The Atlantic, or Malpeque Oyster has several natural predators and pests that have, and can cause, a great deal of problems for the industry. The industry closely monitors a variety of pests and deals with them in different ways. The principal and most abundant threat to oysters is the starfish which can cause a great deal of damage to spat fall and young oysters. In fact it is possible for starfish to consume almost 90% of the spat just after it attaches to the cultch. The predator consumes the oyster by using its muscular body to pry the shell open enough to devour the oyster inside. Once the shell is open, the oyster will certainly perish. There are literally millions of starfish in the waters surrounding PEI which make them a very serious problem for the industry. Even if each starfish ate only one oyster a day, it would result in the loss of millions of oysters and a great deal of money.

There are a couple of ways that fishermen and the PEI Shellfish Association Read More

The Atlantic, or Malpeque Oyster has several natural predators and pests that have, and can cause, a great deal of problems for the industry. The industry closely monitors a variety of pests and deals with them in different ways. The principal and most abundant threat to oysters is the starfish which can cause a great deal of damage to spat fall and young oysters. In fact it is possible for starfish to consume almost 90% of the spat just after it attaches to the cultch. The predator consumes the oyster by using its muscular body to pry the shell open enough to devour the oyster inside. Once the shell is open, the oyster will certainly perish. There are literally millions of starfish in the waters surrounding PEI which make them a very serious problem for the industry. Even if each starfish ate only one oyster a day, it would result in the loss of millions of oysters and a great deal of money.

There are a couple of ways that fishermen and the PEI Shellfish Association have historically dealt with starfish. First of all they would set starfish mops to monitor and remove the nuisance from oyster beds. These “mops” are simply two-foot cotton mop heads attached in a row to a long rod that are dragged behind a power boat at slow speeds. As the mops are pulled over the oyster beds, the small spines of the starfish get tangled in the cotton, pulling them out of the fishing grounds. Secondly, was the practice of spreading quicklime. This substance would cause lesions in the starfish that will spread and killed them in a matter of days. Starfish are basically dealt with in two ways now. The Shellfish Association sets cone shaped starfish traps to remove the pests and they are removed by hand by the fishermen as they are caught.


© Community Museum Association of Prince Edward Island, 2005. All rights reserved.

Trap used to remove starfish from oyster grounds.

PEI Shellfish Museum

© PEI Shellfish Museum


Historically, starfish were killed using quick lime.

PEI Shellfish Museum

© PEI Shellfish Museum


Starfish eating an oyster

PEI Shellfish Museum

© PEI Shellfish Museum


There are a variety of crabs that present a problem to the oyster industry as well, including the Mud Crab, the Rock Crab and most recently the European Green Crab. These predators cause a great deal of damage to oysters due to the great numbers of them. They gain access to the oyster by piercing the softest part of the shell – the area where which it is attached to the cultch. These predators eat a significant amount of small oysters but are unable to gain entry to shells more than 30 millimetres in length because the shells become to strong to enter. Many oyster farmers remove crabs with traps or simply grow their young oysters out of their reach by floating them just under the surface of the water.
There are a variety of crabs that present a problem to the oyster industry as well, including the Mud Crab, the Rock Crab and most recently the European Green Crab. These predators cause a great deal of damage to oysters due to the great numbers of them. They gain access to the oyster by piercing the softest part of the shell – the area where which it is attached to the cultch. These predators eat a significant amount of small oysters but are unable to gain entry to shells more than 30 millimetres in length because the shells become to strong to enter. Many oyster farmers remove crabs with traps or simply grow their young oysters out of their reach by floating them just under the surface of the water.

© Community Museum Association of Prince Edward Island, 2005. All rights reserved.

Green crab

PEI Shellfish Museum

© PEI Shellfish Museum


Other threats to oysters come in the form of “boring” predators, such as the snails. These small but effective pests actually bore tiny holes in the oyster’s shell until it is penetrated. Once the hole is made, the oyster dies and is ingested. Though they pose a small problem to the industry, they can still do significant damage if the numbers are great enough.
Other threats to oysters come in the form of “boring” predators, such as the snails. These small but effective pests actually bore tiny holes in the oyster’s shell until it is penetrated. Once the hole is made, the oyster dies and is ingested. Though they pose a small problem to the industry, they can still do significant damage if the numbers are great enough.

© Community Museum Association of Prince Edward Island, 2005. All rights reserved.

Snails can cause extensive damage to oyster stocks.

PEI Shellfish Museum

© PEI Shellfish Museum


Another threat to the oyster comes not in the form of a sea animal, but rather a plant, known as the “Oyster Thief.” This algae attaches itself to oyster shells that are at between a half to one and a half metres deep. When the tide falls, the algae is filled with air. When the tide returns, the air-filled plant rises to the surface taking the oyster with it. The plant and the oyster are then at the mercy of the tide and current and are usually taken out to deep water where the oyster will not reproduce.
Another threat to the oyster comes not in the form of a sea animal, but rather a plant, known as the “Oyster Thief.” This algae attaches itself to oyster shells that are at between a half to one and a half metres deep. When the tide falls, the algae is filled with air. When the tide returns, the air-filled plant rises to the surface taking the oyster with it. The plant and the oyster are then at the mercy of the tide and current and are usually taken out to deep water where the oyster will not reproduce.

© Community Museum Association of Prince Edward Island, 2005. All rights reserved.

Oyster thief

PEI Shellfish Museum

© PEI Shellfish Museum


The oyster and the industry are under attack by many foes on many fronts, including pests, diseases and illegal fishing, as well as farm and industrial run-off into the streams and estuaries where the valuable resource is grown. There is a great deal of work and countless individuals involved in the continual battle to remain ahead of all the possible problems that could arise as a result of any of these pests or problems getting out of hand. It involves a balancing act that juggles and uses limited resources to do as much as possible to ensure the security and longevity of the oyster industry on Prince Edward Island.
The oyster and the industry are under attack by many foes on many fronts, including pests, diseases and illegal fishing, as well as farm and industrial run-off into the streams and estuaries where the valuable resource is grown. There is a great deal of work and countless individuals involved in the continual battle to remain ahead of all the possible problems that could arise as a result of any of these pests or problems getting out of hand. It involves a balancing act that juggles and uses limited resources to do as much as possible to ensure the security and longevity of the oyster industry on Prince Edward Island.

© Community Museum Association of Prince Edward Island, 2005. All rights reserved.

Learning Objectives

The learner will:
  • complile the list of Malpeque oysters’ predators and how they are a threat to the industry.

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