Habitat heterogeneity facilitates coexistence of native fishes with an introduced predator: the resilience of a fish community 5 decades after the introduction of Nile perch
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The introduction of the large piscivorous Nile perch Lates niloticus (L.) into Lake Nabugabo, Uganda, coincided with a collapse of the native fish community and the development of a fishing industry dominated by Nile perch. Some native fish have persisted in the face of Nile perch predation through use of hypoxic wetlands that may serve as both structural and physiological refugia because Nile perch is sensitive to hypoxic stress. In this study, we analyzed one year of monthly sampling using experimental gill nets to describe the Lake Nabugabo fish community 50 years after the introduction of the Nile perch. Using a multivariate approach, we found that water depth and dissolved oxygen concentration were the main descriptors shaping the fish community distribution in the lake, and that Nile perch and its major prey, haplochromine cichlids, have contrasting ecological requirements. Comparison with previous studies over a 15-year period revealed an overall decline in the catch per unit effort of Nile perch and a resurgence of haplochromine cichlids in certain habitats. We suggest that differences in the abiotic requirements of Nile perch and haplochromines combined with heavy fishing on Nile perch have contributed to the resurgence of the native fauna. This highlights the importance of environmental heterogeneity in mitigating the impact of introduced species on recipient communities; and, in the case of the Lake Victoria basin, underscores the critical need to conserve ecotonal wetlands for their essential role as ecological refugia.
KeywordsExotic species Lake Victoria Hypoxia Haplochromines Habitat refugia Community
We would like to thank Dr. P. Legendre for his advice on statistical analyses, and the Quebec Center for Biodiversity Science R Workshop series. We also thank Dr. D. Twinomugisha for managing field research in Uganda, and the team of field assistants (Mutebi, Sseguya, Kiberu) for data collection. Financial support for this study was provided by grants to EC from Natural Sciences and Engineering Research Council of Canada (NSERC, CGS), Fonds Québecois de la Recherche sur la Nature et les Technologies (FQRNT), Quebec Center for Biodiversity Science, and McGill University, and grants to LJC from NSERC (Discovery Grant) and CRC research funds.
Financial support for this study was provided by grants to EC from Natural Sciences and Engineering Research Council of Canada (NSERC, CGS), Fonds Québecois de la Recherche sur la Nature et les Technologies (FQRNT), Quebec Center for Biodiversity Science, and McGill University, and grants to LJC from NSERC (Discovery Grant) and CRC research funds.
Compliance with ethical standards
Conflict of interest
The authors declare no competing financial interests.
Human and animals rights
This research was conducted with the approval of McGill University’s Animal Care Committee and Uganda National Council for Science and Technology.
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