​​Managing Vibrio risk​

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Vibrio are temperature-dependent bacteria that naturally live in estuarine waters. Numbers increase during periods of warmer water and moderate salinity. If present in high enough levels Vibrio may cause vibriosis illness in consumers.  

Oyster farmers need to take extra precautions during warm weather to keep harvested shellfish cool and reduce Vibrio risk.

What to do

  • Protect harvested shellfish from extreme temperatures and place them under temperature control as soon as possible after harvest. This may include using a cool room.
  • Do not harvest shellfish that may be stressed due to environmental factors or recent handling, such as grading.
  • Transport shellfish in a refrigerated vehicle or packed in an insulated container with enough ice packs to keep them cool.
  • Follow all requirements in the NSW Shellfish Program Relay Procedures (PDF, 134 KB).
  • Comply with all biosecurity requirements, including shipment logbook record keeping.

Reduce the risk  

In addition to the storage temperature requirements outlined in the NSW shellfish industry manual (PDF, 647 KB), the following measures are strongly recommended to reduce the risk of a vibriosis outbreak:  

  • Ensure shellfish are kept cool from the moment they come out of the water, and place under temperature control (for example, in a cool room) as soon as possible.
  • Do not harvest shellfish showing signs of stress, such as gaping or weeping.
  • Return shellfish to the water for at least 48 hours to recover after culling or grading.
  • Harvest shellfish on intertidal leases as soon as possible after they have become exposed on the outgoing tide.  
  • Shade shellfish while transporting from the lease to the shed. Shade cloth may be used to protect them from direct sunlight. Water from the harvest area may be sprayed over them to help keep them cool.  
  • At the shed, unload shellfish immediately and keep them shaded while awaiting further processing or packing.  
  • Store Sydney Rock Oysters at less than 15⁰C whenever the harvest area water temperature is above 20⁰C.  
  • When water temperature is greater than 20⁰C, place:  
    • Pacific oysters under temperature control (below 10⁰C) within 12 hours of harvest. When air temperature exceeds 30⁰C, place  under temperature control within 7 hours of harvest  
    • Sydney Rock Oysters under temperature control below 21⁰C (preferably below 15⁰C) within 12 hours of harvest. When the air temperature exceeds 30⁰C, place under temperature control within 7 hours of harvest.

Relay requirements

The NSW Shellfish Program Relay Procedures (PDF, 134 KB) outline withholding periods prior to harvest for human consumption for shellfish moved between harvest areas, however no withholding period is specified for managing Vibrio risk.  

Following a review, the Food Authority determined an interim 28-day withholding period applies to shellfish relayed from harvest areas that are closed due to Vibrio risk. This may be reviewed as new information becomes available.  

There are no biosecurity restrictions on the movement of oysters based on Vibrio detection in waterways. Various Vibrio species are naturally occurring bacteria that are present in all marine environments. All other biosecurity requirements must be followed.  

More information