| Summary: | Thesis (M.Sc.)--Memorial University of Newfoundland, 1989. Biology Bibliography: leaves 143-149. A five-year ecological investigation into the life history of Salvelinus fontinalis (Mitchill) was undertaken to evaluate its growth in an acidic, dystrophic, headwater habitat and to determine the seasonal aspects of feeding, reproduction and parasitism. - Young of the year fish were found to hatch and grow in water with a stream pH of 4.7 and were subject to parasitism at the onset of exogenous feeding. The growth of these fish was rapid but subject to a great deal of variation due to environmental conditions and initial times of egg deposition. Condition factors of this age group were extremely low. - Fish of age greater than zero were found to be robust, having very high condition factors (greater than 1.00). The condition was variable with season, peaking during July of most years but displaying two low periods associated with fall and spring water temperature changes. -- The changes in condition were attributed to change in food supply and physiological demands. Analysis of parasites revealed only four enteric helminth species which were cyclical in nature, responding to seasonal changes in temperature and intermediate host densities. Metechinorhynchus lateralis, an acanthocephalan, was the only parasite maintained at high numbers throughout the year. This parasite was also the only one which showed increases in prevalence with increase in fish age. Routes of infection for M. lateralis were established. Parasite burden was not found to be associated with condition factor. -- Growth of older fish was comparable to that of fish downstream in the watershed and either habitats which have higher pH values. -- The diets of young of the year fish and that of older fish were similar with the exception of fish eggs which were found only in the stomachs of older fish. These fish utilized all available aquatic insects, molluscs, and crustaceans as well as any available terrestrial food sources. There were no cases of empty stomachs in older fish. Exogenous feeding usually began in May for young of the year fish. They showed a preference for chironomids, coleopterans, trichopterans and ceratopogonids whereas the older fish showed the highest preference for the Odonata, prey size corresponding with an increase in fish age (thus size). Feeding was affected by season and prevalence for some food items and modified by prey availability. The abundance of some food items was correlated with increases in parasitism. -- S. fontinalis was the sole user of the only fluvial habitat available for spawning but was also seen utilizing redds in the pond environment. The initiation of spawning was earlier in the fluvial environment.
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