Observations on the biology of the cichlid fish Tilapia variabilis Boulenger in the northern waters of Lake Victoria (East Africa)

Two species of the genus Tilapia occur naturally in Lake Victoria. Of these the most abundant and therefore the most important economically, is T. esculenta GRAHAM, and it is, for these reasons that more information is available concerning this species than the related T. variabilis BOULENGER. Thus LOWE (MCCONNELL) (1956) who was the first to make a serious study of the Tilapia species of the lake since the pioneering survey of GRAHAM (1929), dealt in considerable detail with T. esculenta but treated T. variabilis much less fully. Later studies (GARROD 1959) have also been concentrated on T. esculenta. Because of a relaxation in certain areas' of net-size regulations (discussed below) T. variabilis has recently assumed greater economic importance than was the case when restrictions were imposed, and this had called for further study of its general biology and the possible effects of commercial exploitation. The following account represents a preliminary contribution to the information required, and deals almost entirely with observations made in the northern waters of the lake and particularly in the vicinity of Jinja (Uganda)