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Environmental control of interactions between larval fish and their prey, and the potential influence of this relationship on fish feeding and recruitment, were assessed using empirical models developed using data drawn from the literature and developed in field studies. Ingestion rates of larval fish in laboratory and natural environments were found to differ in relation to food density. In laboratory studies, larvae show a strong functional response to prey density. Larvae situated in situ consume food at much higher races than would be predicted from laboratory studies and these rates are independent of prey density at known in situ densities. This discrepancy between laboratory and field feeding rate-food density relationships can be partly explained by the in situ contribution of small-scale turbulence to predator-prey encounter rates. Field studies of the influence of wind on nearshore hydrography showed that wind-induced upwelling generated favorable combinations of nutrients, light, and small-scale turbulence for production by phyto- and zooplankton. The distribution of microplankton $(<$80 $ mu$m) that resulted from these upwelling episodes was quantitatively described by the cumulative longshore wind velocity during the summer months. Microplankton abundance was greatest within 4 km of a major spawning site for capelin, Mallotus villosus, an economically and ecologically important forage species in the north Atlantic Ocean. Interannual variability in the intensity and frequency of upwelling-favorable winds was positively and significantly correlated with recruitment levels in the NAFO 2J3K capelin population. A new recruitment forecasting model, using an upwelling-related wind index as an input, explained more of the variance in capelin recruitment than did a previously published model. These results suggest that larval capelin are more likely to be food-limited in years when wind conditions are unfavorable for upwelling, and that recruitment in this fi

The physical and physiological condition of larval fishes throughout their development is believed to influence their survival, and ultimately to contribute to recruitment to the adult population. The study of larval condition is therefore central to larval fish ecology. / In this thesis I sought to (1) carry out an appraisal of the characteristics and the reliability of condition measures now being used, (2) assess the importance of maternal contribution to the nutritional status of larval fish, (3) evaluate the possibility that diel variability in metabolism could lead to serious biasing of the interpretation of condition measures obtained over time, and (4) assess the time course of the condition of larval fishes subjected to periods of intermittent feeding. / The experiments described in chapter 2 were designed (1) to assess the impact of female nutritional status on the quality of the eggs and larvae they produced, (2) to determine which of a series of nucleic acid and protein measurements were most responsive to post-hatching starvation, and (3) to determine whether the starvation dynamics of those measures was affected by female source. No significant correlation could be found between any of the maternal traits studied and eggs and larval measures. The results did show, however, that egg size was more variable between-clutches than within-clutch, was independent of embryonic developmental rate, but was positively related to larval size. / The existence and ontogeny of circadian (24 hrs.) and ultradian (<24 hrs.) oscillations in the nucleic acids and protein content of larval capelin was investigated in the laboratory experiments outlined in chapter 3. The most obvious long-terms trends occurred during the embryonic period when DNA and RNA content increased constantly, and during the post-yolk-sac period when RNA and protein decreased following sub-optimal feeding. / The objectives of the study described in chapter 4 were threefold, (1) to determine which of a series of nucleic acid and protein measurements were affected by intermittent (delayed-fed and delayed-starved) feeding conditions in capelin larvae, (2) to determine the dynamics and shape of the time response, and (3) to determine whether the empirical data gathered were consistent with models developed as a consequence of the review of the literature (chapter 1). Only the dry weight, and the quantity of DNA, RNA, and protein per dry weight differed significantly between starvation and ad libitum feeding controls. Starvation dynamics were less consistent with predictions. Of the indices investigated, the dynamics of the quantity of DNA and RNA per dry weight were the most consistent dynamics with model predictions. (Abstract shortened by UMI.)

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