The breeding programme has been a long term rewarding project continuing into 2007, and there are a number of tasks that we recommend to be undertaken.
Monitoring of the release sites during spring and summer is to be ongoing. It is important to leave the traps for at least half an hour to give a better assessment of fish populations in the release sites. Our sampling time has only been for ten minutes due to lesson and travel constraints, so fish may already be established in the ponds. Seasonal after school sampling is recommended.
As the stock breeding population increases at school, more fish should be released into the city waterways. It could take up to three years to produce a stable population of native fish. The ecology of the breeding pond at the school has greatly developed, and the quality of water should improve over summer with the building of the settling tank in May 2007; this is designed to remove the high levels of iron from the bore water.
The Western Pygmy Perch is valuable as it feeds on the larvae of the midge and mosquito. However it would be most beneficial to continue to develop a breeding and releasing program for the Western Minnow, which feed on adult mosquitoes; this way both stages of the midge and mosquito’s life cycle can be attacked by a natural predator. The Western Pygmy Perch and the Western Minnow naturally occurred together in our waterways around Bunbury, so the reintroduction of these endemic species will greatly enhance the biodiversity of our waterways and further enhance there survival in face of their habitat reduction.
We recommend continuing with the breeding program for both species, but increase numbers of the Western Minnow in the natural open pond in the wetlands, as well a back up population in the smaller tanks and artificial ponds. They are larger and stronger than the Western Pygmy Perch and prefer flowing, open water – so are more likely to breed in Koopoolang Pond.
We have been alerted to a number of problems facing the waterways around Bunbury. These include high numbers of introduced fish, the Gambusia, outbreaks of botulism in water birds, algal growths, and a high level of litter flushed into the waterways.
We recommend the continual capture and removal of the fish, Gambusia. They were introduced in the 1930’s to help control mosquitoes. Unfortunately, studies, including our own at school, indicate that the Gambusia does not prefer to eat the “mozzie” and “midgie”. Our native species, the Western Pygmy Perch and the Western Minnow, are natural predators of the “mozzie” and “midgie”. The Gambusia has been shown to harass and nip fins, causing fin rot and death of the native fish and tadpoles.
Many of the algal growths in the waterways are harmless, even though they may not look very healthy. An example is a green algae, cladophera, which often spreads over areas of Big Swamp in summer; it readily breaks down to return nutrients to the benthic sediments. Concerned residents have reported this over the years. The Western Pygmy Perch pond in the environmental centre has had a “mat” of cladophera present for the last four years, and the fish are thriving. The algae provides oxygen, food, nutrients in the pond floor for microorganisms and midgie larvae (a food source for the fish), egg attachment for the fish, and most importantly a place for juvenile fish to hide from potential cannibal parents. Other areas such as Dodson Lake , where a Blue-green algae outbreak occurred twelve years ago, are also monitored by the City’s Health Department, along with Parks and Gardens. The public are also great “watch dogs”. We recommend this continues.
The lowering water table and drier winters has meant that many of these ponds are threatened with drying up and all the associated problems with concentrated shallow waters. Efforts to improve the natural habitat around these areas could include increasing the belts of natural vegetation around parts of the ponds. Many have pristine, water hungry, introduced lawns which have their fertilizers flushed into the waters – so the planting of more paper barks and wetland undergrowth would reduce this affect. St Mark’s Pond is a good example. Many very well established “Weeping Willow” trees, introduced from Europe suck out millions of liters of precious water from the water table. We recommend they gradually be replaced with native trees such as the peppermint and paper bark trees.
All of these ponds receive runoff through storm water drains. To overcome the flushing of litter into the waterways, netting traps could be added to cover the openings of the drain to capture the litter, which can then be readily collected and removed before it enters the waterway. A similar principal has been adopted in the suburbs of Sydney as a strategy to improve their waterways.
The signs we place at the sites also help to inform the public that these waterways are important, and the current work done by the Bunbury City Council along sections of Five Mile Brook is also a positive action.
Finally we recommend that we continue with this programme, and try and involve more students at our school as part of their required community service hours to have clean up days along Five Mile Brook. It is a great project and a great way to be actively involved in improving our local environment.