Fisheries Behavioral Ecology - Abstracts
Hurst, T.P. and T.A. Duffy. 2005. Activity patterns in northern rock sole are mediated by
temperature and feeding history. Journal of Experimental Marine Biology and Ecology 325:201–213.
Abstract
Studies of activity patterns of fishes rarely consider the impact of environmental conditions or organism state. In this paper
we demonstrate the influence of temperature and feeding history on the diel activity patterns of juvenile (age 1+) northern rock
sole Lepidopsetta polyxystra (Orr and Matarese). Activity type (benthic vs. water column) and level were determined from
hourly video recordings of fish in laboratory tanks with the aid of infrared illumination. Groups of rock sole (n = 4 per group)
were observed at 2, 5, 9 and 13 °C without food and at 9 °C with food offered once in the morning, at dusk or at night. In all
experiments, rock sole exhibited peak activity levels during the dusk and dawn transition periods and a temporal segregation of
activity mode. Daytime and crepuscular activity was predominantly benthic, occurring within a few centimeters of the tank
bottom, whereas a significant fraction of nighttime activity (up to 90%) occurred with rock sole swimming in the water column
or at the water surface. The primary effect of water temperature on rock sole behavior was a reduction in daytime and
crepuscular activity at low temperatures. Conversely, nighttime activity levels were independent of water temperature, resulting
in a thermally induced shift in the primary activity period. Morning and dusk feeding produced a short-term (1 h) elevation in
activity followed by activity suppression until the subsequent crepuscular phase. Nighttime feeding resulted in a longer period
of elevated activity (2 h) and did not suppress further benthic or water column activity. These observations suggest a temporal
segregation of activity between daytime foraging and nighttime movement that balances energetic demands with predation risk.
Last updated
26 April, 2007
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