Fish exploitation and changes in the fish community of Lake George, Uganda

Unlike Lake Victoria, the fisheries of Lake George have undergone gradual changes in the size and proportion of the major commercial fish species, the Nile tilapia (Oreochromis niloticus: cichlidae) in the last 40 years (1950-1989). The size decreased from an average weight of 900g in 1950 to 430g in 1989 while percentage contribution in commercial catches during the same period declined from 92% to 36%. The over all annual commercial catches though showed a steady increase from the period 1950 when the fishery was opened to intensive and controlled exploitation, consistently high catches were observed in the 1960s and 1970s followed by a general decline in the early 1980s to amore or less stable fishery in the late 1980s. These changes are attributed to increased fishing pressure especially on the nil tilapia and to increased use of smaller gill net mesh sizes lower than the recommended 127mm mesh. The changes in gill net mesh have brought O. leucostictus, acichlid, into commercial catches confirming that the 88.9mm mesh size nets are used by the commercial fishermen to harvest smaller fish species. The commercial catches are presently dominated by the piscivorous fishes,(over 60%) whose contribution was less than 10% during initial exploitation of the virgin fishery in 1950.The piscivorous fish are mainly caught using hooks and lines. The entire fishery is believed to be exploited close to the maximum. The above trends serve to show the impact of exploitation on fish species diversity. Quantitive and qualitative changes of the major fish species on lake George are due to exploitation pressure unlike Lake Victoria where it is a combination of both exploitations and impact of fish introductions. There has been no fish introduction in Lake George.

Fishery resources and some economic aspects of four fishing villages on Lakes George and Edward in the Queen Elizabeth National Park, Uganda

The fishery resources of Lake George and Ugandan waters of Lake Edward are described. The main fish species currently observed in the commercial catches were determined and the reasons of changes in species composition of the catches. that occurred in the recent years, are explained. The fishing activity and some economic and nutritional aspects of four fishing villages, selected among the ten present within the Queen Elizabeth National Park boundaries, are analyzed, In the end some suggestions are given for management of the fishery resources of these lakes.

Plankton identified in stomach contents of Oreochromis niloticus (Pisces, Cichlidae) and the water system of Lakes Edward, George, and Kazinga channel - Uganda

The samples were collected from Lake Edward at Rwenshama, Kisenyi and Katwe, and from Lake George at Mahyoro, Kashaka and Kasenyi and in Kazinga Channel at Katunguru. The organisms identified from the water samples obtained irrespective of station or depth were mainly the phytoplankton (diatoms, blue-green algae and green algae). Of the phytoplankton, blue green-algae were the most abundant both in quantity and number of species especially in L. George. In order of importance were Microcystis spp, Planktolyngbya spp and Anabaenopsis spp were the dominant blue greens. Diatoms and green algae were present but less abundant. The estimated proportions of different types of phytoplankton identified in O. niloticus stomach contents indicate that bluegreen algae were the most abundant followed by the diatoms and green algae.

Movements of haplochromines (Pisces: Cichlidae) in Lake George, Uganda

In Lake George, the abundance of haplochromines in inshore regions during the day and at night differs significantly. Futhermore, while by day there are more haplochromines in the lower than the upper layers, at night these fishes appear to be uniformly distributed throught the water column. Regions of the lake near river mouths had fewer haplochromines during the wet than the dry season, while the reverse was true of regions distant form the river mouths. Possible causes of these movements are discussed.