The Native Fish Report Cards are brief overviews of the health of targeted fish species. They report on recent fish data collected through scientific surveys. These data are used to indicate of the status of target fish species in each priority river, by reporting:
- The number of fish per 1km of waterway
- The length and weight of the largest fish caught
- The percentage of the catch that is legal size (if a recreational species that can be taken)
These results are summarised with three Key Health Indicators:
- Recent recruitment – were small fish (presumed less than 1 year old) present, indicating fish are breeding (or being stocked)
- Multiple size classes – were there fish from a variety of sizes, one indicator of healthy populations
- Mature fish present – were mature fish, capable of reproduction, caught
Species that were caught but not targeted by the survey methods (i.e. non-target species) are also reported for each waterway.
Once the dataset is strengthened with further years of data – we can start to investigate trends in the target fish populations.
Are they staying stable, or doing better or worse than they had in the past?
Data collection methods
Data collection (also known as sampling) for the Native Fish Report Card Program commenced in 2017 and is conducted once a year in autumn. Sampling is done in autumn to avoid the spring periods of peak migration when some native fish undertake long distance movements into or out of rivers.
Fish were sampled from multiple sites in each priority waterway, predominantly using electrofishing. Fyke netting was also used in two rivers where the target species included River Blackfish (Gellibrand River) and Freshwater catfish (Wimmera River). These species live on the bottom of the river and can be cryptic, so they are difficult to catch using electrofishing.
Electrofishing and fyke netting are scientific sampling methods used to provide a snapshot of the presence and abundance of fish present in waterways at the time of sampling. However, no method is perfect and able to catch all the fish present in a waterway. Therefore, the numbers of fish presented in the Native Fish Report Cards should be considered a sample only. There are likely to be many more fish in the waterways than just those recorded. Fish may also move about and populations will fluctuate due to natural variations in the environment.
Photo credit: David Sikerdick, Mallee Catchment Management Authority