TN00175 BROWN BULLHEAD ICTALURUS NEBULOSUS
PHYSICAL DESCRIPTION: Head length contained about 3.5 times, body depth about 2.5-4.0 times, in Standard Length *789*. This is a mod- erate-size bullhead, with adults usually attaining a Standard Length of 140-340 mm. It has an emarginate tail, dark chin barbels, and us- ually 13-15 gill rakers. The body is chubby, and compressed posterior- ly. The head is depressed; profile of dorsum straight in juvenile and subadult to distinctly convex in some adults; mouth slightly subter- minal; eye small. In the young, the pectoral spine has 2-3 weak an- terior serrae and 2-4 small and sharp posterior serrae; in the juvenile and in the adult, the anterior serrae are weak, and the posterior ser- rae are moderate. The male genital papilla is elongate and conical; the female lacks a genital papilla; her genital pore is an elongate slit bordered by papillae. Epicranial tissues and nape musculature become swollen in the nuptial male. Head width tends to be greatest in the male. The dorsal fin has 1 spine, 6(7) rays; branched caudal rays 15(16); anal rays (18)20-24; pelvic rays 8; pectoral with 1 spine, (7)8(9) rays; gill rakers (12)13-15(16). Color: Dorsum gray, brown, or black, sometimes with green or olive-gold casts; side with same colors, usually mottled; venter dirty white to yellow; fins usually olive-brown, sometimes black *4205*. REPRODUCTION: Spawns in the late spring and summer, probably May and June when water temperature reaches 21.1 degrees C; in the South, spawning may continue through September and individuals may mate more than once a year; one or both sexes clears a shallow nest, with a diameter just in excess of body length, in a bottom of mud or sand among the roots of aquatic vegetation, in rock cavities, or under overhanging logs and roots, usually near the protection of a rock, stump, or tree; at times nest burrows are built; will also nest under boards, in hollow stumps, or in objects such as sunken pails, and even inside automobile tires nailed on docks as boat fenders; water depth may range from 6 inches to several feet deep *835, 2737, 6595*; spawning takes place during the day, and pairing lasts for one season; there is no mating clasp in this species; females ranging from 201-230 mm length may have from 2,000-13,000 eggs in their ovaries *835*; clutch sizes ranging from 50 to 2000 have been reported, and the number of eggs may exceed 30,000 or more *2927, 1490*; the brood is cared for by both parents, which defend the nesting territory; eggs are at times picked up in the mouth and ejected; this may be necessary because of the gelatinous coat on the eggs; eggs hatch into sac larvae in 6-9 days at 20.6-23.3 degrees C; yolk sac is absorbed in about 12 days; because of heavy yolk sac, the young lie on their side in the nest until about the seventh day after hatching, then begin to swim and feed actively *835*; in Iowa, larvae swim after 10-26 days, with an average of 15 days *6595*; the young form schools, and are shepherded about for several weeks in a loose sphere by one or both parents until they are about 51 mm in length; sexual maturity is usual- ly attained by age 3, with females 203-230mm long, males slightly smaller *835,2927,1490,2737* In New York, young were 3 inches Total Length at the end of their first summer; a few reached 4 inches *1516*; in Iowa, young were 2.5 to 4 inches long at end of their first year, and reached a weight of 2 pounds under ideal conditions *2737*; In Missouri, adults commonly grow to be 7-15 inches long and weigh 0.3 to 2.2 pounds, with a maximum length of 18 inches and maximum weight of 3.7 pounds *1187*; In Iowa, average length was 8 to 10 inches, and the average weight was 1 pound *2737*. BEHAVIOR: territory=breeding/nesting; dispersion=non-random *1490,1514,2927*; periodicity=nocturnal, feed on bottom of lakes, ponds or streams *1511,1131,1516*; their organs of taste and smell are greatly enlarged and extended, so are the regions of the brain involved in these senses; visual abilities reduced or in some cases even absent; territorial, having a dominance hierarchy and can identify individuals of their own species; taste buds and ventral barbels are used to find food and olfactory senses are used to receive chemical communications *1307*; homing was exhibited in a Lake Ontario study, except when fish were released in an area of thermal discharge *6596*; The young eat a variety of microcrustaceans; the omnivorous adults consume algae, plus a broad spectrum of invertebrates and fishes *4205* ORIGIN: Native *835, 1115, 1131*. POPULATION PARAMETERS: In California, annual mortality was 23%, and natural mortality was 16% *1514*. AQUATIC/TERRESTRIAL ASSOCIATIONS: Predators include the chain pick- erel, northern pike, muskellunge, walleye, and sauger *842*. REPRODUCTION: SPAWNING OCCURS FROM EARLY MORNING TO 1400 HOURS AT WATER TEMPERATURE OF 21-25 DEGREES C THE NEST IS USUALLY BUILT BY THE FEMALE BUT OCCASIONALLY BY BOTH PARENTS THEY SUCK PEBBLES UP TO 25 MM IN DIAMETER INTO THEIR MOUTHS AND CARRY THEM AWAY FROM THE NESTING SITE THE NEST IS RARELY IN MUD AFTER COMPLETION OF THE NEST THE 2 SPEND MUCH TIME LYING SIDE BY SIDE, USUALLY IN CONTACT WITH EACH OTHER WITH THEIR TAILS TOWARD THE NEST OPENING THIS IS INTERRUPTED BY SWIMMING IN A CIRCULAR PATH WITH ONE FISH BEHING THE OTHER OFTEN THE TAIL OF ONE WILL SLIP APPARENTLY BY ACCIDENT INTO THE MOUTH OF THE OTHER, WHICH USUALLY CLOSES DOWN UPON IT, IN WHICH CASE THE BITTEN FISH SHOOTS OUT FROM THE NEST, NOT RETURNING UNTIL IT HAS SWAM ABOUT FOR A WHILE FINALLY THE FISH FLATTEN INTO A SIDE BY SIDE POSITION IN CLOSE SONTACT, FACING IN OPPOSITE DIRECTIONS SPAWNING OCCURS A LARGE NUMBER OF SPAWNING ACTS OCCUR UNTIL THE FEMALE IS EMPTIED OF EGGS EGGS ARE PALE CREAM IN COLOR, ABOUT 3 MM IN DIAMETER, ADHESIVE, AND ARE DEPOSITED IN CLUSTERS THOUGH BOTH SEXES HAVE BEEN OBSERVED DEFENDING AND INCUBATING THE EGGS, IT APPEARS THAT THE FEMALE DOES MOST OF THE INCUBATING AND THE MALE MOST OF THE DEFENDING *TN5176* BEHAVIOR: JUVENILES SOMETIMES OCCUR IN SCHOOLS THROUGHOUT THEIR FIRST SUMMER, SUCH SCHOOLS BEING FOUND AMONG VEGETATION OR OTHER SUITABLE COVER OVER MORE OR LESS MUDDY BOTTOMS IN LATE FALL, BROWN BULLHEADS BECOME SLUGGISH AND CEASE FEEDING, OFTEN BURYING THEMSELVES IN THE SOFT MUD ALONG SHORE, LYING SO THAT ONE GILL IS MORE OR LESS POINTED UP THIS OCCURS AT 0- 18.3 DEGREES C IN BURYING THIS WAY, THE MOUTH REMAINS IN DIRECT CONTACT WITH THE WATER FROM THE BEGINNING OF THE FISH SUCKS IN THE SEDIMENT COVERING ITS MOUTH AND EXPELS IT FROM THE UPPERMOST GILL, GEYSER FASHION, FORMING A SMALL FUNNEL OVER IT AND LEAVING AN OPEN PASSAGE OF WATER IS CHIEFLY NOCTURNAL WILL GULP AIR AT THE SURFACE WHEN THE OXYGEN LEVEL IN THE WATER BEOCMES CRITICALLY LOW *TN5176*
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References for Life History Codes
835, 1490, 1115, 1131, 1514, 1511, 1516, 2927, 1307, 789, 842, 4205
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