Ameiurus nebulosus
Brown bullhead
(Also: Brown catfish; Bullhead; Catfish; Common bullhead; Common catfish; Horned pout; Hornpout; Marbled bullhead; Minister; Mudcat; Northern brown bullhead)

Brown bullhead are native to freshwater habitats in Canada and the United States from 25° to 54° north latitude. They are distributed in the Atlantic and Gulf Slope drainages, ranging from Nova Scotia and New Brunswick to Mobile Bay, Alabama, and in the Great Lakes, Hudson Bay, and Mississippi basins from Quebec west to southeast Saskatchewan and south to Louisiana. Brown bullhead have been introduced outside of this range, including countries of northern, western, and eastern Europe, the Middle East, New Zealand, Chile, and Puerto Rico (U.S.). They have also been introduced and well established in the western United States and British Columbia. (American Fisheries Society, 2004; Barnes and Hicks, 2003; Fisheries and Oceans Canada, 2010; Froese and Pauly, 2010; Page and Burr, 1991)

Brown bullhead are found in pools and slower-moving runs of creeks and rivers, reservoirs, ponds, and lakes. They are tolerant of a wide range of environmental conditions, including water temperatures up to 36 degrees Celsius and oxygen levels to 0.2 ppm. They prefer habitats with vegetation and substrate. They survive well in domestically and industrially polluted waters. They are bottom dwelling fish. (Barnes and Hicks, 2003; Becker, 1983; Blazer, et al., 2009a; Blazer, et al., 2009b; Fisheries and Oceans Canada, 2010; Froese and Pauly, 2010; Page and Burr, 1991)

Brown bullhead look very similar to black bullhead (Ameiurus melas) and yellow bullhead (Ameiurus natalis). Brown bullhead are distinguished by 5 to 8 large, serrated teeth on their pectoral spines , mottled coloring on their trunk, lack of dark fin rays, and 11 to 15 gill rakers on their first gill arch. An occasional solid colored trunk has been described. They have 8 dark brown to black barbels on their head (two nasal, two maxillary, and four on the chin) which are sensitive to touch and chemical stimuli. The anterior portion of their body is thicker than the posterior portion. The body is scaleless with a brown to black dorsal side and a lighter ventral side. In captivity, this species loses pigmentation, becoming whitish. They have terminal mouths with a slightly longer upper jaw and a mouth filled with irregular rows of tiny teeth on both jaws. However, Baily et al. (2004) described their jaws as being equal. Their head is dorso-ventrally flattened. They have one dorsal fin, an adipose fin, and a caudal fin with a slightly indented fork. Typical adult length is 200 to 300 mm but they may reach up to 500 mm. Adults typically weigh 0.5 kg, but have been recorded at 3.6 kg. No significant difference has been found between male and female size. (Baily, et al., 2004; Barnes and Hicks, 2003; Becker, 1983; Blumer, 1985; Michigan Department of Natural Resources and Environment, 2010; Nelson, 1984; Page and Burr, 1991; Rasquin, 1949; University of Wisconsin Center for Limnology, et al., 2010)

Mean daily water temperature during reproduction is 14 to 29 degrees Celsius. Once brown bullhead egg clusters are released and fertilized, they take up to 13 days to hatch, but did so on average at day 5.6 during a study by Blumer (1985). Egg diameter is about 2.2 to 2.7 mm. The larval stage lasts 4 to 9 days, but on average lasted 4.4 days in Blumer's study (1985). Hatched larvae are 4 to 8 mm long, lay on nests during early development, and survive on their yolk-sacs. Metamorphosis occurs between the larval and juvenile stage. Juveniles remain in schools. The average length of the juvenile stage to the end of parental care is 5 days. (Becker, 1983; Blumer, 1985; Eycleshymer, 1901)

Brown bullhead are monogamous during the breeding season. Blumer (1985) and Becker (1983) were unable to determine how pairing occurred. Courtship, occurring near nesting sites, involves holding the partners jaw, tail, or head with the mouth, head butting, nibbling bodies, and caressing barbels. Side-by-side swaying has also been observed. Pairs settle over nests and face away from each other during gamete release. (Becker, 1983; Blumer, 1985; Encyclopedia of Life, 2010)

Brown bullhead spawn once during the spring and early summer breeding season. During an extensive four year study in Michigan by Blumer (1985), this species spawned most frequently within the first 16 days of June. He also found that larger males spawned earlier in the season. In New Zealand, these fish spawn between September and December. They reach sexual maturity at 3 years of age. Nests, typically built by females but sometimes by pairs, are excavations made in the sand, gravel, mud, under roots, and within the shelter of logs and vegetation in shallow water. Substrate is sucked into the mouth and relocated during nest building. Sheltered nests are thought to provide protection from predators. Eycleshymer (1901) noted nests in pieces of stovepipe and a bucket. During nest construction males are territorial. Egg clusters contain 50 to 10,000 eggs. Brown bullhead demonstrate iteroparity. Fertilization is external. (Barnes and Hicks, 2003; Becker, 1983; Blumer, 1985; Eycleshymer, 1901; Michigan Department of Natural Resources and Environment, 2010)

Demersal eggs are incubated and guarded by one or both parents who fan the eggs with their fins, which may minimize fungal infection and help with development. After hatching, larvae on the nest and schooling juveniles are guarded by one or both parents who chase away other fish. If juveniles leave the school, parents will capture them and return them with their mouths. Blumer (1985 and 1986a) found males to be primary caregivers: 56.2% of broods were cared for by both sexes, 39.3% by males only, and 4.5% by females only. Maximum length of parental care is 29 days. (Becker, 1983; Blumer, 1985; Blumer, 1986a; Blumer, 1986b)

Brown bullhead live 6 to 8 years. Maximum age of brown bullhead is 9 years. Predation pressure is strongest during the egg and larval stages. (Blumer, 1986b; Froese and Pauly, 2010; Michigan Department of Natural Resources and Environment, 2010)

Brown bullhead are a non-migratory species. They are social fish that spend time in schools. (Blazer, et al., 2009a; Blazer, et al., 2009b)

Home range sizes of brown bullheads are not reported.

Brown bullhead are notable for their sound production, likely produced by rubbing body parts together. In the lab, they produce sound during aggressive, conspecific encounters. Sound production, thought to be a response to disturbances, was recorded in the field and identified with captured fish. Grouped in the superorder Ostariophysi, they share the derived trait of the alarm response (Shreckstoff). (Anderson, et al., 2008; Fine, et al., 1997; Helfman, et al., 2009)

Brown bullhead are benthic, opportunistic omnivores. In aquarium settings they eat most food given to them. Juveniles eat zooplankton, including chironomids, cladocerans, ostracods, and amphipods, insects, including mayfly larvae and caddisfly larvae, and plants. Adults feed on insects, small fish, fish eggs, mollusks, plants, leeches, worms, and crayfish. They typically are nocturnal feeders, but have been observed feeding during the day. They use their barbels to locate food. (Barnes and Hicks, 2003; Becker, 1983; Fisheries and Oceans Canada, 2010; Froese and Pauly, 2010; Kline and Wood, 1996; Raney and Webster, 1940)

Predators of brown bullhead include northern pike (Esox lucius), muskellunge (Esox masquinongy), walleye (Sander vitreus), snapping turtles (Chelydra serpentina), water snakes (Nerodia species), and green herons (Butorides virescens). Minnows (Pimephales and Notropis species), yellow perch (Perca flavescens), and sunfishes (Lepomis species) are the most common predators on eggs. (Becker, 1983; Blumer, 1986b; Michigan Department of Natural Resources and Environment, 2010)

Brown bullhead are predatory fish and prey on other animals.

Brown bullhead are the subject of a small scale recreational and commercial fishery in Canada and in the United States. They have been important research animals for the study of sensory hair cells as well as physiological changes due to temperature, taste, oxygen usage, and osmoregulation. They are also an important indicator species in pollution studies. (Becker, 1983; Blazer, et al., 2009a; Blazer, et al., 2009b; Bowen, 1931; Christensen, et al., 1972; Fisheries and Oceans Canada, 2010; Lesko, et al., 1996; Michigan Department of Natural Resources and Environment, 2010; Sakaris and Jesien, 2005; West, et al., 2006)

There are no known adverse effects of brown bullhead on humans.

Brown bullhead are not listed for protection under the IUCN Red List, the United States Endangered Species Program, or under a CITES appendix. (International Union for Conservation of Nature and Natural Resources, 2009; U.S. Fish & Wildlife Service, 2010; United Nations Environment Programme and World Conservation Monitoring Centre, 2010)