The effects of environmental filtering on Kuhlia rupestris distribution in the Daintree rainforest region of the Australian Wet Tropics

Abstract

The effects of flow velocity in freshwater streams on biodiversity are well documented and reveal a role as a potential environmental filter. For the Kuhlia rupestris, one of the most abundant fish in the Australian Wet Tropics Bioregion, understanding distribution is integral to anticipating the impacts that any change to the environment may have on the species’ diversity. Due to the linear relation between body size and top speed we expect to see high flow rates restricting the habitat of smaller K. rupestris. Through underwater visual censuses and flow rate measurements in two coastal streams it was found that smaller fish comprise a lesser proportion of the population in pools preceded by higher flow velocity. Similarly, smaller K. rupestris are restricted from the high flow microhabitats farther from the streambed. Changes to these aquatic environments may affect the distribution of K. rupestris and the resulting impact they have on the surrounding biome.