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<br />3 <br />experiment was set up to study the effect of cold shock on squawfish <br />larvae. <br />T31.!11 <br />Cold shock experiments were conducted on 14-day-old fish in 1984 and <br />1985, and on 40-day-old fish in 1984. Adults were spawned and eggs <br />incubated at Dexter National Fish Hatchery- One-day-old sac fry were air <br />mailed to Logan; Utah on-June 11, 1984 and on June 3, 1985. Larvae were <br />held at the Utah Water Resources Research Laboratory at 22 C in 74 liter <br />aquaria, and fed an excess of brine shrimp throughout the study. All fish <br />were moved to bioassay aquaria by siphoning. A random sample of fish was <br />taken at the beginning of each experiment to record average fish length. <br />Bioassays were run in 3.7-liter, plastic aquaria in which flow rates <br />were 0.25 liter/minute. The light regime was 14 hr light x'10 hr dark <br />throughout all experiments. Test water had a hardness of 174 mg/l, ph of <br />7.1, and dissolved oxygen from 7.9 to 10.0 mg/i. Two aquaria with 100 <br />larvae/aquaria were used for each treatment in 1984; three aquaria with 50 <br />larvae/aquaria were used in 1985. <br />Temperature control was achieved differently each year. In 1984, water <br />that had trickled down a 1-m degassing column entered aquaria at 7 C and <br />was heated by an aquarium heater to the desired temperature. This <br />technique probably caused supersaturation (112;x) which might have added an <br />additional stress. Saturation of 112% has caused partial larval mortality <br />in some species but not others (Weitkamp and Katz 1980). However, <br />squawfish did not exhibit symptoms of gas bubble disease before or during <br />the experiment e.g. bubbles in the digestive tract, swimming and