The central mudminnow is a small fish in the family Umbridae

Umbridae

Umbridae are a family of Actinopterygii, ray-finned fish, that inhabit freshwater environments in temperate regions across the northern hemisphere...

 of the order Esociformes

Esociformes

Esociformes is a small order of ray-finned fish, with two families, the Umbridae and the Esocidae . The pikes of genus Esox give the order its name. There are ten species — five in each family....

. It is found in central and eastern North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 in productive waters. It is fairly tolerant of low oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 concentration

Concentration

In chemistry, concentration is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration...

s and, as a result, it is sometimes the only, or one of a very few, fish species present in waters susceptible to winter- or summerkill.

Abstract

The central mudminnow, or Umbra limi, lives in slow-moving water around ponds, lakes, and streams in central North America and ranges in length from 51–102 mm. It burrows tail-first in mud and can tolerate low oxygen levels, allowing it to live in waterways unavailable to other fishes. Its coloration matches this habitat, being brownish above with mottled sides and a pale belly. It is eaten by many species of fish such as grass pickeral, sunfishes, northern pike, and catfishes; also preyed upon by birds, foxes, and snakes when caught out of water. According to Paszkowski and Tonn, mudminnows perform better in environments with other fish species than in environments with just mudminnows, because the "interspecific interactions override a similar contribution for the mudminnow, which is regarded as a fugitive species". Central mudminnows are known to eat a large variety of zooplankton and benthic and epiphytic macroinvertebrates. Adults are also known to feed energetically in the winter months on littoral fish. One experiment conducted by Colgan and Silburt resulted in mudminnows typically feeding more on benthic than plaktonic resources, with zooplankton making up only 0.7 items out of 511 items found in the stomach. This mudminnow uses a modified gas bladder to breath air pockets that are trapped between the ice and water during the winter months to feed and stay active.

Geographic Distribution of Umbra limi

Umbra limi is a widely distributed species that inhabits many freshwater systems such as lakes, streams, and wetlands near the littoral zone, or near the shore, and around dense cover in central North America west of the Appalachian Mountains (1,3). including the St. Lawrence River, Great Lakes, Hudson Bay (Red River, and the Mississippi River basins from Quebec to Manitoba and south to central Ohio, western Tennessee, and northeastern Arkansas. The mudminnow has also been introduced into many of the tributaries in Connecticut and Massachusetts. The introduction and movement of this species into Connecticut, Massachusetts, and even Maine is unknown. Their habitats being marshy lands and rivers are under attack by human development and contact constantly and is likely causing a decline in their populations.

Ecology

The central mudminnow is carnivorous and typically feeds in the benthic area of freshwater habitats. According to Colgan and Silburt, it prefers amphipods, coleopterans, and anisopterans while avoiding zooplankton and other planktonic species (1984). In a study conducted by Colgan and Silburt, they found that an average of only 0.9 percent (out of 511 items) of the contents of dissected stomachs of Umbra limi contained zooplankton. Chironoids and gastropods, when taken from the dissection, had a combined volume of about 60 percent which proves that the mudminnow feeds mainly in benthic areas (1984).

Umbra limi prefers water with low dissolved oxygen levels, warmer temperatures, and low flow. It is able to live hypoxic, or lack of dissolved oxygen, conditions because of its ability to breath outside of water. This species is also known to feed in the winter months in temperatures as low as 1.1 degrees Celsius. According to Jenkins and Miller, some animals that feed on the mudminnow are the grass pickeral, sunfishes, northern pike, and catfishes; also preyed upon by birds, foxes, and snakes when caught out of water. This mudminnow is known to bury itself in the mud or sand to avoid capture in some situations. Also, in a study done by Jenkins and Miller, they found that the mudminnow is a shoaling fish, that is they prefer to be with other mudminnows other than by themselves. This shoaling mechanism seems reduce their predation risk

Life History

The central mudminnow tends to spawn in mid-April in temperatures of 13 degrees Celsius with the higher temperature stimulating the spawning. The spawning can take place in shallow waters producing up to 2,500 eggs in one season. According to Robinson et al. the average age of the central mudminnow is three while they can reach ages of five or six, according to their study in 2009. They also found that females are typically larger than males when compared around age two. The egg stage is generally 6 days and then they enter the larval stage of development.

Current Management

The human dimension is causing a decline in populations due to habitat destruction. A way to reduce the impact that humans have on the central mudminnow's environment could be to have more protection over the marshes and swampy areas that they inhabit. Invasive species are also a problem in the over-predation of the mudminnow. Many of these species are introduced to an environment with high populations of mudminnows and the results are devastating. There are not management plans that are available but there needs to be something implemented or the species is going to have a short future.

Management Recommendations

Since the species is having habitat destruction in many cases, it seems necessary to implement more strict law pertaining to the construction of urban and rural communities. A law that suggests that any water habitat that is needed to be destructed should undergo a complete analysis of the species contained in it. It should be seined and or electroshocked to determine actually how many mudminnows inhabit the habitat and then determine if it is necessary to build there or if the species' can be relocated to a new habitat. Since relocating is easier said than done, the construction of such urban or rural communities should not be allowed near habitats that contain the central mudminnow.