Territoriality in channel catfish is identifiable by a change in body odor, which is recognizable by other members of the same species. This chemical change in the amino-acid composition of the skin mucus can be noted by chromatographic methods, and are not long-lasting; rather, they last only long enough to communicate to other fish in the vicinity. Changes may be the result of the release of the contents of the club cells. These cells do not open directly to the surface of the skin, but injury caused by fighting and other agonistic behaviors may release the cells’ contents. Since catfish have a dominance hierarchy system, information relative to the change of status of any fish is important in recognition of the social strata.