We met the Goulburn Broken Catchment Management Authority electrofishing team as they worked their way upstream from Gooram. Not a bad workplace at all.
Upstream from the site.
A view downstream to the pool to be surveyed.
Data collection and sampling occurred on the sandy beach.
The electrofishing equipment consists of a battery backpack generating 330 volts of direct current that travels between a submerged wire cathode and flat net anode.
The anode pole has a deadman’s switch to protect the operator. Insulating gloves and waders protect the 2 man crew from electroshock when in the water. Bystanders must be clear of the water during electrofishing.
Charged water leaking into the waders may cause leakage of current as well. Any tingling necessitates immediate silicone patchwork.
The team work together to retrieve stunned fish from likely haunts. The current affects fish within a 1 – 1.5m area. Generally, stunned fish have mild muscle contractions that move them toward the anode net. However, sometimes fish also roll toward the cathode.
With frequently slippery and unstable footing carefully coordinated retrieval is important.
Recovery times vary from 2 to 10 minutes, this trout cod recovered quickly.
These trout cod and Macquarie perch took a bit longer.
Getting uncooperative and slippery fish onto the ruler and scales cradle can be a challenge at times.
Data gathered is confirmed and recorded.
This Macquarie perch lay still for its weigh in
Others had to be held down more firmly for an accurate length measurement.
Confirming a length.
Fish are scanned for previously inserted chips. This trout cod was the biggest fish we saw, weighing in at 1198g.
A small snip of tail fin is taken.
Collecting genetic material from fish gives parent and gene pool information.
The tissue is transported to the lab in test tubes.
Each location has all fish caught recorded as a data set.
Fish are gently returned to the water.
Some are more ready than others.
This large trout cod was still fairly stunned.
It needed some further encouragement to get to safer waters.
Electrofishing is a useful survey method for assessing fish populations and species composition. The Sevens above Gooram has the special status of good habitat for endangered native fish species including trout cod, Macquarie perch and blackfish. It is illegal for anglers to fish in these waters downstream from Polly McQuinn’s.
These native fish are very vulnerable to predation by the introduced and aggressively invasive redfin species (European or English perch). Redfin are present in the same waters. Native fish caught during electrofishing are returned to the water unharmed. Redfin are destroyed.