Effects of two acclimation temperatures, 7 and 14 degrees C, on baseline physiological parameters of Atlantic salmon (Salmo salar) parr

The purpose of these experiments was to determine baseline physiological parameters in Atlantic salmon (Salmo salar) acclimated to two different temperatures of 7 and 14&deg;C and to look at how these physiological parameters are affected by time and acclimation temperature. Gut contractility, liver enzymes, blood plasma levels of cortisol, sodium, potassium, chloride and glucose, and growth were examined in these studies.Initial studies on the isolated intestine were done to determine optimal in vitro conditions for the experiments. Subsequent studies were done with serotonin (5-HT) and transmural stimulation (TS) in a Krebs-Henseleit solution containing HEPES, buffer maintained at pH of 7.85 and temperature of the experimental group.The activities of three liver enzymes, Uridine diphosphate (UDP)-glucuronyl transferase, sulfotransferase and glutathione S-tansferase (GST) and the blood plasma levels of cortisol, chloride, sodium potassium ratio (Na:K), and glucose were studied.Growth parameters (weight and fork length) in first section of the study, demonstrated significant differences in month, treatment and month by treatment interaction (p < 0.001). The 14&deg;C group was generally largest. The overall health (condition index) of the groups acclimated at 7 and 14&deg;C groups showed significant differences over temperature (p = 0.032), time and time by temperature interaction (p < 0.001). In the second part of the study, where acclimation histories differed, significant differences were demonstrated for weight and fork length in time, treatment and time by treatment interaction (p < 0.001). Condition factor was not significantly different between treatment, but there was a significant month effect and month treatment interaction (p < 0.001). The specific growth rates, from July to January demonstrated significant differences (p < 0.05).The overall summary conclusion from this research is that there is temporal variance in many sets of data. This suggests that time is a potential confound and should be examined in other studies which are carried out over a prolonged period of time. There was little difference between blood indices, gastrointestinal (GI) activity and selected liver enzyme activity of the two temperature treatment groups. Acclimation was demonstrated by the recurrence of seasonal cycling. Many studies have shown seasonal cycling of hormones, GI activity, and liver enzyme activity. It was interesting that similar trends were found in fish maintained at two temperatures, in spite of differences in growth between the two groups. Thew studies lay the groundwork for further research with Atlantic salmon. More study is needed to replicate these experiments using many tanks and fish to determine true baselines for Atlantic salmon at these temperatures as well as throughout the temperature range of these animals. (Abstract shortened by UMI.).Source: Masters Abstracts International, Volume: 38-03, page: 0629.Adviser: J. F. Burka