How can we measure sustainability?

The environmental sustainability of aquaculture is measured against environmental standards. For example, the "Consensus" project (a multi stakeholder platform for sustainable aquaculture in Europe) has agreed a total of 8 indicators of sustainability, based on environmental standards and their implementation. These range from application of environmental regulation for measuring the impact in relation to environmental capacity, to highlighting advantages of aquaculture on the environment through indicators which measure the improvement of water quality parameters.

The assessment of social and economic viability requires a multidisciplinary approach and the participation of diverse groups of society.

How can we help to ensure sustainable practice?

Effective selection of suitable sites for any type of aquaculture is crucial to environmental sustainability, but it is also a difficult parameter to implement. This is currently achieved through an Environmental Impact Assessment (EIA), as part of the planning process for new sites. An EIA requires that the potential physico-chemical, conservation and visual impacts of the fish farm be addressed and the implications on other resource users be considered.

Environmental monitoring is a standard method of environmental regulation of aquaculture where various measurements of physico-chemical and biological parameters are taken in order to judge the short and long term environmental impact. An assessment is made by comparison of measured levels with derived environmental quality standards (EQS's). These EQS's should be adapted according to the type of aquaculture system (freshwater, marine, closed / open etc.).

The calculation of the "carrying capacity" of the environment, or the level at which the aquatic environment can assimilate nutrient and chemical waste without environmental degradation, is important for aquaculture development as well as environmental health.

What are the challenges to sustainable fish farming?

• The inconsiderate location of fish farms, due to a lack of suitable sites, can have consequences for the preservation of surrounding natural habitats.
• An incomplete knowledge of the reproductive biology of some species means that they cannot be bred in captivity and hence juveniles must be taken from the wild to be grown-on for the market, placing great pressure on wild populations.
• The reliance on the use of fishmeal and fishoil in fish feeds is unsustainable and places pressure on wild populations of fish and on oceanic ecosystems as a whole.
• The reliance on the use of antibiotics to treat or prevent disease; as it is not feasible to treat individuals, dosing is either carried out in the basins or via the feed, both methods resulting in residues reaching the natural environment.
• The invasion of ecosystems by non-native species, which have escaped from farms (mainly sea cages).
• The equitable division of profits.