The Minnow family Cyprinidae is perhaps the most diverse and dynamic group of fishes in the world. Members of this family can be found in all of our rivers and streams and in most lakes. Their range of environmental tolerance varies from those that are on the very extremes of their natural continental distribution and are threatened with extirpation through habitat alteration and destruction to those which have taken advantage of habitat modifications and have expanding distribution and abundance. Minnows form the basis of our natural stream fish fauna, and they have filled most of the habitat niches through evolution and natural selection.
Couesius plumbeus – Lake Chub, one member of the large Minnow Family
The list of minnows in Canada and the United States contains 221 species in 43 genera.
Many small fishes, regardless of species, are erroneously called “minnows”, which leads to misidentification. Cyprinids are small in size, rarely reaching more than 30 cm (12 in.) in length – even as adults.
Because of their small body size and only slight differences in external characteristics, cyprinids are among the most difficult of our fish fauna to identify. Familiarity with such taxonomic terms as barbel, pharyngeal teeth, eye to head ratio, fin ray counts, lateral line scales, mouth angle, peritoneum color, gut length, and scale elevation is necessary to master the art of “keying” minnows.
Cyprinids share several common taxonomic characters, which separate them from the other fish families. External features include: scaleless head, toothless jaws, lack of adipose fin, lack of appendages at the base of the pelvic fins, and a single, soft dorsal fin in native species that has less than 10 rays.
Internal anatomical features are: cyprinids have fewer than 10 teeth in any row on the pharyngeal arch, an enlarged intestine instead of a true stomach, and a series of bones called weberian ossicle that form a rudimentary ear.
Minnow abundance varies greatly within the diverse geographical locations. Each cyprinid, like all fish, has a range of environmental and habitat requirements which are paramount to its integrity as a viable population. Several of the minnows have been unable to adapt to changing habitats – so they have perished or are threatened with extirpation from our waters.
Geological history originally formed the basics for minnow distribution and abundance, but man, through his treatment of the land and constant modification of stream courses, has dramatically changed stream and lake habitats and, as a result, has altered the fish fauna.
The role of minnows in the scheme of aquatic life is manifold. Each species occupies a niche and performs a distinct function within the ecosystem. Many are primary consumers, feeding on bottom ooze, algae, or aquatic plants, while others are secondary consumers, ingesting zooplankton, crustaceans, insects, worms, and other minnows. Minnows themselves become forage for tertiary consumers, such as predatory birds, mammals and fishes. In the final analysis, most of the game fishes which are the favorite of anglers depend on minnow prey in their diet. Most anglers, at one time or another, utilize minnows as bait. Many Northwestern Ontario outdoor businesses benefit from the minnow family directly through minnow sales.