Percoidei II

(Bluefishes, dolphinfishes, roosterfishes, and remoras)

Class Actinopterygii

Order Perciformes

Suborder Percoidei

Number of families 4

Evolution and systematics

The suborder Percoidei contains more than 70 families and 2,800 species. This chapter focuses on the families Pomatomidae, Coryphaenidae, Nematistiidae, and Echeneidae. The bluefish (Pomatomidae) and the dolphinfishes (Coryphaenidae) are two small families of streamlined pelagic fishes. The bluefish is monotypic and dates from the Miocene epoch. The dolphinfishes consist of just one genus, Coryphaena, and two species. These fishes likely date from the Eocene and sometimes are grouped together with the Nematistiidae (roosterfish), Echeneidae (remoras), Rachycentridae (cobia), and Carangidae (jacks and trevallys). The roosterfish, Nematistius pectoralis, is a monotypic species within its family. Remoras consist of four genera and eight species. The genera are Echeneis (two species), Phtheirichthys (one species), Remora (four species), and Remorina (one species).

Physical characteristics

Percoids have elongated, fusiform bodies with forked or slightly forked caudal fins. Bluefishes have two dorsal fins, a long anal fin, and a mouth well armed with sharp, compressed teeth arrayed in a single series. They grow to about 51 in (130 cm) in length. Adult male dolphinfishes have pronounced bony crests on the heads; these fishes also have long, continuous dorsal and anal fins and brilliant yellow, green, and blue coloration. They grow to about 83 in (210 cm) in length. The roosterfish has an elongated, fusiform body with a raised head profile dorsally and a dorsal fin containing seven remarkably long spines. The remoras are streamlined, elongated, or club-shaped, with a flattened head that has a sucking disc modified from a dorsal spine. The disc has between 10 and 28 movable lamina that allow it to grasp the body surface of a host. The dorsal fin is positioned just ahead of the caudal peduncle and has 18–40 soft rays. The anal fin also has 18–40 soft rays. The scales are cycloid and small, and the swim bladder is absent. Remoras have a highly modified dorsal surface on the head that acts as a suction disc. This disc allows remoras to attach themselves to the body surfaces of various hosts. Body coloration ranges from black to combinations of blue, black and white. Body sizes range from 20 to over 44 in (50 to over 110 cm). Remoras are remarkably adapted for a commensal relationship with numerous host organisms and clean their hosts in exchange for "hitching rides" and feeding on leftover food items. The bluefish, the dolphinfishes, and the roosterfish have evolved to become efficient predators in open waters or inshore habitats.

Distribution

The bluefish ranges widely across three oceans and is found in marine and brackish waters of the eastern and western Atlantic Ocean, the Mediterranean Sea, the Black Sea, the Indian Ocean, and the southwest Pacific Ocean; it is absent from the eastern and northwestern Pacific and almost all of the central Pacific. The dolphinfishes occur in tropical and warm temperate marine waters of the Atlantic, Indian, and Pacific Oceans. The roosterfish is distributed in the eastern Pacific from southern California south to Baja California, Mexico, the Galapagos Islands, and Peru. The remoras occur in tropical and warm temperate waters of the Atlantic, Indian, and Pacific Oceans.

Habitat

The bluefish is pelagic but generally is found inshore off headlands and beaches and enters brackish water habitats, such as estuaries, to forage. Dolphinfishes are pelagic in surface

waters but also move inshore to forage, usually at insular localities where deep water is close to shore. The roosterfish prefers inshore areas, particularly sandy beaches; this species also frequents the water column away from beaches. Juveniles appear in tide pools. The remoras utilize their hosts as a microhabitat, whether swimming in surface waters of the pelagic realm or in inshore habitats.

Behavior

Bluefishes form schools or loose aggregations that are effective in hunting prey. These schools migrate seasonally, moving predictably to warm water during the cool or winter season and to cooler water during the warm or summer season. Dolphinfishes form schools that migrate over large distances on a seasonal basis. Small groups hover under floating objects, such as tree trunks or fish aggregation devices, and schools also follow boats and ships. The roosterfish may be solitary and usually swims inshore along sandy beaches as it forages for food. Remoras utilize their specialized sucking discs to attach themselves to sharks, skates, rays, billfishes, and other large fishes as well as sea turtles, dolphins, and whales. Occasionally, they are seen swimming freely. The attachment behavior allows them to function as transportation parasites, in that their host species do most of the swimming while the remora goes along for the ride, moving only to change position along the host's body, when feeding or moving between hosts, or when reproducing.

Feeding ecology and diet

Bluefishes, dolphinfishes, and roosterfishes are predators. Bluefishes are voracious predators of fishes, squids, and other shoaling animals and continue to attack prey even after satiation. Dolphinfishes feed upon small fishes, squids, and other pelagic prey. The roosterfish feeds on smaller fishes and other pelagic prey inshore or just offshore. In contrast, remoras feed on external parasites, mainly copepods, of host organisms but also take leftover items not consumed by their predatory hosts.

Reproductive biology

Bluefishes court and spawn in schools or groups, spawn seasonally, and produce pelagic eggs and larvae. Dolphinfishes court and spawn in schools or groups and produce pelagic eggs and larvae. One species has been spawned in captivity. The reproductive biology of roosterfishes apparently is not well known. They are likely pelagic spawners, perhaps in groups, and they produce pelagic eggs and larvae. Little is known about the reproductive biology of remoras. They presumably pair-spawn. Eggs and larvae probably are pelagic.

Conservation status

None of these fishes is listed by the IUCN, but they are subject to overfishing, either commercial or sport, or are caught as by catch.

Significance to humans

The bluefish and the dolphinfishes are very important commercial, recreational, and subsistence fishes. Both the bluefish and the common dolphinfish have been raised by aquaculture. The roosterfish is an important game fish that also is taken in subsistence and artisanal fisheries. Remoras may be taken incidentally for display in public aquaria.

Species accounts

List of Species

Pompano dolphinfish

Coryphaena equiselis

family

Coryphaenidae

taxonomy

Coryphaena equiselis Linnaeus, 1758, type locality not specified.

other common names

English: Pompano dolphin; Japanese: Ebisu-shiira.

physical characteristics

Body is fusiform and elongate, with a vertical head profile and a bony crest in adults, especially males; it is much less pronounced than in the common dolphinfish. The single dorsal fin has 52–59 soft rays and extends from just behind the gills down to the caudal peduncle. The anal fin is long, with 24–28 soft rays, and extends from the anus to the caudal peduncle. The caudal fin is forked. Body color is metallic blue and green on the back and silver with gold spots and a golden sheen on the flank, with a dark dorsal fin. Upon death, the dorsal color fades to gray. The caudal fin margin of juveniles is white. Grows to 50 in (127 cm) in length but lives only 4 years.

distribution

Tropical and some subtropical seas worldwide.

habitat

Pelagic but ventures inshore to forage off reefs or emergent rocks.

behavior

A schooling species that swims in pelagic surface waters but also ventures inshore. Follows boats or hovers under floating structures, such as tree trunks or palm leaves. Attracted to fish aggregation devices.

feeding ecology and diet

Preys on smaller fishes and squids in addition to miscellaneous pelagic prey, which it hunts in schools or groups.

reproductive biology

Reproduction is not well known, but apparently it courts and spawns in groups or aggregations and produces pelagic eggs and larvae.

conservation status

Not listed by the IUCN, but may be vulnerable to overfishing. Recognized under Annex I of the 1982 Convention on the Law of the Sea because of its migratory habits.

significance to humans

A minor commercial species sought after by consumers for its excellent food quality. It is highly prized in sport fisheries, especially off South America. Also taken in subsistence fisheries.

Common dolphinfish

Coryphaena hippurus

family

Coryphaenidae

taxonomy

Coryphaena hippurus Linnaeus, 1758, type locality not specified.

other common names

English: Dolphin, dorado, mahi-mahi; Spanish: Dorado; Hawaiian: Mahi-mahi; Japanese: shiira.

physical characteristics

Elongate and fusiform body. A long dorsal fin, with 58–66 soft rays, arises above the eye and extends to the caudal peduncle. The anal fin is concave, has 25–31 soft rays, and extends from the anus to the caudal peduncle. The pectoral fin is more than half the length of the head, and the caudal fin is forked. Adult males have a pronounced bony crest on the front of the head. Brilliantly colored, with metallic greens and blues on the back and flanks, gold on the flanks, and yellow and white shades on the venter. Juveniles and young adults have vertical bars on the flanks. Grows to longer than 83 in (210 cm) but lives for only about 5 years.

distribution

Tropical, subtropical, and warm temperate waters worldwide.

habitat

Inhabits pelagic surface waters but ventures inshore to forage. Reported to enter brackish waters, such as estuaries.

behavior

Forms highly migratory schools, aggregations, or groups. Attracted to boats, ships, and floating objects, such as palm fronds or tree trunks. Also attracted to fish aggregation devices.

feeding ecology and diet

A predator upon smaller fishes and squids but also takes pelagic crustaceans and even macroplankton.

reproductive biology

This species matures sexually in the wild at only 4–5 months. Females mature at about 13.5 in (34.3 cm) and males at 16.5 in (42 cm) fork length (the distance between the snout and the midpoint in the "fork" of the caudal fin). Eggs are pelagic, buoyant, spherical, about 0.05 in (1.4 mm) in diameter, and clear in color; the oil globule is yellow. Eggs hatch after 1.5 days and larvae measure just under 0.16 in (4 mm) at hatching. Melanophores develop on the head, trunk, and tail soon afterwards. Larvae begin to feed upon planktonic copepods after the yolk sac is absorbed, and growth is rapid.

conservation status

Not listed by the IUCN, but may be vulnerable to overfishing. Recognized under Annex I of the 1982 Convention on the Law of the Sea because of its migratory habits.

significance to humans

A highly prized commercial and game fish that also is taken in subsistence fisheries. Reported to be ciguatoxic in some areas. Ciguatera poisoning is caused by the cumulative deposition of a class of polyether toxins within the tissues of fishes. The toxins are produced by certain microscopic dinoflagellate organisms of the genus Gambierdiscus, and are transmitted by the mechanism of the food chain, increasing in intensity by a factor

of ten in each successive level within the chain. The common dolphinfish acquires these toxins from prey fishes, which in turn acquire them from smaller fishes or zooplankton that have ingested dinoflagellate during feeding. If this fish is consumed by man, the concentrated poison contained within its tissues causes neurological damage that may be fatal.

Common remora

Remora remora

family

Echeneidae

taxonomy

Remora remora Linnaeus, 1758, Indian Ocean.

other common names

Japanese: Nagakoban.

physical characteristics

Body is elongate, robust, and clublike, with a large, flat head and a large sucker disc. Dorsal and anal fins are positioned just forward of the caudal peduncle. There are 22–26 soft rays in the dorsal fin and 22–24 soft rays in the anal fin. The caudal fin is large and somewhat truncated. The coloring is a dark, brownish gray. Reaches nearly 35 in (90 cm) in length and just over 2.2 lb (1 kg) in weight.

distribution

Circumglobal in tropical, subtropical, and warm temperate waters of the Pacific, Atlantic, and Indian Oceans. Also found in the Mediterranean. Reported from Iceland and Scandinavia, presumably during warmer months.

habitat

Attaches to host organisms, such as sharks, rays, seaturtles, bill-fishes, other large fishes, and even ships. Pelagic but also appears inshore.

behavior

Attaches itself to host organisms and hitches rides. Swims freely, on occasion. Otherwise, behavior is not well known.

feeding ecology and diet

Feeds on parasitic copepods attached to host organisms. Also takes leftover scraps from the host's feeding events.

reproductive biology

Not well known. Likely pair-spawns pelagic eggs and has pelagic larvae. Spawning may be seasonal, especially at higher latitudes.

conservation status

Not listed by IUCN.

significance to humans

May be taken incidentally for public aquaria or as bycatch from shark fisheries.

Roosterfish

Nematistius pectoralis

family

Nematistiidae

taxonomy

Nematistius pectoralis Gill, 1862, Cape Saint Lucas, Baja California, Mexico.

other common names

None known.

physical characteristics

Body fusiform and elongate, with a raised profile of the head that extends to the dorsal fin. The first dorsal fin has seven long spines that retract into a groove; it may have a signal function, or it may be used in maneuvering when attacking prey. A second dorsal fin has 25–28 soft rays. There are three spines and 15–17 soft rays in the anal fin. The caudal fin is forked. Body color is blue dorsally and silvery white ventrally. There are black stripes positioned obliquely on the dorsal surface; one runs up onto the upper lobe of the caudal fin. Grows to nearly 65 in (165 cm) in length, with a weight of nearly 115 lb (52 kg).

distribution

Eastern Pacific from southern California, where it is rare, south through Baja California, Mexico, and the Gulf of California, where it is more common, and down to Peru and west to the Galápagos Islands.

habitat

Mainly inshore or near-coastal habitats, especially off sandy beaches.

behavior

Not well known. Usually solitary or travels in small groups.

feeding ecology and diet

A predator upon fishes and other smaller pelagic organisms.

reproductive biology

Reproduction not well known. Likely a pelagic spawner, with pelagic eggs and larvae. May spawn in groups. Spawning probably is seasonal, especially at higher latitudes.

conservation status

Not listed by the IUCN, but vulnerable to overfishing.

significance to humans

An important game fish that also is taken as a commercial and subsistence food fish. Some collected incidentally for public aquaria.

Bluefish

Pomatomus saltatrix

family

Pomatomidae

taxonomy

Pomatomus saltatrix Linnaeus, 1766, Carolina, United States.

other common names

English (Australia): Tailor.

physical characteristics

Body fusiform and elongate, with two dorsal fins, an elongate anal fin, and a slightly forked caudal fin. There are seven to eight spines in the first dorsal fin and one spine and 13–28 soft rays in the second dorsal fin. The anal fin has two to three spines and 12–27 soft rays. Both the dorsal and anal fin soft rays have a scaly appearance. There is a black blotch at the base of each of the pectoral fins. The mouth has sharp and

compressed jaw teeth arranged in a single prominent series. The preopercle has a membranous flap that extends over the subopercle. Color is silvery blue or greenish blue on the back, with silvery flanks and belly. Grows to 51 in (130 cm) length and lives as long as nine years.

distribution

Favors subtropical waters but enters tropical and temperate waters seasonally. In the eastern Atlantic it occurs from Portugal south to South Africa, including Madeira and the Canary Islands; it also may be found in the Mediterranean and Black Seas. In the western Atlantic, it is distributed from Canada to Florida and Bermuda and south as far as Argentina. In the Pacific, it is found throughout most of Australia, except for the Northern Territory but is absent from the northwest Pacific, virtually all of the central Pacific, and the eastern Pacific. In the Indian Ocean, this species ranges from East Africa and Madagascar north to southern Oman and east to southwest India, the Malay Peninsula, and Western Australia. Records from Hawaii and Taiwan require verification, and those from New Guinea, Indonesia, and the Northern Territory of Australia probably are in error.

habitat

Pelagic but prefers inshore waters and often is found off rocky or sandy headlands, beaches, and breakwaters. Enters estuaries. Moves with the tide.

behavior

Adults form schools or loose aggregations. Individuals are reported to move in association with sharks and billfishes. Juveniles form schools. Schools migrate seasonally.

feeding ecology and diet

Highly predatory. Schools or aggregations forage inshore and in open water, attacking schools of prey, mainly smaller fishes and squids, and continues to attack after having fed to satiation. Dangerous if handled, because it bites out of water and reportedly has severed fingers or caused serious wounds. Is reported to attack splashing swimmers, too.

reproductive biology

Spawning is seasonal, usually in spring and summer months (May–August in the northwest Atlantic; March–May and September–November in the southwest Atlantic, north of the equator; September–December in the Southern Hemisphere), and occurs serially. Females are remarkably fecund, with egg counts ranging from 400,000–2,000,000 depending upon body size of the female. Eggs are pelagic and buoyant, about 0.04 in (1.09 mm) in diameter, and hatch after 1.5–2 days. Larvae are pelagic, possess large heads and mouths, and acquire teeth on both jaws by the time they reach 0.13 in (3.3 mm) in length. The yolk sac disappears soon afterwards and larvae become predacious. Dorsal, anal, and caudal fins differentiate at about 0.25 in (6.35 mm), and fin rays appear at about 0.33 in (8.4 mm). Dorsal spines develop more fully at 1.1 in (27.9 mm). Pigmentation is apparent on the head dorsally and on the gut at 0.33 in (8.4 mm), with very small dots appearing on the entire body at 1.1 in (27.9 mm).

conservation status

Not listed by the IUCN, but vulnerable to overfishing on both commercial and recreational scales. Has been caught for sport but is wasted because the flesh degrades quickly without proper handling. Population sizes are cyclical.

significance to humans

Very important commercial species that also is a significant and prized game fish.

Resources

Books

Eschmeyer, W. N., ed. Catalog of Fishes. 3 vols. San Francisco: California Academy of Sciences, 1998.

Helfman, Gene S., Bruce B. Collette, and Doug E. Facey. The Diversity of Fishes. Malden, MA: Blackwell Science, 1997.

Kuiter, R. H. Coastal Fishes of South-eastern Australia. Honolulu: University of Hawaii Press, 1993.

Masuda, H., K. Amaoka, C. Araga, T. Uyeno, and T. Yoshino, eds. The Fishes of the Japanese Archipelago. Tokyo: Tokai University Press, 1984.

Myers, R. F. Micronesian Reef Fishes: A Field Guide for Divers and Aquarists. 3rd edition. Barrigada, Guam: Coral Graphics, 1999.

Neira, F. J., A. G. Miskiewicz, and T. Trnski, eds. The Larvae of Temperate Australian Fishes: A Laboratory Guide for Larval Fish Identification. Perth: University of Western Australia Press, 1998.

Nelson, J. S. Fishes of the World. 3rd edition. New York: John Wiley and Sons, 1994.

Smith, M. M., and P. C. Heemstra, eds. Smiths' Sea Fishes. Berlin: Springer-Verlag, 1986.

Organizations

IUCN/SSC Coral Reef Fishes Specialist Group. International Marinelife Alliance-University of Guam Marine Laboratory, UOG Station, Mangilao, Guam 96913 USA. Phone: (671) 735-2187. Fax: (671) 734-6767. E-mail: donaldsn@uog9.uog.edu Web site: <http://www.iucn.org/themes/ssc/sgs/sgs.htm>

Terry J. Donaldson, PhD