Flathead Galaxias (Galaxias rostratus) is a critically endangered native freshwater fish that has undergone substantial recent declines in both population size and distribution. Currently, there is limited information on effective detection methods, population abundance across its range and its habitat associations.
This study aimed to compare the effectiveness of five sampling methods for (1) detection and (2) estimating abundance of Flathead Galaxias, (3) examine relationships between fish abundance and habitat at microhabitat and (4) macrohabitat scales, and (5) assess the presence of the species within the previously unsurveyed Puckapunyal Military Area.
Five sampling methods were used across 27 wetlands along the mid-Goulburn River, Victoria, where the species was previously determined as present, absent and not surveyed. Microhabitat and macrohabitat variables were quantified at all 27 sites and the microhabitat associations with fish abundance for all positive capture sites and macrohabitat associations with fish were assessed.
Single and double-wing fyke nets were most effective for detecting Flathead Galaxias adults, while seine nets and double-wing fyke nets were most effective at detecting juveniles. Fyke nets caught the highest abundance of adults, while seine nets caught the highest abundance of juveniles. Juveniles were detected more frequently, and in a higher abundance, than adults, likely due to the surveys being conducted post-breeding season. At a microhabitat scale, Flathead Galaxias abundance was most positively associated with emergent and submerged vegetation. At a macrohabitat scale, the abundance of Flathead Galaxias was positively associated with increasing emergent vegetation and open water cover and negatively associated with increasing bare substrate cover.
My findings guide improving detection and monitoring of Flathead Galaxias across its current and former range. Standardised sampling methods should be adopted, targeted habitat restoration such as revegetation of emergent and submerged species should occur at low-abundance and translocation sites, which may enhance population recovery and reduce the risk of extinction.