Variation in individual performance and condition appear to play an important role in fish population demography. I determined the separate and combined effects of nutritional condition and refuge availability on survival of the blackeye goby (Rhinogobiops nicholsii), and how condition influenced burst swimming performance to elucidate the mechanisms responsible for the observed patterns of survival. Recent recruits fed high or low rations were placed on standardized plots of rock in the field, and monitored daily to determine mortality. To examine the effects of condition and refuge availability, high- and low-ration fish were placed on plots of high, medium, or low amounts of rock. On standardized plots, low-ration fish experienced higher mortality than high-ration fish; however, swimming ability did not explain these patterns. As expected, survival increased with refuge availability, and low-ration fish experienced higher mortality than high-ration fish at medium and high levels of refuge. Surprisingly, higher mortality was observed for high-ration fish on low-refuge plots. These results indicate that both post-settlement processes and individual condition, mediated by environmental conditions, are important determinants of fish population demography. Pesticide exposure also plays an important role in determining condition, performance, and survival of fishes. Due to increasing use of pyrethroid insecticides, my second objective was to determine the effects of the pyrethroid esfenvalerate on food consumption, growth, behavior, and predation risk in the fathead minnow (Pimephales promelas). For growth experiments, minnow larvae were exposed to five esfenvalerate treatments (control, solvent control, 0.1μg/L, 0.7μg/L, 1.5μg/L) for 4 h. After exposure, unconsumed food and abnormal swimming behavior were recorded daily for 7 d. For predation experiments, minnows from each treatment were transferred to aquaria containing one threespine stickleback (Gasterosteus aculeatus). After 45 min, the number of minnows remaining was recorded. Fish exposed to 1.5 and 0.7μg/L esfenvalerate exhibited impaired swimming and feeding ability and growth relative to fish exposed to 0.1μg/L and controls. Predation risk was significantly higher in minnows exposed to 1.5 and 0.7μg/L esfenvalerate than in control fish. These results demonstrate that larval fish can experience significant growth and swimming impairment, and increased predation pressure, even after short-term exposures to esfenvalerate.