Not all ‘doom and gloom’ for the Swan Canning Estuary

March 11, 2015

Researchers haul nets from the Swan River. Pic: Swan River Trust

Researchers haul nets from the Swan River. Pic: Swan River Trust

Murdoch University researchers monitoring the condition of the Swan Canning Estuary say last year’s fish results have disproved claims the river system is ‘dead’.

Dr Chris Hallett and Dr James Tweedley from the Centre for Fish and Fisheries Research at Murdoch University, said the condition of the estuary in 2014 was generally good to fair, continuing a recent trend.

“The results from last year are consistent with our previous monitoring, which has indicated an overall improvement in the ecological condition of the Swan-Canning Estuary since the mid 2000s,” said Dr Hallett.

The annual monitoring regime, established by the Swan River Trust, employs a Fish Community Index to rate the condition of the estuary from A (very good) to E (very poor). The index combines a range of measures, including diversity and number of fish species, to evaluate the fish community as one measure of estuary health.

The index was developed by Murdoch University over five years in collaboration with the Swan River Trust and the Departments of Water and Fisheries.

Murdoch University scientists sampled fish at 48 locations throughout the estuary during summer and autumn of 2014, and recorded 30,825 fish from 35 species in nearshore waters and 1,601 fish from 21 species in offshore waters.

“The results from 2014 revealed a particularly high diversity of fish species throughout much of the estuary. This reflects the relatively high and stable salinities, higher oxygen levels and the absence of algal blooms across much of the estuary during 2014,” Dr Hallett said.

“Trends over the last five to nine years show that the system is fairly resilient to the algal blooms and low oxygen events that can affect parts of the estuary following rainfall events,” he added.

The team of researchers are currently sampling the estuary again as part of the ongoing annual monitoring regime, and will be reporting on the 2015 results later in the year.

The full 2014 monitoring report has been released by the Swan River Trust and can be viewed here.

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