are predatory, feeding primarily on fishes and invertebrates. They are able to respire via air gulped at the surface and passed into the physostomous gas bladder (Graham, 1997). There are two known species, one in the Atlantic and a second in the Indo-West Pacific. They are very popular sport fishes.
REFERENCES: Ault, 2008; Forey et al., 1996; Graham, 1997; Greenwood, 1970b; Seymour et al., 2008; Smith, in Carpenter, 2003; Wade, 1962.
MEGALOPID CHARACTERISTICS:
1) body elongate, laterally compressed
2) last ray of single dorsal fin elongate
3) mouth terminal to superior, large, extending past eye
4) pelvic fins abdominal
5) caudal fin deeply forked
6) single gular plate
7) scales large, less than 50 in lateral line
ILLUSTRATED SPECIMEN:
Megalops atlantica, SIO 78–124, 270 mm SL
ALBULIFORMES—Bonefishes
This group includes two families, the Albulidae (covered below) and the Pterothrissidae, two genera, and about 13 species. They are silvery fishes with a forked caudal fin in adults as well as in their leptocephalus larvae (also found in the Elopiformes) and are distinctive in a few osteological features (Forey et al., 1996; Wiley and Johnson, 2010).
REFERENCES: Forey et al., 1996; Wiley and Johnson, 2010.
ALBULIFORMES : ALBULIDAE—Bonefishes
DIVERSITY: 1 genus, 11+ species
REPRESENTATIVE GENUS: Albula
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine, occasionally in freshwater; tropical to warm temperate; coastal, demersal over soft bottoms
REMARKS: Bonefishes are coastal fishes characterized by their single dorsal fin, deeply forked caudal fin, and inferior mouth. As indicated by their mouth position, these fishes feed on or near the bottom, on crustaceans and other small invertebrates, as well as fishes. Reaching a maximum size of over 1 m, bonefishes are highly regarded as sport fishes, but are rarely eaten and generally not targeted commercially. Recent researchers have used molecular and morphological characters to determine the presence of several cryptic species (e.g., Hidaka et al., 2008; Pfeiler et al., 2008).
REFERENCES: Ault, 2008; Hidaka et al., 2008; Pfeiler et al., 2008; Smith, in Carpenter, 2003.
ALBULID CHARACTERISTICS:
1) body elongate
2) mouth inferior, small, not extending past eye
3) tail deeply forked
4) single gular plate
5) six to sixteen branchiostegal rays
6) scales small
ILLUSTRATED SPECIMEN:
Albula sp., SIO 62–213, 159 mm SL
NOTACANTHIFORMES—Spiny Eels and Halosaurs
DIVERSITY: 2 families, 6 genera, 27 species
REPRESENTATIVE GENERA: Aldrovandia, Halosaurus, Lipogenys, Notacanthus
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine; tropical to temperate; lower continental shelf to abyssal plain, demersal over soft bottoms
REMARKS: Spiny eels (Notacanthidae) and halosaurs (Halosauridae) are elongate, deepsea fishes that, in addition to the features below, are characterized by a large connective tissue nodule intercalated between the pterygoid arch and the maxilla. Their long anal fin extends nearly half the body length and includes numerous spines. Spiny eels and halosaurs associate with the benthos and feed on small invertebrates (e.g., crustaceans, echinoderms, polychaetes) and detritus. These fishes can regenerate their long tails when broken or injured. The leptocephalus larvae of some notacanthids are known to reach an amazing length of 2 m (Böhlke, 1989).
REFERENCES: Böhlke, 1989; Crabtree et al., 1985; Forey et al., 1996; Smith, in Carpenter, 2003; Sulak et al., 1984.
NOTACANTHIFORM CHARACTERISTICS:
1) tail elongate, tapering posteriorly to a point; caudal fin absent
2) mouth small, inferior, not extending past eye
3) pelvic fins abdominal, connected along ventral midline with a membrane
4) maxilla toothed, in gape, with a posteriorly directed spine
5) base of anal fin extremely long
ILLUSTRATED SPECIMENS:
A) Notacanthus chemnitzii, SIO 87–84, 385 mm TL (Notacanthidae—spiny eels)
B) Aldrovandia phalacra, SIO 68–463, 189.5 mm TL (Halosauridae—halosaurs; tail broken)
ANGUILLIFORMES—Eels
Historically, the true eels have been called the Apodes because they lack pelvic fins and a pelvic girdle. The pectoral fins and caudal fin may be present or absent. Scales are absent in most eels, but if present they are cycloid and imbedded. The gill openings of eels are narrow and gill rakers are absent. Eel leptocephali have a rounded caudal fin that is contiguous with the dorsal and anal fins. The Anguilliformes includes 15 families, 141 genera, and nearly 800 species. They are found in all major aquatic habitats of the world. Protoanguilla palau, recently described from deep reefs of Palau, represents a new genus and unique family of eels, the Protoanguillidae, that is hypothesized to be the sister group of all other eels (Johnson et al., 2012).
REFERENCES: Böhlke, 1989; Johnson et al., 2012; Robins, 1989; Santini, Kong et al., 2013.
ANGUILLIFORMES : ANGUILLIDAE—Freshwater Eels
DIVERSITY: 1 genus, 18 species
REPRESENTATIVE GENUS: Anguilla
DISTRIBUTION: Atlantic, Indian, and Pacific oceans, and all continents except Antarctica
HABITAT: Marine and freshwater; tropical to temperate; catadromous; demersal to benthic in lakes, rivers, and estuaries, benthopelagic in open ocean
REMARKS: Though referred to as freshwater eels,
