EFFECTS OF CLIMATIC TEMPERATURE-CHANGE ON GROWTH, SURVIVAL, AND REPRODUCTION OF RAINBOW-TROUT - PREDICTIONS FROM A SIMULATION-MODEL

The effects of changes in the annual temperature cycle on energy acqui sition and the allocation of that energy to respiration, growth, and r eproduction of female rainbow trout (Oncorhynchus mykiss) are evaluate d using a new type of simulation model. We tested the effects of warme r (+2 and +4 degrees C) and cooler (-2 degrees C) water temperature cy cles. We used Monte Carlo filtering techniques to define the range of parameter sets capable of generating realistic behaviour for individua l female rainbow trout over a single reproductive cycle under the base line temperature regime. The base temperature scenario generally resul ted in maximum growth and reproductive success. Shifts in the annual t emperature cycle of +2 and +4 degrees C decreased growth and reproduct ive success, but most females were in better physiological condition. The -2 degrees C scenario resulted in reduced growth, physiological co ndition, gonad index, and reproductive success. The effects of shifts in the annual temperature cycle varied substantially between individua l 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 var iability in physiological parameters between individuals are not easil y evaluated experimentally. Models are an ideal tool for heuristically exploring such implications.