Seasonal variation patterns of the fish community in the littoral waters of northern Lake Ontario,the Pickering-Darlington area

The ecotone fish community of the littoral waters is a mixture of onshore migratory pelagian species and littoral species. It is characterized by high numeric and diversity variations produced under the effect of migrations, thermal perturbations and the local habitat variations. The sixty analyzed sampling units belong to five years of records, three seasons and three types of littoral habitats. The Kendall tau test identifies the seasonal variation as a significant criterion for sample classification. From the ecological view point it corresponds to phases of the thermal stratification. The start of the thermal stratification identifies the season of a highest pelagian onshore migration. The maximum thermal stratification shows the community structure at the end of a massive pelagian return. The late fall circulation describes the community structure prevailed by the local populations. The quantitative patterns were evaluated for each season based on a 95% confidence interval of the mean and on normalized weighed averages. A comparison of subsequent community structures allowed a species classification by the magnitude of their numeric variations. Regarding the analyses of the diversity variations, a new strategy was introduced based on independently derived indices of the community diversity. The strategy identifies two features: the seasonal models of the diversity variation and the abnormal cases. The models depict the trends/features of the diversity variations. The abnormal cases evaluate the local/temporal side effects.