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No description available.

No description available.

Oxytetracycline (OTC) is one of two antibiotics currently available and approved by the U.S. Food and Drug Administration for use as a chemotherapeutic agent in food fish and is widely used in the aquaculture industry. Previous pharmacokinetic studies of OTC have been conducted in cold water and warm water species of fish. However, no pharmacokinetic studies have been conducted on a cool water species such as yellow perch (Perca flavescens). The yellow perch is a cool water game and commercial species with high aquaculture potential. The pharmacokinetic profiles of oxytetracycline (OTC) was determined by measuring plasma concentrations in yellow perch following intraperitoneal (i.p.), intramuscular (i.m.), per os (p.o.), and intracardiac (i.c.) administration at a single dose of 50 mg/kg body weight. Using a modification of a high-performance-liquid-chromatographic (HPLC) technique, the plasma OTC concentrations were determined for each of the four routes of administration. Plasma concentrations were also evaluated in yellow perch exposed to a static 48-hour OTC water bath (100 mg/l). The terminal half-lives (t1/2) of OTC in yellow perch for i.p., i.m., p.o., and i.c. administrations were 112, 124, 50, and 28 h, respectively. The t1/2 for the i.m. route of administration was significantly longer than in any of the published i.m. OTC fish studies to date. However, the times of maximum OTC concentration (tmax) for the i.p., i.m. and p.o. administrations (2, 4, and 15 h, respectively) occurred relatively early in the plasma concentration-time curves. This suggests, that in yellow perch, OTC is initially absorbed very rapidly. The area under the plasma concentration-time curves (AUC) for the i.p., i.m., p.o., and i.c. routes of administration were 1718, 2659, 383, and 134 mcg·h/ml, respectively. No OTC was detected in the plasma of yellow perch following the water bath route of exposure. Finally, in yellow perch, effective therapy (plasma OTC concentrations above MIC values for most bacteria pathogenic to fish — 4 mcg/ml) would be achieved for up to 168 hours following a single i.p. or i.m. injection of 50 mg/kg and for up to 15 hours following a single p.o dose of 50 mg/kg. / Master of Science

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Conventional wisdom in ecotoxicology predicts reductions in organismal fitness to follow from exposure-related physiological effects. This expectation may be appropriate for controlled laboratory environments, but may not necessarily reflect what is likely to take place in the wild. In an extensive review of the ecotoxicology literature, it was revealed that fish condition factor (an index of energetic fitness) is just as likely to respond favourably to pollutant exposure as it is to respond negatively. The remainder of this thesis examines some of the ecological reasons for this apparent paradox. One possible cause of altered energetic status in wild, pollutant-exposed fish is variable food availability. Addressing this possibility, I showed that consumption rates (estimated using a 137Cesium mass-balance approach) were not related to growth reductions in hormonally-impaired yellow perch ( Perca flavescens) from metal-contaminated lakes. Another possibility is that fish forage less efficiently in metal-polluted lakes as a result of lowered prey choice. In this thesis, I develop an enzymatic and individual-based biomarker for fish activity costs (muscle lactate dehydrogenase, LDH, activity) and show, through the use of this tool that the cost of fish activity is intimately tied to prey type and the ability to make normal ontogenetic diet shifts. Through the application of LDH measurements, as well as through bioenergetic modelling, diet and prey community analyses, a link between decreased prey choice and high perch activity costs leading to zero growth efficiency (energetic bottlenecks) was demonstrated in yellow perch from metal-contaminated lakes. This finding provided one of the first examples in ecotoxicology of a mechanistic link between community and organismal endpoints. The findings of this thesis emphasize the need for ecotoxicology to consider ecology when looking for and interpreting ecologically relevant endpoints. The final chapter of this thesis ex

Metal contamination can disrupt the trophic links in food webs by altering the taxonomic composition and size structure of benthic invertebrate communities. Benthic invertebrate samples and perch (Perca flavescens) were collected from six lakes along a gradient of metal pollution in Rouyn-Noranda, Canada. The benthic communities of the contaminated lakes were less diverse and had smaller individuals (0.09 mg d.w. and 0.16 mg d.w. vs. 0.22 mg d.w. in the reference lake). The stomach contents of perch from contaminated lakes were less diverse, showed a greater reliance on chironomids or zooplankton, and cannibalism than perch from less polluted lakes. The mean size of prey in perch from contaminated lakes was smaller than in reference lakes (3.7 mg d.w. and 7.39 mg d.w. vs. 47.7 mg d.w. and 67.1 mg d.w. in reference lakes). (Abstract shortened by UMI.)

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Selectivity of trawl and experimental gill nets was determined for yellow perch taken from southern Lake Michigan in 1993 to 2006. Gill nets were comprised of 51-, 64-and 76-mm size mesh and showed female modal lengths of 205-, 245-, and 295-mm, respectively, while values for males were 200-, 230-, and 267-mm. Differences between females and males increased with mesh size and was significant. Comparison of nine anterior morphometric features of female and male fish indicated no differences in shape were identified that would cause the disparity in selectivity. Rather, differences in male and female selectivity were more likely due the variant population size structure of the local population sampled, with females the larger sex. A new method to estimate trawl selectivity was developed using a modified catch-curve analysis, which showed a maximum selectivity length value (1.0) of 190-mm for females and 170-mm for males. However, trawls fail to capture larger yellow perch when compared to gill nets using based on length-frequency distributions. Revealing such gear biases may lead to more efficient capture methods, resulting in improved sampling and quantitative assessment of fish populations. / Department of Biology