Behavioural responses of a south‐east Australian floodplain fish community to gradual hypoxia

Abstract

1. Hypoxic conditions occur frequently during hot, dry summers in the small lentic waterbodies (billabongs) that occur on the floodplains of the Murray-Darling River system of Australia. Behavioural responses to progressive hypoxia were examined for the native and introduced floodplain fish of the Ovens River, an unregulated tributary of the Murray River in south-east Australia. 2. Given the high frequency of hypoxic episodes in billabongs on the Ovens River floodplain, it was hypothesised that all species would exhibit behaviours that would confer a degree of hypoxia-tolerance. Specifically, it was hypothesised that as hypoxia progressed, gill ventilation rates (GVRs) would increase and aquatic surface respiration (ASR) would become increasingly frequent. Fish were subjected to rapid, progressive hypoxia from normoxia to anoxia in open tanks. 3. All tested species exhibited behaviours consistent with their use of potentially hypoxic habitats. As hypoxia progressed, GVRs increased and all species, with the exception of oriental weatherloach, began to switch increasingly to ASR with 90% of individuals using ASR at various oxygen concentrations below 1.0 mg O 2 L )1 . Australian smelt, redfin perch and flat-headed galaxias were the first three species to rise to ASR, with 10% of individuals using ASR by 2.55, 2.29 and 2.21 mg O 2 L )1 respectively. Goldfish and common carp were the last two species to rise to ASR, with 10% of individuals using ASR by 0.84 and 0.75 mg O 2 L )1 respectively. In contrast to other species, oriental weatherloach largely ceased gill ventilation and used air-gulping as their primary means of respiration during severe hypoxia and anoxia. 4. Australian smelt, redfin perch and flat-headed galaxias were unable to maintain ASR under severe hypoxia, and began exhibiting erratic movements, termed terminal avoidance behaviour, and loss of equilibrium. All other species continued to use ASR through severe hypoxia and into anoxia. Following a rise to ASR, GVRs either remained steady or decreased slightly indicating partial or significant relief from hypoxic stress for these hypoxia-tolerant species. 5. Behavioural responses to progressive hypoxia amongst the fish species of the Ovens River floodplain indicate a generally high level of tolerance to periodic hypoxia. However, species-specific variation in hypoxia-tolerance may have implications for community structure of billabong fish communities following hypoxic events.

Climate change and its implications for Australia's freshwater fish

“…Climatic warming may compound stressors associated with stream drying through raised water temperatures and associated reduced dissolved oxygen, resulting in the physiological tolerances of at least some species being surpassed (McNeil and Closs 2007;McMaster and Bond 2008). Successful spawning and recruitment under such conditions is highly unlikely, even if a pool ultimately retains enough water to permit survival of the resident fish.…”

Developmental Plasticity, Genetic Differentiation, and Hypoxia-induced Trade-offs in an African Cichlid Fish

“…There are indeed indications of an association between a small brain size and a low predation pressure in fishes [71,72], and a growing body of evidence that hypoxic habitats may serve as a refuge for small fishes from large aquatic predators [73][74][75][76]. For example, in the Lake Victoria basin, swamps serve as both structural and low-oxygen refugia for hypoxia-tolerant fishes from the introduced aquatic predator, the Nile perch (Lates niloticus), a species intolerant of hypoxia [32,43,44,76,77].…”

Aquatic surface respiration and swimming behaviour in adult and developing zebrafish exposed to hypoxia

“…Moreover, Chapman and McKenzie (2009) summarized the ASR thresholds of 63 species and suggested a negative correlation with hypoxia tolerance. McNeil and Closs (2007) determined ASR thresholds of ∼14 mmHg for goldfish (Carassius auratus) and common carp (Cyprinus carpio) -two cyprinid species related to zebrafish. Both goldfish and carp exhibit high levels of tolerance to hypoxia (Stecyk and Farrell, 2002;Lutz and Nilsson, 2004;Bickler and Buck, 2007), and this may account for the relatively lower ASR thresholds observed in these species compared with zebrafish.…”

“…Performance of ASR under conditions of hypoxia effectively maintains or decreases gill ventilation rate (McNeil and Closs, 2007), increases arterial blood O 2 content (Burggren, 1982), and increases survival (Kramer and Mehegan, 1981;Kramer and McClure, 1982;Perry et al, 2009). The behaviour is believed to have evolved as an adaptation for surviving environmental hypoxia, and is thought to be an evolutionary precursor to aerial respiration in vertebrates (Kramer and McClure, 1982;Gee and Gee, 1995;Shingles et al, 2005).…”