Competition is defined as the demand of two or more organisms for the same extrinsic resources in excess of supply. The distribution, movements, behaviour and food of trout and shiners in Paul and Pinantan lakes were studied in order to determine the item's and mechanisms of interspecific competition between them. Data from recent years were compared with data for years when trout alone inhabited the lake. No interspecific aggression was observed. The possibility that the two species were competing for space was discounted. Stomach contents of shiners in Pinantan Lake revealed a marked qualitative diurnal food cycle. In Paul Lake, shiners have drastically reduced the Gammarus population relative to its pre-shiner abundance. This overgrazing was caused by the concentration of large numbers of shiners over the shoals where Gammarus are also present in their highest concentrations and the ability of shiners to pursue food deeper into the weeds and to graze an area more thoroughly than trout. In Pinantan Lake shiners have apparently-reduced the density of Daphnia to a point where trout are unable to feed on them as rapidly as in pre-shiner years. The ability of both species to utilize many types of food tends to reduce the intensity of competition. The study demonstrates how false implications may arise from a delayed appraisal of competition. If observations had not been made on Paul Lake until after competition had been observed the importance of Gammarus as an item of competition would have probably been overlooked and the whole competitive relationship misconstrued. Included among the basic mechanisms of competition is the consumption by one or more organisms of something in short supply before it reaches a potential habitat where it would become available to another organism or group. Environmental factors and behaviour were shown to be important influences in the dynamics of competition. The physical and biological environment and the distribution and behaviour of competitors may be in states of continual flux. Hence natural competitive relationships can be considerably more complicated and variable than situations described by the most elastic of theoretical models. / Science, Faculty of / Zoology, Department of / Graduate

The expression of the estradiol-responsive genes in the liver of rainbow trout, Salmo gairdnerii, has been studied as a system which may permit quantitative measure of adverse sublethal effects of various xenobiotics. Upon administration of 17 β-estradiol to male or immature female rainbow trout, the expression of two genes are markedly enhanced. One of these genes codes for the egg yolk precursor protein, vitellogenin, whereas the other codes for another, as yet unidentified, protein. Complementary DNA (cDNA) genes of these two proteins have been employed as probes to characterize the dose-response relationship as well as the time course induction of these two classes of transcripts in liver both in vivo and in vitro. The maximal net transcription of pRTC 2 occurs at 20 ug β -estradiol per 100 gram fish body weight whereas those encoded for by pRTC 5 display maximal transcription at 5 μg β-estradiol per 100 gram fish body weight. With doses exceeding the dose required for maximal induction of transcripts, both classes of transcripts reach their maximal levels between 4 and 8 hours after primary and secondary induction. Transcripts homologous to pRTC 5 return to control levels by 16 hours and 2 days after primary and secondary induction respectively. Those homologous to pRTC 2 however, were not observed to recover to normal levels in the primary induction even 16 days after stimulation with estradiol. However, upon secondary induction pRTC 2 transcripts returned to control levels 8 days post-inoculation with estradiol. The effect of various xenobiotics on the induction of these two estradiol-responsive genes was investigated. Pretreatment with β-naphthoflavone resulted in neither the induction or repression of both classes of transcripts. Administration of Kepone prior to a subsequent stimulation with estradiol, resulted in a decrease in the accumulation of pRTC 2 transcripts only. In contrast, an isomer of DDT, p,p'-DDT, was found to enhance the expression of pRTC 5 transcripts in fish subsequently administered β-estradiol. Oncogenes have been found to be activated in transformed cells or cells treated with various xenobiotics. In this study, I have shown that the cellular oncogene, pRTC-myc 1-81, is expressed in the liver at an elevated level in response to estradiol treatment. The two classes of polyadenylated transcripts were detected (2.5 kb and 5.6 kb). The three estradiol-responsive genes mentioned above (pRTC 2, pRTC 5, and pRTC-myc 1-81) were also shown to be transcribed in an established rainbow trout hepatoma cell line. Transcriptional activities of all three genes, as well as the translational activity of vitellogenin, were diminished upon growth in serum stripped of endogenous hormones. Further characterization of this rainbow trout hepatoma cell line is warranted so that it may be employed in a sensitive and quantitative bioassay for assessing the pathobiochemical effects of environmental xenobiotics on fish reproduction. Such an index may be beneficial for establishing adequate guidelines for water contaminants that potentially could affect aquatic and human reproductive success. / Thesis / Master of Science (MS)

Different strains of rainbow trout (Salmo gairdneri), Ten Sleep, Sand Creek, Beitey, Shepherd-of-the-Hills, New Zealand, Fish Lake- Desmet, Desmet, were compared for survival to the creel, growth and catchability after being stocked in a fluctuating 80 ha Utah reservoir . Fish were stocked in the spring and fall as fingerlings and monitored by creel censusing, gill netting and electrofishing. Fish were tagged with coded wire snout tags prior to stocking . An angler opinion survey was conducted to determine angler satisfaction with numbers and size of fish caught. Regardless of strain, spring stocking was superior to fall stocking in survival to the creel. In the spring 78 stocking the Ten Sleep strain had the highest survival to the creel (33.7 percent), followed in order by Shepherd-of-the-Hills (11.0 percent), Beitey (5.5 percent), Sand Creek (5.4 percent), New Zealand (4.1 percent), and Fish Lake-Desmet (2 .9 percent). In the spring 79 stocking the Shepherd-of-the- Hills strain had the highest survival to the creel (7 .6 percent), followed in order by the Sand Creek (7.3 percent) and the Ten Sleep (6.5 percent). Similar trends in survival were found in gill netting and electrofishing samples. Migration out of the reservoir was negligible for each strain. There were no strain differences in catchability by different methods (shore, boat) or gear (bait, artificial lure). Differences in growth between the fastest growing strains (Ten Sleep, Sand Creek) and the slowest growing strains (New Zealand, Fish Lake-Desmet) averaged as great as 16 mm in length and 43 g in weight. Differences in growth and survival among strains were great enough to span the range of angler satisfaction with numbers caught and size of fish caught from satisfactory to unsatisfactory. Therefore, strain selection can be a useful tool to improve fingerling stocking programs and manipulate the number of anglers who are satisfied with the angling experience.

Effects of exercise, social facilitation, and delayed conditioning after vi exercise on the learning behavior of 5 to 6-inch rainbow trout, Salmo gairdneri, was measured in a conditioned avoidance response apparatus. The conditioning schedule contained an intertrial interval between alternate presentations of conditioned (light) and unconditioned (shock) stimuli. This randomization eliminated learning losses found in a previous study. Mean percentage avoidance, the measurement of learning, did not decrease significantly during conditioning trials. Exercised fish learned avoidance better than did non-exercised fish. Mean percentage avoidance for fish exercised at 0.5 ft/sec was 66.3; at 1.0 ft/ sec, 1.5 ft/sec, and no-exercise, mean percentage avoidance was 68.2, 68.9 and 65.0, respectively. Social facilitation affected learning in the one, two, and three fish per cell tests, where mean percentage avoidance was 55.5, 68.9, and 81.0 percent, respectively. A delay of 24 hours between exercise and conditioning resulted in decreased learning levels. Mean percentage avoidance was 60.3, 63.5, 67.7, and 53.7 for the 1-, 2-, 2-, and 24-hour delay tests, respectively; however, mean percentage avoidance for the last 60 trials of each test indicated the 1-, 2-, and 4-hour delay tests were all similar, over 70 percent, while mean percentage avoidance for the 24-hour delay test was only 57.8 percent.

Rainbow trout lactate dehydrogenase (LDH) B2' B2' , B2' B2" and B2" B2" phenotypes were tested under a variety of conditions for swimming endurance, oxygen consumption rates, and blood pH, p02, and lactate. The B2" B2" phenotype exhibited a lower swimming endurance, under a limited oxygen supply, than the B2' B2' and B2' B2" phenotypes. Blood pH at fatigue did not differ among the LOH phenotypes that swam under low oxygen conditions (2 mg/1). Blood p02 at fatigue was significantly higher for females than for males under low oxygen conditions. Oxygen consumption rates were significantly higher for males than for females at dissolved oxygen concentrations of 3 mg/1 to 8 mg/1. The depression in oxygen consumption rates at low oxygen levels was greater for males than for females. The increase in blood lactate with swimming under low oxygen concentrations and static exposure to low oxygen depended on LOH phenotype. The adaptive significance of the LDH B2' and B2" alleles was discussed. Thirteen populations of Intermountain cutthroat trout were sampled for biochemical genetic variation. Variation was observed in muscle aspartate aminotransferase for all populations which would fit a genetic model of two loci and three alleles. Unique muscle A group lactate dehydrogenase variation was observed in Snake Valley cutthroat trout which suggested the presence of several variant alleles. Allele frequencies for tetrazolium oxidase changed during three consecutive years in Bear Lake cutthroat trout that were trapped and spawned artificially. The possible causes of those changes were discussed. No variation was observed in alphaglycerophosphate dehydrogenase, isocitrate dehydrogenase, eye lactate dehydrogenase or muscle malate dehydrogenase in cutthroat trout.