Ultrasonic tracking of activity and movement patterns of female cunner, Tautogolabrus adspersus, in Broad Cove, Conception Bay, Newfoundland

Bradbury, Carole G. J. (1993) Ultrasonic tracking of activity and movement patterns of female cunner, Tautogolabrus adspersus, in Broad Cove, Conception Bay, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Ultrasonic tracking using a fixed hydrophone array system was conducted in conception Bay, Newfoundland, to study the activity and movement patterns of female cunner, Tautogolabrus adspersus, (Walbaum 1792). Eight female cunner were monitored at various times from June 17 to November 24, 1991, providing 107 days of tracking. The tracking system provided positional information on individual cunner at 15- second intervals. Ultrasonic transmitters had an average life of 17 days. Transmitters were attached externally through the dorsal musculature. Transmitters had no adverse effect on equilibrium or swimming ability and produced no detectable changes in female activity or movement. -- Fish were active diurnally, commencing activity on average 55 minutes after sunrise and ceasing activity about 60 minutes after sunset. Fish were assumed active whenever positional information was obtained on movement. The active period, ranging from 11 to 16.5 hrs, corresponded to the interim between daily onset and cessation of activity and was interrupted by periods of inactivity lasting between 5 and 15 minutes. Several factors influenced the activity of female cunner. As daylength shortened, cunner had a corresponding decrease in the duration of their diurnal activity. Increases in water temperature resulted in a decrease in the length of inactivity bouts. At temperatures below 5°C cunner seek shelter and remain inactive. During increased surface waves cunner remained inactive for longer periods of time. -- Activity was uninfluenced by cloud cover and tidal cycle. Activity did not differ between morning and afternoon observations, but over the observation period between June and November inactivity bouts became more numerous and lasted for longer periods. -- Female cunner exhibited limited movements, remaining within 80m of their original point of capture. The home range areas of 8 female cunner ranged in size from 300 to 2353 m². Females utilized space disproportionately within the boundaries of their home ranges, spending 60% of their time in 30% of their home range. -- As water temperatures increased, both on a daily and seasonal basis, females occupied smaller home ranges. Home range areas were larger during the afternoon than the morning. Size of home range areas were not affected by sea state, but increased as cloud cover increased. Seasonally the largest home ranges occurred in June-July, followed by October-November, and lastly August-September. -- While daily changes in environmental variables (Le. Water temperature, cloud cover, and sea state) affect activity and movement patterns of female cunner, changing energetic requirements associated with spawning and overwintering torpor appear to play a more important role.

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