Diel and seasonal activity patterns of adult tautog, Tautoga onitis, in lower Chesapeake Bay, inferred from ultrasonic telemetry

Recent advances in ultrasonic telemetry have enabled researchers to simultaneously collect telemetry data on numerous tagged individuals without remaining in direct contact with them. We present a low cost, commercially available automated acoustic receiver system from which presence/absence data can be used to infer diel activity patterns. We monitored a large, temperate labrid, Tautoga onitis, but the methods and analyses presented here have direct application to other marine species. Data were analyzed using graphical analysis, harmonic analysis, and empirical eigenfunction analysis. Diel activity patterns were expressed in the context of photoperiod, water temperature, and tidal flow. Detection periodicity was strongly diel (24-h cycle), with detection predominantly during daylight hours only (diurnal). Diurnal detection persisted throughout the study. Daily detection was greatest in the morning or afternoon during slack tide. Daily detection varied seasonally with ambient water temperature and was greatest between 13-20 degreesC, corresponding to the primary fishing seasons for Tautoga onitis in spring and fall. This study represented the first use of automated acoustic receivers to investigate seasonal changes in diel activity patterns of adult tautog and only the second application of ultrasonic telemetry to study this species. This study was also the first to address diel activity patterns of adult tautog in the southern range of this species' distribution.