About 580 aquatic species are currently farmed all over the world, according to the UN Food and Agriculture Organisation (FAO), which says it is "practised by both some of the poorest farmers in developing countries and by multinational companies".

Increasing global demand for protein through seafood is driving increasing demand for aquaculture, particularly given the pressures on certain commercially caught wild stocks of fish. The FAO says that "eating fish is part of the cultural tradition of many people and in terms of health benefits, it has an excellent nutritional profile, and "is a good source of protein, fatty acids, vitamins, minerals and essential micronutrients".

Aquaculture now accounts for 50 per cent of the world's fish consumed for food, and is the fastest-growing good sector.

China provides over 60 per cent of the world's farmed fish. In Europe, Norway and Scotland are leading producers of finfish, principally farmed salmon.

For farmed salmon, the feed conversion ratio, which is the measurement of how much feed it takes to produce the protein, is 1.1, as in one pound of feed producing one pound of protein, compared to rates of between 2.2 and 10 for beef, pork and chicken. However, scientists have also pointed out that certain farmed fish and shrimp requiring higher levels of protein and calories in feed compared to chickens, pigs, and cattle.

Tilapia farming which originated in the Middle East and Africa has now become the most profitable business in most countries. Tilapia has become the second most popular seafood after crab, due to which its farming is flourishing. It has entered the list of best selling species like shrimp and salmon.

There are 278 aquaculture production units in Ireland, according to Bord Iascaigh Mhara (BIM) *, producing 38,000 tonnes of finfish and shellfish in 2019 and with a total value of €172 million

There are currently almost 2,000 people directly employed in Irish aquaculture in the Republic, according to BIM.

BIM figures for 2019 recorded farmed salmon at almost 12,000 tonnes, valued at €110 million; rock oysters reached 10,300 tonnes at a value of €44 million; rope mussels at 10,600 tonnes were valued at €7 million; seabed cultured mussels at 4,600 tonnes were valued at €7 million; "other" finfish reached 600 tonnes, valued at €2 million and "other" shellfish reached 300 tonnes, valued at €2 million

Irish aquaculture products are exported to Europe, US and Asia, with salmon exported to France, Germany, Belgium and the US. Oysters are exported to France, with developing sales to markets in Hong Kong and China. France is Ireland's largest export for mussels, while there have been increased sales in the domestic and British markets.

The value of the Irish farmed finfish sector fell by five per cent in volume and seven per cent in value in 2019, mainly due to a fall on salmon production, but this was partially offset by a seven per cent increased in farmed shellfish to a value of 60 million euro. Delays in issuing State licenses have hampered further growth of the sector, according to industry representatives.

Fish and shellfish farmers must be licensed, and must comply with regulations and inspections conducted by the Sea Fisheries Protection Authority and the Marine Institute. Food labelling is a function of the Food Safety Authority of Ireland. There is a long backlog of license approvals in the finfish sector, while the Department of Agriculture, Food and Marine says it is working to reduce the backlog in the shellfish sector.

The department says it is working through the backlog, but notes that an application for a marine finfish aquaculture licence must be accompanied by either an Environmental Impact Statement (EIS) or an Environmental Impact Assessment Report (EIAR). As of October 2020, over two-thirds of applications on hand had an EIS outstanding, it said.

The EU requires member states to have marine spatial plans by 2021, and Ireland has assigned responsibility to the Department of Housing, Planning and Local Government for the National Marine Planning Framework (NMPF). Legislation has been drawn up to underpin this, and to provide a "one stop shop" for marine planning, ranging from fish farms to offshore energy – as in Marine Planning and Development Management Bill. However, the Department of Agriculture, Food and Marine confirmed last year that it intends to retain responsibility for aquaculture and sea-fisheries related development – meaning fish and shellfish farmers won't be able to avail of the "one stop shop" for marine planning.

Fish and shellfish health is a challenge, with naturally occurring blooms, jellyfish and the risk of disease. There are also issues with a perception that the sector causes environmental problems.

The industry has been on a steep learning curve, particularly in finfish farming, since it was hailed as a new future for Irish coastal communities from the 1970s – with the State's Electricity Supply Board being an early pioneer, and tobacco company Carrolls also becoming involved for a time. Nutrient build up, which occurs when there is a high density of fish in one area, waste production and its impact on depleting oxygen in water, creating algal blooms and "dead zones", and farmers' use of antibiotics to prevent disease have all been concerns, and anglers have also been worried about the impact of escaped farmed salmon on wild fish populations. Sea lice from salmon farmers were also blamed for declines in sea trout and wild salmon in Irish estuaries and rivers.

BIM says over 95% of all salmon farmed in Ireland are certified organic. Organically grown salmon are only fed a diet of sustainable organic feed. They are also raised in more spacious pens than traditional farmed salmon. The need to site locations for fish farms further out to sea, using more robust cages for weather, has been recognised by regulatory agencies. There is a move towards land-based aquaculture in Norway to reduce impact on local ecosystems. The industry says that antibiotic use is declining, and it says that "safe and effective vaccinations have since been developed for farmed fish and are now widely used". Many countries are now adopting a more sustainable approach to removing sea lice from salmon, using feeder fish such as wrasse and lumpsucker fish. Ireland's first lumpsucker hatchery was opened in 2015.

BIM says over 95% of all salmon farmed in Ireland are certified organic. Organically grown salmon are only fed a diet of sustainable organic feed. They are also raised in more spacious pens than traditional farmed salmon. The need to site locations for fish farms further out to sea, using more robust cages for weather, has been recognised by regulatory agencies. There is a move towards land-based aquaculture in Norway to reduce impact on local ecosystems. The industry says that antibiotic use is declining, and it says that "safe and effective vaccinations have since been developed for farmed fish and are now widely used". Many countries are now adopting a more sustainable approach to removing sea lice from salmon, using feeder fish such as wrasse and lumpsucker fish. Ireland's first lumpsucker hatchery was opened in 2015.

Yes, as it is considered to have better potential for controlling environmental impacts, but it is expensive. As of October 2020, the department was handling over 20 land-based aquaculture applications.

The Irish Farmers' Association has represented fish and shellfish farmers for many years, with its chief executive Richie Flynn, who died in 2018, tirelessly championing the sector. His successor, Teresa Morrissey, is an equally forceful advocate, having worked previously in the Marine Institute in providing regulatory advice on fish health matters, scientific research on emerging aquatic diseases and management of the National Reference Laboratory for crustacean diseases.

BIM provides training in the national vocational certificate in aquaculture at its National Fisheries College, Castletownbere, Co Cork. It also trains divers to work in the industry. The Institute of Technology Carlow has also developed a higher diploma in aqua business at its campus in Wexford, in collaboration with BIM and IFA Aquaculture, the representative association for fish and shellfish farming.