Wild shellfish

Public Health advice

• The advice on this page is about collecting and eating wild shellfish.
• There is always a risk of illness from eating wild shellfish that you have collected.
• Poor water quality and harmful algal blooms increase the risk of illness from eating wild shellfish.
• Shellfish collected in Hobart’s Derwent Estuary and Launceston’s Tamar Estuary are always unsafe to eat because the shellfish concentrate the heavy metals present in these waters.
• Shellfish from shops and restaurants in Tasmania are safe to eat. This is because the safety of commercially grown shellfish is closely monitored.

Do not eat wild shellfish

There is always a risk to your health from eating wild shellfish that you have collected. Wild shellfish include oysters, mussels, clams, pipis, cockles and wedge shells.

• Water quality affects shellfish quality.
• Poor water quality can be caused by rainfall run-off, sewage and other outfalls. It is often hard to know if water quality is poor.
• Shellfish are filter feeders. They feed by filtering large volumes of water.  Bacteria, viruses, other harmful germs, and metals in poor quality water can build up in the shellfish.
• It is always unsafe to eat wild shellfish from:
  • near marinas or other places where boats discharge waste
  • near sewage, industrial or stormwater outfalls
  • in areas near septic tanks
  • in places affected by recent heavy rain
  • from the Derwent and Tamar Estuaries.

You can get gastro if you collect and eat wild shellfish like oysters, mussels, clams, pipis, cockles and wedge shells from areas where the water quality is poor. Seek medical attention if you get sick after eating wild shellfish.

Current wild shellfish health alerts

Seafood in shops and restaurants

Seafood in shops and restaurants is safe to eat because the Tasmanian Shellfish Quality Assurance Program monitors the safety of commercially grown shellfish. This program is managed by the Department of Natural Resources and Environment Tasmania.

Toxic algal blooms

There is an extra risk to your health when there is a toxic algal bloom (also known as harmful algal blooms).

• Harmful algae in the water can affect shellfish.
• Large numbers of harmful algae in water are called a harmful algal bloom.
• You can't see any change to the water when a harmful algal bloom is present. The water looks and smells normal.
• Some types of naturally-occurring algae make toxins. When shellfish feed on these algae the toxins build up in their flesh.
• The harmful algal bloom can persist for weeks and the shellfish take even longer to clear the toxins from their flesh.
• Shellfish can be affected even in places where there are no warning signs.

Shellfish eaten during a harmful algal bloom can cause serious illness

• You can become seriously ill with shellfish poisoning if you collect and eat shellfish with toxins from a harmful algal bloom.
• Shellfish toxins are not destroyed by freezing or cooking.
• Symptoms of shellfish poisoning can occur from minutes to hours after eating shellfish.
• Paralytic shellfish poisoning is the most common form of shellfish poisoning in Tasmania.
• Shellfish poisoning symptoms include:
  • tingling or numbness
  • weakness
  • blurred vision
  • difficulty breathing
  • vomiting
  • diarrhoea.

Oysters, mussels, clams, pipis, cockles, wedge shells, abalone, scallop roes and the intestines and livers of rock lobster can be affected by toxins.

The toxins can cause four types of human poisoning:

• paralytic shellfish poisoning
• amnesic shellfish poisoning
• neurotoxic shellfish poisoning
• diarrhetic shellfish poisoning.

What causes toxic algal blooms?

Environmental conditions play an important role in the occurrence and spread of toxic algal blooms (also known as harmful algal blooms).

Ongoing research by the Institute for Marine and Antarctic Studies at UTAS and CSIRO is investigating the likely environmental triggers for the growth of species of harmful algae such as Alexandrium catenella in Tasmanian coastal waters.

The following are being considered as possible bloom triggers:

• cold water temperature windows of between 10C and 15C
• rainfall/land-runoff
• water column stratification (distinct layers of temperature and salinity in the water body with varying depth).

Researchers aim to use these triggers in the future in a predictive model for forecasting the occurrence of harmful algal blooms.

Learn more about biotoxin fishery events

Signage around Tasmania

More than 70 permanent wild shellfish warning signs are now displayed at popular boat ramps and public jetties along Tasmania’s east, north-east and south-east coastline.

There are two types of signs that warn of the ongoing risk of illness from eating wild shellfish.

• Public Health Warning signs are permanently on display.
• Danger (do not eat wild shellfish) signs are displayed when harmful algal blooms are present in the water.

Wild shellfish can also cause illness when collected from places with no warning signs.

Public Health Warning signs

The blue Public Health Warning signs explain that:

• Wild shellfish can cause illness
• It is unsafe to eat wild shellfish collected near:
  • marinas or other places where boats discharge waste
  • sewage, industrial or stormwater outfalls
  • areas with septic tanks
  • places affected by recent heavy rain.
• You can get gastro if you eat wild shellfish like oysters, mussels, clams, pipis, cockles and wedge shells.
• Toxic algal blooms can occur in these waters and make wild shellfish dangerous to eat.
• Seafood in shops and restaurants is safe to eat.

Danger signs

The red danger (do not eat wild shellfish) signs warn that:

• Toxic algal blooms are now present in Tasmanian waters
• Eating wild shellfish during algal blooms can cause shellfish poisoning
• Cooking or freezing does not make shellfish safe
• Shellfish poisoning symptoms include
  • tingling or numbness
  • weakness
  • blurred vision
  • difficulty breathing
  • vomiting
  • diarrhoea
• Seek urgent medical help if you get sick after eating wild shellfish

More information

For current information on algal blooms and fishery closures please visit the Department of Natural Resources and Environment Tasmania website or call the Public Health Hotline on 1800 671 738.