Mechanisms of Resilience and Vulnerability

Summary

Why do some fish species flourish while others decline? Answers to this question can be a basis for designing effective management measures the sustainability and resilience of fish biodiversity and the dependent ecosystem services.

Environmental change threatens sustainable development in sub-Saharan Africa, where majority of the population depend on natural resources for their livelihoods (FAO, 2010).  Uganda is rich in fish biodiversity (Turner et al. 2001) of economic and ecological importance. Fish biodiversity dependent fisheries in the country support: 2.5% of the national GDP; employment for 1.2 million people (MAAIF, 2012). However, the biodiversity is threatened by multiple stressors including land use and change (e.g. Hecky et al. 2017). The impacts of these threats are widespread and include fish species loss, for instance in Lake Victoria where >200 species of haplochromine cichlids and native commercially important species such as Oreochromis variabilis and O. esculentus have been lost (Barel et al. 1985; Witte et al., 1992; Goudswaard et al. 2002). The loss of species has been accompanied by loss of fishing opportunities, trapping fishing communities into poverty and its social manifestations of conflicts (Glazer et al. 2013), gender inequality (Medard et al. 2002) and disease (Opio et al. 2013). The challenge is how to sustain fish biodiversity, fisheries and dependent ecosystem services amidst the multiple stressors.

The fish biodiversity response to the environment change challenges is species or species group specific, with some fish species or groups declining or disappearing while others persist and maintain effective population sizes and beneficial fisheries.  In Lake Victoria, for example, some haplochromine cichlids once thought to be extinct are recovering (Witte et al. 2007). The Lates niloticus (Nile perch) has maintained steady biomass and catches despite deterioration of its life history and population traits (Njiru et al. 2007). The biomass of a native species, Rastrineobola argentea, is increasing (Taabu-Munyaho et al. 2016). Conversely, some species such as the native tilapias and catfishes have either disappeared from the lake or are currently overfished (Ogutu-Ohwayo, 1990; Goudswaard et al. 2002; Taabu-Munyaho et al. 2016).

These fish species or group specific responses to environment change challenges can be attributed to differences in life history and ecological traits that enable fish species to survive and recover from environmental change impacts__resilience; or make them susceptible to negative impact__vulnerability (McKinney, ‎1997). For instance, the decline and survival of some species of haplochromine cichlids in Lake Victoria, following the introduction of the Nile perch (a predator) was associated to their trophic guild, size, abundance and habitat preferences (Witte et al. 1992). Understanding which traits ensure resilience or increase vulnerability is important in predicting future changes in relation to the changing environment and could be harnessed to conserve or restore fish species, sustain or build fisheries.

Using biodiversity data including species presence (occurrence), life history and ecological traits, indicators of ecosystem health (physico-chemical, habitat, and biological), this project aims to enhance understanding of mechanisms of resilience and vulnerability of fish biodiversity in Uganda as a path way to better management measures to sustain fish biodiversity and ecosystem services.

References

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