Albuliformes

(Bonefishes and relatives)

Class: Actinopterygii

Order: Albuliformes

Number of families: 3

Evolution and systematics

The order Albuliformes includes three extant families: Albulidae, Notacanthidae, and Halosauridae. The bonefish family (Albulidae) contains two genera: Albula, with possibly eight species, and Istieus, with two species. The halosaur family (Halosauridae) contains three genera: Aldrovandia, with six species; Halosaurus, with nine species; and Halosauropsis, with one species. The marine spiny eel family (Notacanthidae) contains three genera: Lipogenys, with one species; Notacanthus, with six species; and Polyacanthonotus, with four species. The fossil record for this order extends back almost 100 million years.

Physical characteristics

In Albulidae (bonefishes) the body is moderately slender. The snout is distinctively pointed and conical. The mouth is inferior, and the snout projects well beyond the tip of the lower jaw. All fins lack spines. The dorsal fin originates at about the midpoint of the body in Albula. In Istieus the dorsal fin origin is more forward, and the fin is elongate, extending nearly to the caudal fin. The anal fin is short and originates well behind the base of the dorsal fin. The pelvic fins are positioned below the last dorsal fin rays in Albula and under the middle of the dorsal fin in Istieus. Scales are small. Most fishes are less than 3.3 ft (1 m) in length. The back of Albula is blue-green in color, with narrow, dark horizontal lines that fade rapidly after death. The sides are silvery.

Halosaurs have an elongate, eel-like body, which tapers to a point. There is no caudal fin. The anal fin is elongate and extends along the posterior half of the body. There is a single short dorsal fin located just before the midpoint of the body. All fins have soft rays with no spines. The mouth is inferior, and the snout projects well beyond the tip of the lower jaw. Most fishes are less than 3.3 ft (1 m) in length. Colors range from tan to black.

The Notacanthidae, or marine spiny eels, have an elongate, eel-like body, which tapers to a point with little or no caudal fin. The anal fin is elongate and extends along the posterior half of the body. The anal fin consists of spines anteriorly grading to soft rays posteriorly. The dorsal fin in most species has from 26 to 41 isolated spines, from which the family's common name "spiny eels" derives. The mouth is inferior, and the snout projects beyond the tip of the lower jaw. Most fishes are less than 3.3 ft (1 m) in length. The coloring is typically tan.

Distribution

This order is worldwide in distribution. The family Albulidae occurs in shallow tropical waters worldwide. The Notacanthidae and Halosauridae are little-known families of deep-sea fishes that occur along the continental slope and rise of the world's oceans at depths from 3,281 to 9,843 ft (1,000–3,000 m). Bonefish (Albula) frequent coastal and inshore waters of tropical seas worldwide. In the western Atlantic, bonefish regularly occur in the Florida Keys and the Bahamas and throughout the Caribbean. Halosaurs and spiny eels are deep-sea fishes of worldwide distribution.

Habitat

Bonefish are common in tropical shallow-water areas. They are most abundant at depths of less than 115 ft (35 m) and often feed in water less than 3.3 ft (1 m) deep. Bonefish can be found over shallow grass flats and in sandy areas. Juvenile bonefish and metamorphic larvae occur along sandy beaches with scattered patches of sea grass in water from 1 to 4.3 ft (0.3–1.3 m) deep. In southern Florida bonefish larvae recruit to sandy beaches during winter and early spring and are found in water temperatures ranging from 60.8 to 82.8°F (16.0–28.2°C) and salinity levels ranging from 10.4 to 37.0 ppt.

Halosaurs typically are found at depths of 1,640–13,123 ft (500–4,000 m) on the continental slope and rise. Spiny eels usually are found at depths of 656–11,483 ft (200–3,500 m) on the continental slope and rise. They generally hover just above the bottom.

Behavior

Bonefish are remarkable because of their common presence in extremely shallow water (less than 1.6 ft, or 0.5 m). The fisheries for bonefish in most areas require specialized boats capable of entering shallow water with little or no noise. Fish typically swim in small schools of five to 20 individuals, although larger schools of more than 100 individuals are not uncommon. Anglers searching for bonefish often detect their presence by spotting their tails protruding from the water as the fish dig in the bottom to feed.

Feeding ecology and diet

Bonefish feed on a variety of small benthic and epibenthic invertebrates and fishes. Feeding often takes place in shallow water, where foraging bonefish are seen with their fins protruding from the water. As they forage, bonefish schools frequently dig in the bottom and disturb considerable quantities of mud and sand. Xanthid crabs, toadfish (Opsanus beta), portunid crabs, alpheid shrimp, and penaeid shrimp make up most of the diet of populations in southern Florida. In some areas mollusks and small worms are important in the diet. Juvenile bonefish feed on a variety of polychate worms and small crustaceans, principally copepods, amphipods, and caridean shrimp. Bonefish are subject to occasional predation by sharks.

Halosaurs feed primarily on benthic prey, including worms and small benthic and epibenthic mollusks and such crustaceans as decapods and amphipods. Larger species also consume various fish. Spiny eels feed mainly on small benthic macrofauna, including worms and small crustaceans, such as amphipods and mysids. Species of the genus Notacanthus have specialized teeth that form a continuous serrated cutting edge probably used to crop sessile invertebrates. Little is known about which animals prey on halosaurs or spiny eels.

Reproductive biology

In Florida male bonefish reach sexual maturity at a fork length (measured from the tip of the snout to the fork in the tail) of about 15.7 in (400 mm) and an age of about 3.5 years. Florida females reach sexual maturity at a somewhat larger size, about 19.7 in (500 mm), and an age of about four. Gonadal activity is seasonal and peaks from November to May. Yolked oocytes are present in the ovaries in every month except August and September and are most abundant November to May. In Florida juvenile bonefish and post larvae recruit to sandy beach areas during winter and spring. Total fecundity ranges from 0.4 million to 1.7 million oocytes and increases with fish weight. Spawning areas of bonefish are unknown. Larvae reach a maximum size of about 3 in (76 mm). Bonefish live for at least 19 years. Growth of the bonefish is rapid until the age of about six years and then slows considerably.

Little is known about halosaur or spiny eel reproduction. In halosaurs spawning appears to be seasonal in some species, but others spawn year-round. It is unknown where the eggs and larvae develop. In spiny eels spawning occurs year-round. It is unknown where the eggs and larvae develop. Spiny eels have remarkable leptocephalus larvae that can reach lengths of 3.3–6.6 ft (1–2 m). Aside from their extremely large size, the larvae resemble those of eels in appearance.

Conservation status

No species of Albuliformes are included on the IUCN Red List.

Significance to humans

In many areas of the species' range, including the waters off the Florida Keys, bonefish are the basis of economically important recreational fisheries, among them a for-hire charter boat fishery in the Florida Keys. Bonefish are renowned by anglers for their wariness and fighting abilities and often are caught in water as shallow as 1 ft (0.3 m). In the Florida Keys fishing for bonefish is a year-round activity and provides a significant source of income to professional fishing guides. The commercial sale of bonefish in Florida is prohibited; the limits placed upon the recreational fishery for bonefish are a bag limit of one fish per angler per day and a minimum fish size of 18 in (457 mm) in total length. Bonefish are not considered a food fish in Florida, and most bonefish are released when caught. Halosaurs and spiny eels are of no commercial value.

Species accounts

Resources

Hildebrand, S. F. "Family Albulidae." In Fishes of the Western North Atlantic, edited by H. B. Bigelow. Vol. 3. New Haven: Sears Foundation for Marine Research, Yale University, 1963.

Colborn, J., R. E. Crabtree, J. B. Shaklee, E. Pfeiler, and

B. W. Bowen. "The Evolutionary Enigma of Bonefishes (Albula spp.): Cryptic Species and Ancient Separations in a Globally Distributed Shorefish." Evolution 55, no. 4 (2001): 807–820.

Crabtree, Roy E., Christopher W. Harnden, Derke Snodgrass, and Connie Stevens. "Age, Growth, and Mortality of Bonefish, Albula vulpes, from the Waters of the Florida Keys." Fishery Bulletin 94 (1996): 442–451.

Crabtree, Roy E., Derke Snodgrass, and Christopher W. Harnden. "Maturation and Reproductive Seasonality in Bonefish, Albula vulpes, from the Waters of the Florida Keys." Fishery Bulletin 95 (1997): 456–465.

Crabtree, Roy E., K. J. Sulak, and J. A. Musick. "Biology and Distribution of Species of Polyacanthonotus (Pisces: Notacanthiformes) in the Western North Atlantic." Bulletin of Marine Science 36, no. 2 (1985): 235–248.

[Article by: Roy E. Crabtree, PhD]