Towards aquatic assessment of Lake Tumba, DR Congo

• The livelihoods of most communities around the 765 km2 Lake Tumba are dependent on fish from the lake. Artisanal fishing and other pressures on the aquatic ecosystem are likely to have increased over the last half century. However, few monitoring programs follow these pressures and their influence on the aquatic ecosystem. The main objective of this thesis was to contribute to an improved understanding of the fish population in Lake Tumba to support the development of strategies for improving the fishery as well as assessing changes in the fish population over time. The fish population was characterized through regular monitoring from 2005 to 2010, with an emphasis on the methodology. This monitoring was complemented by a survey of breeding sites for Tilapia congica within Lake Tumba, and an investigation of the relationship between land use and fish catch around islands in the Congo River. The Catch Per Unit Effort (CPUE) and Number Per Unit Effort (NPUE) differed between sites and seasons, and with water depth and distance from shore. The greatest fish weight was caught between 3.0 and 4.5 m depth, which might explain the larger CPUE during the rainy season, as the water was deeper at the fixed fishing sites. The local population has larger catches during the dry season. Fewer species (n=42) were found in this study than in the 1959 survey (n=65 species). However, due to the difference in fishing methods, location and effort, it was difficult to draw strong conclusions about how much the fish population had actually changed. The study of T. congica identified four major breeding sites, one of which was about 10 km long, and most nests were found in conjunction with Hippo grass (Vossia cuspidata) and Water lily (Nymphaea stellata). The study of fish near the Congo Islands caught 29 fish species. Cultivation area was related to erosion and the number of species nested offshore from each island. Due to the growing demand for fish, and the likelihood of more dramatic environmental change in the future, there is a need for developing management and governance strategies, as well as for scientific monitoring of the ecosystem on which to base management. The methodological aspects of this study and the actual findings about current fish status can be of value in this development.

Ämnesord

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Fisk- och akvakulturforskning (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Fish and Aquacultural Science (hsv//eng)

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