Introduction

The prediction of the global warning scenario is a 1–5 °C increase in the mean global temperature as a result of a doubling of the so-called greenhouse gases; methane, carbon dioxide and nitrous oxide (Schneider, 1990; Mohnen & Wang, 1992). A variety of physiological parameters of poikiliothermic fish are directly and indirectly impacted by changes in environmental temperature, including metabolism (O2 consumption), growth, cardiac output, ventilation and excretory processes. Specifically, environmental temperature determines the rate of chemical reactions such that, in general, a 10 °C increase in temperature enhances reaction rates by 2–3-fold (Q10 = 2–3). It is well established that fish do have some capacity to compensate for changes in environmental temperature (see Hazel, 1993). However, in many natural situations the predicted change in the temperature will not be the only environmental stressor with which the fish must cope because many environments are no longer pristine. The metabolic cost of living in polluted environments has yet to be clearly established, though it is likely to be substantial (Calow, 1991). Therefore, the anticipated alterations in fish physiology associated with global warming have the potential to increase the burden of stress already experienced by fish living in marginalized environments.

The study of the relationship between environmental temperature and pollutant toxicity in fish is not a new endeavour, but the literature describing temperature effects on toxicity affords little in terms of reliable generalization.