AbstractFour mountain lakes were studied. Two are eutrophic, one is mesotrophic and one is oligotrophic. The first three have a well‐developed phyto‐ and zooplankton, with a relatively high diversity index. There are differences between the faunas that may be ascribed to differences in surface, depth, altitude and also to biological phenomena such as interspecies competition. The Ifni Lake is a genuine high‐mountain lake, subject to severe environmental conditions. It has a very simple food chain: there is only one species of algae, an unicellular blue‐green, one copepod species, one rotifer and one fish. In general some features of a definite interest for fundamental limnology were found: the presence of a pelagic Rhabdocoelid in Dayat Ifrah, some particularities in the vertical distribution of a number of plankton species, the existence of a layer of relatively warm water near the bottom of Lake Ifni. The latter is explained by a strong bottom current which flows through the lake between its phreatic in‐ and outlets.Finally, stress is laid on the under‐exploitment of Moroccon inland waters with respect to a freshwater fishery.Yet, perspectives are good and some suggestions ar