The generally accepted 2% ratio of transmitter weight to body weight constrains or precludes telemetry studies examining the timing and location of spawning of small adult westslope cutthroat trout Oncorhynchus clarkii lewisi in headwater streams. We empirically determined effects of surgically implanted dummy transmitters ranging in weight from 1 to 5 g on the swimming stamina and growth of small (81.3–206.9 g) adult westslope cutthroat trout in the laboratory to establish acceptable transmitter weights for field studies on this species. Mean growth rates and swimming stamina were not significantly different among treatments, including controls. No precipitous decline or threshold beyond which performance deteriorated markedly was observed. Data collected using telemetered westslope cutthroat trout implanted with transmitters less than about 4% of body weight should therefore approximate information about untelemetered individuals without significant bias. However, we also detected subtle effects on growth within this transmitter weight range related to individual transmitter–body weight ratios (0.5–5.3% initially), and there were indications that swimming stamina was affected similarly. Each 1% increase in transmitter– body weight ratio elicited an 11.6% decrease in growth and a possible 5.6% decrease in swimming stamina at 6 weeks postimplantation. Therefore, transmitter selection should weigh the costs of increased transmitter weight on fish performance against the benefits of longer transmission durations. In the case in which transmitter weights approaching 4% of body weight are necessary to complete a study and slight decreases in performance are not expected to affect findings materially, such weights may be acceptable. In other cases, researchers should choose the lightest possible transmitters that allow study goals to be achieved and not automatically select transmitters weighing 4% of body weight.

Water temperature plays a key role in determining the persistence of shovelnose sturgeon Scaphirhynchus platorynchus in the wild and is a primary factor affecting growth both in the hatchery and in natural waters. We exposed juvenile shovelnose sturgeon to temperatures from 88C to 308C for 87 d to determine the effect of temperature on growth, condition, feed efficiency, and survival. Growth occurred at temperatures from 128C to 308C; the optimal temperature predicted by regression analysis was 22.48C, and the minimum temperature needed for growth was greater than 10.08C. The maximum feed efficiency predicted by regression analysis was 24.5% at 21.78C, and condition factor was highest in the 188C treatment. Mortality was significantly higher at 288C and 308C than at lower temperatures but less than 10% across the thermal regimes tested and 0% at 14-188C. Mortality was observed at and below 128C, suggesting that extended periods of low temperature may deplete energy reserves and lead to higher mortality. Rearing juvenile shovelnose sturgeon at temperatures above 248C reduced the growth rate and feed efficiency and increased mortality. Temperatures in the range 18-208C appeared to maximize the combination of condition, growth, and feed efficiency while not increasing thermal stress. This study corroborates field studies suggesting that altered temperature regimes in the upper Missouri River reduce the growth of shovelnose sturgeon. This information may help protect the thermal habitat critical to the species and guide restoration efforts by delineating temperature regime standards for regulated rivers and those affected by hydroelectric facilities and suggesting new criteria for conservation propagation.

Determining the optimal rearing temperature for the June sucker Chasmistes liorus has been identified as a key component necessary for the design of a new June sucker hatchery and for achieving the June Sucker Recovery Implementation Program supplementation goal of 350,000 fish of 20‐cm length annually. A laboratory study was conducted to monitor the performance of June suckers reared at average temperatures of 8.3, 10.1, 12.3, 14.0, 16.1, 18.5, 20.5, 21.8, 23.9, 25.9, 27.9, and 29.7°C for 16 weeks. In this study, quadratic regression analysis was used to determine maximum condition factor and weight gain, respectively, and 22.5°C and 21.9°C were identified as the maximum water temperatures. According to this same regression analysis, the maximum feed efficiency and total length increase occurred at 21.6°C and 23.7°C, respectively, during the 16‐week study. The modified acclimated chronic exposure water temperature (50% survival for 60 d) was greater than 27.9°C. Spinal and fin deformities increased during this study in all treatments, and these malformations appear to be diet related. There was no temperature effect on deformities, but temperature did affect overall survival.

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