Aquaculture is the term used for the farming of fish and other marine creatures. The environmental impacts of aquaculture largely depend on the circumstances in which the fish are produced, and in turn affect the sustainability of the industry due to its unregulated nature in many areas.
In 2010, the total value of aquaculture production globally was estimated to be US $119.4 billion . The industry has shown significant signs of growth and doubled in production between 2000 and 2012. This a direct result of stagnating and declining trajectory of wild capture fisheries which peaked in the 1990’s .
The question therefore exists as to whether the aquaculture industry can be a sustainable and viable commerce to help feed the world’s 7 billion people. By 2050 there are expected to be over 9 billion people on the planet, 800 million of which already suffer from chronic malnourishment .
Environmental risks of marine aquaculture
The effects of fish farming on the environment are an increasingly important issue as aquaculture operations expand globally.
These impacts are largely dependent on:
- the intensity of production
- the species farmed
- the farm location
For example, South-East Asia, where finfish and shellfish are heavily produced and poorly managed, experiences fairly heavy environmental impacts. This is because finfish production is intensive form of fish farming and involves an addition of solids and nutrients to the marine environment to help fish grow.
This process is generally recognized as being harmful to the environment. Such a rapid unnatural build-up of organic material negatively affects native aquatic flora and fauna. In some cases, this can cause major changes to the sediment chemistry and affect the overlying water column location .
The effect of farmed fish on local wild fisheries is also a real environmental concern in South-East Asia and elsewhere. Outbreaks of disease from fish farms can spread quickly due to the high concentrations in which fish are retained and is easily spreadable into wild fish populations if uncontrolled.
Aquaculturalists used to tackle these outbreaks with antibiotics in fish feed until concern mounted over the effect of the drugs on local aquatic ecosystems as well as on consumers. Currently, vaccinations are readily available for farmed fish and the practice of using drugs to tackle disease is seldom used in Western aquaculture anymore .
Additional impacts related to aquaculture may also occur as a result of other farm discharges and waste products. These includes:
- waste from shore-based stun and bleed operations
- the escaping of non-native fish species
- transmission of disease and (lack of) control over predatory species.
Where species such as shellfish compete with other organisms, such as native seagrass, for survival, displacement can occur which has a potentially spiraling effect on the native wildlife [3,4].
Positive effects of fish farming on the environment
Despite a negative outlook there are also some positive environmental impacts to be recognized from aquaculture. These can be found in (artificially or naturally) nutrient enriched areas where the farming of filter feeders such as shellfish improve water quality.
Farmed fish are also generally free of environmental contaminants such as mercury and heavy metals as they exclusively eat human-processed feed of which toxin levels are regulated [3,4].
3 Ways to make aquaculture more sustainable for the future
There are several ways in which the aquaculture industry can become more sustainable, but perhaps the three most efficient ways would be to:
- invest in new technology
- reduce the dependency on ocean-caught fish for fish feed
- focus attentions on the wider environmental impacts the industry creates
Research has identified that the most harvested farmed fish are carp and oysters which account for around 17 percent of global finfish production ; however, their introduction into non-native habitats comes with significant socio-economic and environmental consequences.
Not only do native species of fish become threatened by potential invasion of exotic species, the local water source often becomes polluted with chemicals and disease from their farming which can at times be devastating .
One way to tackle this problem would be to regulate fish farms at a higher, broader level instead of the conventional focus in the individual farm . The impacts of one single farm can often be magnified, particularly if there are several farms adjacent to one-another, so the effect of having broader management frameworks would be more effective across the area.
The management of marine fisheries across the high seas and oceans is perhaps equally important for farmed fish production. In 2012, maximum production of 86.6 million tons of fish were caught in the oceans, but this figure excludes the catch of anchovies .
Anchovies and other juvenile fish are caught to be used predominantly as feed for farmed fish in one of the great marine paradoxes.
This is a truly unsustainable model which would massively benefit from a shift towards a genuine focus on plant-based aquaculture production.
Aquaculture can be made more sustainable by producing the fishmeal and fish oil used in feeds from seafood waste. This type of recycling in the feed industry has been on the rise in recent years. Regulatory bodies have also recognized the problems with algae blooms and implemented measures to prevent them such as the use of cages to wash away effluent in locations where strong currents are existent.
Study and examination into this concept as well as the wider industry is crucial. Understanding, predicting and accounting for this is going to be a significant challenge for the next decade. Research has been pivotal in providing sustainable technologies and strategies for conventional farming and fishing and is therefore likely to be a major player in creating a more sustainable aquaculture industry.
The development of new techniques for controlling disease, pests, feeding and infrastructure will aid fish farmers into adopting more sustainable approaches which will inevitably also benefit themselves and their livelihoods .
Whether it is farmed or wild, fish continue to be one of the most traded consumable commodities in the world. Whilst trade and money are fundamental to the industries and its players, a shift towards a more sustainable strategy will be vital in securing its long-term future so research, technology, management and cultural changes are necessary to provide prosperity for all.
Achieving the sustainable use of aquacultural techniques and aquatic ecosystems has the predominant objective of fisheries managers for decades; however, it has arguably failed due to lack of governance. Natural variability and climate change have also had significant implications for the productivity and management of aquaculture and catastrophic natural events continue have significant impacts on resources, infrastructures and people.