Mississippi Office of Pollution Control staff collected catfish from 69 sites from 1991-1994 for contaminant monitoring. Of these, 12 sites were sampled 5 or more times per year. Environmental conditions varied dramatically between site and season facilitating observations for effects of both intersite variability (e.g., water conductivity and manipulation of pulsator settings) and intrasite seasonal variability (e.g., water temperature and river stage). Flathead catfish {Pylodictis olivaris) and blue catfish (Ictalurus furcatus) were most susceptible to the gear in water temperatures >22 C, while channel catfish (/. punctatus) were efficiently collected from cooler waters. Flathead catfish were susceptible to low pulse frequencies and these frequencies were necessary to collect this species from preferred deep water habitats. Channel and blue catfish were collected over a wide range of pulse frequencies. Catch per unit effort (CPUE) for settings and conditions considered optimum ranged from 1.6-2.1 fish per minute for the 3 species.
