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Government of Western Australia - Department of Fisheries
​Black-lipped oysters at Karratha
Thursday 9 January 2020

Investigation into mortality of wild oysters in Pilbara coastal waters

​​​​Update to Fish Kill Notification
- 9 January, 2020 at 11am

Investigation into any relationship between the oyster mortalities and weather and tide conditions has now been completed. 

The analysis indicates that high air temperatures combined with low tide events, which occurred at the same time as the fish kill and which probably stressed the oysters, were likely contributing factors.

Fish kills should be reported to our FishWatch 24-hour hotline on 1800 815 507

Update to Fish Kill Notification
- 10 December, 2019 at 3.10pm

Small numbers of affected oysters have recently been observed at the mouth of the Fortescue River, south-west of Karratha, and at Balla Balla, east of Karratha. Many of the animals affected were juveniles in more exposed areas.

Weather in the area remains extremely hot and windy, with water temperatures reported to be around 32 degrees.

Investigation into any relationship between the oyster mortalities and weather and tide conditions has now commenced.

Testing can take some time and it may not be possible to identify a single definitive cause for a fish kill, but every effort is made to establish probable factors.

Report fish kills to the 24 hour FishWatch line on 1800 815 507.

Update to Fish Kill Notification
- 9 December, 2019 at 5.25pm
 
Water sample test results available to the Department of Primary Industries and Regional Development (DPIRD) indicate a very low density of phytoplankton cells was detected.

DPIRD laboratory examination of the oyster samples is being finalised, but testing to date has not identified any infectious disease as the cause of the mortalities. Weather in the area remains extremely hot.
 
Report fish kills to the 24 hour FishWatch line on 1800 815 507.

Update to Fish Kill Notification
- 20 November, 2019 at 4pm
 
The Department of Primary Industries and Regional Development (DPIRD) has not received any further reports of dying oysters in Pilbara coastal waters, since Monday, but further checks will be made in Flying Foam Passage and near Collier Rocks tomorrow.

Samples of the dead wild oysters are now undergoing testing in DPIRD's laboratories.

A working group, involving a local rock oyster industry representative and officers from DPIRD and the Department of Environment and Water Regulation, are monitoring the situation. Further updates will be available here, when new information comes to hand.
 
Report fish kills to the 24 hour FishWatch line on 1800 815 507.

Update to Fish Kill Notification
- 18 November, 2019 at 4.30pm

Samples of dead oysters and water, from three coastal sites where mortality among wild stock oysters has been detected, have been flown to Perth today for a series of laboratory tests in a bid to determine a cause for the deaths of the shellfish.
 
Native Black-lipped rock oysters (Saccrostrea cucullata) have perished near Karratha’s Back Beach Boat Ramp, in Flying Foam Passage and at another site near Collier Rocks, but the numbers affected vary between locations. It is estimated that thousands of oysters, which grow wild in the area, have been affected, however Milky oysters (Saccrostrea scyphophilla) – currently being cultivated in a trial in Flying Foam Passage – do not appear to have been affected.

Surveys have been made east and west of these sites, in a bid to determine the extent of the wild oyster mortalities. 
 
The Black-lipped oysters occur higher in the water column than the Milky species and recent high water and air temperatures in the area are said to have been between 38 to 42 degrees over the last few weeks, which could be a factor in the mortalities. 
 
A separate report at 40 Mile, south west of Karratha, has recorded Milky rock oyster mortalities and arrangements are being made to collect samples there as well.

An algal bloom, thought be sea sawdust (Trichodesmium), has also been observed in many areas.
 
A working group, involving a local rock oyster industry representative and officers from the Department of Primary Industries and Regional Development and the Department of Environment and Water Regulation are monitoring the situation. Further updates will be made when new information comes to hand.

Report fish kills to the 24 hour FishWatch line on 1800 815 507.

Fish Kill Notification
- 16 November, 2019

Officers from the Department of Primary Industries and Regional Development are inspecting several sites on the Pilbara coast, where mortality among wild oyster populations has been reported.
 
Samples of dead oysters and water are being collected near Karratha, including at Back Beach Boat Ramp and from Flying Foam Passage. The black-lipped oysters (Saccrostrea cucullata) grow wild in the region and early reports estimate one in five of these oysters have been impacted, perhaps over the last few weeks. There are no reports of cultivated oysters being affected.
 
The oyster and water samples will undergo laboratory testing. Water and air temperatures in the area recently are reported to have been unseasonably high, which could be a factor.


The cause of wild oyster mortalities in the Pilbara is being investigated

Updates will be issued, when further information is available. In the mean-time people are reminded to stay safe around fish kills. We urge people to follow the general Department of Health advice:

  • not to swim in areas of water with large numbers of dead and decomposing fish because they may contain high levels of bacteria and have an objectionable odour;
  • not to fish in water with large numbers of dead fish;
  • not to handle, collect, relocate or use dead fish for bait or consumption because of the risk of high levels of bacteria, and the potential for infection through handling or ingestion; and
  • not to allow pets and other animals to come into contact with dead or decomposing fish either in the water or on shore.

Anyone who has handled dead or dying fish and experiences any inflammation on their hands around any cuts or abrasions should see a doctor.

Fish kills should be reported to our FishWatch 24-hour hotline on 1800 815 507.

FURTHER INFORMATION:
The Department of Primary Industries and Regional Development (DPIRD) is responsible for responding to fish kill events that occur in ocean environments.

The Department of Water and Environmental Regulation manages investigations on fish kills that occur in estuaries, rivers and naturally occurring inland water bodies.

In both circumstances, DPIRD’s laboratories carry out testing of any fish samples assessed as suitable for that purpose to determine if diseases are present. This can take some time and it may not be possible to identify a single definitive cause, but every effort is made to establish probable factors.

More information on fish kills can be found on the Fisheries website at www.fish.wa.gov.au.

Last modified: 9/01/2020 11:00 AM

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