Carp-catchers or more precisely, feral-fish catchers, caught my eye on this morning’s walk on Subiaco Common. There have been odd-looking structures in Lake Mere for several weeks. They’ve piqued my curiosity but today I caught up with two young men to find out about the structures. They seemed so out of place on the apparently pristine lake I wanted to know more.
Dressed for work in the hot sun in gum boots, rubber pants, wet-weather shirts and sun hats, the men waded knee-deep in muddy water. They paused happily to talk about their contribution to a better environment and also to pose for photos.
My post this week differs from those I usually write, even though I include environmental issues among my passions. As well as that, I’m keen to explore new ideas and to share information. Catching feral fish seems like an amazing job. I couldn’t resist talking to the workers in turn who were happy to tell me about their project.
In the olden days pre-COVID-19, when we took travel outside Western Australia for granted, a project like this in another country would have absorbed my attention.
About feral fish in our waterways
A variety of feral fish live in our Australian waterways. They include carp (Cyprinus carpio) and goldfish (Carassius auratus), which are prevalent in the South-West of Western Australia. Some rivers in the eastern states also experience problems with feral fish. Originally from South East Asia, some species can grow to eight kilograms, a good size for any fish.
People in other parts of the world consider carp a culinary delicacy although not they’r not widely eaten in Australia. If you’ve been on rivers in Asia, you may have seen carp in large numbers. In some areas, locals tend fish farms full of these species.
I don’t know how much the one below, caught in Lake Mere, weighs. But it’s a big fish for a small lake.
Although it looks yellowish in the photo, this overgrown feral gold fish appeared more olive-green in daylight.
Introduced species dig or burrow in lakes and rivers and change the habitat, upsetting native fish and reducing their numbers. Feral fish uproot water plants and muddy the water. They increase nutrients in the water which increases blooms of toxic algae. This, in turn, reduces natural food and cover for other species. They then compete with native species for food and may eat young indigenous fish.
How they get into lakes and rivers
At some stage, migrants introduced non-native fish as a food source. Others introduced them for sport-fishing. They soon became feral. There are even reports of hybrid fish in some waterways.
Still more feral fish result from owners of pet fish who try to dispose of their unwanted pets or those that have grown too large for their tank or fishbowl.
Goldfish or carp that have grown too large for a tank should be kept in concrete ponds from which they can’t escape, or disposed of humanely. Obviously they should never be released into ponds, lakes or rivers. Click for more information about feral fish in Western Australia.
While watching the carp-catchers, I remembered the children’s book, Fish out of Water (1961) written by Helen Palmer Geisel and illustrated by P. D. Eastman. I read the book over and over to my children in the 1960s and 1970s. It became a firm favourite.
In the story a little boy, Otto, buys a goldfish from Mr Carp, who tells the boy not to feed the fish too much. Of course, the child takes no notice and overfeeds it. The fish fills the fishbowl and then a series of increasingly larger containers.
The boy puts his pet in the bath. Eventually his mother calls the police and fire brigade who move it to the local pool. Soon, it fills the pool. Someone calls Mr Carp, who gets into the pool and reduces the fish to its original size.
The boy takes it home and presumably feeds it properly.
The work of carp-catchers
The company for which the young men work guarantees to remove feral fish from the waterway. At Mere Lake, they set up seven elaborate fish traps an equal distance from each other, close to the edges of the lake.
The carp-catchers fill the bucket-like container at the top of the trap with fish food which drips slowly into the water so that it attracts feral and native fish into nets below the surface. Workers empty the traps manually several times a day. They release the native species back into the water and also euthanise feral fish humanely.
City of Subiaco and the environment
I’m always pleased to see new environmental initiatives especially those undertaken by my local council. The City keeps residents informed of its activities through its Facebook page, notices in local papers and notices like the one below, displayed on the edge of the lake. We should congratulate our local government for the work it does.