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EVALUATION OF CURRENT MANAGEMENT PRACTICES AND ASSESSMENT OF RECRUITMENT, GROWTH AND CONDITION OF WALLEYES IN TENNESSEE RESERVOIRS

Tennessee's walleye stocking program was evaluated by releasing fry and fingerlings marked with oxytetracycline (OTC). Marking efficacy was high (>99%) for walleyes immersed in 500 mg/L OTC for 6 hours and mortality was negligible. Subsequent recaptures of age-1 walleyes revealed that little or no natural reproduction occurred in 1999 and 2000 in the five study reservoirs (Center Hill, Norris, South Holston, Tellico, Watauga). The contribution of stocked walleyes to those two year classes ranged between 92 and 100%.

Adult walleyes were sampled with experimental gill nets in six reservoirs (the five mentioned above and Dale Hollow). The oldest walleyes (up to age-21) were in Watauga Reservoir; the youngest population was in Center Hill Reservoir, where only one fish was older than age-4. The age-class structure in the six reservoirs indicated that most of the walleye fisheries were dependent on TWRA's stocking program because natural reproduction was usually low or inconsistent over the last decade.

Trout stocking rates and threadfin shad catch rates together explained a significant amount of variation in adult walleye robustness. The heaviest walleyes were in South Holston, Dale Hollow and Watauga Reservoirs. Significant between-year variation was also detected for four of the six populations sampled.

No threadfin shad were collected in Watauga Reservoir, but they were caught in similar numbers in the other five reservoirs. Alewives were in all six reservoirs and their catch rates varied significantly; mean catch rates were higher in Watauga and Dale Hollow (207-300/net night) than in the other four reservoirs (7-23/net night).

Walleyes grew rapidly in all reservoirs; the average time to reach 406-mm total length ranged from 1.7 to 2.1 years.

Fishery yields under different minimum size limits were simulated using the Beverton-Holt equilibrium yield model. Three size limits (381-, 406-, and 457-mm total length) increased yield in all reservoir compared to no size limit at most levels of exploitation when conditional natural mortality rates were low (less than 20%). At higher natural mortality rates, the benefits of a minimum size limit were eliminated. The observed longevity of walleyes (maximum age averaged 13 years over all reservoirs) indicated that natural mortality rates were low; thus, minimum size limits were appropriate management actions in all reservoirs. Although yield was usually highest under simulated 457-mm length limit, the benefits were slight unless conditional fishing mortality rates were high (>40%) and natural mortality rates were low (10%).

Only one walleye population (Center Hill) exhibited characteristics of heavy exploitation. Although most populations were sustained through a stocking program, the abundance and size structure of most populations was excellent. Large variations among reservoirs in walleye robustness and forage abundance suggested that stocking rates should be matched to the supply of available forage.