Significance To Humans

Stout beardfishes are of some commercial importance, particularly in Madeira, where they are marketed fresh and frozen. ♦

Acanthopterygian Fishes, with Special Reference to Those of the English Chalk." Philosophical Transactions of the Royal Society of London 3 (1994): 213-482.


"Coelacanths: Coelacanth Fact Sheet." South African Institute for Aquatic Biodiversity. Ichthos, 2001. (March 20, 2003). <>

Melanie Stiassny, PhD

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(Troutperches and relatives)

Class Actinopterygii Order Percopsiformes Number of families 3

Photo: Troutperch (Percopsis omiscomaycus) combine the characteristics of spiny-rayed and soft-rayed fishes, resembling both trout and perch. (Photo by Animals Animals ©Raymond A. Mendez. Reproduced by permission.)

Photo: Troutperch (Percopsis omiscomaycus) combine the characteristics of spiny-rayed and soft-rayed fishes, resembling both trout and perch. (Photo by Animals Animals ©Raymond A. Mendez. Reproduced by permission.)

Evolution and systematics

The oldest fossils date back to the Paleocene Paskapoo Formation (between 60 and 62 million years ago) in western Canada. The Percopsiformes may be related remotely to the codfishes (Gadiformes) and toadfishes (Batrachoidiformes). One point of controversy about their phylogeny is that they show primitive conditions, such as the presence of an adipose fin, which suggests character reversal in their evolutionary history. The monophyly of this group has been questioned. Murray and Wilson proposed removal of the am-blyopsid family from the group and created a new order: Am-blyopsiformes.

There are two recognized suborders. The first, the Per-copsoidei, is characterized by the presence of an adipose fin and a complete lateral line. The suborder is represented by one family: Percopsidae, or troutperches, with one genus and two species. The second, the Aphredoderoidei, is characterized by the absence of an adipose fin and includes two families: Aphredoderidae (pirate perch, one species) and Amblyopsidae (swampfishes and cavefishes, four genera and six species).

Physical characteristics

These are small fishes (less than 8 in, or 20 cm) with a mosaic of primitive characters, such as an adipose fin, and advanced characters, such as a pelvic girdle located farther back from the cranium compared with most other fishes. They also have fewer fin spines and ray-supported dorsal and anal fins, each usually with one to four anterior soft spines. If pelvic fins are present, they are located in a position below the abdomen and behind the pectorals, with three to eight soft rays. The body is covered with cycloid or ctenoid scales.


The troutperches are distributed in North America from Alaska and the Great Lakes drainage to the southern and eastern United States.


All species are freshwater, with two species found in swamps, one as a facultative cave dweller. Four species are obligatory cavernicoles (cave dwellers).


Besides the fact that all species are solitary, little is known about their behavior. The exception is certain types of behavior studied among cavefishes. At least two of the non-cavernicolous species are nocturnal.

Feeding ecology and diet

Members of this order are opportunistic predators that eat a variety of food items; at least one species is cannibalistic. Percopsiformes are preyed upon by other fishes, water snakes, and fish-eating birds. Fish larvae may be preyed upon by aquatic insects. Cavefishes are not generally preyed upon since they are the top predators in their habitats.

Reproductive biology

They are oviparous, but nothing else is known at the family level. Spawning (at least for the noncavernicolous species) takes place in the spring. Fecundity tends to be low.

Conservation status

The IUCN Red List includes four species from this order, all of which are cave-dwelling species from the family Am-blyopsidae. Speoplatyrhinus poulsoni is listed as Critically Endangered, while Amblyopsis rosae, A. spelaea, and Typhlichthys subterraneus are listed as Vulnerable.

Significance to humans

Some species can be found in both the commercial trade and public aquaria. Cave species have been important in understanding evolutionary issues.

1. Alabama cavefish (Speoplatyrhinus poulsoni); 2. Ozark cavefish (Amblyopsis rosae); 3. Swampfish (Chologaster cornuta); 4. Spring cavefish (Forbesichthys agassizii); 5. Southern cavefish (Typhlichthys subterraneus); 6. Northern cavefish (Amblyopsis spelaea); 7. Sand roller (Percopsis transmontana); 8. Troutperch (Percopsis omiscomaycus); 9. Pirate perch (Aphredoderus sayanus). (Illustration by Emily Damstra)

Species accounts

Ozark cavefish

Amblyopsis rosae

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