Aims
This project aims to develop an environmental DNA (eDNA) tool to detect and estimate the biomass of both native and non-native fish species in Victoria’s streams. The specific objectives of this experiment are to determine if there is a measurable difference in the eDNA concentration relative to the biomass of fish present, to assess whether that difference is large and consistent enough to form the basis of population models, and to examine how stream flow rates may alter the distance in which fish DNA is detectable.
Methods
This project consisted of two parts, the collection of water samples for eDNA analysis and a standard electrofishing survey for measurement of fish biomass. A site consisted of a 250m stretch of steam sectioned into five 50m zones with stop nets. Each zone had an eDNA sample taken at its downstream end at three locations, each stream bank and the midstream. At these same locations, stream depth and water velocity measurements were taken to measure stream flow rates. Starting from the most downstream zone, an electrofishing survey made three electrofishing passes. Individuals of the three target species (brown trout, rainbow trout and river blackfish) were counted, measured, and weighed to determine the biomass of each fish species in each zone. The process was repeated moving upstream in each of the other 4 zones. For eDNA measurement, a single-species primer will be used to find the eDNA concentration. eDNA concentration will be compared with fish biomass using ANOVA analysis.
Results
Field work was undertaken in May 2022 at three sites around Lake Eildon, Victoria. We collected 17 brown trout, 48 rainbow trout and 227 blackfish. eDNA analysis is planned for July, 2022.