Ocean Reef fish kill due to lack of oxygen in water

Department of Fisheries’ pathologists have completed a range of tests, following a recent fish kill near the Ocean Reef Marina and found it to be caused by a lack of oxygen.

Fish Kill Incident Response Co-ordinator Paul Hillier said the results had confirmed his early assessment and had now conclusively ruled out disease or algal blooms as causes for the fish deaths on Tuesday 27 May 2008.

“We examined a range of fish species and some crabs collected from the beach on that day and they all showed signs of anoxic (or lack of oxygen) conditions in the water,” Mr Hillier said.

“The fish collected included mullet, yellowfin whiting, trumpeter, and bream.

“Their gills all showed numerous swollen blood capillaries – a change commonly associated with a response to low dissolved oxygen and this is a frequent finding in fish kills that are due to anoxic water conditions.”

Mr Hillier said that water samples collected on the same day showed no toxic algal species present and no significant bacterial isolates were recovered.

“While there are still some water sample tests that we don’t have back, there is enough information for me to be confident the cause was a lack of oxygen – perhaps a still body of water that the fish swam through that morning that was very low in dissolved oxygen and that would have been enough to kill them,” he said.

“As in this case, we appreciate the early notification of fish kills because it makes the testing simpler and more effective if we can get samples that are still in good post mortem condition.

“The Department of Fisheries has a Fish Kill Incident Response Plan for Western Australia. We work with other government agencies and, since 2005, there have been more than 160 people, from around the State, trained in the use of special fish kill sampling kits.”

Mr Hillier said this helped the agencies involved to respond as rapidly as possible and ensure the collection of proper samples for prompt analysis.

“It is important for a local community to find out as soon as possible whether a fish kill has been caused by natural events, as in this Ocean Reef case, or if it has been triggered by disease or potentially toxic algal species or chemicals in the water,” he said.

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Ocean Reef fish kill due to lack of oxygen in water