Premium
Studies on the effects of abnormally high water levels on the ecology of fish in certain shallow regions of Lake Victoria
Author(s) -
Welcomme R. L.
Publication year - 1970
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1970.tb03090.x
Subject(s) - biology , ecology , habitat , vegetation (pathology) , fish <actinopterygii> , waves and shallow water , shore , population , fish pond , fishery , oceanography , medicine , demography , pathology , sociology , geology
Between 1961 and 1964 the water levels of Lake Victoria increased abruptly. This increase produced changes around the shoreline of the lake, creating new habitats in the form of lagoons. Such lagoons were cut off from the main lake by differing widths of floating vegetation. Chemically and physically these new regions resembled small tropical fish ponds, with a nocturnal reduction in both dissolved oxygen and temperature. The lagoons were occupied shortly after their appearance by characteristic groups of fishes, which depended for their species composition on the degree of isolation of the different bodies of water from the main lake. It was generally found that the more isolated the lagoon, the more impoverished it was in numbers of species. The most successful colonizers of these waters were Tilapia leucosticta and Haplochromis nubilus , which were present in all lagoons. Populations of these two species showed a tendency to stunt, which was more marked in the more isolated populations. This, together with the population changes associated with isolation, suggests that the mat of floating vegetation, by reason of the de‐oxygenated conditions that exist under it, acts as a form of biological filter. Thus fish from the lake can only penetrate to the nearer lagoons, the populations in the more isolated waters remaining more or less segregated.