are generally catadromous. While they live most of their adult lives in freshwater, they spawn in open ocean, far from land (Tsukamoto et al., 2011). Freshwater eels are also semelparous, meaning they die soon after spawning. Recent studies have shown that they are related to a group of deep-sea marine eels, the Nemichthyidae and Serrivomeridae (Inoue et al., 2010). Anguillids are generalized predators and feed on other fishes and benthic invertebrates. Freshwater eels are commercially important food fishes and several species support a large aquaculture enterprise.
REFERENCES: Inoue et al., 2010; Smith, 1989; Tesch, 1977; Tsukamoto et al., 2011.
ANGUILLID CHARACTERISTICS:
1) lower jaw projecting beyond upper jaw
2) pectoral fins well developed
3) scales small, embedded in skin
4) teeth small, in bands
5) trunk lateral-line canal complete
ILLUSTRATED SPECIMEN:
Anguilla japonica, SIO 85–138, 356 mm TL
ANGUILLIFORMES : MURAENIDAE—Moray Eels
DIVERSITY: 15 genera, 198 species
REPRESENTATIVE GENERA: Echidna, Gymnothorax, Muraena, Uropterygius
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine, occasionally freshwater; tropical to temperate; continental shelf to upper continental slope, benthic on or in coral and rocky reefs, as well as soft bottoms
REMARKS: Unlike most eels, morays can be quite colorful with distinctive markings. They range in size from ∼20 cm to 3.75 m in total length, and are among the world’s largest eels. In addition to their laterally compressed head and body, morays have a characteristic raised-head profile behind the eyes. These eels are both predators and scavengers and eat living or recently dead fishes or crustaceans. Piscivorous species are characterized by long, needle-like teeth and highly mobile pharyngeal jaws (Mehta and Wainwright, 2008), while species specializing on crustaceans may have molariform teeth. Care should be taken when eating large morays as they are responsible for many cases of ciguatera poisoning. The phylogenetic relationships of morays were hypothesized by Tang and Fielitz (2013) based on molecular data.
REFERENCES: Böhlke et al., 1989; Böhlke and McCosker, 2001; Böhlke and McCosker, in Carpenter and Niem, 1999; Mehta and Wainwright, 2008; Smith, 2012; Tang and Fielitz, 2013.
MURAENID CHARACTERISTICS:
1) pectoral fins absent
2) posterior nostril high on head
3) head and body laterally compressed for entire length
4) gill opening reduced to small round hole or slit
5) scales absent
6) trunk lateral-line canal absent
ILLUSTRATED SPECIMENS:
A) Uropterygius versutus, SIO 59–7, 289 mm TL
B) Gymnothorax moringa, SIO 71–275, 377 mm TL
C) Enchelycore octaviana, SIO 65–33, radiograph
ANGUILLIFORMES : OPHICHTHIDAE—Snake Eels and Worm Eels
DIVERSITY: 52 genera, 318 species
REPRESENTATIVE GENERA: Muraenichthys, Myrichthys, Ophichthus
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine, occasionally in freshwater; tropical to temperate; continental shelf to continental slope, usually benthic on or in soft bottoms, with some species occuring in midwaters of the mesopelagic
REMARKS: The Ophichthidae is a large family of eels with considerable morphological diversity. For example, the pectoral, dorsal, anal, and caudal fins can be either present or absent, and the origin of the dorsal fin, when present, can be over the pectoral fin or well posterior. The unusual basket-like structure formed by the branchiostegal rays often involves rays that are detached from any other bone. Some species in the Ophichthinae use their hard, pointed tails to burrow backward, and their burrowing lifestyle implies that the bulk of their diet is likely benthic invertebrates. They are abundant in certain areas, caught by hook-and-line, and occasionally consumed by humans.
REFERENCES: Böhlke and McCosker, in Carpenter and Niem, 1999; McCosker, 1977, 2010; McCosker et al., 1989; McCosker and Rosenblatt, 1998.
OPHICHTHID CHARACTERISTICS:
1) posterior (excurrent) nostril on upper lip (usually) or inside mouth
2) tail usually hard, pointed; caudal fin absent in most species (present in Myrophinae)
3) branchiostegal rays numerous (15–49), overlapping at ventral midline to form a basket
4) scales absent
5) trunk lateral-line canal complete, left and right sides connected by a canal across nape
ILLUSTRATED SPECIMENS:
A) Callechelys eristigma, SIO 65–263, 503 mm TL, holotype
B) Scolecenchelys chilensis, SIO 65–645, 284 mm TL, holotype
ANGUILLIFORMES : CONGRIDAE—Conger Eels
DIVERSITY: 32 genera, 196 species
REPRESENTATIVE GENERA: Conger, Heteroconger, Paraconger
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine; tropical to temperate; continental shelf to abyssal plain, benthic on soft bottoms, often burrowing into substrates
REMARKS: Like the Ophichthidae, the Congridae is a speciose family exhibiting significant morphological and ecological variation, and is difficult to characterize. Conger eels generally have well-developed pectoral fins and large eyes for use in visual predation, but there are exceptions to both traits. They live in association with the benthos and range from depths of less than 5 m to more than 2,000 m. Most species actively feed on small fishes and invertebrates at night, but the Heterocongrinae form vast “gardens” in sands adjacent to reefs and are visual plankton pickers. Conger eels are important in the fish leather industry (Grey et al., 2006).
REFERENCES: Castle and Randall, 1999; Grey et al., 2006; Smith, 1989b; Smith, in Fischer et al., 1995.
