Martha Wells, Jacki Dow, Frederick Moody, Charlotte McCracken and Christopher O'Bara, Center for the Management, Utilization and Protection of Water Resources, Tennessee Technological University, PO Box 5033, Cookeville, TN 38505

Abstract. The characterization of fatty acid of fishes has been used primarily in forensic related-tasks or in the aquaculture industry. The premise of the characterization is that fatty acid profiles of a given fish should partially reflect its feeding habits, as well as its environment. Investigators have successfully demonstrated that for black and white crappie, and largemouth bass fatty acid profiles can be used as a means to differentiate individuals as to their origin. In an effort to provide an easier and more efficient method, supercritical fluid extraction (SFE) method was compared to the traditional Folch method. Fish samples were prepared using both methods as defined by a factorial screening study. Fatty acid concentrations were compared using a comparison t-test and results showed no significant differences. Wild black crappie of several age classes from Norris Reservoir and Chickamauga Reservoir, as well as largemouth bass and walleye from TWRA Eagle Bend Hatchery and Doakes Nursery Pond were compared using both methods. In addition, striped bass, Cherokee bass and white bass were evaluated from Cherokee and Norris reservoirs. No significant differences were found between methods, but significant differences were found between origins (i.e. reservoirs, hatcheries). Interestingly, within a reservoir, no differences were found between age classes indicating a fairly permanent mark. The identification of introduced fish into an environment has always been important in the evaluation of stocking programs. It appears that the use of fatty acid profiles is a viable approach to identifying fish in stocking programs. The method is self-marking, non-lethal, long-lasting, and with new analytical methods, efficient.