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TWRA Fisheries Management Division

FACTORS ASSOCIATED WITH RECRUITMENT OF SAUGERS IN TENNESSEE AND CUMBERLAND RIVER RESERVOIRS, TENNESSEE, 1990-1997

Important seasonal fisheries exist for indigenous saugers Stizostedion canadense in the mainstream impoundments of the Tennessee and Cumberland Rivers, Tennessee; however, extreme fluctuations in abundance of sauger populations result in cyclical fisheries. Experimental gill nets were used to collect sauger over eight years in four Tennessee River reservoirs (Watts Bar, Chickamauga, Guntersville, and Kentucky) and one Cumberland River reservoir (Old Hickory) during spawning migrations (January - April). Between 1990 and 1997, 634 saugers were collected from the Cumberland River and 3,179 were collected from the Tennessee River. Saugers ranged from age-1 to age-10; however, 97% of the saugers were less than age-4. Due to the absence of older saugers, all fisheries were dominated by saugers less than 400 mm TL. Age- 1 and age-2 sauger catches were used as indices of recruitment in the Tennessee River and Cumberland River, respectively. Sauger recruitment was modeled as a function of the amount of water discharged and number of fingerlings stocked in previous years. Sauger recruitment in two upper Tennessee River reservoirs was related to total volumes discharged the previous spring (February to April; r>+0.91; P=0.0001); no significant relationship between spring discharges and recruitment was evident in two lower Tennessee River reservoirs or Old Hickory Reservoir on the Cumberland River. Current models suggest that February-April discharges between 8.4 x 109 and 15.4 x 109 m3 may enhance recruitment in the Tennessee River; whereas, discharges above or below this range are detrimental. Optimal discharges cannot occur simultaneously throughout the Tennessee River. Based on empirical relationships between discharge, recruitment, and river reaches, we concluded that strong recruitment throughout the Tennessee River cannot occur in the same year. Recruitment was not related to fingerling stockings in two upper Tennessee River reservoirs; however, age-2 sauger catches in Old Hickory Reservoir on the Cumberland River were related to the number of fingerlings stocked two years earlier (r=+0.99; P=0.0001). Gonadosomatic index values were either zero for immature or spent male and female saugers, or >0.075 and >0.025 for mature female and male saugers, respectively. Total length (TL) at maturity for female and male saugers was approximately 300-325 mm TL and 225-250 mm TL, respectively. The 381-mm minimum size limit in the upper Tennessee and Cumberland River protected 73-85% and 32-52% of mature male and female saugers, respectively. The 356-mm minimum size limit in the lower Tennessee River protected 78% and 47% of the mature male and female saugers, respectively. Saugers collected in the upper Tennessee River were significantly older and longer, on average, than saugers collected from the lower Tennessee River in most years. The pooled average age of saugers in the Tennessee River over their eight-year study was 1.99 years. We propose that mean ages falling outside the range of 1.5 to 2.5 years (+2 S.D) will characterize populations suffering from over-exploitation or consistently poor recruitment.

 

 

 

 

 

 

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