Abstract
Common snook Centropomus undecimalis in Florida are thought to move from open estuarine and coastal marine habitats into rivers during colder months to overwinter; however, this paradigm has never been formally tested. Seasonal electrofishing surveys (2004–2006) were conducted to determine the distribution, abundance, and size of common snook in the three major rivers leading to the Charlotte Harbor estuary, Florida. Common snook abundance in the tidal freshwater portions of all three rivers was high in spring and summer, and then doubled in fall. In the open estuary, haul seine data (1997–2007) were used to examine seasonal trends; common snook abundance was significantly lower during winter. No specific size group alone appeared to be involved in these seasonal changes, as length frequencies did not differ between seasons. Although these results provide evidence that a portion of the population moves between the rivers and the open estuary, the reasons for these movements require further study. The strong presence of common snook in the rivers during summer and their peak abundance in fall as opposed to winter, were unexpected and suggest that there may be interactions between their use of freshwater and marine environments that are more complex than previously considered.