Elopiformes

(vertebrate zoology) A primitive order of actinopterygian fishes characterized by a single dorsal fin composed of soft rays only, cycloid scales, and toothed maxillae.

(Ladyfish and tarpon)

Class: Actinopterygii

Order: Elopiformes

Number of families: 2

Evolution and systematics

Tarpon, along with bonefish and ladyfish, are primitive fishes, and while tarpon and ladyfish are considered to be more closely related to each other than to any other elopomorph group, their distinct lineages extend more than 100 million years back in the fossil record. The structure of the skull, fin placement, and large thick scales are characteristic of ancient fishes.

Tarpon and ladyfish are united by the common possession of a leptocephalus larvae and a variety of primitive features. The leptocephalus larvae is shared with a diverse group of other elopomorph fishes including the eels; however, the leptocephalus larvae of tarpon and ladyfish are the smallest of all leptocephali and possess a forked tail. Leptocephali of some albuliformes also have a forked tail.

The order Elopiformes contains two families: the Elopidae and the Megalopidae. The family Megalopidae contains the single genus Megalops. Two species of tarpon exist worldwide. The Atlantic tarpon occurs in the eastern and western Atlantic, and the oxeye tarpon occurs in the Indian and Pacific oceans. Morphologically the two species are quite similar; however, the Atlantic tarpon reaches a much larger size and can exceed 220 lb (100 kg) and a length of over 6.6 ft (2 m). The oxeye tarpon is smaller and seldom exceeds 3.3 ft (1 m).

The family Elopidae contains the single genus Elops, which occurs worldwide. As many as six morphologically similar species of Elops are thought to exist. The genus is in need of revision, and the total number of species is unclear.

Physical characteristics

These are silver, elongate herring-like fishes with large upturned mouths, large eyes, and deeply forked tails. An important structural character is the presence of a long, bony gular plate between the branches of the lower jaw, a feature that the ladyfish shares with the tarpon but not with herring.

Distribution

The Megalopidae and Elopidae occur worldwide in tropical and subtropical seas.

Habitat

Tarpon and ladyfish are coastal in habitat and often occur in estuarine waters. Both tarpon and ladyfish are quite tolerant of low salinities. Tarpon commonly enter freshwater and often travel far up freshwater rivers and enter lakes far from sea.

Behavior

Tarpon and ladyfish are pelagic predators that feed principally on mid-water prey. Both have small sandpaper-like teeth, and their prey is swallowed whole. They often occur in large schools in shallow coastal and inshore waters.

Feeding ecology and diet

Small tarpon feed predominantly on cyclopoid copepods, fishes, caridean shrimp, and mosquito larvae. No detailed studies have examined the feeding habits of large tarpon, but anecdotal information suggests that a wide variety of fishes are consumed. Ladyfish feed principally in midwater on pelagic prey. Feeding is mainly on fish, but decapod crustaceans also are consumed.

Ladyfish are probably preyed upon by a wide variety of inshore predators including sharks, porpoises, snook, and tarpon. They are occasionally used as bait by recreational anglers for tarpon and other species. Juvenile tarpon are also likely preyed upon by a variety of species such as gar, snook, and larger tarpon. Because juvenile tarpon are most often found in poorly oxygenated waters, they are probably vulnerable to a more limited suite of predators than ladyfish. Large tarpon are preyed upon only by large coastal sharks including bull sharks and hammerheads.

Reproductive biology

Both tarpon and ladyfish spawn offshore in high salinity oceanic waters. Precise spawning areas are unknown, and fertilized eggs are undescribed. Tarpon and ladyfish are broadcast spawners that produce large numbers of buoyant eggs that float in the surface waters of the ocean. The eggs hatch into the distinctive leptocephalus larvae characterized by an elongate, laterally compressed body consisting principally of an acellular mucinous material, large well-developed eyes, and large fang-like teeth. Larvae of tarpon and ladyfish reach a length of from 1.0 to 2.0 in (25–50 mm) before metamorphosis. Metamorphosis occurs as the larvae enter coastal waters and pass through inlets into the inshore waters where juveniles are found. Recruitment of tarpon through inlets appears to be pulsed and related to storm events.

Conservation status

Tarpon and ladyfish are abundant, and there is no evidence that stocks of these species have been depleted by overfishing. It is unknown to what extent habitat loss has affected stocks.

Significance to humans

Tarpon support important recreational fisheries in Florida and the Caribbean. Ladyfish are a food fish of minor importance in some areas.

Species accounts

Resources

Hildebrand, S. F. "Family Elopidae." In Fishes of the Western North Atlantic, edited by H. B. Bigelow. New Haven, CT: Sears Foundation for Marine Research, 1963.

Andrews, A., E. Burton, K. Coale, G. Cailliet, and R. E. Crabtree. "Radiometric Age Validation of Atlantic Tarpon, Megalops atlanticus." Fishery Bulletin 99 (2001): 389–398.

Crabtree, R. E., E. C. Cyr, R. E. Bishop, L. M. Falkenstein, and J. M. Dean. "Age and Growth of Larval Tarpon, Megalops atlanticus, in the Eastern Gulf of Mexico With Notes on Relative Abundance and Probable Spawning Areas." Environmental Biology of Fishes 35 (1992): 361–370.

Crabtree, R. E., E. C. Cyr, D. Chacon, W. O. McLarney, and J. M. Dean. "Reproduction of Tarpon, Megalops atlanticus, from Florida and Costa Rican Waters and Notes on Their Age and Growth." Bulletin of Marine Science 61 (1997): 271–285.

Geiger, S. P., J. J. Torres, and R. E. Crabtree. "Air-breathing and Gill Ventilation Frequencies in Juvenile Tarpon, Megalops atlanticus: Responses to Changes in Dissolved Oxygen, Temperature, Hydrogen Sulfide, and pH." Environmental Biology of Fishes 59 (2000): 181–190.

Zale, A. V. and S. G. Merrifield "Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (South Florida)—Ladyfish and Tarpon." U.S. Fish and Wildlife Service Biological Report 82 (1989).

[Article by: Roy Eugene Crabtree, PhD]

A primitive order of soft-rayed, teleost fishes, including the tarpons, bonefishes, and their relatives, that was formerly included in the Clupeiformes. The elopiforms have a single dorsal fin composed of soft rays only (see illustration).

Tarpon (Megalops atlantica). 1 in. = 2.54 cm. (After G. B. Goode, Fishery Industries of the United States, Sect. 1, 1884)

The most important characteristic of the order involves the occurrence in early development of a leptocephalous larval stage. This larva is translucent, ribbonlike, and strongly toothed; eventually it passes through a marked transformation to adult form. This developmental pattern characterizes only two other orders of teleosts, the Notacanthiformes (spiny eels and halosaurs) and the Anguilliformes (true eels), groups which are therefore believed to be descendants of elopiforms. See also Anguilliformes; Clupeiformes; Notacanthiformes.

The elopiforms have a well-represented paleontological history since the Jurassic, on all continents. They were especially abundant in the Cretaceous. Extant forms are classified in 2 families, 4 genera, and 12 species. Most inhabit tropical to temperate shore waters of all oceans, but tarpons invade rivers, sometimes for long distances. See also Actinopterygii.

Elopiformes Fossil range: Early Cretaceous–Recent PreЄ Є O S D C P T J K Pg N [1]
Tarpon, Megalops sp.
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Elopiformes
Families
Elopidae Megalopidae

Elopiformes (pronounced /ɨˌlɒpɨˈfɔrmiːz/) is the order of ray-finned fish that includes the tarpons, tenpounders, and ladyfish, as well as a number of extinct types. They have a long fossil record, easily distinguished from other fishes by the presence of an additional set of bones in the throat.^[1]

They are related to the order of eels, although the adults resemble herrings in appearance. The larvae, however, are leptocephali, looking very similar to those of eels.^[1]

Classification

Although many fossil forms are known, the order is relatively small today, containing just two genera and eight species:^[2]

Order Elopiformes

• Family Elopidae (Ladyfish)
  • Genus Elops (6 species)
• Family Megalopidae (Tarpons)
  • Genus Megalops (2 species)

References

1. ^ ^{a b c} McCosker, John F. (1998). Paxton, J.R. & Eschmeyer, W.N.. ed. Encyclopedia of Fishes. San Diego: Academic Press. pp. 85-86. ISBN 0-12-547665-5. 
2. ^ "Elopiformes". FishBase. Ed. Ranier Froese and Daniel Pauly. January 2009 version. N.p.: FishBase, 2009.

• "Elopiformes". FishBase. Ed. Ranier Froese and Daniel Pauly. May 2006 version. N.p.: FishBase, 2006.
• Mikko's Phylogeny for Elopiformes

External links

• The inshore grand slam Article about bonefish, ladyfish and tarpon.

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