Respiratory characters of three species of haplochromine cichlids: Implications for use of wetland refugia

Respiratory characters of three east African haplochromine cichlid species that differ in their use of hypoxic wetlands were examined to consider the potential of dissolved oxygen as one factor affecting habitat use. All thre e species had a large gill surface area, ranging from the 67th (Pseudocreni labrus multicolor victoriae) to 98th (Astatotilapia velifer) percentile of the known gill size range for freshwater fishes. Pseudocrenilabrus multicol or victoriae was the most tolerant to hypoxia exhibiting the lowest aquatic surface respiration (R-S) thresholds and lowest critical oxygen tension of the three species. Astatotilapia velifer had the highest ASR thresholds, g ill ventilation rates, and level of surface activity of the three species, indicating a relatively low tolerance to hypoxia. Prognathochromis venator was intermediate in its response to hypoxia. These findings are discussed i n light of survivorship and distribution patterns of these species followin g Nile perch introduction into Lake Nabugabo. (C) 2000 The Fisheries Societ y of the British Isles.