal structure. (3) Small rounded pectoral fins. Supplementary description: Body deep, about 1.5 longer than high in young specimens, almost circular in adults. Silvery-grey to milky-grey, sometimes with pale blotches; back and fins darker. Habitat and behaviour: Typically offshore, fairly often observed near surface, with the dorsal fin emerging. Large individuals sometimes stay close to the bottom to get cleaned, by Symphodus melanocercus for example. Rare to occasional. Approach: This fish often swims away when approached but sometimes inexplicably accepts the presence of divers (less prone to flee when being cleaned).

Truncated sunfish (= Slender sunfish) Ranzania laevis (Pennant, 1776) Molidae Smaller and more elongated than Ocean sunfish. (1) Funnel-shaped lips, closing in a vertical slit. (2) Pectoral fins pointed. Back blue-black, sides greyish to brown with silvery vertical lines, more obvious on head and belly. Size: 60-100 cm. Depth: 0-140 m. Often gregarious. Tropical Atlantic to British Isles; Mediterranean. This Truncated sunfish has been caught in the Atlantic in tropical waters (NOAA).


Open Water Swimmers It is quite rare to observe a living Oceanic puffer (Bay of Biscay, in aquarium, LOP). When caught, this fish is able to inflate with water or air (fish caught in Southern Brittany, IGS).


Rachycentron canadum (Linnaeus, 1766) Rachycentridae A tropical species, rare in our regions. (1) Dorsal fin quite elevated, preceded by a series of short spines. (2) Tail triangular, forked in adult. Slender, spindle-shaped body, reminding a sharksucker, but with no head sucking disk. Back and sides dark grey to brown, belly pale; two white longitudinal lines, fading in adults. Size: 1.1-1.5 (2) m. Depth: 0-1 200 m. Found worldwide in tropical seas, recorded once in the Eastern Mediterranean (Israel). A young Cobia (KUR), and an adult in a fish farm (ALJ/NOAA). Sharksucker species attach to their host with their cephalic sucker, sometimes upside down like on this Sandbar shark ( & aquarium photos, LOP).


Odd shapes Oceanic puffer

Lagocephalus lagocephalus (Linnaeus, 1758) Tetraodontidae

Lagocephalus lagocephalus

Size 50-55 cm (61 cm)

Depth 0-30 m (?)

Identification criteria: (1) Beak made of two teeth on each jaw. (2) Back blue to bluegreen. (3) Dorsal and anal fins opposed, flapping laterally. Supplementary description: Body slender but broad, quadrangular in cross-section. No pelvic fins. Tail with lower lobe longer. Sides grey-brown to silvery, belly white; fins dark. Habitat and behaviour: Offshore but usually not really far from coasts, occasionally entering estuaries. A rare species. Possible misidentification: All the other Pufferfish in the area live close to the seabed (see pp 238-241). The Oceanic porcupinefish (p. 243) have spines. Danger: In all Tetraodontidae, skin and flesh may be very toxic. Also be careful to avoid bites: the beak is strong enough to break a finger!

Slender suckerfish

Phtheirichthys lineatus (Menzies, 1791) - Echeneidae Rare in our area. (1) Cephalic disc short, reaching to about pectoral fin base. (2) body very thin, head small. (3) Dorsal and anal fins long, deeper anteriorly. Cephalic disc with 9-11 laminae. Often with a dark-brown longitudinal stripe, but body sometimes uniformly whitish, or brownish-black. Size: 45-76 cm. From tropical Atlantic to the English Channel. Rare. This 6 cm long juvenile can be identified thanks to the low number of laminae on the cephalic disk (tropical Africa, IRD).

Live sharksucker (= Striped suckerfish) Echeneis naucrates Linnaeus, 1758 Echeneidae

Echeneis naucrates

Size 0.9-1 m (1.1 m)

Depth 0-15 m (30 m ?)

Identification criteria: (1) Black longitudinal stripe edged with white lines. (2) Dorsal and anal fins long, elevated anteriorly. Supplementary description: Cephalic disc (sucker) reaching to middle of pectoral fin length, with 20-28 laminae. Pectoral fins pointed. Tail rounded in young, truncated in adult. Habitat and behaviour: As with other Remoras, this fish is found attached to large marine vertebrates: sharks, and also rays, groupers, sea turtles and Cetaceans. However, it may be seen swimming freely near shore. Common in tropical waters, this fish is occasionally seen in the warmer parts of the Mediterranean. Possible misidentification: With other Remoras (above and next page). Remora and Remorina species have rounded pectoral fins, and much shorter dorsal and anal fins. The Cobia (this page) has no cephalic sucking disk


Open Water Swimmers Common remora (= Sharksucker) Remora remora (Linnaeus, 1758) Echeneidae

Mainly on Sharks, but also on other large fish and sea turtles. (1) Cephalic disc almost reaching to pectoral fin tips. (2) Body and fins brownish-grey to brownish-black. Body rather stocky. Disc with 16-20 laminae. Size: 65-86 cm. Depth: 0-100 m. Quite common in warm waters. From tropical Africa to British Isles, Mediterranean. A common sharksucker attached upside down on the head of a Manta ray, an usual position for this fish (tropical Atlantic, NOP)

Marlin sucker (= Marlin remora) Remora osteochir (Cuvier, 1829) Echeneidae Mainly on Marlins and Sailfish. (1) Cephalic disc very long, reaching well behind pectoral fins. (2) Body grey-black. Disc with 15-19 laminae. Back darker; fins blackish. Size: 35-45 cm. Depth: 0-50 m (?). Offshore. From tropical Africa to south of Western Mediterranean.

A Marlin sucker caught in tropical Africa (IRD).

Oarfish often swim in a vertical position, by undulating the dorsal fin. Their silvery flanks reflect the blue colour of the surrounding water. Dark spots and blue markings are more or less visible depending on the orientation of the light (close to an oceanographic buoy in the Ligurian Sea, LUD).


Odd shapes Spearfish sucker (= Spearfish remora) Remora brachyptera (Lowe, 1839) Echeneidae

Mainly on Marlins and Spearfish. (1) Cephalic disc quite short, not reaching to pectoral fin tips. (2) Body white, more or less bluish. Disc with 15-18 laminae. Overall colour pattern uniform. Size: 30-40 (50) cm. Depth: 0-50 m (?). Offshore. From tropical Africa to south of Western Mediterranean (and Eastern?). A spearfish sucker attached to a Sailfish in the Western Atlantic (Mexico, NOP).


Remora australis (Bennett, 1840) - Echeneidae Only on Cetaceans. (1) Cephalic disc elongated, reaching well behind pectoral fin tips (2) Body uniformly brownish. Sucking disc with 25-28 laminae. Size: 40-76 cm. Depth: 0-50 m (?). A rare very little known fish. From tropical Africa to Morocco, doubtful in the Mediterranean.

White suckerfish Remora albescens (Temminck & Schlegel, 1845) (= Remorina albescens) - Echeneidae Mostly on Mantas. (1) Cephalic disc broad, almost circular, reaching to pectoral fin tips. (2) Dorsal and anal fins very short. (3) Body often whitish (but sometimes grey-brown). Cephalic disc with 13-14 laminae. Size: 25-33 cm. Depth: 0-40 m (?). Offshore. From tropical Africa up to south of Portugal.

King of herrings (= Oarfish) Regalecus glesne Ascanius, 1772 Regalecidae

Regalecus glesne

Size 3-5 m (11 m)

Depth 20-200 m (1-1 000 m)

Identification criteria: (1) Dorsal fin with an anterior crest of long free rays. (2) Pelvic fins made of a single elongate ray with fleshy membrane at tip. (3) Tail rudimentary. Supplementary description: Body long, ribbon-like. Dorsal fin runs all along the body. Pectoral fins short. No anal fin. Mouth protrusible (can be extended into a tube), oriented upwards. When alive, this fish is silvery, sometimes with irregular bright blue vertical dashes and/or rounded darkish spots. Fins are mostly hyaline (they may become red only after death). Habitat and behaviour: According to the rare sightings of this fish, it seems to favour an oblique or vertical position, head upwards, and swims by undulating its dorsal fin. It may sometimes be encountered close to immersed objects (oceanographic devices, deep water moorings, fish aggregating devices - FAD…). Note: This is the largest of the bony fish!


Open Water Swimmers This young Mediterranean dealfish, encountered close to shore, was about 50 cm long. Small juveniles (10-15 cm) display very long fin rays looking like the stinging tentacles of a jellyfish (French Riviera, HIB).

A 1.50 m long Dealfish caught in 5 meters, which is an unusually shallow depth for this species (southern Brittany, IGS) . This illustration of an Atlantic dealfish was published prior to 1880 in the book “Voyage en Islande et au Groenland” directed by Paul Gaimard (Library of the Marine Museum of Biarritz, France). A small juvenile Scalloped ribbonfish observed close to shore ( Sicily, BRM), and an adult caught by a longliner off Corsica ( PAM).


Extrait Marine Fish - Éditions Ulmer  
Extrait Marine Fish - Éditions Ulmer  

Already considered as a reference in most of Europe, this book is now presented in a new, completely reviewed and updated English version in...