Transporting spat and machinery used on marine farms around the country can spread diseases and pests  

Good management, including careful washing and drying of equipment before transportation, should be adopted to prevent spread of disease and pests

Fixed structures used by the marine farm can attract biofouling species which can spread to the surrounding environment 

Fixed structures should be regularly cleaned to prevent the build-up of biofouling species

Copper from antifouling paints can build up on the seabed to toxic levels  

Marine farms should either manually defoul equipment or use paints which are free of copper

Alteration of the behaviour of marine mammals as a result of marine farms obstructing access to, or use of, feeding grounds and other areas of their habitat 

Marine farms should be carefully located in order to ensure that access by marine mammals to habitual feeding, haul out, migratory routes and other areas is not obstructed.

Marine farms should not be located where they interfere with cooperative hunting.

Potential for marine mammals to become caught in longline or finfish nets used on the marine farm

Marine farms should use the best available technology and best techniques to minimise the risk that marine mammals will become trapped in nets (such as adequate net tension, enclosing anti-predator nets at the bottom, eliminating food waste and reducing the mesh size of nets) ¹⁷⁴⁷

Debris from poorly maintained farms can be a hazard to other water users and to marine fauna

All non-biodegradable waste material should be removed from the coastal marine area, and structures should be adequately maintained to ensure their integrity. Lines should be kept under tension (this reduces likelihood of nuisance for other users and reduces likelihood of marine mammal entanglement)

Degradation of landscape values and natural character of the area

Marine farms should be sited away from areas where they would interfere with outstanding landscape or outstanding natural character values

Marine farms should be sited away from areas where the visual effects of the farm could be significant on landscape or natural character values

Marine farms can pose a hazard to watercraft and navigation 

Marine farms should be adequately lit at night to ensure safety of navigation

Marine farms should not be located in areas which unduly obstruct navigation or safe anchorage, such as shipping routes and popular recreational vessel routes and anchorages

Effects on water quality through excretion of faeces and alteration of naturally occurring currents

Marine farms should be designed to minimise effects on currents, should be sited in areas with adequate flushing, and should be stocked with lower densities as to allow reduced build-up of faeces in the area

Depletion of naturally occurring plankton leaving less available for wild species  

The effects of shellfish farming on the amount of plankton available should be carefully managed, including the cumulative effects of having more than one shellfish farm in the same area

Effects on light-sensitive marine flora as a result of shading by the farm structure  

Marine farms should be located away from areas where they can have negative impacts on seagrass and other light sensitive species such as seaweeds

Changes to the seabed through deposition of shell, shellfish and faeces

Marine farms should be sited in areas where benthic habitats are less sensitive to impacts such as areas with a muddy substrate rather than rocky or sandy areas 

Effects on wild species as a result of changes to their environment  

Marine farms should be located away from areas where they can have negative impacts on species or habitats with special conservation value or of ecological importance 

Changes to patterns in the current and natural flow of water as a result of farms, particularly oyster racks, causing sand build up under the farm  

Proposals for marine farms should be accompanied by an assessment of the hydrodynamic patterns at the subject site, with current speeds and directions, flushing times and water dispersion patterns and modelling of how this will be affected by the proposed farm. 

Marine farms should not be sited in poorly flushing areas.

Abandonment of marine farm sites and structures when farming ceases  

If marine farming activity ceases, all structures associated with its use should be removed and the site rehabilitated. The consent authority should require this as a condition of consent or require a bond or payment to cover the cost of removal by the local authority 

Increased likelihood of disease 

Good husbandry, reducing stress and appropriate nutrition can all help prevent disease outbreaks

Farms should be maximally spaced to provide a biosecurity barrier to potential between-farm disease transfer. 

Ideally, there should be single year class fish farms

Depletion of fish stocks when farmed fish are fed wild-captured fish or feed pellets made from wild-captured fish 

Minimise the proportion of wild-captured fish protein and oil used to produce harvest fish.  

Only use wild fish from sustainable capture fisheries

Deposition of faeces and uneaten food causing changes to the physical, chemical and biological nature of the seabed and water quality

Seabed effect should be managed to Best Management Practice guidelines: benthic. This can be through use of appropriate management practices and technologies.

Farms should be located in areas which suit the species and have good environmental characteristics such as good water flows.

Where appropriate there may be an opportunity to adopt integrated co-culture/multi-trophic aquaculture for example where finfish, mussels, seaweed and other species are grown where one species benefits from co-existing with another.

Effects on local biodiversity as a result of changes to their environment  

Marine farms should be located away from areas where they can have negative impacts on species or habitats with special conservation value or ecological importance 

Escape of farmed fish and spread of diseases to wild fish

Fish farms should be designed to minimise escapees

Breeding of escaped fish with wild fish that adversely affects the genetic robustness of the wild population

All reasonable efforts should be made to prevent the escape of farmed fish, including utilising new technology where available 

Harm to the marine environment and to humans consuming the products from chemicals used to treat the fish 

Finfish should be farmed in preferred environmental conditions and according to best practice to minimise the potential for disease and therefore reduce the potential requirement for chemical intervention.