Ictalurus nebulosus (Lesueur, 1819)
The brown bullhead (Ameiurus nebulosus) is a fish of the Ictaluridae family that is widely distributed in North America. It is a species of bullhead catfish and is similar to the black bullhead (Ameiurus melas) and yellow bullhead (Ameiurus natalis). It was originally described as Pimelodus nebulosus by Charles Alexandre Lesueur in 1819, and is also referred to as Ictalurus nebulosus.
The brown bullhead is also widely known as the "mud pout," "horned pout," "hornpout," or simply "mud cat," along with the other bullhead species.
The brown bullhead is important as a clan symbol of the Ojibwe group of Native Americans. In their tradition, the bullhead or "wawaazisii" is one of six beings that came out of the sea to form the original clans. 
The brown bullhead grows to be approximately 21 inches in length  and is darker brown green dorsally growing lighter green and yellow towards the ventral surface. The belly is off white or cream, and the fish has no scales.  Additionally there are darker brown black speckles along the entire surface of the fish. The brown bullhead has two dorsal fins, a single adipose fin, abdominal pelvic fins, and an anal fin with 21 to 24 rays. The tail is only slightly notched, having dorsal and ventral lobes angling inward. The fish has barbels around the mouth and on the pelvic spine. The barbels around the mouth are black to yellowish brown on the chin and saw-like on the pelvic spines.  Juvenile brown bullheads are similar in appearance but are more likely to be of a single solid color.  The brown bullhead's mouth is slightly subterminal, with the upper jaw extending slightly past the lower jaw. This position enables bottom feeding. The brown bullhead may be distinguished from similar species by its absence of a tooth patch on its upper jaw with the lateral backwards extensions.  Adult brown bullheads range in size from 200mm to 500mm and weigh between 0.5 kg to 3.6 kg in extreme cases. Brown bullheads are ectothermic, heterothermic, and bilaterally symmetrical.  Brown bullheads can be distinguished from black and yellow bullheads with their yellow- black chin barbels, missing bar at the base of tail present in black bullheads, and 21-24 anal fin rays. 
The native range of the brown bullhead is in the Atlantic and Gulf Slope drainages. More specifically, it is found from Nova Scotia and New Brunswick to Mobile Bay, Alabama, and in the St. Lawrence- Great Lakes, Hudson Bay, and Mississippi River basins (from Quebec to Saskatchewan and south to Louisiana and west to Texas ). However, there is evidence that the brown bullhead was historically absent from the Gulf Coast west of Apalachicola and east of the Mississippi River. The species is also abundant in many regions as a result of stocking for food and/or sport. These locations include Alabama, Arizona, Arkansas, California, Colorado, Hawaii, Idaho, Kansas, Kentucky, Louisiana, Maine, Missouri, Nebraska, Nevada, New Hampshire, New Mexico, Ohio, Oklahoma, Oregon, Virginia, and Washington.  Brown bullheads are a social non migratory species that lives the majority of its life in schools. 
The brown bullhead thrives in a variety of habitats, including lakes, ponds, and slow moving streams with low oxygen and/or muddy conditions. In many areas of the United States, brown bullheads are opportunistic bottom feeders. It has few natural predators and is not popular with fishermen, so it has thrived. For native fish species, this predatory fish is a disaster. Catfish are found in a variety of habitats, from lakes or murky ponds to drainage ditches. They are scarce during the day but come out at night to feed, searching the bottom of a lake or river for food.  They eat insects, leeches, snails, fish, clams, and many plants. They are also known to eat corn, which can be used as bait. Similar to other catfish, they spawn only after the temperature of the water has reached 80 degrees Fahrenheit (27 °C) (cooler in the northern US) in June and July.
Brown bullheads can withstand a wide range of water temperatures and low oxygen levels. Brown bullheads can survive waters with heavy pollution and dissolved oxygen values as low as 0.2ppm.  Because of bullheads tolerance of low oxygen levels, they are less threatened by winter kill and capable of survival in relatively extreme environments. 
This catfish is easily caught with natural bait such as worms and chicken livers. They have a scrappy but not unusually strong fight. Anglers often catch them by fishing off the bottom. When caught in very clear water when the flesh is firm and reddish to pinkish, the hornpout is quite edible and delicious. Nevertheless, its genial cousins such as the channel catfish and the blue catfish are better known for their consumption qualities. In most areas, they will not exceed two pounds in weight, with a current IGFA world's record of 7 lb 6oz, by Glenn Collacuro, Lake Mahopac NY, August 1, 2009. 
Brown Bullheads typically live between six and eight years (but have been recorded as old as fifteen in captivity), and spawn between April and June. During the duration of each breeding season, females will be monogamous. The females lay eggs in dark shallow locations like under rocks and inside logs, and nests are primarily created by the females. The fertilization is external and the fish face opposite one another during the process. There are no consistent behaviors of mate attraction. The eggs are protected by both the males and the females who additionally will guard their offspring for a while following their hatching.  The eggs will hatch in 13 days but often closer to six days. Additionally, following the hatching the parents will generally care for their offspring for five days.  Adults, male and female, will reach sexual maturity around age three and in their lifetime can produce between 10 and 10,000 offspring. Brown bullheads have additionally been recorded eating their own eggs occasionally. 
The fish has been introduced into many European countries such as Poland, Germany, Sweden, Norway, Finland, Romania,Estonia, Hungary,Serbia and Croatia as well as Western North America, Chile, Puerto Rico and New Zealand. 
Countries who have reported adverse effects from the introduction of the brown bullhead species include Iran and Turkey. 
Brown Bullheads are omnivorous benthic bottom feeders. Their diet consists of algae, mollusks, crustaceans, insects, crayfish and other smaller fish species.  Brown bullheads are typically nocturnal feeders, but have been reported to feed diurnally. Bullheads have poor eye sight and are heavily reliant on their sensitive barbels to locate their food.  Bullheads are omnivorous and will reportedly eat almost anything that fits in their mouth. 
Brown bullheads are the most susceptible to predators in their developmental stages (primarily as eggs) and include but are not exclusively prey to; northern pike, muskellunge, walleye, snapping turtles, water snakes, green herons, minnows, yellow perch, and sunfish.  Additionally, brown bullheads are also used for small scales commercial fishing, recreational fishing, and more specifically for consumption and research. Predation by other fish and coexisting species is only a realistic threat to bullheads under four inches, while the biggest threat to adult bullheads are humans. Brown bullheads have camouflage coloration to avoid predation.  As a mode of physical defense against predators, bullhead species have a sharp spine on the leading edge of their dorsal and pectoral fins. To use this adaptation as a defense mechanism, bullheads will stiffen the spine while being attacked impeding the predators ability to swallow while simultaneously releasing a poison to sting and burn the predator. 
Brown bullheads hold no special status on the International Union for Conservation of Nature and Natural Resources, the United States Endangered Species Program, or under the CITES appendix.  Brown bullheads can tolerate very low dissolved oxygen levels that result from industrial and domestic pollution, aiding in their overall high rate of survivorship.  Brown bullheads are the most abundant species in many lakes and streams continentally.
- NatureServe (2015). "Ameiurus nebulosus". IUCN Red List of Threatened Species. Version 4.1 (4.1). International Union for Conservation of Nature. Retrieved February 25, 2016.
- "Archived copy". Archived from the original on 2005-11-25. Retrieved 2005-09-15.
- Page, L & Burr, B. 1990. Peterson field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Harcourt
- "Brown Bullhead". University of Wisconsin Sea Grant Institute=20 Apr 2017. 2013.
- "Brown Bullhead, Ameiurus nebulosus". Michigan Department of Natural Resources=20 Apr 2017. 2017.
- "Ameirus nebulosus: Brown Catfish (Also: Bullhead; catfish; Common bullhead, Common catfish)". University of Michigan Museum of Zoology. 2011. Retrieved 4 May 2017.
- Craig, Cody A.; Vaughn, Christopher R.; Ruppel, David S.; Bonner, Timothy H. (2015-06-01). "Occurrence of Ameiurus nebulosus (Brown Bullhead) in Texas". Southeastern Naturalist. 14 (2): N35–N37. doi: 10.1656/058.014.0213. ISSN 1528-7092.
- "Ameiurus nebulosus". USGS=20 Apr 2017. 29 May 2012.
- "Brown Bullhead Catfish." Aliens Among Us. N.p., n.d. Web. 27 Oct. 2014. < http://alienspecies.royalbcmuseum.bc.ca/eng/species/brown-bullhead-catfish Archived 2012-04-08 at the Wayback Machine.>.
- "Species Profile- Bullheads". Minnesota Department of Natural Resources. May 2012. Retrieved 4 May 2017.
- IGFA Brown Bullhead Records
- "Brown Bullhead". Chesapeake Bay Program. 2012. Retrieved 4 May 2017.
- "Ameirus nebulosus: Brown Bullhead". fishbase.org. 1998. Retrieved 4 May 2017.
- "Ictalurus nebulosus". ISSG. 11 April 2006. Retrieved 17 July 2010.
- "Brown Bullhead". Chesapeake Bay Program. 2012. Retrieved 20 Apr 2017.
|Wikimedia Commons has media related to Ameiurus nebulosus.|
|Wikispecies has information related to Ameiurus nebulosus|