220 research outputs found
Nouvelle contribution à la connaissance des insectes et arachnides en culture cotonnière au Paraguay
The past history and present trends in the fisheries of Lake Chad
Lake Chad is a very large, shallow eutrophic lake shared by Chad, Nigeria, Niger and Cameroun. It supplies approximately 13% of Nigeria's inland fish. It however lies in an unstable ecological environment characterised by intermittent period of rainfall and drought. This creates a very large draw down area. Consequently, the fisheries are affected by the oscillation in the size of lake due to the drought. Other factors affecting the volume of water are the numerous dams on the inflow rivers. The fishery is also subjected to intense overfishing and may be affected by pollution and other land use practices. The paper discusses changes that took place over the years as a result of the factors of drought, effect of dams on the inflow rivers. The fishery is also subjected to intense overfishing and may be affected by pollution and other land use practices. The paper discusses changes that took place over the years as a result of the factors of drought, effects of dams and overexploitation. Previous records of fish production, species composition and distribution, the status of the fish stocks, their sizes are compared with more recent data. The status of the fishery before and after the contraction of the lake is discussed. Suggestion for a national exploitation of the lake based on habitat improvement, increasing the volume of the water in the lake through controlled use of the influent rivers as well as reduction in overfishing are mad
Results of the Swedish expedition to Spitzbergen in 1924 : 1: Quaternary geology of the region around the Kjellström valley
Verschillen in bedrijfsgrootte, opbrengsten en kosten op glasgroenteteeltbedrijven in het Zuidhollands glasdistrict in 1970 en 1971
Control optimization, stabilization and computer algorithms for space applications
Research of control optimization, stochastic stability, and air traffic control problem
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