In 1995, the Caney Fork River below Center Hill Dam, Tennessee, was stocked with 108,830 harvestable (> 200 mm total length) rainbow trout Oncorhynchus mykiss and 20,949 harvestable brown trout Salmo trutta. Cohorts of both species (N = 3,000-4,000) were microtagged and released into the tailwater on 6 April 1995. An additional cohort of tagged rainbow trout was stocked on 30 June (5,877 fish). From 5 April to 30 September, a stratified roving creel survey collected information on angler use, catch, and harvest of marked and unmarked trout. Fishing pressure in 1995 was estimated at 74,534 h and nearly 10 times as many rainbow trout (41,382) than brown trout (4,210) were harvested, despite the fact that only 4 times as many rainbow trout were stocked. Return rates for tagged cohorts of rainbow trout ranged from 55% to 71%, but only 13% of the tagged brown trout were harvested. The harvest of tagged rainbow trout stocked on 6 April and 30 September approached zero about 140 d and 50 d post-stocking, respectively. In late summer, dissolved oxygen concentrations routinely dropped below 3 mg/L at the onset of generation. Once discharge ceased, dissolved oxygen concentrations slowly increased until generation resumed. Temperatures also decreased from 16 degrees C to 12 degrees C during generation.

Approximately 30 rainbow trout (150-160 mm total length) were placed into each of three 341-L tanks and temperatures were manipulated to simulate three possible temperature regimes present below Center Hill Dam: constant 12 degrees C (control), fluctuations from 12 to 17 degrees C, and fluctuations from 12 to 22 degrees C. A flucuation cycle lasted 5 d and at the end of six full cycles, fish were individually placed into a stamina tunnel. After a habituation period of five min at 7 cm/s, the velocity was abruptly increased to 20cm/s. Fish held at a constant 12 degrees C had the greatest stamina (P=0.05). Instantaneous growth rates varied significantly (P=0.05), and differences in mean total lengths and mean weights at the end of the experiment, absolute growth rates, and relative growth rates were marginally significant (P=0.09-0.13). Fish reared in the 12 to 17 degree C regime grew the slowest, had the lowest stamina, and had the lowest liver somatic index.

  

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