Ecological Effects
Presently, the effects of salmon farming in New Zealand’s marine environment tend to be highly localised and largely reversible.
The most common effects are localised changes to the seabed and water column through the deposition of organic wastes from the farm (faeces and uneaten feed). These effects can be managed in various ways to meet acceptable standards. And at the present low level of salmon production around New Zealand, they are well within the carrying capacity of the environment.
The magnitude and extent of effects depends on the site conditions - water depth, wave exposure, seabed type and currents - and farm management practices.
In New Zealand, both marine and freshwater farms are planned and managed under the Resource Management Act (1991). Under the resource consent process, a salmon farm applicant must provide a comprehensive and independent scientific investigation of the potential ecological effects of the proposed farm. Decision-makers must then analyse this information and be satisfied the ecological effects of the proposed farm would not be significant or unduly adverse.
Controls can be placed on how much water a freshwater farm uses and what state the water must be in when it is returned to a natural water body. Freshwater farms are also subject to the Freshwater Fish Farming Regulations.
Also, councils require regular environmental monitoring of operational salmon farms to ensure ecological effects on the seabed and water column from the farm remain acceptable.
The known ecological effects of marine finfish farming in New Zealand are summarised in a technical review by scientists from the Cawthron Institute.
