Thermal effects on behavior of juvenile walleye pollock ( Theragra chalcogramma): implications for energetics and food web models

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Author: Hurst, Thomas P
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2007
• Subjects: Theragra chalcogramma
• Online Access: http://dx.doi.org/10.1139/f07-025; http://www.nrcresearchpress.com/doi/pdf/10.1139/f07-025

The behavioral responses of fishes to temperature variation have received little attention despite their direct implications to bioenergetics-based models of production and encounter-based models of food web dynamics. Behavioral characteristics of juvenile walleye pollock (Theragra chalcogramma), a pelagic marine zooplanktivore, were examined between 2 and 9 °C in large arenas. Routine swim speed, path sinuosity, and schooling cohesiveness of fish in small groups were described from overhead video observations. In a separate experiment, maximum swimming speeds were measured in a recirculating flume. Routine and maximum swimming speeds had contrasting responses to temperature demonstrating a behavioral rather than physiological regulation of activity level. Routine swim speed was 48% faster at 2 °C than at 9 °C. This result is inconsistent with the assumption of a constant activity multiplier for metabolism incorporated into most bioenergetics models of fish growth. Increased swim speed, along with the reduced path sinuosity observed at low temperatures, may reflect kinetic aspects of habitat selection. Group cohesion increased at low temperatures, with nearest neighbors averaging 32% closer at 2 °C than at 9 °C. These results demonstrate that representative models of energy flow through marine food webs depend on an improved understanding of the behavioral as well as physiological responses of fishes to thermal variation.