Trials and Tribulations of Fish Relocation during Dam Dewatering

Wednesday, 10 April, 2019

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ELA's Aquatic Ecologist (and primary eel wrangler) Emily Messer talks trials, tribulations and learnings of dam-dewatering projects.

Firstly, what is dam dewatering?

A dam dewatering is basically the draining of a dam. The water is either pumped out using a large pump or the wall of the dam is breached and the water is released into a paddock. The dams are usually then filled in to make land for development. The dam in Orange was drained because it was a risk for a development to the north. There was concern that if the dam wall failed it would flash flood the new town. 

What's involved in these types of projects?

Fauna relocation projects usually come about when someone wants to drain a dam. As part of their conditions, an Ecologist must be on-site to remove the fauna. Usually, we relocate animals from small to medium size dams in the Sydney region which can be tackled in a day, but we did have a monster dam out in Orange that presented a great challenge at the end of last year. In this dam we relocated Bidyanus bidyanus (Silver Perch), Chelodina longicollis (Eastern Long-necked Turtle), Cherax destructor (Common Yabby) and Macquaria ambigua (Golden Perch).

What have been the major challenges?

In general, the challenges of a dam include thick mud that is hard to walk in and easy to get stuck in with eels and turtles that aren’t too keen to be caught in a net.  Keeping the eels in the buckets for transportation can also be a challenge, they are slimy creatures that seem to be able to fit through the tiniest of cracks. There is nothing more disturbing then looking in the rear vision mirror to see a huge eel flop around in the tray of the ute. 

The major challenge of the Orange dam was the size and dealing with species we don’t usually get in dams along the coastline. We were inventive with our use of nets (some success and some failures) and how we transported the fish. We ended up catching some huge perch which was incredible. Luckily the mud wasn’t too thick, and the bottom was relatively flat so we were able to move around reasonably easily. We did get bogged, but luckily got out ok. As the mud was too thick to drive the car to the edge of the dam we had to use a pump to get the water from the dam into the tubs in the back of the car. The water also wasn’t as low as we would have liked, and the dam wasn’t completely dry when we left. 

What are some of the achievements you have had with this project?

We rescued a good number of fish and yabbies (and a turtle). It was a great learning curve on how to approach something of this scale. I definitely nabbed the biggest fish I’d ever caught (not sure if it counts though being in a net). 

I learnt how to fix a gill net, which is harder than it sounds. Lots of patient tying of tiny knots to reattach all the parts and make the holes link back together. 

What’s the one thing you are most proud of achieving?

The best achievement would have to be the camaraderie in the team. There was lots of heavy lifting, some stressful times trying to get fish out of the nets (the fish were annoyingly oddly shaped), and it did get very hot, but we were always cracking jokes and laughing. We had lots of fun, which made it a good week. 

Dam dewatering in general inspires this sense of fun, as there is always the chance to be inventive using different materials (e.g. pallets or large foam boxes) to use as platforms in the mud, and an eel trying to get out of the bucket always inspires a squeal and laugh.

What are the major factors you are looking for in the success of these types of projects?

A major success factor is the relocation of as many fish as possible. Ideally, the dam is completely drained when we finish up, but that's not always the case.

For this particular project in Orange, one huge success was the scale of learning. It was the perfect opportunity to try new things and figure out what net positions worked best over multiple nights. We tried using bait, un-baited, putting nets in deeper water, shallower water, in weed and in the open. There aren’t many chances to test out so many things and see what works best.

Anything else you would like to add?

I hope the fish we relocated are having a great time in their new home.