Implications of hypoxia tolerance for wetland refugia use in Lake Nabugabo, Uganda

Abstract

Aquatic hypoxia can affect predator‐prey interactions by altering the success rate of the predator and/or the vulnerability of prey. For example, in the Lake Victoria basin of East Africa, native prey exploit hypoxic wetlands as refugia from predation by introduced Nile perch (Lates niloticus). Here, it is predicted that species exploitation of wetlands depends on their hypoxia tolerance relative to the heterogeneity of wetland hypoxia. In this study, we compared the hypoxia tolerance of four fish taxa that differ in their use of hypoxic wetlands in Lake Nabugabo, Uganda: the cichlid Pseudocrenilabrus multicolor victoriae that inhabits the dense swamp interior; and three taxa that inhabit wetland ecotones including Nile tilapia (Oreochromis niloticus), L. niloticus and juvenile endemic haplochromine cichlids. We characterised hypoxia tolerance by exposing fish to progressive hypoxia and quantifying variation in aquatic surface respiration (ASR). The effect of body size on tolerance was explored in L. niloticus by quantifying ASR behaviour across a range of size classes. ASR behaviour was also compared between O. niloticus groups from wetland versus open‐water habitats to detect habitat‐associated intraspecific variation. The most tolerant taxon was the swamp specialist P. multicolor, indicated by its low ASR thresholds and small percentage of fish using ASR during the final sample interval. The other three taxa did not differ in ASR behaviour, and no differences were detected between O. niloticus groups. Body size effects were present for L. niloticus suggesting a lower tolerance to hypoxia in larger‐bodied individuals, thus limiting their ability to penetrate wetlands.

Take time to look at the fish: Behavioral response to acute thermal challenge in two Amazonian cichlids

“…Jung et al (2020) did not find a difference between CT max of Apistogramma borelli in normoxia and hyperoxia; however, future experiments that measure CT max across a range of DO in M. insignis and A. agassizii will be important in determining the link between environmental hypoxia and thermal tolerance in these species. Although ASR has been reported in many tropical fishes (Chapman et al, 2002; Chapman & Mckenzie, 2009; Kramer & McClure, 1982; Reid et al, 2013), this is the first report of ASR in A. agassizii and M. insignis and the second report of ASR during CT max trials under normoxic conditions. The greater use of ASR in M. insignis than in A. agassizii may reflect differences in their ecology.…”

Shrinking body sizes in response to warming: explanations for the temperature–size rule with special emphasis on the role of oxygen

“…Woods, in preparation). There is also evidence that larger individuals are more prone to oxygen limitation in some fish species (Burleson, Wilhelm, & Smatresk, 2001; Robb & Abrahams, 2003; Reid et al ., 2013), but it is difficult to generalize this to all fish, given the many different strategies for coping with hypoxia (Chapman & McKenzie, 2009). Indeed, fish may deal with hypoxic stress in a size‐dependent manner, with larger animals relying more on anaerobic metabolism (Goolish, 1989; Urbina & Glover, 2013; Lv et al ., 2018).…”

The role of floods and droughts on riverine ecosystems under a changing climate

“…For organisms that prefer shallow and low-velocity zones (e.g. invertebrates Opportunism Time and juvenile fish), or that are tolerant to high temperature and low oxygen, the amount of suitable habitat may initially increase (Reid, Farrell, Luke, & Chapman, 2013). As wetted area further declines, the densities of these organisms increase (Dewson et al, 2007;Matthews, Harvey, & Power, 1994;McIntosh, Benbow, & Burky, 2002).…”