Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 419485
Title Collapse and reorganization of a food web of Mwanza Gulf, Lake Victoria
Author(s) Downing, A.S.; Nes, E.H. van; Janse, J.; Witte, F.; Cornelissen, I.J.M.; Scheffer, M.; Mooij, W.M.
Source Ecological Applications 22 (2012)1. - ISSN 1051-0761 - p. 229 - 239.
DOI http://dx.doi.org/10.1890/11-0941.1
Department(s) Aquatic Ecology and Water Quality Management
WUR GTB Teelt & Bedrijfssystemen
Aquaculture and Fisheries
IMARES
WIAS
Publication type Refereed Article in a scientific journal
Publication year 2012
Keyword(s) african great-lakes - nile perch - morphological-changes - lates-niloticus - east-africa - fish - biodiversity - challenges - fisheries - predator
Abstract Lake Victoria (in East Africa) is the world's second largest fresh-water system. Over the past century the ecosystem has undergone drastic changes. Some 30 years after the introduction of Nile perch and tilapia in the 1950s, the highly diverse community of native haplochromines collapsed, leaving a system dominated by only four species: the native cyprinid dagaa and shrimp Caridina nilotica, as well as the introduced Nile perch and Nile tilapia. More recently, an unexpected resurgence of haplochromines has been reported. To better grasp these changes in terms of ecosystem functioning and of changes in growth of trophic groups, we created mass-balances of the food web near Mwanza (Tanzania) before, during and after the Nile perch boom (1977, 1987 and 2005), using the application ECOPATH. We connected these mass-balances with a dynamic model assuming linear trends in net growth rates of the trophic groups. Our analysis suggests that the Nile perch boom initially altered the biomass distribution over trophic levels. Also, results indicate that not only fishing but also changes at the detritivores' trophic level might have played an important role in driving changes in the system. Both the mass-balances and the dynamic model connecting them reveal that after a major distortion during the Nile perch boom, the biomass distribution over the main trophic levels had largely recovered to its original state by 2005. However, no such return appeared in terms of community structure. Biodiversity in the new state is dramatically lower, consisting of introduced species and a few native surviving species. We conclude that at an aggregate level Lake Victoria's ecosystem has proved to be resilient in the sense that its overall trophic structure has apparently recovered after a major perturbation. By contrast, its intricate functional structure and associated biodiversity have proven to be fragile and seem unlikely to recover
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