Farm Site Operations
Net Cage Attachment Points and Jump Nets
The Aquaculture Regulation specifies that the primary point of attachment for net cages is at the water line rope. The water line rope is designed in a manner to support the heavy load of a containment net. Secured to this water line rope are numerous reinforced tie-off points that take the bulk of the strain on the nets once they are deployed. Nets should not be supported by the stanchions or uprights as these are normally not designed to withstand the load and can fail under extreme conditions. The regulation also requires that net stanchions and net cage railing are not used to moor large vessels that could cause damage during strong wind or tidal exchanges.
Jump nets are the portions of net that extend above the water and are designed to prevent fish from jumping over the containment system. The regulation specifies the height of these jump nets must extend at least one meter above the surface of the water.
A Net Cage Attachment Point
Jump Nets
Net Cage Weighting
All equipment that comes into contact with containment nets must have a smooth exterior designed to prevent snagging the net on rough edges that might result in tears and loss of fish. This includes both external weight and internal weights as well as any attachment points that might come into contact with the containment nets. It is also important to maintain the equipment to prevent heavy fouling with marine organisms, which may lead to snagging or tears.
The weighting system must be designed so that net weights are sufficient to prevent excess billowing of the net. A taut net is important, as billowing nets are more subject to becoming snagged as well as more susceptible to tears or damage from predators.
On a site-specific basis, the engineering and infrastructure of each farm site is reviewed through the Management Plan during the application process. Each site is evaluated based on its own specific traits, such as size, location, and water conditions.
In investigations of incidents where fish have been lost or suspected losses have occurred, it has been found that some tears and subsequent loss of fish can be attributed to improper weighting or through contact with various components of the net weighting or system anchoring points. Industry is continually reviewing these aspects of containment structures and improvements are constant.
Boat Docking
To reduce or eliminate potential damage to net cages from vessels traveling to and from farms, a specific docking site for vessels that are not involved in fish cultivation must be identified on the site. The regulation requires this docking site must be designed and located in a manner to prevent propeller damage to the cage systems and must have proper signage. Boat operation and maintenance activities must be included in the best management practices plan for each aquaculture facility with the objective of preventing escapes of finfish into the environment.
A Docked Work Boat
Catch Nets
Catch nets must be used as a precautionary or secondary containment net when operators are conducting higher risk activities such as transporting, harvesting, grading, sampling or moving fish. This will prevent loss of fish due to human error or equipment failure.
Feed Storage
To reduce the risk of attracting potential predators onto the net cage system it is important that feed is stored in a secure manner and that all walkways and pen systems are kept clear of feed.
Feed Storage within an Onsite Warehouse Barge
Predator Control
All salmon farms are required to have Best Management Practice Plans to manage and prevent predation of farmed stock by animals such as seals, birds and otters. Farmers must also check any fish mortalities for signs of predator attack. If a pattern of predator attacks is established and mortalities are experienced at a specific location, holders must initiate measures to prevent net damage and loss of fish. Failure to comply with these requirements could be viewed as failure to take reasonable measures to prevent an escape.
Common types of predator systems include predator nets, shark guards, and bird netting. Proper weighting of cages is also important to deter seals and sea lions from attacking cages.
Example of a Predator Net Surrounding a Net Cage
Example of Bird Netting Overtop a Net Cage
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