Fish Faunal Resurgence in Lake Nabugabo, East Africa

Abstract: In Lake Nabugabo, Uganda, a small satellite of the equatorial Lake Victoria, approximately 50% of the indigenous fish species disappeared from the open waters subsequent to establishment of the introduced predatory Nile perch (   Lates niloticus ). However, several of these species persisted in wetland refugia. Over the past decade, Nile perch in Lake Nabugabo have been intensively fished. Herein we report a resurgence of some indigenous species in open waters. In a multiyear study, we used annual transects in inshore and offshore waters of exposed ( no wetland ) and wetland habitats to document the pattern of resurgence. In 1995, haplochromine cichlids were largely confined to inshore areas, particularly wetland ecotones, and were rare in Nile perch stomachs, as were most other indigenous species. By 2000 haplochromine cichlids were abundant in inshore and offshore areas of both exposed and wetland transects. Several indigenous noncichlids also reappeared in the main lake, including three of the four original mormyrid species. Between 1995 and 1999, there was a dramatic increase in the proportion of haplochromines in the diet of Nile perch. When haplochromines were rare ( 1995 ), Nile perch switched from an invertebrate‐dominated diet to piscivory at a large size ( 30 cm total length ). In 2000, however, Nile perch were strongly piscivorous by 5–10 cm total length. The pattern of faunal loss and recovery in Lake Nabugabo demonstrates the importance of refugia in providing the seeds of resurgence and provides a model with which to understand some changes in Lake Victoria.

[1]  T. Goldschmidt,et al.  Recovery of cichlid species in Lake Victoria: an examination of factors leading to differential extinction , 2000, Reviews in Fish Biology and Fisheries.

[2]  L. Chapman,et al.  Interactions Between Nile Perch, Lates niloticus, and Other Fishes in Lake Nabugabo, Uganda , 1999, Environmental Biology of Fishes.

[3]  Kees Goudswaard Frans Witte.  The catfish fauna of Lake Victoria after the Nile perch upsurge , 1997, Environmental Biology of Fishes.

[4]  T. Goldschmidt,et al.  The destruction of an endemic species flock: quantitative data on the decline of the haplochromine cichlids of Lake Victoria , 1992, Environmental Biology of Fishes.

[5]  W. Ligtvoet,et al.  Changes in the diet of Nile perch, Lates niloticus (L), in the Mwanza Gulf, Lake Victoria , 1992, Hydrobiologia.

[6]  R. Ogutu-ohwayo,et al.  The decline of the native fishes of lakes Victoria and Kyoga (East Africa) and the impact of introduced species, especially the Nile perch, Lates niloticus, and the Nile tilapia, Oreochromis niloticus , 1990, Environmental Biology of Fishes.

[7]  R. Welcomme.  River fisheries in Africa: their past, present, and future. , 2003 .

[8]  L. Chapman,et al.  Decline of the African lungfish (Protopterus aethiopicus) in Lake Victoria (East Africa). , 2002 .

[9]  L. Kaufman,et al.  Nile Perch Population Dynamics in Lake Victoria: Implications for Management and Conservation , 2002 .

[10]  F. Witte,et al.  Dwelling at the oxycline: does increased stratification provide a predation refugium for the Lake Victoria sardine Rastrineobola argentea? , 2001 .

[11]  L. Chapman,et al.  Hypoxia tolerance of introduced Nile perch: implications for survival of indigenous fishes in the Lake Victoria basin , 2000 .

[12]  F. Witte,et al.  Rapid Morphological Changes Following Niche Shift in the Zooplanktivorous Cyprinid Rastrineobola Argentea From Lake Victoria , 2000 .

[13]  L. Chapman,et al.  Hypoxic wetland tributaries as faunal refugia from an introduced predator , 1999 .

[14]  O. Seehausen.  A reconsideration of the ecological composition of the cichlid species flock in Lake Victoria before and after the Nile perch boom , 1999 .

[15]  C. Chapman,et al.  Hypoxia Tolerance of the Mormyrid Petrocephalus catostoma: Implications for Persistence in Swamp Refugia , 1998 .

[16]  D. Schindler,et al.  Ecological Consequences of Alternative Gill Net Fisheries for Nile Perch in Lake Victoria , 1998 .

[17]  O. Seehausen,et al.  Cichlid Fish Diversity Threatened by Eutrophication That Curbs Sexual Selection , 1997 .

[18]  O. Seehausen,et al.  Patterns of the Remnant Cichlid Fauna in Southern Lake Victoria , 1997 .

[19]  Daniel E. Schindler,et al.  THE NILE PERCH IN LAKE VICTORIA: INTERACTIONS BETWEEN PREDATION AND FISHERIES , 1997 .

[20]  L. Kaufman,et al.  Evolution in fast forward: haplochromine fishes of the Lake Victoria region , 1997 .

[21]  C. Chapman,et al.  Wetland ecotones as refugia for endangered fishes , 1996 .

[22]  L. Kaufman,et al.  Refugia for Endangered Fishes from an Introduced Predator in Lake Nabugabo, Uganda , 1996 .

[23]  O. Seehausen.  Lake Victoria rock cichlids : taxonomy, ecology, and distribution , 1996 .

[24]  L. Kaufman,et al.  Deoxygenation of the deep water of Lake Victoria, East Africa , 1994 .

[25]  R. Ogutu-ohwayo.  The Effects of Predation by Nile Perch, Lates niloticus L., on the Fish of Lake Nabugabo, with Suggestions for Conservation of Endangered Endemic Cichlids , 1993 .

[26]  R. Hecky,et al.  The eutrophication of Lake Victoria , 1993 .

[27]  Les Kaufman,et al.  Evolutionary and Conservation Biology of Cichlid Fishes as Revealed by Faunal Remnants in Northern Lake Victoria , 1993 .

[28]  E. Lippitsch.  A phyletic study on lacustrine haplochromine fishes (Perciformes, Cichlidae) of East Africa, based on scale and squamation characters , 1993 .

[29]  Les Kaufman,et al.  Catastrophic Change in Species-Rich Freshwater EcosystemsThe lessons of Lake Victoria , 1992 .

[30]  L. Brown,et al.  Changes in Habitat and Microhabitat Partitioning within an Assemblage of Stream Fishes in Response to Predation by Sacramento Squawfish (Ptychocheilus grandis) , 1991 .

[31]  W. Ligtvoet,et al.  Species Extinction and Concomitant Ecological Changes in Lake Victoria , 1991 .

[32]  J. Kitchell,et al.  Direct and Indirect Effects of Predation on a Fish Community: A Whole-Lake Experiment , 1990 .

[33]  P. H. G. Frs.  The Nile perch in Lake Victoria , 1986 .

[34]  A. J. Stewart,et al.  Grazing Minnows, Piscivorous Bass, and Stream Algae: Dynamics of a Strong Interaction , 1985 .

[35]  R. Dorit,et al.  Destruction of fisheries in Africa's lakes , 1985, Nature.

[36]  P. Greenwood.  Towards a phyletic classification of the `genus' Haplochromis (Pisces, Cichlidae) and related taxa. Part II; the species from lakes Victoria, Nabugabo, Edward, George and Kivu. , 1980 .

[37]  W. Dolling.  A revision of the African pod bugs of the tribe Clavigrallini lHemipterac Coreidaer with a checklist of the world species , 1979 .

[38]  P. Greenwood.  The Cichlid fishes of Lake Nabugabo, Uganda , 1965 .

[39]  G. Fryer.  Concering the Proposed Introducton of Nile Perch Into Lake Victoria , 1960 .

[40]  E. Worthington.  A report on the fisheries of Uganda investigated by the Cambridge Expedition to the East African Lakes, 1930-31 Zoological Laboratory, Cambridge, June, 1932 , 1933 .