Tropical fishes: patterns and propensities

When key biological statistics (growth parameters, mortality rates, etc.) of a large number of fish species are plotted against other variables (notably maximum size and mean habitat temperature), clear trends or patterns tend to emerge. These patterns are usually not perceived as requiring explanation, as reflected in the rarity of pertinent hypotheses in the literature, relative to the ubiquity of the patterns. A theory is presented which has the potential to explain the propensities behind many of these observed patterns. This theory, based on the author’s earlier work, is built around the notion that gill area severely constrains the respiration and hence the growth of fishes (and other water-breathing animals). The patterns generated by growth-related processes, such as mortality, reproduction or food consumption can then also be explained. In this theory, tropical fishes are not different from other fishes, once account is taken of the fact that tropical fish are, not metaphorically but literally, in hot water.