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Amazon Catfish Taxonomy - Catfish Classification Overview

The Catfish Order (Siluriformes)

Taxonomic Grouping	Latin Descriptor	English Translation
Kingdom	Animalia	animals
Phylum	Chordata	with spinal cords
Subphylum	Vertebrata	with back bones
Superclass	Gnathostoma	jawed vertebrates
Grade	Osteichthes	bony fishes
Class	Actinopterygii	ray-finned fishes
Division	Teleostei	completed bones
Subdivision	Ostarioclupeiomorpha	bone-shield-form
Superorder	Ostariophysi	bone-bladder
Series	Otophysi	ear-bladder
Order	Siluriformes	catfishes

All species of catfish belong to the order Siluriformes, within the grade Osteichthes or bony fishes. Catfish are found the world over with approximately 2,900 species known. They are among the most successful of Amazon fish orders with approximately 1300 Neotropical species, accounting for almost half of all the world's catfish species and almost half of Amazonia's enormous overall fish diversity.

Amazon catfish have long had great commercial importance as food fish, aquarium fish and more recently as some of the world's most exciting sportfish. Although many are bottom-dwellers (benthic), there are also a great number of predatory, pelagic (open-water) feeders, with a free-swimming (and free-fighting) habit. This, coupled with their sheer size has brought them to the attention of anglers and created new recognition of their exciting sporting potential.

Catfish - General Characteristics

Catfish do not possess scales and they range from entirely smooth-skinned species to groups of fishes almost entirely covered by bony plates. Like the rest of the fishes in the series Otophysi, catfish possess a series of bones called the Weberian apparatus that connects their swim bladders with their inner ears for the transmission of sound. Unlike peacock bass (and other Perciforme fishes), catfish jaws are not protractile. They generally possess small, rasp-like teeth (although there are exceptions with complex dental apparatus) and most species possess up to 4 pairs of barbels. Species with bony fin rays have the unique ability to lock the the spiny second ray of their pectoral and dorsal fins, as many anglers who've ever handled (or mishandled) a bullhead probably know painfully well. A well-developed adipose fin is usually present.

Most Siluriformes possess various adaptations associated with a benthic habitat. Some may have a vertically compressed form, like the redtail or pirarara, while others may possess a reduced swim bladder. Their association with deep holes or nocturnal feeding habits has led to great dependence on and development of sensory organs other than sight. Many species have highly developed olfactory (smell) or chemical sense receptors, allowing them to find food in the relatively low light conditions associated with their habitat. Many benthic catfish have reduced visual acuity.

Catfish - Variability and Specializations

In spite of their overall similarities, Amazon catfish possess an incredible range of variation in form, behavior, habitat, feeding habits and specializations. They have adapted to every available ecological niche in Amazonia. There are species that feed on planckton, species that are piscivorous (fish eating) and even groups of parasitic species. There are broadly built species, long, thin species and species ranging from some of the world's smallest to some of the world's largest freshwater fishes.

Like many other Amazon fishes, catfish taxonomy has been somewhat problematic due to the great difficulty of thoroughly exploring and sampling this enormous region. Due to a constant stream of newly discovered species, catfish taxonomy has undergone many recent updates and revisions. Currently, scientists recognize 15 families of Amazon catfish, with several other families represented elsewhere in South America.

Neotropical and South American Catfish Families

Diplomystidae	Called " Velvet Catfishes", their skin is entirely covered with papillae. Considered to be the most primitive of Siluriforme families, they lack some of the characters shared by other families. Found in small waters (typically at high altitudes) in Argentina and Chile. No species of angling interest
Cetopsidae	Smooth bodied catfishes with an absence of spines. Their dorsal fin is placed unusually forward on their bodies. Known as whale-like catfishes (not due to their size). Amazonian, but not of angling interest, some species are notorious for attacking and damaging live fishes in nets (and on occasion, humans). A number of undiscovered and undescribed species remain in this family.
Helogenidae	Smooth bodied catfishes with an absence of spines, their dorsal fin is placed posterior (rearward) on their bodies. Well developed barbels. Amazonian but not of angling interest. Family combined with Cetopsidae in recent redescription.
Aspredinidae	Known as banjo catfish due to their unique shape. There are 12 genera in the family, occurring primarily in Amazonia. Characterized by rows of tubercules and a flattened anterior (front) body, these catfishes lack an adipose fin and have a very small gill slit. Small-sized catfishes, typically less than 12 inches in length. None are of angling interest, however they are popular in the aquarium trade.
Nematogeneidae	Mountain catfishes of central Chile. Elongated and entirely smooth bodies, they possess three pairs of barbels and lack adipose fins. This family currently includes only one known species, Nematogenys inermes. Not of interest to anglers.
Trichomycteridae	With over 200 species, this family includes parasitic species of which legends are made, notably the infamous "Candiru", known to enter the urethra of living animals (including humans). There are species that feed on blood from host fishes gills and others that specialize in parasitizing body mucous. With many specialized anatomical features, the naked and elongate Trichomycteridae could easily have been the inspiration for the chest-bursting creature made famous by the movie "Alien". In spite of these biological horror models, most species in the family feed on small invertebrates. No species of angling interest.
Callichthyidae	This large family is comprised of armored catfishes with two rows of overlapping bony plates extending along their sides. They have strong locking spines on their dorsal and pectoral fins. Their small, downward facing mouth has one or two pairs of barbels. They are obligatory air breathers. Callichthyidae utilize atmospheric air to augment the oxygen supply available through their gills. They engulf and swallow air at the surface while gas exchange takes place in their stomachs. The family includes the popular "Corydoras", ubiquitous in home aquaria. Although several larger species are occasionally caught on rod and reel, and some are popular baits, none are of significant interest to anglers.
Scoloplacidae	Containing one genus with 4 known species, this family of very small fishes is not of interest to anglers. They possess two rows of bony plates with tooth-like projections on their bodies, hence the name spiny dwarf catfishes. They lack an adipose fin.
Astroblepidae	Found in fast-water Andean streams, the generally small fishes in this family have disc-shaped ventral, sucker mouths and unique adaptations to their pelvic musculature. They are well-designed for their high altitude, fast current existence, but not of interest as a sportfish.
Loricariidae	The largest family of catfishes with almost 700 species, they are covered with up to five rows of bony plates. Their ventral, disc-like sucker mouths help identify this family which includes several species widely-known as "plecostumus", popular aquarium favorites. Although barbels are not always predominant, their lower lips are often edged with papillae (fleshy protuberances).
Pseudopimelodidae	Called bumble-bee catfishes, this family, until recently, was considered a subfamily of Pimelodidae. The Psuedopimelodidae is comprised of 26 species in 5 genera. Characterized by wide mouths, short barbels and small eyes. Some species have contrasting coloration with attractive patterns and are of interest to aquarists.
Heptapteridae	These poorly-known, generally small, naked catfishes were also at one time considered a subfamily of Pimelodidae. With 13 genera, these fishes comprise a species-rich family, with many species yet to be described. A few species, including Rhamdia quelen (sebae), are of angling interest.
Pimelodidae	This family is characterized by naked bodies, a well-developed adipose fin and three pairs of relatively long barbels. Ranging from very small to the most enormous of all Amazon catfishes, Pimelodidae contains many of the species most desired by anglers. Among their diverse members are the gigantic piraiba, the powerful jau, the speedy suribim and the big and prolific redtail.
Hypopthalmidae	With eyes placed laterally and visible from below, they are called lookdown or loweye catfishes. This family of four species is distinguished by its exceptionally long anal fin. Taxonomists have reclassified Hypopthalmidae and now consider it to be included in the family Pimelodidae.
Ariidae	These medium to large sized, world-wide, marine catfishes are parental caregivers, with males commonly protecting eggs and young in their mouths. Although some species move into brackish or fresh waters, they are absent from the fisheries generally of interest to Amazon anglers.
Doradidae	Known as the thorny catfishes, these bottom dwellers possess bony plates and generally well-developed spines. Although ranging from small to quite large, they are not generally of interest to anglers. An exception is the cuiu-cuiu, or ripsaw catfish (Oxydoras niger) which can exceed 20 pounds and a meter in length and is often sought by anglers.
Auchenipteridae	Known as the driftwood catfishes, these nocturnal catfishes are distributed in 20 genera with approximately 100 species. Known for their sexual dimorphism and internal insemination (males and females may differ greatly in size) they are not of interest to anglers.
Ageneiosidae	With an extremely flattened head and a rapidly thickening midsection, these fishes have a unique appearance, prompting the name "bottlenose catfishes". Their laterally positioned eyes can see downward. This previously recognized family is now included in Auchenipteridae.
	Preserved specimens photographed at INPA (National Institute of Amazon Research), Manaus, Brazil

References

Froese, R. and D. Pauly. Editors. 2009. FishBase. World Wide Web electronic publication. www.fishbase.org, version (06/2009).

Lundberg, J. G., and M. W. Littmann. 2003. Family Pimelodidae. in CLOFFSCA: Check List of Freshwater Fishes of South and Central America.

Nelson J, (2006) Fishes of the World. John Wiley & Sons, Inc. Hoboken, New Jersey, USA

Stiassney M, et al (1996) Interrelationships of Fishes. Academic Press. San Diego, Califórnia, USA

Rapp Py-Daniel, L, (2007) Classification of Fishes, Graduate Course; coursework, reference material and lectures, INPA (National Institute of Amazon Research), Manaus, Brazil