|
These are small, soft-rayed fishes, with scales (cycloid in Great Lakes species) on head as well as body. Most species, including all in the Great Lakes region, have the head flattened on top toward the snout and have a mouth that opens along the upper surface of the head. The upper lip is separated from the head by a groove. These are adaptations to the distinctive surface-feeding habits of the group. Furthermore these species are markedly barred or striped and more or less sexually dimorphic. Topminnows occur in the temperate and tropical parts of North America. The group is best developed in Gulf coastal waters; two live in southern and Baja California. Over 2 dozen occur in southeastern U.S. in fresh, brackish, and salt water. They are common in shallow, inshore waters of the Great Lakes and many lakes and streams in the drainage. Some are surface feeders and all are important in the food web. They are all small, no more than 7-11 cm long, and are good aquarium fishes.
|