Central Mudminnow

Family: 
Umbridae (mudminnows) in the order Esociformes (mudminnows and pikes)
Description: 

A small, mottled-brown, moderately slender fish with a rounded tail fin, a rather blunt head and a terminal mouth. The top and sides of head are fully scaled. Upper lip is attached to the snout at its midline by a bridge of skin (frenum). All fins without spines. Lateral line absent. The dorsal fin is larger than the anal fin and located far back on the body, with the front of its base just behind bases of the pelvic fins.

Back and sides are dark brown with greenish reflections, the brown on sides interrupted by vertical pale zones, and with a narrow blackish bar at the base of the tail fin. Belly is buff-white. Fins are plain.

Unlike killifishes, mudminnows have the base of the dorsal fin well forward of the base of the anal fin, and they have a bridge of skin (a frenum) connecting the upper lip to the snout. Unlike young bowfins, mudminnows don’t have a lengthy dorsal fin, and have scales on the head.

Size: 
Length: 2-4 inches (adults); maximum about 5 inches.
Habitat and conservation: 
Mudminnows typically inhabit bogs, sloughs, swamps and sluggish streams. In our state, this fish is rare and was not recorded within our borders until 1978. Its Clark County locale is a marsh with deep muck overlying sand, with cattails, lotus, sedges, watercress and more. The mudminnow is one of the hardiest of fishes and can tolerate highly acid water. It survives low oxygen levels by gulping air and absorbing it via its swim bladder. It also tolerates colder water than many other fishes.
Foods: 
During warm weather, this species focuses on both aquatic invertebrates and land insects that fall into the water. In winter, mudminnows can remain surprisingly active, even under ice cover, and turn their attention to other small fishes, which become more sluggish and vulnerable as the temperature drops. A study in Manitoba demonstrated that in winter, when the availability of insect foods decreases, female mudminnows ate mostly other fishes.
Distribution in Missouri: 
Populations have been noted along the Mississippi near New Madrid (probably swept there from Reelfoot Lake in Tennessee) and in a marsh and nearby ditches on the Mississippi floodplain in Clark County. Historically, they probably lived in southeastern Missouri.
Status: 
Central mudminnows are rare in Missouri and have been listed as Endangered in our state. A Species of Conservation Concern. It does live elsewhere in the eastern United States, but overall its numbers are declining due to destruction of its marshy habitats. Mudminnows are a small family of only six species and are most closely related to the pikes. This is the only mudminnow that occurs in our state, and it occurs only in a few marshy locations near the Mississippi River.
Life cycle: 
In springtime, mudminnows move into flooded areas after heavy rains, scatter their eggs over vegetation and leave the young to hatch and survive on their own. At the end of their first year of life, they are over 1½ inches long; at the end of the second, they are over 2 inches. A 3-inch mudminnow may be four years old. The maximum lifespan is about 7 to 9 years.
Human connections: 
The central mudminnow, taken on its own terms, is a surprisingly hardy fish, able to survive low oxygen, high acid and extreme cold—but it cannot survive when its entire habitat is destroyed. It is up to humans to protect the marshes and swamps that are its home.
Ecosystem connections: 
This fish plays the dual role of predator and prey, hunting smaller creatures (amphipods, insects and little fish) but being hunted by larger fish, birds, snakes and even mammals, especially when stranded out of water. Mudminnows, as a small, curious group, are a unique part of the world’s fauna.