South-east Regional Marine Plan National Oceans Office, 2001.

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• Impact of aquaculture

About the report

Aquaculture in the South-east Marine Region is comprised of finfish and shellfish farming. Presently, no other species are farmed in the sea.

The intensity and type of environmental impacts of aquaculture are dependant upon the species farmed, the intensity of production and on the farm location.

Impacts of aquaculture are an increasingly important issue as aquaculture operations in the South-east Marine Region continue to expand.

Finfish and shellfish aquaculture impact on the environment in different ways.

Finfish culture is usually an intensive industry that involves an addition of solids and nutrients to the marine environment, and is recognised as potentially causing environmental degradation through these inputs.

A build up of organic material beneath fish farms can impact on the flora and fauna of an area, in some cases causing major changes to sediment chemistry and in turn affecting the overlying water column.

Additional impacts may occur as a result of other farm discharges and waste products, for example from shore based stun and bleed operations.

The escaping of exotic species, transmission and control of disease, and control of predatory species are also areas of concern in this type of aquaculture.

In contrast, shellfish farming usually results in a net removal of nutrients from the water column, and is generally considered to cause less environmental damage.

Nevertheless, shellfish production can cause a build up of organic material on the seabed below as a result of particulate fallout from the shellfish or from the altered hydrodynamics around the farm.

Additionally, a net removal of nutrients from the water column may have either positive or negative repercussions for the natural system.

Positive impacts are apparent in nutrient enriched areas, while negative impacts can occur if the shellfish compete with other organisms for survival (eg. seagrass).

Other potential negative impacts from shellfish farming include physical impacts associated with farming structures and farm operations, reductions in native stocks caused by the collection of result wild seed (eg. mussel culture) and impacts associated with the introduction of exotic species.