Distribution of the Lake Eacham rainbowfish in the Wet Tropics region, North Queensland

The Lake Eacham rainbowfish, Melanotaenia eachamensisAllen & Cross, 1982, was thought to be extinct in the wild until recentresearch demonstrated the presence of wild populations in a few tributaries ofthe upper Johnstone River and the upper Barron River, north Queensland, byusing the technique of DNA sequencing. We present the results of amultivariate analysis of a range of morphological and meristic characters ofrainbowfish collected from rivers of the Wet Tropics region, particularly theJohnstone River, that demonstrate that M. eachamensis iswidespread in the upper and lower reaches of the North and South Johnstonerivers and tributaries of the upper Tully River.M. eachamensis was most often the dominant species inthose locations where sympatry withM. splendida splendida was observed.M. eachamensis should be considered a stream-dwellingspecies rather than a lacustrine species although a significant lacustrinepopulation (Koombooloomba Dam) was detected

Fish assemblages in subtropical rivers: low-flow hydrology dominates hydro-ecological relationships

Effective environmental flow management depends on identification of ecologically-relevant flow attributes to maintain or restore flows in the context of other natural and human influences on stream ecosystems. This study in subtropical eastern Australia identified associations of fish with climatic and flow gradients, catchment topography, reach geology, habitat structure and land use across 20 catchments. Land-use patterns and associated stressors accounted for very little variation in fish assemblage structure. Of the 35 fish species analysed, 24 were strongly associated with gradients in mean daily flows and their variability, baseflow, number of zero-flow days and high-flow pulses, magnitude of the 1-year annual return interval flood and the constancy and predictability of monthly flows. The finding that 22 species (benthic and pelagic) were associated with gradients of antecedent low-flow hydrology indicates that these species (or functional trait groups) should be the focus of further analysis to explore hydro-ecological relationships in systems with regulated flow regimes

Environmental flow assessment with emphasis on holistic methodologies

In Welcomme, R. L.; Petr, T. (Ed.), Proceedings of the Second International Symposium on the Management of Large Rivers for Fisheries, Volume 2: Sustaining Livelihoods and Biodiversity in the New Millennium, Phnom Penh, Kingdom of Cambodia,11-14 February 2003. Bangkok, Thailand: FAO. RAPRAP publication 2004/1

Postflood movements and population connectivity in gambusia (Gambusia holbrooki)

A population of the exotic pest fish Gambusia holbrooki inhabiting a drainage channel was sampled regularly to record responses to flooding and subsequent population reestablishment. The flood reduced numbers in the channel to near-zero levels. After remaining very low for 2 months, densities increased steadily through juvenile recruitment and the concentration of fish in drying pools. Tagging revealed that in general, movements between pools separated by only a few metres were relatively limited. There was evidence for habitat segregation and population subdivision, as fish from different pools varied markedly in terms of mean population density, movement behaviour, sex and size composition and juvenile recruitment. The most favoured pool was relatively deep, well lit and had the greatest habitat diversity. Gambusia control measures are likely to be most effective if timed to coincide with floods (which reduce local population densities) and/or droughts (which concentrate fish and allow targeting of source populations)