Heat transfer in fish: are short excursions between habitats a thermoregulatory behaviour to exploit resources in an unfavourable thermal environment?
Temperature is the primary environmental factor affecting physiological processes in ectotherms. Heat-transfer models describe how the fish's internal temperature responds to a fluctuating thermal environment. Specifically, the rate coefficient (k), defined as the instantaneous rate of change in body temperature in relation to the difference between ambient and body temperature, summarizes the combined effects of direct thermal conduction through body mass, passive convection (intracellular and intercellular fluids) and forced convective heat transfer (cardiovascular system). The k-coefficient is widely used in fish ecology to understand how body temperature responds to changes in water temperature. The main objective of this study was to estimate the k-coefficient of brook charr equipped with internal temperature-sensitive transmitters in controlled laboratory experiments. Fish were first transferred from acclimation tanks (10°C) to tanks at 14, 19 or 23°C (warming experiments) and were then returned to the acclimation tanks (10°C; cooling experiments), thus producing six step changes in ambient temperature. We used non-linear mixed models to estimate the k-coefficient. Model comparisons indicated that the model incorporating the k-coefficient as a function of absolute temperature difference (dT: 4, 9 and 13°C) best described body temperature change. By simulating body temperature in a heterogeneous thermal environment, we provide theoretical predictions of maximum excursion duration between feeding and resting areas. Our simulations suggest that short (i.e. <60 min) excursions could be a common thermoregulatory behaviour adopted by cold freshwater fish species to sustain body temperature below a critical temperature threshold, enabling them to exploit resources in an unfavourable thermal environment.
Centre de recherche sur les interactions bassins versants - écosystèmes aquatiques (RIVE), and Groupe de recherche interuniversitaire en limnologie et en environnement aquatique (GRIL), Université du Québec à Trois-Rivières, C.P. 500, Trois-Rivières, QC, Canada G9A 5H7 marc.pepino@uqtr.ca.
Marc
M
Pépino
Centre de recherche sur les interactions bassins versants - écosystèmes aquatiques (RIVE), and Groupe de recherche interuniversitaire en limnologie et en environnement aquatique (GRIL), Université du Québec à Trois-Rivières, C.P. 500, Trois-Rivières, QC, Canada G9A 5H7.
Katerine
K
Goyer
Centre de recherche sur les interactions bassins versants - écosystèmes aquatiques (RIVE), and Groupe de recherche interuniversitaire en limnologie et en environnement aquatique (GRIL), Université du Québec à Trois-Rivières, C.P. 500, Trois-Rivières, QC, Canada G9A 5H7.
Pierre
P
Magnan
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001831:Body Temperature; D001833:Body Temperature Regulation; D017753:Ecosystem; D013696:Temperature; D013997:Time Factors; D014337:Trout / Q000502:physiology*
Ectotherm; Internal fish tags; Non-linear mixed modelling; Radiotelemetry; Salvelinus fontinalis; Temperature; Thermoregulation