McGill University
M.Sc. candidate
Supervisor: Anthony Ricciardi
Lauren Chapman
Start: 2010-09-01
End: 2012-12-15
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Project

Predicting peak refugia for mitigating impacts of invasive predatory fishes
Areas outside the distributional boundaries of an introduced predator may be exploited by native prey as refugia from predation. A classic example is the Lake Victoria basin of East Africa where hypoxic (low oxygen) wetlands serve as refugia for some native fishes from introduced Nile perch (Lates niloticus). In my thesis I quantified patterns of wetland refugia use in Lake Nabugabo, Uganda, a satellite of Lake Victoria, to achieve two primary goals: (i) identify peak refugia, where the greatest abundance and richness of native fishes persist, and (ii) directly link hypoxia tolerance of native and introduced fishes to their wetland distributions. A field survey indicated that peak refugia occur at the lake-wetland edge, and that strong edge-related gradients are shaping the fish assemblage structure of wetland habitats. Species richness and diversity were positively related to dissolved oxygen availability, and negatively related to temperature, pH, and vegetation density. Experiments quantifying the behavioural response of fish to progressive hypoxia revealed the highest tolerance to hypoxia in the swamp specialist Pseudocrenilabrus multicolor, when compared with three taxa found at the lake-wetland edge: juvenile endemic haplochromine cichlids, Nile tilapia (Oreochromis niloticus), and Nile perch. Tolerance to hypoxia decreased with increased body size in Nile perch, which may limit penetration of the wetland edge in larger bodied Nile perch. By establishing a link between physico-chemical gradients and peak refugia, our study points to the importance of invader-edge dynamics in determining the outcome of interactions between introduced predators and resident prey.

Keywords

wetlands, conservation biology, aquatic surface respiration, introduced predator, Nile perch, native prey

Publications

1- Patch depletion behavior differs between sympatric folivorous primates
Tombak, Kaia J., Andrea J. Reid, Colin A. Chapman, Jessica M. Rothman, Caley A. Johnson, Rafael Reyna-Hurtado
2011 Primates

2- Wetland edges as peak refugia from an introduced piscivore
Reid, Andrea J., Lauren J. Chapman, Anthony Ricciardi
2013 Aquatic Conservation: Marine and Freshwater Ecosystems

3- Implications of hypoxia tolerance for wetland refugia use in Lake Nabugabo, Uganda
Reid, Andrea J., Maxwell J. Farrell, Max N. Luke, Lauren J. Chapman
2013 Ecology of Freshwater Fish