Minnows

Minnows are a diverse group of about 1,600 species of small exclusively freshwater fish in the family Cyprinidae. The most familiar of these fish are carp, minnows, tenche, and barbs. Species in the minnow family occur in Africa, Asia, Europe, and North America. In addition, some cultivated and game species have also been introduced to South America, New Guinea, Australia, New Zealand, and some other places. The greatest numbers of species of Cyprinidae occur in tropical Africa and in South and Southeast Asia.

Most species of minnow have a laterally compressed body, a terminal mouth, and relatively large, shiny scales. Minnows also have pharyngeal teeth in their throat, which are used to grind their food against a hard pad at the base of the skull. Male minnows are often smaller than females, and many species develop beautiful colors during the spawning season.

Most species of minnows are planktivorous, meaning they eat small crustaceans, insects, and other aquatic animals floating in the surface waters. Some of the larger species of minnow, such as carp, are omnivorous, eating both aquatic plants and animal matter.

Minnows are important in the food web of their freshwater ecosystems because they are the food base for many species of predatory fish and other animals; minnows that are food for economically important sportfish are sometimes referred to as "forage" fish. Some North American species of minnows are also valuable as baitfish for sport fishing and are sold in large numbers for this purpose.

Some of the larger species in the Cyprinidae are cultivated as food in many parts of the world. The most important species in aquaculture is the common carp ( Cyprinus carpio), along with the grass carp ( Ctenopharyngodon idella), bighead carp ( Aristichtys nobilis), and silver carp ( Hypophthalmichtys molitrix). Enormous quantities of these fishes are grown in some parts of the world as food for humans, especially in Asia.

Several other species in the Cyprinidae are commonly kept as pets, either in indoor bowls or tanks, or in outdoor pools. The goldfish ( Carassius auratus) is probably the world's most common pet fish. The koi is a golden-colored variety of the common carp that is often kept as a pet, especially in Japan. Many varieties of goldfish and koi have been developed by fish breeders. Some of these fish have bizarre shapes and behaviors, which would be totally maladaptive in wild fish, but are prized as unusual traits by many aficionados of these pet fish.

About 200 species of fish in the minnow family are native to North America, with about 100 of them included in a single genus, Notropis, most of which are commonly called shiners. Minnows native to North America are all small species, while several larger, Eurasian species have been introduced to North America and now occur in self-sustaining populations.

The most widespread native species is the common or silver shiner (Notropis cornutus), which is virtually ubiquitous in many surface waters east of the Mississippi in the United States and is also widespread in eastern Canada. This species is important as a forage fish, and as a baitfish.

The pearl or northern dace (Semotilus margarita) is a widespread species that is especially important in brown-colored, boggy waters. The fallfish (S. corporalis) occurs in northeastern North America, and can grow as large as 18 in (45 cm), and is sometimes eaten by people.

The golden shiner (Notemigonus crysoleucas) occurs throughout the Great Lakes and Hudson Bay drainage, and is an important forage fish and common baitfish. The fathead minnow (Pimephales promelas) has a similar distribution and is also used as a baitfish.

The stoneroller (Campostoma anomalum) digests nutrients out of the copious quantities of mud that it ingests. The stoneroller has an enormously long intestine that coils 15 times around its air bladder.

In addition to the various native members of the minnow family, several species have been introduced to North America. The most familiar introduced species is the common carp (Cyprinus carpio). This fish is commonly cultivated as food in Europe and Asia, and it was released to many North American lakes in the hope of establishing a food resource that many immigrants would like to eat. Unfortunately, the common carp has caused some important ecological damage in many of the waterbodies where it has become established, resulting in the displacement of native species of fish and other animals and damage to aquatic vegetation.

The goldfish (Carassius auratus) has also been introduced to many ponds and lakes in North America, either deliberately as an ornamental fish, or more-or-less accidentally when unwanted pet goldfish were released into nearby ponds, or just flushed down a toilet. Like the common carp, alien populations of goldfish cause important ecological damage in many of the places where they have become well established.