Fish larvae, growth and biomass relationships in an Australian arid zone river: links between floodplains and waterholes

Abstract

1. Floodplain inundation provides many benefits to fish assemblages of floodplain river systems, particularly those with a predictable annual flood pulse that drives yearly peaks in fish production. In arid-zone rivers, hydrological patterns are highly variable and the influence of irregular floods on fish production and floodplain energy subsidies may be less clear-cut. To investigate the importance of floodplain inundation to a dryland river fish assemblage, we sampled fish life stages on the floodplain of Cooper Creek, an Australian arid-zone river. Sampling was focused around Windorah during a major flood in January 2004 and in isolated waterholes in March 2004 following flood drawdown. 2. Of the 12 native species known to occur in this region, 11 were present on the floodplain, and all were represented by at least two of three life-stages -larvae, juveniles or adult fish. Late stage larvae of six fish species were found on the floodplain. There were site-specific differences in larval species assemblages, individual species abundances and larval distribution patterns among floodplain sites. 3. Significant growth was evident on the floodplain, particularly by larval and juvenile fish, reflecting the combination of high water temperatures and shallow, food rich habitats provided by the relatively flat floodplain. 4. Low variation in biomass, species richness and presence/absence of juvenile and adult fish across four floodplain sites indicates consistently high fish productivity across an extensive area. 5. Similarities and differences in fish biomass between the floodplain and isolated postflood waterholes suggest high rates of biomass transfer (involving the most abundant species) into local waterholes and, potentially, biomass transfer by some species to other waterholes in the catchment during floodplain inundation and after floods recede. 6. The high concentration of fish on this shallow floodplain suggests it could be a key area of high fish production that drives a significant proportion of waterhole productivity in the vicinity. The Windorah floodplain provides favourable conditions necessary for the spawning of some species and juvenile recruitment of the majority of species. It is also appears to be a significant conduit for the movements of fish that underpin high genetic similarity, hence population mixing, of many species throughout the Cooper Creek catchment. The high floodplain fish production in turn provides a significant energy subsidy to waterholes after floodwaters recede.

The spatial pattern of larval fish assemblages in the lower reach of the Yangtze River: potential influences of river–lake connectivity and tidal intrusion

“…Thus, our results suggest that spawning of most fish occurs at a high water level and water runoff and when water temperature is appropriate. Flooding enhances recruitment by either directly stimulating spawning, or indirectly enhancing larval and juvenile survival by transporting larvae to habitats with rich food resources on the inundated floodplain (Harris & Gehrke, 1994;Balcombe et al, 2007). Our results showed that the abundance of larval fish peaked in May in the early flooding season.…”

“…We suggest that the larger number of species and higher abundance of larval fish at AQ than at NJ reflect an influence of the connectivity of the Poyang Lake with the Yangtze River upstream of AQ, and the delayed bloom of larval fish and the occurrence of estuarine species at JJ reflect the influence of tidal intrusion from the estuary. Life histories of many fish species have evolved to adapt to the hydrological regimes of river-floodplain system by spawning in the river and nursing in the floodplain habitats (Fernandes, 1997;Balcombe et al, 2007;Osorio et al, 2011). Lateral connectivity between river and the floodplain habitats is essential for these fishes to complete their life cycles (Junk et al, 1989;Bayley, 1991).…”

“…Landscape pattern plays an important role in structuring larval fish assemblages in large river basins (Balcombe et al, 2007;Osorio et al, 2011).…”

Fish Distribution in Far Western Queensland, Australia: The Importance of Habitat, Connectivity and Natural Flows

“…Stephen also has extensive experience working in the river systems that were studied and in other arid and semi-arid Australian systems [28,39,47].…”

Spatial and temporal distribution of native fish larvae in seasonal and perennial tributaries of the Sacramento River, CA, USA

“…In California, the protracted availability of seasonal habitats coincides with the spawning period of many native fishes (Villa 1985;Moyle 2002). Thus, seasonal floodplains and other similar habitats peripheral to the mainstem of rivers and streams are increasingly recognized as important breeding and nursery areas for many species of freshwater fish (Turner et al 1994;Balcombe et al 2007). Seasonal inundation significantly increases the total amount of available aquatic habitat and provides greater habitat heterogeneity than is found in the main channel (Power et al 1995;Sommer et al 2002Sommer et al , 2004.…”