The effects of temperature and dissolved oxygen on a model fish population

Environmental and chemical stressors affect the physiological processes of aquatic or-ganisms in many ways. The effects of changes in temperature and dissolved oxygen concentration on the dynamics of a model fish population are the primary focus of this research. Also discussed is the effect of a nonpolar, lipophilic narcotic adminis-tered at a level slightly below the lethal concentration (LC₅₀) for two-year simulation periods. Temperature and dissolved oxygen concentration ranges for persistence of the population are given for a number of different scenarios, including simulations with the presence of a toxicant. The result of the study of the individual dynamics was that optimal growth for an individual occurred at a temperature of 18°C and for dissolved oxygen concentra-tions greater than 7.84 ^{mg⁄_l. The initial simulations for use in studying the population dynamics demonstrated the differences in optimal temperatures and dissolved oxygen concentrations for the population as opposed to the individual as well as the impor-tance of allowing the temperature to fluctuate with the time of year. The population was able to persist in a fluctuating temperature environment for dissolved oxygen con-centrations above 4.3 mg⁄_l. With the addition of a toxicant for a two-year simulation, the population persisted in the same range of dissolved oxygen concentrations, with the exception of some of the ecotypes in the first age class, who went to extinction.}