topminnows

Topminnows are small freshwater and brackish-water fishes that belong to the family Fundulidae. In common usage, the term refers to several North American species that occupy shallow streams, ponds, marshes, and estuaries. The group is most often represented by species in the genus Fundulus, along with a few related genera. Topminnows are generally non-migratory and adapted to surface feeding.

They are distributed from southern Canada through the United States and into parts of Central America, with a preference for quiet, vegetated waters where they can hover near the surface to feed on insects and small crustaceans. They typically reach only a few centimeters in length. Morphologically they are slender, with a laterally compressed body and a mouth oriented upwards. Color patterns vary by species and sex; males usually become more vividly colored during the breeding season.

Ecology: Topminnows are omnivorous or insectivorous and feed mainly at the water’s surface or among aquatic vegetation. They are egg-layers; females lay adhesive eggs on submerged vegetation or other substrates. In many species, males defend small territories and perform courtship displays to attract females. Parental care is minimal or absent after spawning.

Conservation: Habitat loss, pollution, and water management threaten several species with restricted ranges. While many topminnows are common, others are endangered or threatened in portions of their range, so regional assessments apply.

Examples: Notable North American topminnows include the blackstripe topminnow (Fundulus notatus) and the banded topminnow (Fundulus diaphanus). See also Fundulidae and killifish.