Intensive fish farming projects and are planned for Galway Bay and elsewhere - the environmental impacts could be huge

An Taisce supports the sustainable development of aquaculture, in keeping with other objectives for the relevant area. That is, aquaculture projects should be developed in a balanced manner which does not cause degradation in the area of the aquaculture facility, for example through habitat destruction, by way of habitat alteration, or by degrading water quality. In essence, any aquaculture development must ensure that local habitats, flora, fauna, and avifauna are not adversely impacted.

The marine environment is a fragile ecosystem where irreversible changes can occur if practices employed are not environmentally sensitive. Aquaculture can have negative impacts on the marine environment, including through the accumulation of waste (waste feed and faecal pellets) under fish farm cages, changes in macrofauna benthic communities, alteration of the nutrient balance within the system, reduction in gene pool strength due to escaping aquaculture stock mating with wild populations, and transmission of diseases to wild stocks. In areas where there is a large amount of aquaculture, this is likely to lead to environmental degradation as well as very poor aquaculture growth rates. Therefore, in bays where too many aquaculture projects are operating, aquaculture is likely to have detrimental effects on the yields of the different aquaculture businesses, meaning that both the marine environment as well as the aquaculture industry will suffer from over stocking. Bad aquaculture planning and management can also have negative impacts on important recreational industries such as angling and ecotourism.

Environmental Impact Assessments (EIA) should be carried out to assess the in combination effects of all aquaculture activities within each bay, rather than assessing licences on an individual basis. Annex III of EIA Directive 2011/92/EU refers to the characteristics of projects that must be considered for an EIA. Paragraph 1(b) of Annex III refers to the cumulation with other projects, indicating that cumulative impacts of aquaculture operations are an important factor for EIA purposes. EIAs should also take into account the potential impact of the aquaculture facility over its entire lifecycle, including the construction, operation and decommissioning phases of the facility.

Further, whole bay management plans ought to be developed for bays supporting aquaculture, to ensure the level of aquaculture does not exceed the carrying capacity of the bay. These management plans should set out the need for rigorous and independently informed cumulative impact assessment as part of the EIA consent process for aquaculture, together with an independent and regular monitoring system. In addition, in areas where there are a significant number of activities and anthropogenic demands and influences on a coastal zone, a Strategic Environmental Assessment should also be carried out.

Finfish aquaculture is sometimes referred to as being a key component in meeting future seafood demand. However, finfish farms for carnivorous fish, such as salmon farms, require considerable amounts of fishmeal and oil by way of feed, which is mainly produced from small, oil-rich pelagic fish. Thus, this type of aquaculture does not reduce our dependence on wild fisheries and should be taken into account during the EIA process.

Some key considerations

There are several principles which, if appropriately applied, would help to reduce the negative impacts of aquaculture activities:

1. Precautionary principle

The precautionary principle is an approach to human activity that attempts to minimise potential damage to the environment. In the present context, the precautionary principle is particularly relevant with regard to the lack of scientific certainty, in some cases, regarding the cumulative impacts of aquaculture. The precautionary principle should be applied in Ireland to ensure that an aquaculture project is not permitted unless adverse impacts of the project, in combination with other activities in the area, can be excluded. The onus should be on aquaculture developers to demonstrate beyond reasonable scientific doubt that there will not be such adverse impacts.

2. Ecosystem-based management

Aquaculture activities should be considered at an ecosystem level. “An ecosystem approach for aquaculture (EAA) is a strategy for the integration of the activity within the wider ecosystem in such a way that it promotes sustainable development, equity, and resilience of interlinked social and ecological systems.” An ecosystem-based approach should ensure that the methods used to assess and manage marine living resources are geared towards maintaining and monitoring biodiversity, productivity, and the physical and chemical properties of an ecosystem.

3. Cumulative impacts

The cumulative impacts of the multiple environmental pressures within a bay should be assessed in conjunction – i.e. the cumulative impacts from one sector should not be viewed in isolation from other environmental impacts.

4. Carrying capacity

The aquaculture within a bay should not exceed the carrying capacity of that area. "Carrying capacity" is a term used to describe the maximum average number of organisms that can be sustained so that they can survive and reproduce in the long term (i.e. without degrading the surrounding environment). The extent of aquaculture should not exceed what an area can naturally sustain and assimilate to ensure no environmental degradation.

5. Invasive species

Aquaculture should not put the environment at risk from invasive species; instead native species should preferentially be cultivated. In this regard, of particular concern is the fast growing Gigas (Pacific) oyster (Crassostrea gigas), introduced to Ireland from the Pacific, and now the main cultivated oyster species here. The Pacific oyster was originally thought to be of no threat to European wildlife as it was believed it would not spawn in our cold waters. However, this proved incorrect and the Pacific oyster is now established as an invasive alien species in Lough Swilly, Lough Foyle and Strangford Lough. Despite this, the Pacific oyster continues to be used by aquaculture businesses in Ireland, and it is now establishing “self-sustaining feral populations” here.

6. Aquaculture operations must be appropriately sited

Aquaculture operations should be appropriately sited to ensure minimal impacts. Locations should be selected not only on the basis of growing conditions, availability and accessibility, but also on the basis of environmental impacts. For example, the disturbance impacts of noise on foraging wild fauna.

The EIA process should act as a catalyst for better research into the suitability of locations for aquaculture activities within the marine environment. The process should also ensure the collection of baseline information which will help in terms of measuring and assessing any changes over time.

7. Considerations under the Habitats and Birds Directives

In addition to the need to consider any potential impacts of aquaculture on Natura 2000 sites (i.e. SACs under the Habitats Directive and SPAs under the Birds Directive), the aquaculture licensing process and subsequent monitoring processes should take account of the continuing legal obligation to avoid, in such sites, the deterioration of natural habitats and the habitats of species as well as disturbance of the species for which the areas have been designated, in so far as such disturbance could be significant. Further, in respect of species listed on Annex IV to the Habitats Directive - including otters and cetaceans, for example – it is prohibited, without a licence, to (amongst other things): deliberately capture or kill any specimen of these species; deliberately disturb these species, particularly during the period of breeding, rearing, hibernation and migration; or damage or destroy a breeding site or resting place of these animals. “Deliberately” has been interpreted very broadly by the European Court of Justice for these purposes, to include proceeding having accepted the possibility of a prohibited act being committed. Thus, it would be an offence to, for example, capture or kill an otter in an aquaculture facility (e.g. through entanglement and drowning) having accepted the possibility that this might happen.

As a more general point, in 2007 Ireland was found in breach of EU law by the European Court of Justice for failing to ensure that aquaculture projects likely to have a significant effect on Natura 2000 sites, either individually or in combination with other projects, are made subject to an appropriate prior assessment. This is a major concern which remains to be fully addressed.

Legislative reform

Ireland currently implements a disjointed 'project-by-project, permit-by-permit' approach to marine, aquaculture and coastal development. Following a recent government consultation on the subject, we are presented with an important opportunity to better integrate marine planning and development management into other sectoral policy areas including terrestrial spatial planning, river basin management, biodiversity protection and heritage conservation. With this in mind, An Taisce believes the time is right for Ireland to develop – similar to many European countries – a strategic and integrated statutory Marine Spatial Planning system.
A major undertaking such as this would also be a good time to tackle some of the detailed problems presented by aquaculture, such as the need to amend the European Communities (Birds and Natural Habitats) Regulations 2011 (SI 477 of 2011) to add the Pacific oyster to the Third Schedule, thus effectively prohibiting use of the Pacific oyster for aquaculture purposes in Ireland.

More Information: Environmental impacts from aquaculture

Shellfish aquaculture

Shellfish farming is assumed by many to be an environmentally benign industry. However, some practices have a negative impact and this may intensify given that the government’s Harnessing our Ocean Wealth plan proposes increasing aquaculture volume production by 78% by 2020. Potential negative impacts of shellfish farming include, for example, the loss of feeding areas for birds, and disturbances caused by increased human activity; some other potential negative impacts are explained below.


Nutrient Enrichment

Mussel excretions are rich in nitrates, and produce a significant amount of ammonium and phosphates. These wastes change the composition of sediments beneath. Beneath areas used for mussel cultivation is often found a black anoxic hydrogen sulphide rich mud. As a result the benthic fauna will be dominated by opportunistic species, while others will not survive. There are also often significant changes to the nutrient balance of the ecosystem resulting from mussel culture. All of these impacts tend to result in changes in species composition and community structure, sometimes dramatic changes. This is an issue which should be thoroughly examined during impact assessment processes.

Seed Harvesting

A key problem in relation to mussel fisheries has been the perceived conflict with the conservation of bird populations, since some birds feed on mussel seed stocks. Thus, bird species which may utilise areas used for mussel aquaculture could be impacted (e.g. by scaring devices). This is especially important as many mussel aquaculture sites are located within Special Protection Areas designated under the Birds Directive for the conservation of birds of conservation concern in Europe. Birds may also be disturbed through noises associated with aquaculture operations.


Invasive species

Examples of alien species which have been transported into Ireland, most likely by aquaculture, which have had a negative impact on the marine environment include the invasive seaweed Sargassum muticum and the parasitic protist Bonamia ostreae, which devastated native oyster populations in the 1970s. Currently the Pacific Oyster (Crassostrea gigas) is a major cause for concern, as set out above.

Disturbance to birds and other species

Certain aquaculture activities can have an effect on bird species. According to a study by Gittings and O’Donoghue [1], carried out in Dungarvan Bay SPA, it was found that some species of birds demonstrated a negative response to oyster trestle aquaculture; Shelduck, Ringed Plover, Lapwing, Sanderling, Dunlin, Black-tailed Godwit, Bar-tailed Godwit and Great Black-backed Gull.
The response is suggested in the study to be “a behavioural response by species where the oyster trestles interfere with their flocking behaviour”, making it difficult“for individuals in large flocks to remain in contact as they become dispersed across several lines of trestles.”

Additionally, potential disturbance in other SPAs and SACs has been acknowledged in Appropriate Assessments of some of these areas, including the potential in-combination effects of aquaculture with other activities such as recreation or development. One particular example is Inner Galway Bay, and the potential displacement of species such as Great Northern Diver and Ringed Plover due to the in-combination effects arising from additional development, such as the Mutton Island Wastewater Treatment Plan.

There is also the potential of bottom mussel aquaculture to impact on some tern species in terms of their food sources and thus potentially the productivity of the breeding colony. While some levels of disturbance have been predicted to be below the threshold for given species, more data and consideration of potential impacts are necessary. It is important to follow the precautionary principle, not only be in regard to one type of aquaculture, but also in cases where data on effects to species of cumulative effects is lacking and where it is not possible to discount potential negative impacts.

Finfish aquaculture

Finfish farming in Ireland mainly consists of salmon farming. There are a number of negative impacts associated with this type of aquaculture. Some of these impacts could be addressed by moving away from open sea cages towards closed containment systems. As the David Suzuki Foundation comments, “an increasing body of evidence shows that land-based, closed-containment aquaculture is an environmentally, technically and economically viable option to net-pen aquaculture....It's generally accepted that closed containment aquaculture has the ability to drastically reduce environmental impacts on the marine environment.”

Nutrient input

One of the main issues in finfish aquaculture relates to the output of uneaten fish food and fish faecal deposits entering the water body. This causes a decrease in available oxygen, leading to negative changes in the benthic community on the sea floor. In many cases, the output far exceeds the normal carrying capacity of these water bodies. It is therefore crucial that regular monitoring of the water body takes place prior to and after an aquaculture license is granted. This would help to ensure that negative environmental consequences are identified and addressed quickly. A recent data release by the Scottish Environmental Protection Agency (SEPA) revealed that assessments of the seabed conditions under and around fish farms in Scotland found that 44% were “unsatisfactory” (i.e. beyond the assimilative capacity of the local environment), 21% were “borderline” (i.e. close to having an unsustainable impact), while only 34% were found to be “satisfactory”.

Fish Food

Marine finfish aquaculture is heavily dependent on wild fish for use as feed, which serves to increase fishing pressure on marine fish stocks. Salmon are carnivores and pellets made from fishmeal and fish oil resources are the most commonly used food for such aquaculture. The fish used in this feed are caught from the wild and it is estimated that for each 1 kg of farmed salmon, 4 kg of wild caught fish is needed. At a time when a huge number of the world’s fisheries are overfished, it is important to ensure that the fish going into salmon food is sustainably caught by responsible operators. As salmon farming increases, there will be further pressure on these wild populations.


A further problem is the introduction and spread of disease and parasites as a consequence of aquaculture. For example, one of the most contentious issues in relation to the farming of salmon is the link between the production of sea lice on fish farms and the decline in wild sea-trout and salmon populations in the west of Ireland (and elsewhere). (It is worth noting that Atlantic salmon is an Annex II protected species under the Habitats Directive.) Research investigating this issue has been carried out in Ireland, Scotland and elsewhere. The findings of several studies suggest that sea lice from salmon farms play a major role in the collapse of wild sea-trout populations and are implicated in declines in salmon numbers. Dr. Mark Costello of the Institute of Marine Science, University of Auckland, and a Technical Consultant to Ireland’s Aquaculture Licences Appeals Board in its early years, recently intervened in this debate, e-mailing Minister Coveney to express his surprise “at some of the recent incorrect information in the media about whether sea lice from salmon farms can cause problems on wild fish”. As Dr. Costello makes clear, sea lice “have proven difficult to control on farms, especially large farms because it is difficult to treat all fish simultaneously against the parasite”; furthermore, lice emanating from farms have, Dr. Costello reports, “been linked to epizootics (mass fatal parasite infestations) on wild salmonids (salmon, trout and their relatives) in Ireland, Scotland, Norway and Canada”. Such reflections clearly have serious implications for large aquaculture proposals such as the enormous salmon farm proposed for Galway bay.

Another potential problem is the increasing resistance of sea lice to current treatments, which results in fish farmers using higher doses of chemicals to treat for sea lice. Data released by SEPA showed that there was a 110% increase in the amounts of chemicals used to treat sea lice due to increasing resistance. However, there was only a 22% increase in the level of salmon production in the same period. The chemicals used can be highly toxic to marine species such as lobsters and prawns.


The impact of escaped farmed salmon on the genetic integrity of wild stocks also poses a potential threat. A 37-year study of the influence of farmed fish on wild populations in the Burrishoole River catchment in Co. Mayo found that ‘hybrid’ Atlantic salmon showed significantly reduced survival capacity compared with wild fish.

Alternatives - Closed Containment Systems

“An increasing body of evidence shows that land-based, closed-containment aquaculture is an environmentally, technically and economically viable option to net-pen aquaculture....It's generally accepted that closed containment aquaculture has the ability to drastically reduce environmental impacts on the marine environment.” [2] Many benefits have been reported with regard to closed containment systems. Disease is one of the major considerations, as closed systems are reported to reduce or eliminate the interaction between wild and farmed fish populations, therefore preventing spread of sea lice to juvenile wild salmon. Additionally, the solid barrier of closed systems should reduce or eliminate the need for chemical and antibiotic treatment. Closed containment also facilitates the recovery of solid waste, which can be treated and composted. It is also possible for water to be recycled. With regard to inputs, due to more controlled conditions, closed systems can also use significantly less feed during shorter growing periods. A major benefit of closed systems is the elimination of the risk of escapes, which will help to protect the genetic integrity of wild populations. It also eliminates interaction with marine predators, which in turn ultimately protects those species from interference in their own habitats. The ecological footprint of open net-pen aquaculture can be significant and thus many of the issues could be mitigated by closed containment systems. The question of energy consumption arises in relation to closed containment systems and this must also be taken into consideration with regard to sustainability.


[1] Gittings, T. & O’Donoghue, P.D. (2012). The effects of intertidal oyster culture on the spatial distribution of waterbirds. Report prepared for the Marine Institute. Atkins, Cork.

[2] David Suzuki Foundation