Fish Farming in Ireland

Aquaculture is the sea or land based cultivation of marine, brackish or freshwater aquatic organisms including zooplankton, shellfish (molluscs) such as mussels and oysters, crustaceans such as brine shrimps, echinoderms such as sea urchins, finfish such as salmon and trout, and aquatic plants including seaweed and other algae [1]. Sea-based or marine aquaculture is also known as "mariculture".

Fish farming in particular is a form of intensive animal husbandry in which there is some form of intervention in the rearing process to enhance shellfish or finfish production, such as regular restocking, feeding and protection from predators.

Shellfish species

The cultivation of wild stocks of shellfish has been practised in Ireland for over a century. Extensive cultivation of native/flat oysters (Ostrea edulis) and blue mussels (Mytilus edulis) on managed natural beds is still carried out at a number of locations around Ireland. The cultivation of blue mussels on ropes — usually seen suspended between floating plastic barrels — began in the early 1970s and annual production continues to rise.

Since the late 1980s, the cultivation of native/flat oysters has declined markedly following the spread of Bonamia disease. This resulted in a shift to intensive cultivation of non-indigenous Pacific oysters (Crassostrea gigas) using hatchery-reared stocks.

Mussel cultivation in Ireland

The native blue mussel is widely distributed and adapts itself to a wide variety of ecological situations. Mussels are filter-feeders, feeding on phytoplankton and suspended organic matter, thus feeding entirely on natural food present in the water column. This reliance on a natural food source, coupled with their general sessile nature, makes them ideal for cultivation.

In Ireland, two distinct methods of mussel cultivation are practised: bottom and suspended (rope) culture.

Bottom culture, which accounts for about twice as many mussels as produced on ropes, involves the location, collection and transplantation of wild mussel spat into richer, shallower waters using a dredger. Successful on-growing of re-laid spat requires sandy shallow beds. When the mussels reach commercial size 9-18 months later, they are harvested by dredger.

For suspended culture, mussel spat is collected either directly from the water by larval settlement on pegged nylon spat ropes where they on-grow in situ, or is else scraped from the rocks during spring or early summer and fed into mesh stockings where the mussels grow until they reach market size. These mussel culture support structures are suspended in the water from either longlines or rafts in the on-growing areas. Mussel rafts are usually based around a catamaran design and consist of a set of beams strung across two flotation hulls. The mussel ropes are attached to these beams and hang down into the water.

Longlines are a more popular method due to the better overall growth rate achieved. They consist of flotation barrels that are used to support a stout double headrope from which the mussel ropes (or stockings) are suspended.

Heffernan 1999

There is increasing interest in the scallop (Pecten maximus) and queen scallop (Chlamys opercularis), and in small-scale operations for the hatchery and ongrowing of both European abalone (Haliotis tuberculata) and a Japanese species, the Pacific abalone (Haliotis discus hannai). Increasing quantities (154 tonnes in 2003) of non-indigenous Manila clams (Tapes semidecussatus or Ruditapes phillipinarum) are also cultivated.

The Manila clam is very similar to the native species, but with better growth and survival rates compared to the native species. It was first introduced to Ireland in the early 1980s. After successful trials, supported by BIM, at Martin Ryan Institute (NUI Galway) laboratory at Carna, Co Galway, commercial Manila clam seed became available in 1982.

"Growth trials set up around the country found that the best method for cultivating clams was the Parc method. This is where half grown clams are placed into the shore with netting being used to protect against predators and to hold the clams within a confined area. Suitable sites are hard to find and this has resulted in limiting its spread around the country. Production is now concentrated in the Sligo area" (Watson and Stokes 2004).

Shellfish aquaculture takes place around the coast of Ireland except, in general, on the east coast.

Finfish species

Finfish farming in Ireland began in the 1970s and finfish farms have since spread to nearly every coastal county. The first species to be commercially farmed were salmonids: rainbow or sea trout (Oncorhynchus mykiss) reared in sea cages, followed by cage production of Atlantic salmon (Salmo salar) in 1981 when 100 tonnes were marketed.

The finfish farming industry developed rapidly during the 1980s following a change from small sea cages to large pens. The 1992 production of farmed Atlantic salmon was 9,231 tonnes; a figure that grew to 22,294 tonnes in 2002. This compares to a total of 705,307 tonnes of farmed Atlantic salmon produced in the North Atlantic area in 2002, of which Norway (436,103 tonnes), Scotland (159,060 tonnes), Faroes (45,150 tonnes) and Canada (34,190 tonnes) accounted for the most (ICES 2003).

The main salmon farming areas are on the south-west, west, north-west and north coasts of Ireland.

In recent years, considerable research and development effort has been expended on extending the range of finfish species farmed and small quantities of turbot (Scophthalmus maximus) and halibut (Hippoglossus hippoglossus) are now being produced in Ireland, on Cape Clear Island, Co Cork. Trials conducted in Norway, Scotland, Canada and the USA to develop farming of new temperate water species such as Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and hake (Merluccius merluccius) are likely to spread to Ireland in the near future. (See Novel Species).

Finfish cultivation in Ireland

The natural breeding cycle of the Atlantic salmon requires spawning in freshwater, migration and growth in the sea until the sexual maturity is reached, at which point the fish returns to its parent river to spawn. This anadromous habit causes salmon farming to be divided into two separate stages, freshwater and marine, for which clean, cool, well oxygenated water is required. The complete life cycle of the salmon can be reproduced in a period of 3-4 years using intensive farming systems. The production process begins the freshwater hatchery. The fish are then transferrred to freshwater tanks or cages and here the fish mature from 'fry' to 'parr' and then to 'smolt' which is the transitional period of adaptation to sea water. After smolting, fish (aged about 17 months) are transferred into, floating net cages at sea, where market size (ranging from 2-5kg) is obtained in a period of 1-2 years.

Sea trout are much bigger than freshwater trout. They are usually grown to 1kg in a manner similar to salmon.

Halibut and turbot are currently grown in onshore facilities into which sea water is pumped; by 1999, successful trials meant that consideration was being given to using modified salmon cages for halibut production.

Heffernan 1999

Socio-economic Significance

Finfish and shellfish aquaculture operations have become an increasingly significant socio-economic activity for marginalized communities around Ireland's coasts, as reflected in the significant growth in Irish marine aquaculture production over the last two decades (Table 1). This of course goes hand-in-hand with a boom time both for the funded academic research and development (R&D) sector, and the numerous — mainly overseas — companies and corporations in the aquaculture services sector that supply everything from fish feeds to cage engineering to veterinary pharmaceuticals to product packaging.

Aquaculture is also increasingly important for the consumer. According to the Food and Agriculture Organisation of the United Nations (FAO), aquaculture now produces a third of the fish we eat, a figure that will rise to half by 2030.

In 1999 the value of marine aquaculture production accounted for one-third of the value of Ireland's total marine food output (FIS). In 2002 Irish aquaculture production (including freshwater) was some 62,686 tonnes valued at €117.4 million. Salmon production accounted for 61% of the total value (€71.7 million).

Ireland's coastal waters — already under pressure from numerous pressures such as climate change and overfishing — face a rapid, large-scale expansion of marine aquaculture activities for both shellfish and finfish species.

Annual aquaculture production is forecast to increase from around 60,000 tonnes in 2001 to just over 97,000 tonnes valued at nearly €176 million in 2008, to a staggering 160,000 tonnes in 2017 (BIM). It is likely that salmon and mussels will continue to dominate production as they did in 2002 (Table 3).

In Ireland, total employment in the marine food ("seafood") sector, which embraces all economic activities deriving from the biologically productive capacity of the seas, is around 15,720 persons (EPA 2000). Of these, aquaculture employs an estimated 2,200 persons, and fish processing some 4,000 persons, on both a full- and part-time basis (BIM). Many of these jobs are located in existing sea fisheries centres such as Castletownbere in Co Cork and Killybegs in Co Donegal. A significant number, however, are found in many small rural communities scattered around Ireland's coast, particularly in the west.

Footnote

1. In Ireland, the following interpretation of aquaculture is given in Section 3(1) of the Fisheries (Amendment) Act, 1997: "aquaculture" means the culture or farming of any species of fish, aquatic invertebrate animal of whatever habitat or aquatic plant, or any aquatic form of food suitable for the nutrition of fish.    [Back]

References

BIM. Bord Iascaigh Mhara (The Irish Sea Fisheries Board).

CSO. Central Statistics Office, Ireland. CSO Fishery Statistics 2002. (pdf 115k)

EPA. 2000. Ireland's Environment: A Millennium Report. Environmental Protection Agency. April 2000.

Heffernan M.L. 1999. A review of the ecological implications of mariculture and intertidal harvesting in Ireland. Irish Wildlife Manuals, No. 7. Dúchas, The Heritage Service, Department of Arts, Heritage, Gaeltacht and the Islands, Dublin, Ireland.

ICES. 2003. Atlantic Salmon in the North Atlantic Area. Chapter 2 of the 2003 Report of the Working Group on North Atlantic Salmon. ICES. 24/6/03.

Watson L. and Stokes A. 2004. Seahorses to sea urchins: The next big splash in Irish aquaculture. BIM Aquaculture Development Division, Bord Iascaigh Mhara, Dun Laoghaire, Co. Dublin, Ireland. (pdf 1.6Mb)