What are fish?
The group of animals commonly referred to as "fish" is a paraphyletic group of some 30,000-plus described species (
http://www.fishbase.org/). That is, it includes all of the descendants of the common ancestor of the vertebrates (subphylum Vertebrata) with the
exception of the tetrapods (subclass Tetrapoda–amphibians, reptiles, birds, mammals, totaling around 23,000 species), a fairly
significant branch of the subclass Sarcopterygii alongside lungfish and coelacanths. Included are the hagfish (order Myxiniformes),
lampreys (order Petromyzontiformes), sharks, rays and chimaeras (class Chondrichthyes; sharks and rays comprise the subclass
Elasmobranchii), the sturgeon and paddlefish (order Acipenseriformes), bowfin (order Amiiformes), gars (order Semionotiformes),
and the hugely diverse teleost fish (division Teleostei), which comprise about 96% of extant fishes. For the sake of simplicity,
the cartilaginous fish are often referred to simply as elasmobranchs, although this group excludes about 30 species of chimaeras,
and the bony fish as teleosts, although the teleosts do not include other ray-finned fish such as gar, bowfin, paddlefish
or sturgeon. Care must be taken when speaking inclusively of the whole or parts of the "fish" assemblage.
Tropical fish kept in aquaria include both freshwater and marine species. The vast majority of over 1000 species of fish
kept by hobbyists are small freshwater. Marine tanks are more involved to keep and maintain, so numerically tropical marine
fish comprise a much smaller portion of the pet fish population, but species diversity is comparable. Greater than 95% of
freshwater fish in the pet trade are produced in aquaculture facilities, while the opposite is true for marine fish. Singapore
is the world's largest exporter of tropical fish, while in the United States, Florida is the leading tropical fish aquaculture
producing area, with much of the industry within an hour's drive of Tampa/St. Petersburg.
Common groups of freshwater fishes kept by hobbyists:
• Cyprinidae, the minnows, over 2000 species. Barbs, rasboras, danios, (also carp, koi and goldfish).
• Osteoglossidae, bony-tongues, 6 species. Arowanas.
• Catfishes, 15 families, over 2000 species. Including Loricaridae(including plecostomus and other "algae eaters", Callichthyidae
(including Corydoras spp.), Aspredinidae (banjo catfishes), Schilbeidae (glass catfishes).
• Cichlidae, cichlids, over 900 species (over 700 from Africa). Extensive adaptive radiation of cichlids in African
rift lakes has received considerable study in evolutionary biology. Also includes the South American freshwater angelfish
(Pterophyllum) and discus (Symphysodon).
• Electrophoridae, electric eel or electric knifefish, one species. Requires acid water (pH 6), can breathe air.
• Mormyridae, elephant fish or elephant-nosed fish, nearly 200 species. Africa, weak electric organ, large cerebellum.
• Anablepidae, four-eyes, three species. Surface dwellers with 2 anterior chambers per eye, South America.
• Labyrinth fishes (Superorder Anabantoidei, including families Anabantidae, Helostomatidae, Belontiidae, and Osphronemidae),
about 80 species. Gouramis, kissing gourami, betta. Anabantoid fishes have a suprabranchial organ called the labyrinth organ
used for air breathing.
• Cobitidae, the loaches, about 110 species.
• Characidae, characins, over 1000 species. Tetras, pacu, piranha. Adipose fin.
Some representative marine fish families:
• Grammidae, basslets.
• Tetraodontidae, blowfishes
• Chaetodontidae, butterflyfishes
• Pomacanthidae, angelfishes
• Pomacentridae, damselfishes and anemonefishes
• Balistidae, filefishes
• Gobidae, gobies
• Serrandidae, groupers
• Scorpaenidae, lionfishes, scorpionfishes
• Zanclidae, Moorish idol, one species.
• Scaridae, parrotfishes
• Syngnathidae, seahorses and pipefishes
• Acanthuridae, tangs and surgeonfish
• Balistidae, triggerfish
• Ostraciidea, trunkfishes, and boxfishes
• Labridae, wrasses