The toxicity of four insecticides and a herbicide under tropical conditions

The toxicities of four insecticides and a herbicide to Tilapia macrochir were tested in the laboratory. The 24 hour LC50's were estimated as follows: Endrin 20% ,0.008 ppm; Lindane 5% granules, 4.6 ppmm; Synexa 50 (HCH) 50%), 5.6 ppm; Synex 25 (HCH 25%), 14.8 ppm; TOK herbicide (Nitrofen), 100% survival for 24 hours at 100 ppm. These estimates agree with results obtained by other workers elsewhere in the world. The laboratory determination of toxicity is important in estimating the direct effects of poisonous substances on fish, but other indirect effects may result from their use. These should be investigated in the field

A description of certain indigenous fishing methods from Southern Dahomey

A survey of certain Dahomean fishing methods showed them to be specifically adapted to the exploitation of floodplains and shallow water lagoons. Several types of fish-parks are described, ranging from small installations thaI funclion as refuge traps, to larger constructions that act as a form of fish culture. Ponds are also dug in the floodplains in order to conserve fish isolated during the dry season. These methods all give high yields and are worthy of consideration for use elsewhere on the African continent

Studies on enclosed lagoons in the Jinja area

A number of lagoons have been studied in the Jinja region and a visit has been made to waters in Mwanza. Observations from aircraft have shown lagoons to be widely distributed at least throughout the northern and eastern shores of the lake, and because sand and rocky shores have remained relatively unaltered by the rising water level it seems possible that the flooding of swampy shores to form lagoons has been the principal environmental change due to rising water level

The possible role of marginal lagoons and beaches in the improvement of the quantity of tilapia stocks in lake Victoria

Since 1962 the level of the Lake Victoria has increased by one metre over the previous highest record (I, 2). The effects of this rise within the lake have been most obvious on the shallow marginal waters where the inundation of the previous lake shore has produced a series of beaches or lagoons. In such places open water has replaced what were either areas choked with aquatic vegetation or were dry land. In time some of these places may become overgrown once more and in fact in the three years of their existence they have already become partly weed-covered in some instances. This period, therefore, is a transitory phase in the lake's history but one that points a way towards some artificial improvements of the quantity of Tilapia stocks in Lake Victori

A note on the breeding biology of Aplocheilichthys pumilus (Boulenger)

Aplocheilichthys pumilus is a small cyprinodont commonly found in shallow swampy areas around Lake Victoria. In the lagoons the species was especially common in the shallow grass swamps and in the slightly deeper water amongst stands of Typha and Cyperus flanking the main lagoon