Effects of climatic temperature change on growth, survival, and reproduction of rainbow trout: predictions from a simulation model 1 Webb Van Winkle, Kenneth A. Rose, Brian J. Shuter, Henriette I. Jager, and Brady D. Holcomb Abstract: The effects of changes in the annual temperature cycle on energy acquisition and the allocation of that energy to respiration, growth, and reproduction of female rainbow trout (Oncorhynchus mykiss) are evaluated using a new type of simulation model. We tested the effects of warmer (+ 2 and + 4°C) and cooler (–2°C) water temperature cycles. We used Monte Carlo filtering techniques to define the range of parameter sets capable of generating realistic behaviour for individual female rainbow trout over a single reproductive cycle under the baseline temperature regime. The base temperature scenario generally resulted in maximum growth and reproductive success. Shifts in the annual temperature cycle of + 2 and + 4°C decreased growth and reproductive success, but most females were in better physiological condition. The –2°C scenario resulted in reduced growth, physiological condition, gonad index, and reproductive success. The effects of shifts in the annual temperature cycle varied substantially between individual model trout having relatively small differences in parameter values. These differences may be considered analogs of genotypic differences among individual trout in the field. The long-term implications of variability in physiological parameters between individuals are not easily evaluated experimentally. Models are an ideal tool for heuristically exploring such implications. Résumé : Nous évaluons les effets des changements du cycle annuel de température sur l’acquisition d’énergie et l’allocation de cette énergie à la respiration, à la croissance et à la reproduction chez des truites arc-en-ciel (Oncorhynchus mykiss) femelles, à l’aide d’un nouveau type de modèle de simulation. Nous avons testé les effets de cycles thermiques de l’eau plus chauds (+ 2 et + 4°C) et plus froids (–2°C). Nous avons eu recours aux méthodes de filtrage Monte Carlo pour définir la plage de séries de paramètres permettant de générer un comportement réaliste des individus femelles pendant un cycle de reproduction sous un régime thermique de base. C’est le scénario thermique de base qui donnait généralement le maximum de croissance et de succès de reproduction. L’accroissement du cycle annuel de température de + 2 et + 4°C faisait baisser la croissance et le succès de reproduction, mais la plupart des femelles se trouvaient en meilleure condition physiologique. Le scénario à –2°C occasionnait un ralentissement de la croissance, une baisse de la condition physiologique, de l’indice gonadique et du succès de reproduction. Les effets des modifications du cycle annuel de température variaient de façon importante dans le modèle entre des individus présentant des différences relativement faibles dans les paramètres. Ces différences peuvent être considérées comme analogues aux différences génotypiques entre les individus dans la nature. Les incidences à long terme de la variabilité des paramètres physiologiques entre individus sont difficiles à mesurer expérimentalement. Les modèles constituent un outil idéal pour explorer de façon heuristique ces incidences. [Traduit par la Rédaction] Introduction Predicted gradual warming of the earth’s climate would likely have effects at all levels of biological organization. Effects observed at higher levels of organization would reflect the net or integrated effects at lower levels. Fish population responses to warmer temperatures would be an emergent property of the varied direct responses of individual fish. DeAngelis and Cushman (1990) and Shuter and Meisner (1992) emphasize that linking simulation models, including physiological process models, across different levels of biological organiza- tion provides a powerful framework for assessing the effects of climate change. Physiological process models have been used to predict the bioenergetic consequences for fish exposed to climatic tem- perature change associated with global warming. Temperature effects simulated include colder and longer winters, extended growing seasons, and hotter and longer summers (e.g., Hill and Magnuson 1990; Shuter and Post 1990). These analyses fo- cused on how fish growth, survival, timing of spawning, prey Can. J. Fish. Aquat. Sci. 54: 2526–2542 (1997) Received September 3, 1996. Accepted May 7, 1997. J13634 W. Van Winkle, 2 K.A. Rose, and H.I. Jager. Environmental Sciences Divison, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6038, U.S.A. B. J. Shuter. Ontario Ministry of Natural Resources, Maple, ON L6A 1S9, Canada. B.D. Holcomb. Computational Physics and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, U.S.A. 1 Publication No. 4632 of the Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tenn., U.S.A. 2 Author to whom all correspondence should be addressed. e-mail: wvw@ornl.gov 2526 © 1997 NRC Canada