four inches, while the biggest threat to adult bullheads is humans. Brown bullheads have protective 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 predator's ability to swallow while simultaneously releasing a venom to sting and burn the predator. Conservation 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 across the continent. In Missouri, the brown bullhead is listed as a Species of Conservation Concern and is threatened by habitat destruction, particularly the drainage of swamps in the Missouri Bootheel for conversion into farmland. See also Bullhead catfish (general) Rough fish References External links Ameiurus nebulosus, German language; originally published in: Datz-Aquarienpraxis 11/2004, S. 10f. Ameiurus Freshwater fish of the United States Fish of Canada Fish of the Eastern United States Fish of the Great Lakes Freshwater fish of the Southeastern United States Fish described in 1819 Freshwater fish of New Zealand Taxa named by Charles Alexandre Lesueur