I 



D. H. Fickeisen 

 J. C. Montgomery 

 R. W. Hanf, Jr. 



Effect of 



Temperature on 



Tolerance to 



Dissolved Gas Supersaturation 



of Black Bullhead, Ictalurus melas 



ABSTRACT 



Black bullhead, Ictalurus melas, were acclimated to 8, 12, 16, and 

 20°C in Columbia River water, and were tested at each of the 

 acclimation temperatures to determine acute tolerance to dis- 

 solved atmospheric gas tensions in excess of equilibrium satura- 

 tion. The data were subjected to probit analysis and mean 96-hr 

 TL^ values were 126.7% of equilibrium saturation at 8°C, 125.1% 

 at 12°C, 123.8% at 16°C, and 124.4% at 20°C, indicating a slightly 

 elevated tolerance at the lowest test temperature. These values, 

 while indicating a statistically significant difference in tolerance, 

 do not indicate an ecologically significant effect of temperature 

 on acute tolerance of black bullhead in the range of tem- 

 peratures tested. 



Preliminary bioassays of tolerances of several 

 selected freshwater teleost species to dissolved 

 atmospheric gas supersaturation which were con- 

 ducted at 20°C (Fickeisen, Schneider, and Mont- 

 gomery, 1973) demonstrated an apparently lower 

 tolerance for the species having "cold water" 

 preferenda than for the "warm water" species 

 tested. In addition, for several years the literature 

 has held that increased temperature decreases 

 tolerance to supersaturated dissolved gases, but 

 little experimental evidence has been available, 

 especially for non-salmonids (Anonymous, 1971; 

 Weitkamp and Katz, 1973). We therefore began an 

 extensive series of acute bioassays of the effect of 

 excess atmospheric gas tension at different tem- 

 peratures on black bullhead (Ictalurus melas), 

 pumpkinseed sunfish (Lepomis gibbosus), and rain- 

 bow trout (Salmo gairdneri). Tests were to be con- 

 ducted under non-shock conditions, that is, the fish 

 were to be acclimated to the test temperature prior 

 to exposure to supersaturation. This paper is a 

 progress report of studies that are continuing, and 

 describes the effects of temperature on tolerance 

 of black bullhead. 



MATERIALS AND METHODS 



Adult black bullhead were collected by beach 

 seine and by hook and line from a backwater pond 



72 



of the Columbia River in the McNary Wildlife Refuge 

 at Burbank, Washington. The common stock was 

 held in circular tanks receiving flowing Columbia 

 River water and were fed trout pellets. As required 

 for prophylaxis, the stocks were treated with mala- 

 chite and with Diquot as well as fed pellets contain- 

 ing antibiotics. Prior to being tested, the required 

 number of fish were brought to the test temperature 

 at a rate of 1°C per day. They were held at the test 

 temperature for a period of at least 10 days. Tem- 

 perature fluctuation during this acclimation period 

 was less than 1°C. Throughout the holding period 

 all of the stock tanks were heavily aerated and 

 experience has shown that under these conditions 

 gas tensions range generally between 95 and 105% 

 of equilibrium value. 



Water supersaturated with atmospheric gases 

 was generated in a pressure vessel which received 

 an air-water mixture at about 40 psig. Control of 

 the dissolved gas tension was provided by an adjust- 

 able standpipe with a float valve to release excess 

 gas, thereby permitting an adjustable head space of 

 air over the water by adjusting the backpressure 

 and turnover time, and by adjusting the rate of air 

 inflow. 



The testing facility consisted of four rectangular 

 tanks, each 1.17 by 0.46 m with the water level 

 maintained at a depth of 35 cm to minimize hydro- 

 static pressure compensation for excess gas tension. 

 One of the tanks was supplied with water from the 

 supersaturation system. Two of them recefved 

 supersaturated water mixed with normally saturated 

 water to control gas tension, and the fourth tank 

 was a control and received normally saturated 

 water. Turnover time in each tank was calculated to 

 be less than 20 min based on the flow rate. Tem- 

 perature in all tanks was maintained within 0.5°C 



Fickeisen, Montgomery, and Hanf: Battelle-Northwest, Eco- 

 systems Department, Richland, Washington. 



