Temperature and Fish

Abstract

It has been a prime assumption of those working in the laboratory that physiological experiments would have direct ecological significance. Further, it was assumed that by studying static, limited cases (monofactorial) on intact animals it would be possible to unravel some of the more important interrelations of stimulus and response which characterize the dynamic, unlimited natural environment. In theory, given enough time, this should prove correct. But to date there are only suggestions of cause and effect regarding the ecological role of temperature, and time is pressing. While the monofactorial approach will continue to provide physiological insight, the introduction of multivariable factorial experiments, including multivariate responses, holds greater promise for revealing the respective roles of environmental factors. Two areas of biological inquiry are likely to provide greatest insight: 1)development, involving growth and differentiation, and 2)energetics, involving metabolism, performance and efficiency of energy transformation. Unless these functional capacities can be maintained at a high level, abundance and well-being cannot prevail. They constitute key responses of the whole organism to sublethal effects, particularly in the case of an environmental entity like temperature which acts as a “controlling” factor,without threshold levels within the tolerance zone. In those exceptional cases where fish have been found living close to their lethal limit the above functions have been maintained at a relatively high level. The inclusion of a biotic factor (e.g., food, yolk, activity, age, weight) in multifactorial experiments has considerably improved their predictive power for assessing the ecological consequences of changed environments.