The tilapiine fish stock of Lake Victoria before and after the Nile perch upsurge

Publication Type:Journal Article
Year of Publication:2002
Authors:F. Witte, Goudswaard, P. C. , Katunzi, E. F.
Journal:Journal of Fish Biology
Volume:60
Pagination:838-856
Date Published:Apr
ISBN Number:0022-11121095-8649
Accession Number:5393087
Keywords:01523 Conservation, wildlife management and recreation, Article Geographic Terms: Africa, Victoria L., Article Subject Terms: Competition, Article Taxonomic, Depleted stocks, Fishery, Fishery resources, Freshwater, Introduced species, Lake Fisheries, Man-induced effects, MANAGEMENT, Nile perch, OREOCHROMIS, Oreochromis esculentus, Overfishing, Q1 01483 Species interactions: general, Q3 01582 Fish culture, Q5, Stock assessment, Terms: Lates niloticus, variabilis
Abstract:

Since the beginning of fisheries in Lake Victoria, two native tilapiine species, Oreochromis esculentus and Oreochromis variabilis, were the main target of the local fishermen. A continuous increase in fishing pressure led initially to a declining catch per unit of effort, and a smaller average fish size; eventually, there was a reduced landing of tilapiines. To boost the fisheries, three alien tilapiine species and the Nile perch Lates niloticus were introduced. Thirty years after its introduction, Oreochromis niloticus appeared to be the most successful tilapiine species. It replaced the indigenous tilapiines almost completely before the Nile perch came to dominate the ecosystem of Lake Victoria. Reduced fishing pressure on the tilapiines in the 1980s, due to the shift of the local fishery towards the Nile perch, resulted in an increase in the stock of O. niloticus and an increase in average fish size. Subsequently, the total mass of O. niloticus landed increased. The stocks of the indigenous tilapiines did not recover but declined to extremely low levels, or vanished from the main lake. Currently, these species still occur in satellite lakes of Lake Victoria, from which O. niloticus is absent. Nile perch feed on O. niloticus; however, the limited overlap in distribution between piscivorous Nile perch and O. niloticus of consumable sizes is probably an important factor in explaining the coexistence of the two species. The main cause of the disappearance of the native tilapiine species is presumed to be competitive dominance by O. niloticus. Copyright 2002 The Fisheries Society of the British Isles. Published by Elsevier Science Ltd. All rights reserved.

Alternate Journal:J. Fish Biol.

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