Factors Influencing the Seasonal and Daily Patterns of Alewife (Alosa pseudoharengus) Migration in a Rhode Island River

Abstract

Continuous time series records of numbers of fish ascending a Denil-type fishway on the Annaquatucket River, North Kingstown, R.I., were obtained with a Smith-Root electronic fish counter during 1971 and 1972 spawning migrations. Seasonal trends in numbers of fish counted per day were unimodal and showed similar time patterns in both years. Water temperatures delimited the seasonal migration period. Short-term fluctuations in fish movement showed a significant zero-lag positive correlation with fluctuations in water temperature and a significant positive correlation with fluctuations in volume outflow when lagged 2 days behind outflow. A 10–14-day cycle appeared in fish migration data. Light intensity determined when alewife (Alosa pseudoharengus) movement would occur during a 24-h period, whereas water temperature controlled the pattern of movement exhibited during daylight hours. Fish responded to hourly water temperatures on the basis of their value relative to a changing baseline temperature.