The brown bullhead may vary from yellow-brown or chocolate brown to olive, gray, or bluish-black. The sides are often lighter and may be mottled with brown blotches and the belly is yellow or white. Very round brown bullheads are jet black and are often mistakenly believed to be black bullheads. Coloration is not a dependable distinguishing characteristic with this species and it is important to observe other physical characteristics in order to make a positive identification. The brown bullhead and the yellow bullhead have sharp, tooth-like serrations along the rear edge of the pectoral spine, found at the top of the pectoral fin. The black bullhead lacks any such serrations or has only extremely weak serrations that are negligible by comparison. In the brown and black bullheads, the tail is squarish (truncate) or slightly emarginate, while in the yellow bullhead the tail is slightly rounded. The brown bullhead is frequently mottled while the yellow is never mottled and its chin barbels are yellow, buff, or pale pink in color (the upper barbels are light to dark brown). In the brown bullhead all of the barbels are dark brown to nearly black, but in some cases there may be pale yellow or white at the base of the chin barbels only. The Brown Bullhead is by far the most common of the three bullhead species found in Washington. It can be identified by the presence of strong barbs or serrations on the back edge of its pectoral spines, and pigmentation in the chin barbels. 

Habitat. The brown bullhead thrives in a variety of habitats, including lakes, ponds, and slow-moving streams with low oxygen or muddy conditions. In many areas of the United States, brown bullheads are opportunistic bottom feeders. 

They live in the shallows containing low oxygen levels, usually the mud-bottomed lakes, ponds, streams, reservoirs, and rivers' backwaters. 

Habitat. The brown bullhead thrives in a variety of habitats, including lakes, ponds, and slow-moving streams with low oxygen or muddy conditions. ... They are scarce during the day, but come out at night to feed, searching the bottom of a lake or river for food.

this fish lives in areas where the water is clear

Brown trout spawn in the fall (usually from September to December) when the water temperature ranges around 44°F to 48°F degrees. The spawning period typically last 2-4 weeks.

Feeding. Brown bullheads are bottom-feeders that eats algae, insects, mollusks, crustaceans, crayfish and other fish, using their long barbels to taste for prey.

Predators of brown bullhead include northern pike, muskellunge, walleye, snapping turtles, water snakes, and green herons. Bluntnose minnows and shiner minnows, yellow perch, and sunfishes are the most common predators on eggs.

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.

Currently the human being has not put this fish in danger of extinction

The fish has been introduced into many European countries, such as Poland, Germany, Sweden, Norway, Finland, Romania, Estonia, Hungary, Serbia, and Croatia. Brown bullheads have also been introduced to western North America, Chile, Puerto Rico and New Zealand.

nebulosus is a fish of the Ictaluridae family, commonly known as a brown bullhead. ... This diet results in predation on a wide variety of native invertebrates, small vertebrates and fish eggs. Conversely, its stout shape and strong dorsal and pectoral fin spines would minimize predation by native predators.