A new report has found that the health of Perth's iconic Swan-Canning Estuary has improved in recent years.
Scientists from Murdoch University's Centre for Fish, Fisheries and Aquatic Ecosystems Research applied a newly developed Fish Community Index to assess the structure and diversity of the fish community in the waterway.
"Fish communities respond to their habitat conditions. If the estuary is in poor condition, we would expect this to impact the creatures who live, feed and breed in it," said senior researcher Dr Chris Hallett.
During the first half of 2012, Murdoch University scientists sampled and assessed more than 27,000 fish at 48 locations throughout the estuary.
The report, commissioned by the Swan River Trust, found that the Canning Estuary and upper part of the Swan Estuary continue to suffer periodically from problems due to a lack of dissolved oxygen in the water.
Dr Hallett said that despite short-term challenges, including algal blooms, the estuary was found to be in good to fair condition overall.
"There were specific conditions that led to the occasional poor rating. For example, in summer 2012, the upper Swan Estuary was recovering from a fish kill event caused by widespread deoxygenation after significant rainfall.
"Given the publicity around the supposedly poor state of the estuary in recent years, the results were perhaps a little surprising."
While the results are promising, Dr Hallett said nutrient levels in the estuary are still a cause for concern, and could continue to pose a challenge in the years ahead.
"I think efforts to reduce nutrient inputs are well intentioned, and some good work is being done to improve the water quality and habitats within the estuary," he said.
"In the longer term, we all need to change our behaviours to help solve the estuary's problems. A big part of that is raising awareness in the community."
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