ABSTRACT
Fish experience great differences in conditions in the wide array of habitats they occupy. In the case of freshwater ‘shes, we have seen that they may occur in isolated single species populations such as desert environments (e.g., Devils Hole) or in mixed populations of hundreds of species, such as in the African great lakes. On the other hand, marine ‘shes are seldom completely isolated, but they do occur in locations, such as the epipelagic zone of the open ocean, which have low ‘sh species diversity per volume. They also occur in mixed aggregations of ‘shes in such species-rich systems as coral reefs. Factors affecting the distribution and abundance of these species obviously cannot be precisely the same.
