Spatial and temporal variation in fish-assemblage structure in isolated waterholes during the 2001 dry season of an arid-zone floodplain river, Cooper Creek, Australia

Abstract

Spatial and temporal variation in fish-assemblage structure within isolated waterholes on the floodplains of Cooper Creek, Australia, was studied during the 2001 dry season, a period of natural drought in this arid-zone river. Spatial variation in fish-assemblage structure and the abundance of five species in disconnected waterholes early in the dry season (April 2001) were related to the extent of floodplain inundation 14 months previously, and to the interconnectedness of waterholes and waterhole habitat structure. As the dry season progressed, waterhole volumes decreased owing to evaporative water loss and structural habitat elements (anabranches, bars, boulders) became exposed. Marked changes in fish assemblage structure between the early (April) and late (September) dry season were related to habitat loss but not to water chemistry. Interactions between flow and habitat across a nested hierarchy of spatial scales (the floodplain, the waterhole and habitat patches within waterholes) were crucial to the persistence of fish assemblages through the 2001 dry season. We conclude that the magnitude, timing and frequency of floodplain inundation and natural variations in waterhole volume must be maintained if we wish to sustain the distinctive habitats and fish assemblages of this arid-zone floodplain river.

Seasonal flooding, instream habitat structure and fish assemblages in the Mulgrave River, north-east Queensland: towards a new conceptual framework for understanding fish-habitat dynamics in small tropical rivers

“…Spatial variability in fish assemblage structure Spatial variability in fish assemblages has been well documented in a range of river systems from the temperate zone (Koehn et al 1994;Gehrke et al 1999;King 2004), the sub-tropics (Pusey et al 1993;Arthington et al 2005) and the tropics (Gorman and Karr 1978;Martin-Smith 1998;Pusey et al 1998;Bishop et al 2001). These studies typically demonstrate that fish assemblages are influenced simultaneously by a variety of factors operating at various scales and along longitudinal gradients (Sheldon 1968;Schlosser 1982;Angermeier and Schlosser 1989;Harvey 1991;Arunachalam 2000).…”

“…As habitat availability varies spatially across the riverine landscape, so too does the abundance of individual species and the composition of species assemblages because fish seek areas that best suit their ecological requirements (Davies 1989;Arthington et al 2005;Rice 2005). In the present study, habitat use by fish species was consistent with their published habitat preferences (Pusey et al 2004) -some species were ubiquitous across sites (e.g.…”

“…Arthington et al (2005) described seasonal change in the fish assemblages of Cooper Creek, an arid-zone floodplain river. They found that marked changes in fish community structure between the early (April) and late (September) dry season were related to habitat loss: as water levels receded and pools dried up, within-waterhole features, such as boulders, root masses and large woody debris, were exposed and the number of sheltered places where fish could rest and forage was reduced (Arthington et al 2005). Unlike systems in these drier areas, perennial rivers in the Wet Tropics remain connected throughout the dry season, and the extreme habitat shortages described by Arthington et al (2005) are not encountered.…”

“…They found that marked changes in fish community structure between the early (April) and late (September) dry season were related to habitat loss: as water levels receded and pools dried up, within-waterhole features, such as boulders, root masses and large woody debris, were exposed and the number of sheltered places where fish could rest and forage was reduced (Arthington et al 2005). Unlike systems in these drier areas, perennial rivers in the Wet Tropics remain connected throughout the dry season, and the extreme habitat shortages described by Arthington et al (2005) are not encountered. Although the latter conditions could lead to relatively stable fish assemblages, seasonal habitat preferences of fish species in the present study matched variations in habitat availability within the main channel.…”

Detecting range shifts among Australian fishes in response to climate change

“…1b), resulting in highly variable patterns of occurrence through time (Unmack 2001;Arthington et al 2005;Bunn et al 2006). In such systems, detection of range shifts becomes difficult because vagrant and previously unsurveyed populations are likely to be encountered relatively often.…”