Movement, reproduction, habitat use, trophic status, and the fishery of Labeo victorianus in Lake Victoria (Tanzania)

A study on the fishery, reproductive cycle, trophic status, movement patterns, and habitat use by Labeo victorianus was carried out in the Speke and Mwanza gulfs, Lake Victoria, between October 1999 and September 2001. Labeo victorianus locally known as ningu, is an endemic fish species of the Lake Victoria basin, now considered a threatened species.; The fishery of ningu is carried out near river mouths where they are intercepted during the rainy season on their annual spawning migration. Although fishermen still catch adult ningu, their decline in fishermen's catches since the early 1950s can be attributed to recruitment overfishing, environmental degradation, reduced food resources, blocked access to spawning grounds and little enforcement of fisheries regulations.; Currently, monitoring of ningu fishery and other nearshore fish resources is poor because of few fisheries personnel, lack of working facilities, few beach fish recording stations and much emphasis being directed towards the Nile perch fishery, which brings the country much-needed foreign exchange.; Ningu is very fecund, producing up to 270,000 eggs. In the Speke Gulf, ningu mature earlier than those living in the northern part of Lake Victoria and have two spawning peaks coinciding with the two rainy seasons. Most ningu spawn during the long rains (February to May). The presence of spent individuals in the lake suggests that ningu now heavily blocked by nets and reed fences from migrating into spawning ground upstream and flood plains, could be spawning in the lake.; Currently is absent in offshore waters, spends most of the time in rocky habitats and under vegetation cover, and performs restricted movements, perhaps because of the presence of another predator, the Nile perch, that was the introduced into the Lake Victoria since the late 1950s and 1960s. Other populations of ningu have been found in satellite lakes in the basin. The recent signs of recovery of Ningu and other threatened fish species of Lake Victoria has coincided with the decline in catches of the Nile perch since the mid 1990s.; Stable isotope analysis reveals that there are several populations of ningu, and that ningu is a primary consumer, feeding mostly on benthic algae. However, the benthic algae production is now threatened by eutrophication, and some of the satellite lakes are being heavily encroached. The recovery of Ningu and other nearshore fish communities of Lake Victoria calls for proper enforcement of fisheries regulations and curbing all human-related activities that contribute to environmental degradation of nearshore habitats and the satellite lakes, where ningu and other threatened fish species now take refuge. The recently established village based Beach Management Units (BMUs), as part of co-management of fisheries resources of Lake Victoria, will be more effective only if they continually get logistical support and scientific advice from the Tanzania Fisheries Division.