Oyster mortality

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Why report oyster mortality?

A number of oyster diseases pose a significant threat to the NSW oyster industry; these diseases are listed as declared diseases under the Fisheries Management Act 1994 (Schedule 6B). These diseases include QX disease (caused by Marteilia sydneyi) and Winter Mortality (causative agent currently under review, previously thought to be caused by Bonamia [Mikrocytos] roughleyi).

Reporting unusual mortality and/or suspected disease events is a requirement and condition of every Class A Aquaculture Permit:

The permit holder must report to the local fisheries office the details of any suspected disease or unusual mortality affecting the fish or marine vegetation on the leased area, as soon as practical, and no later than 48-hours from becoming aware of any such occurrence.

Protocol for reporting oyster mortality:

In the event that a significant oyster disease/mortality is observed:

1. Within 48 hours phone either:

  • Fishers Watch 24 hour hotline 1800 043 536
  • your local DPI Fisheries office, and ask to speak to a Fisheries Officer
  • Manager Aquatic Biosecurity & Risk Management (02) 4982 1232

2. Complete a DPI Fisheries Veterinary Laboratory Specimen Advice form and an Oyster Mortality Report form. Accurate information is required as it may assist in determining the cause of the mortality. Please provide comments on any suspected cause or unusual environmental conditions.

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3. Collect and package the samples as directed by NSW DPI.

4. Attach these forms, taped in a plastic bag, to the outside of the container in which the samples are being sent to the laboratory. If possible, take a copy of the forms and put the copy inside the container with the specimens.

5. Arrange freight of samples to State Veterinary Diagnostic Laboratory at Elizabeth Macarthur Agricultural Institute (EMAI) or seek assistance from DPI or your local Fisheries Office.

6. Await laboratory diagnosis. While awaiting this result stock movements should be minimised, in case you may be spreading an infectious agent (eg virus, new parasite).

Oyster mortality is often due to predation or environmental effects such as heat or freshwater input and may not be the result of a disease. Even so, it is important that all events of unusual mortality are reported. Some unusual mortalities may potentially be a result of diseases which are not visually/obviously apparent. DPI encourages farmers to report unexplained mortalities to the department so that a disease investigation can be initiated.