A discussion is presented on the topic of species introductions as a means of improving reservoir of lake productivities. Reference is made to the successful introduction of the sardine Limnothrissa miodon into Lake Kariba, pointing out that the success of an introduction in one water body does not automatically indicate that introductions elsewhere will be successful. An examination is made of alternative means of increasing fish production in reservoirs; the possibility of exploiting native riverine species which colonize reservoirs and migrate into rivers and streams to reproduce is suggested.