An automatic recording system for fish counting and for the monitoring of water temperature, dissolved oxygen, pH and solar radiation was employed on a newly constructed fishway on the Annaquatucket River, North Kingstown, Rhode Island. Records of fishway utilization by the alewife, Alosa pseudoharengus and of the environmental variables were critically examined by time series autocorrelation and crosscorrelation techniques. It was demonstrated that migratory activity was harmonic with a diurnal periodicity and was closely associated with incident solar radiation. Suggestions for an improved monitoring system and further analysis were made.