Stock Containment in Net-Pen Systems

Preventing breaches of containment

On infrequent occasions, fish may escape from cages.  Governments have worked with industry to identify common causes of escapes and means to reduce these escapes in order to minimize any potential impacts on the ecosystem. For the industry, escapes also represent a significant economic cost.

Federal regulatory measures are in place in British Columbia that require licence holders to put in place measures to reduce risks of escapes and, if escapes do still occur, to immediately report estimated losses and to undertake activities to recapture those fish.  Causes of breaches are investigated and remedial measures put in place as appropriate.  Provinces are responsible for similar regulations in other jurisdictions.

Causes of escapes

Some of the causes of farmed fish escapes are:

• Severe storms and weather that damage nets and anchor lines
• Boat propellers that damage nets
• Attacks by predators such as seals and sea lions
• Human error in handling farmed fish
• Vandalism
• Equipment deficiencies – inadequate or damaged parts

Fisheries and Oceans Canada has many years of experience in researching and monitoring the causes and effects of farmed-salmon escapes.

Measures to prevent fish escapes

• Advanced cage technology and management practices
• Improved maintenance of nets and anchoring
• Stricter guidelines for operation of vessels near farms
• Double netting to deter predators
• Improved training of staff
• Development of containment management plans
• Locating farms in appropriate areas

All provinces which have net-pen farming of Atlantic salmon have Standard Operating Procedures for containment on salmon farms that specify cage system design standards and mandatory reporting of escapes.

Cage system design is an important preventative measure and Canada is actively involved in the development of new international standards for cage technology. Fisheries and Oceans Canada and representatives from the Canadian aquaculture industry sit on a working group of the International Organization for Standardization (ISO) which is drafting new standards for cage technology. Learn more about the ISO standards in development for fisheries and aquaculture.

Do escapes of farmed salmon affect wild salmon?

Many years of research through DFO’s Atlantic Salmon Watch Program has shown that escaped farmed salmon – in either the Pacific or Northwest Atlantic oceans – have a low survival rate in the wild because they are accustomed to being fed. The stomachs of recaptured farmed salmon are usually empty, meaning it’s unlikely they compete for food with other fish. Research has also shown that Atlantic salmon cannot successfully mate with wild Pacific salmon.

It is possible for farmed Atlantic salmon to mate successfully with wild Atlantic salmon, but it is too early to speculate on the overall effect of escaped farmed Atlantic salmon on wild Atlantic salmon in Eastern Canada. We are conducting research in collaboration with the Atlantic Salmon Federation which we hope will help us find answers to these important questions. At the same time, it should not be assumed that farmed Atlantic salmon escapes have caused declines in wild Atlantic salmon as wild populations have been in decline across the region, in many areas where there are no salmon farms at all.

Learn more:

• Fact Sheet: Escape Prevention
• Fact Sheet: Ecological Interactions between Wild and Farmed Fish
• Provincial and Territorial Regulations