Impacts of Aquaculture
As the Irish marine aquaculture industry continues to grow, so
do the ecological, human health and animal welfare problems associated
with the sector. The fact that marine aquaculture the aquatic
version of industrial agriculture takes place in coastal
waters, where biodiversity is high and pressures from multiple
interacting human activities are increasing, both complicates
and amplifies the potential environmental impacts of the sector.
All forms of mariculture, regardless of physical
structure or economic motivation, affect biodiversity at genetic,
species and ecosystem levels. At the ecosystem level, both goods
and services functions can be affected, with widespread consequences
and knock-on long-term effects. Therefore, the interconnected
nature of aquatic communities require that impacts on aquatic
ecosystems should be considered in a holistic manner, both in
the short and long terms.
Secretariat of the Convention on Biological Diversity 2004
An integrated ecosystem-based approach has yet
to be applied to the management of marine aquaculture in Ireland.
Most environmental impact studies have been conducted at project
development (i.e. single fish farm) level. Whereas the local scale
effects are well documented, the effects at the ecosystem or regional
scale remain largely unknown. The different sensitivities of different
ecosystems to potential impacts, and the different capacities
of different ecosystems to absorb changes resulting from aquaculture
activities mean that assessing the potential cumulative impacts
of marine aquaculture at ecosystem level is difficult. Nevertheless,
a strategic environmental assessment of the marine aquaculture
sector is a long overdue, vital first step towards integrating
marine aquaculture into the overall process of integrated coastal
zone management (ICZM).
General conclusions about the impacts of marine aquaculture cannot
easily be drawn because the impacts depend on the finfish and
shellfish species, culture methods, stocking densities, feed types,
site hydrographic properties, operational and management practices,
and other variables involved. However, key environmental concerns
- Accumulation of organic waste (fish faeces and uneaten fish
feed) and mass mortalities resulting in localised but profound
water quality deterioration and changes to benthic (seabed)
communities, biodiversity and nutrient balances.
- Introduction and spread of diseases and parasites from farmed
fish to wild populations and vice versa.
- Chemical usage, including antibiotics and other chemotherapeutants
used to prevent and treat diseases and parasites in farmed fish,
and pesticides (antifoulants) used to prevent biofouling of
net cages and other submerged structures, leading to toxicity
and bioaccumulation of persistent chemical residues in the food
- Accidental introductions (escapes) from fish farms, including
of non-indigenous (also called new, novel, exotic or alien)
species and strains and genetically modified (transgenic) fish,
and subsequent interbreeding and transfer of undesirable genetic
traits to wild populations.
- Ecological interactions between marine aquaculture operations
and co-occurring wild species, including protected bird species,
seals and other predators.
- The use of "industrial fishing" to provide large
quantities of often contaminated fish feed for farmed fish,
and the net loss of protein in the global food supply because
it takes between 2.5-5kg of wild fish to grow 1kg of farmed
- The welfare of intensively farmed fish, which has implications
for human health.
- Spatial conflicts with other sea and coastal resource user
groups, such as fisheries, offshore wind farming, angling and
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