Central mudminnows are native to the Nearctic, found in both Canada and the United States. Their native range includes the Great Lakes, Hudson Bay, the St. Lawrence, Red, and Mississippi River basins from Quebec to Manitoba and south to central Ohio, Tennessee, and northeastern Arkansas. There are isolated populations in the Missouri River basin in South Dakota and Iowa. Montana, Oklahoma, and Texas have had reports of isolated, non-native occurrences. Reports of introduced central mudminnow populations or individuals in eastern North America, including Connecticut, Massachusetts, and Maine have been made in the last twenty years. (Schilling, et al., 2006)
Central mudminnows are resilient and thrive in waters with dense vegetation, low dissolved oxygen levels, minimal flow, and thick layers of organic substrate (Schilling et al. 2006; Becker 1983; Peckham and Dineen 1957). Their name is derived from the Latin umbra meaning shadow or phantom and limi meaning mud. They are also known as mudfish, mudpuppy, or dogfish (Tomelleri and Eberle 1990). They inhabit both lotic and lentic habitats, providing that the waters are still or slow moving and there is dense cover available (Chilton et al. 1984). They are most commonly encountered in water less than five meters deep (Becker 1983). In Wisconsin, this species is commonly found among cattail, waterweed, eel grass, bulrush, yellow water lily, water buttercup, and filamentous algae (Becker 1983). They are a predominantly benthic fish, provided the stream bed or lake bottom is within the preferred depth. During periods of high flow, central mudminnows move from their normal habitats and venture into the flooded areas along the banks to avoid strong water currents (Peckham and Dineen 1954). They can endure hypoxic conditions for short periods of time via facultative air breathing (Tomelleri and Eberle 1990; Schilling et al. 2006; Rahel and Nutzman 1994; Klinger et al. 1982; Chilton et al. 1984; Tonn and Paszkowski 1986). Central mudminnows may be considered habitat specialists based on their adaptation for living in areas with dense macrophyte communities (Peckham and Dineen 1954). (Becker, 1983; Chilton, et al., 1984; Klinger, et al., 1982; Peckham and Dineen, 1957; Rahel and Nutzman, 1994; Schilling, et al., 2006; Tomelleri and Eberle, 1990; Tonn and Paszkowski, 1986)
Central mudminnow adult sizes range between 50 to 115 mm (Tomelleri and Eberle 1990). The average adult size is 60 mm (Becker 1983). Young-of-year average length is 29.5 mm and yearling average length is 41.5 mm (Applegate 1943). Schilling et al. (2006) recorded a maximum standard size of 140 mm. The body has a nearly round cross section and robust appearance. The snout is stubby with a terminal mouth. The premaxillary and lower jaws and roof of mouth all have small villiform teeth. The dorsal fin is set back towards the posterior half. The caudal fin is convexly rounded. The anal fin is larger than the pelvic and longer in males, almost reaching the caudal fin. Males also develop a blue-green coloration on the anal fin during spawning season. There is no gross sexual dimorphism in length (Applegate 1943). Meristic features include 13 to 15 short gill rakers, 4 to 5 branchiostegal rays, 13 to 15 dorsal fin rays, 7 to 9 anal fin rays, 14 to 16 pectoral fin rays, and 6 to 7 pelvic fin rays (Becker 1983).
Overall coloration is dark olive-green to brown-black with 14 vertical dark brown bars along the lateral surfaces. The scales are large and cycloid. The top of the head, cheeks, and opercles are scaled. There is a prominent, vertical, dusky bar at the caudal base. The ventral surface is yellow to white. Central mudminnows use a diodontiform swimming pattern with undulation of median or pectoral fins. Central mudminnows can be mistaken for banded killifish (Fundulus diaphanus). Differentiation between the two species can be made by examining the mouth; Fundulus diaphanus has a supraterminal mouth whereas U. limi has a terminal mouth. (Apllegate, 1943; Becker, 1983; Tomelleri and Eberle, 1990)
Fry are transparent and approximately 5 mm upon hatching (Peckham and Dineen 1957). Fry become pigmented and dark on their 16th day after hatching. Until young reach 25 mm they have a notochord lobe above the developing caudal fin (Becker 1983). When young reach 30 mm they move from flooded margins and pools back into the main stream or preferred adult lentic habitats. Becker (1983) notes the timing of length attained in southern Wisconsin young-of-year as late June - 28 mm, mid-July - 35 mm, late July - 39 mm, mid-August - 43 mm, and 55 mm by October. Applegate (1943) noted that, with increasing size and age, the relative abundance of males decreases and the larger and older fish were mainly female. (Apllegate, 1943; Becker, 1983; Peckham and Dineen, 1957)
Additional study of reproductive behaviors may be warranted, as there is little information on mating behavior.
Spawning is most likely prompted by warming water temperatures and flooding in spring (Becker 1983; Peckham and Dineen 1957). Preferred water temperature for spawning is 12.8⁰C but can occur at up to 15.3⁰C (Becker 1983). Many references note spring migration of central mudminnows into flooded areas. Spawning habitat is preferably flooded stream margins and pools with slow or no flow (Tomelleri and Eberle 1990). Eggs are demersal and adhesive. Females affix eggs individually directly to vegetation (Peckham and Dineen 1957). Fecundity is 425 to 450 eggs per female on average. Eggs are yellow or orange and measure about 1.6 mm in diameter. Within individual ovaries all eggs were the same size before spawning season and ripen at the same time, indicating a short spawning season (Peckham and Dineen 1957). There is some egg guarding behavior by the female (Becker 1983). (Becker, 1983; Peckham and Dineen, 1957; Tomelleri and Eberle, 1990)
There is some egg guarding behavior by the female (Becker 1983). (Becker, 1983)
It is thought that central mudminnows live for approximately 7 to 9 years. Age is usually determined by otoliths and opercula since the scales do not contain annuli (Becker 1983; Applegate 1943). (Apllegate, 1943; Becker, 1983)
Jenkins and Miller (2006) found that central mudminnows prefer to be near a shoal of conspecifics, therefore showing social versus solitary behavior. This could be attributed to either predator evasion tactics or increased foraging success in larger groups (Jenkins and Miller 2006). Tonn and Paszkowski (1986) found that central mudminnows tend to congregate in groups of twelve or more in aboratory experiments. Central mudminnows were mistakenly thought to hibernate in mud in early accounts (Peckham and Dineen 1954). They were also inaccurately purported to burrow into sediment tail first to escape predation and to survive drought periods. It has since been shown that they flee into soft sediment and ooze when threatened (Becker 1983). Central mudminnows are facultative air-breathers. This behavior is possible through the presence of both alveoli and a highly vascularized gas bladder (Becker 1983; Klinger et al. 1982). In winter, central mudminnows can survive hypoxic conditions that kill many other fish (Tonn and Paszkowski 1986; Klinger et al. 1982; Chilton et al. 1984). These fish use an interesting behavior where they ingest air bubbles trapped on the underside of ice-covered lakes (Rahel & Nutzman 1994, Klinger et al. 1983). Central mudminnows also spend time foraging for invertebrate prey organisms in hypoxic waters of stratified lakes. This is sometimes accomplished through the closing of their gill covers and ceasing respiration in oxygen-poor waters (Rahel & Nutzman 1994), the equivalent of a terrestrial, air-breathing organism holding its breath to forage in aquatic habitats. It is thought that they resort to anaerobic metabolism during these dives into hypoxic waters (Rahel & Nutzman 1994). Rahel and Nutzman (1994) also found that they only tolerate hypoxic waters for a short period of time and cannot remain in those conditions for long before low oxygen levels result in mortality. The abilities to actively forage during winter and digest meals relatively rapidly at cold temperatures serve as niche-broadening mechanisms and increase the chances of survival. These cold-water foraging adaptations could be an important factor contributing to the development of female gonads over the winter. Winter gonad growth allows for early spring spawning and provides the longest amount of time for the young of year to develop before their first winter (Chilton et al. 1984). (Becker, 1983; Chilton, et al., 1984; Jenkins and Miller, 2006; Klinger, et al., 1982; Peckham and Dineen, 1957; Rahel and Nutzman, 1994; Tonn and Paszkowski, 1986)
Home range sizes of central mudminnows are not reported.
Jenkins and Miller (2006) demonstrated that central mudminnows use visual clues to compare the size of shoals. Although this study did not include laboratory tests to test olfactory or tactile cues that may be used in their natural habitat, it was noted that these sensory systems play a major role in shoaling decisions. These findings are not direct evidence of communication but reflect the use of visual, olfactory, and tactile cues in social behaviors such as shoaling. Further study of communication in this species may be warranted. (Jenkins and Miller, 2006)
Central mudminnows are primarily bottom feeders (Becker 1983) and generally carnivorous (Peckham and Dineen 1957). Central mudminnow diet includes small crustaceans, amphipods, isopod crustaceans, crayfish, chironomid larvae, culicid larvae and pupae, dixid larvae, long-legged fly larvae, crane flies, mayflies, earthworms and a variety of small fishes. The potential for cannibalism was briefly discussed by Peckham and Dineen (1957), but the presence of mudminnow scales in sampled mudminnow stomachs could have been accidental ingestion.
Juvenile winter diet of Age 0 included copepods and larval chironomids (Chilton et al. 1984). Young-of-year also feed on ostracods and cladocerans (Becker 1983). Peckham and Dineen (1957) noted that young fish (19 mm) fed on newly hatched snails, while Chilton et al (1984) found Age 1 consumed both chironomids and fishes. Small central mudminnows were not found foraging in hypoxic waters that larger central mudminnows use and might be attributed to their inefficiency in capturing the primary prey item, Chaoborus larvae, found in those waters (Rahel and Nutzman 1994). Chilton et al. (1984) detected piscivory only in female central mudminnows. They typically capture prey head first but as the temperature drops to around 1.1 ⁰C, capture is side-on and then reoriented to head first substantially increasing handling time to ~10 minutes. (Becker, 1983; Chilton, et al., 1984; Peckham and Dineen, 1957; Rahel and Nutzman, 1994)
Central mudminnows are preyed on by grass pickerel, chain pickerel, northern pike, sunfishes, catfishes and sculpins (Peckham and Dineen 1957; Becker 1983). Their chief predator are mottled sculpin (Cottus bairdii) according to Peckham and Dineen (1957). The same study noted that one 111 mm male mottled sculpin stomach contained a 72 mm female central mudminnow. Terrestrial predators include herons, muskrats and foxes according to Becker (1983). A Wisconsin-based study that focused on Perca-Umbra assemblages suggested that size-dependent predator-prey interactions between perch and central mudminnows was a driving mechanism in population organization (Tonn and Paszkowski 1986). This same study noted that U. limi could briefly override this relationship during winterkill events via facultative breathing behaviors. (Becker, 1983; Peckham and Dineen, 1957; Tonn and Paszkowski, 1986)
Since central mudminnows are able to survive in relatively hypoxic conditions when many other species are killed, they play an important role in their ecosystems (Tonn and Paszkowski 1986). Their preference for, and success in, heavily vegetated habitats also makes them a specialist (Peckham and Dineen 1954). They are an important prey item for many species. In the Umbra-Perca assemblages studied by Tonn and Paszkowski (1986), size-dependent predator-prey interaction between the two species (Umbra limi and Perca flavescens) was a major organizational mechanism of the assemblage. (Peckham and Dineen, 1957; Tonn and Paszkowski, 1986)
Fishermen are familiar with central mudminnows as hardy bait fish. Their facultative air-breathing and overall tolerance of extreme environmental conditions make them an excellent bucket fish (Schilling et al. 2006). Long-lived, attractive, and easy to care for, U. limi is an interesting fish in aquaria. Individuals can easily be trained to take food pieces from people (Becker 1983). Jenkins and Miller (2006) note that they are well suited for laboratory study, most likely for the reasons listed above. They also mention that few studies have been conducted on the behavior of central mudminnows. (Becker, 1983; Jenkins and Miller, 2006; Schilling, et al., 2006)
There are no known adverse effects of Umbra limi on humans.
Currently, central mudminnows are listed as state threatened in Kentucky; state endangered in South Dakota, and are a candidate species in Pennsylvania. They are protected or of special concern in Missouri and North Dakota (Tomelleri and Eberle 1990). (Tomelleri and Eberle, 1990)
Alexis Growe-Raney (author), Northern Michigan University, Rachelle Sterling (editor), Special Projects, Jill Leonard (editor), Northern Michigan University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.
an animal that mainly eats meat
uses smells or other chemicals to communicate
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
fertilization takes place outside the female's body
union of egg and spermatozoan
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
Animals with indeterminate growth continue to grow throughout their lives.
An animal that eats mainly insects or spiders.
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
marshes are wetland areas often dominated by grasses and reeds.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
uses sight to communicate
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
Apllegate, V. 1943. Partial analysis of growth in a population of Umbra limi (Kirtland). Copeia, 1943: 92-97.
Becker, G. 1983. Fishes of Wisconsin. Madison, WI: University of Wisconin Press.
Chilton, G., K. Martin, J. Gee. 1984. Winter feeding: an adaptive strategy broadening the niche of the central mudminnow, Umbra limi. Environmental Biology of Fishes, 10: 215-219.
Jenkins, J., B. Miller. 2006. Shoaling behavior in the central mudminnow (Umbra limi). American Midland Naturalist, 158: 226-232.
Klinger, S., J. Magnuson, G. Gallepp. 1982. Survival mechanisms of the central mudminnow (Umbra limi) and brook stickleback (Culaea inconstans) for low oxygen in water. Environmental Biology of Fishes, 7: 113-120.
Peckham, R., C. Dineen. 1957. Ecology of the central mudminnow, Umbra limi (Kirtland). American Midland Naturalist, 58: 222-231.
Rahel, F., J. Nutzman. 1994. Foraging in a lethal environment: fish predation in hypoxic waters of a stratified lake. Ecology, 75: 1246-1253.
Schilling, E., D. Halliwell, A. Gullo, J. Markowsky. 2006. First records of Umbra limi (central mudminnow in Maine. Northeastern Naturalist, 13: 287-290.
Tomelleri, J., M. Eberle. 1990. Fishes of the Centeral United States. Lawrence, KS: University of Kansas Press.
Tonn, W., C. Paszkowski. 1986. Size limited predation, winterkill and the organization of Umbra-Perca fish assemblages. Canadian Journal of Fisheries and Aquatic Sciences, 43: 194-202.