Chemical orientation of brown bullheads, Ameiurus nebulosus, under different flow conditions.

The spatiotemporal information in chemical signals provides critical information for organisms during chemical orientation. Information in chemical signals is influenced by the hydrodynamic conditions of the environment. Hydrodynamically distinct environments will contain different types of information, which will influence how organisms orient. This study was designed to examine how the orientation behavior of the brown bullhead (Ameiurus nebulosus) is influenced by flow regime. The experiment was conducted in a flume under two different flow conditions. Treatments consisted of control (no odor) and plain gelatin (odor). Percent success, swimming speed, turning angle, heading angle, heading angle upstream, and net-to-gross ratio were analyzed. Brown bullheads were 100% successful in finding the odor source under no flow and 57% successful in flow. Bullheads swam differently in the no-flow condition when compared to the flow condition. Since, these fish did not orient the same under different flow conditions, it appears that hydrodynamics plays a role in shaping their behavior.