Dam construction is a major driver of ecological change in freshwater ecosystems. Fish populations have been shown to diverge in response to different flow velocity habitats, yet adaptations of fish populations to river and reservoir habitats created by dams remains poorly understood. We aimed to evaluate divergence of morphological traits and prolonged swimming speed performance between lotic and lentic populations of Australian smelt Retropinna semoni and quantify the relationship between prolonged swimming speed performance and morphology. Prolonged swimming speed performance was assessed for 15 individuals from each of three river and two reservoir populations of R. semoni using the critical swimming speed test (U crit). Body shape was characterized using geometric morphometrics, which was combined with fin aspect ratios and standard length to assess morphological divergence among the five populations. Best subsets model-selection was used to identify the morphological traits that best explain U crit variation among individuals. Our results indicate R. semoni from river populations had significantly higher prolonged swimming speed performance (U crit = 46.61 ± 0.98 cm s −1) than reservoir conspecifics (U crit = 35.57 ± 0.83 cm s −1 ;

The use of macroinvertebrates in the assessment of wetland ecosystem integrity is an increasingly common tool used for management and conservation. The sensitivity of macroinvertebrates to ecological fluctuation makes them reliable and appealing indicators of ecosystem integrity. However, there is little or no published data available for assessment of wetland ecosystem integrity on the basis of macroinvertebrate species diversity in constructed wetlands of metropolitan Melbourne. The aim of the following study was to assess significant differences in macroinvertebrate diversity in three constructed wetlands in South East metropolitan Melbourne and consequently, suitability as a universal measure of wetland ecosystem integrity.Three wetlands were chosen randomly, with the requirement that they were entirely man-made, from a list of constructed wetlands in South East metropolitan Melbourne. Between 481 and 629 organisms were found in each wetland comprising 16 different taxa. The one-way ANOVA for species richness (P > 0.05, F = 0.19) and Shannon-Weiner diversity index (P > 0.05, F = 2.54) indicate no significant differences between the wetlands in both of these measures. The data collected in the present study compared with published species richness and Shannon-Weiner diversity index data suggests macroinvertebrate species diversity can be used as a universal measure of wetland ecosystem integrity in constructed wetlands in South East metropolitan Melbourne. This is important where there is need for a rapid and streamlined tool for assessment of ecosystem integrity and consequently, the management and conservation of constructed wetlands.

Different populations of organisms can vary widely in their responses to environmental conditions and this variation is fundamental to the persistence of species. Using a common garden experiment, we examined temperature-specific growth and survival responses of larvae among populations of Murray cod (Maccullochella peelii) from four regions of the Murray–Darling Basin (MDB), Australia. Fish larvae from the four regions differed significantly in their growth and survival responses at high water temperatures ≥26°C. At 30°C, survival rates of larvae by Day 20 ranged from 0% in the Lachlan region to 82% in the southern region. Opposite to the geographical differences in survival, growth of larvae was highest in the Lachlan (14.8–15.4-mm standard length 95% CI) and lowest in the southern region (13.4–13.9-mm standard length 95% CI) at 26°C where sufficient numbers survived for comparison. Geographical differences in growth and survival responses did not follow a consistent latitudinal gradient as observed for other species, but were closely linked with previously described genetic structure. Our results suggest that the upper thermal limit of M. peelii larvae is near common river temperatures in the MDB and that maintaining functional response diversity and underlying genetic diversity will be important for ensuring the resilience of this apex predator under future climate change.