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 . 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.
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
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.
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
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
Shellfish aquaculture takes place around the coast of Ireland
except, in general, on the east coast.
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
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
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.
| Table 1. Marine aquaculture
production in Ireland 1980-2002 (tonnes)
| * includes freshwater
(Bord Iascaigh Mhara)
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).
|Table 2. Aquaculture
production value 1998-2002 (€,000)
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).
| Table 3. Marine aquaculture:
Top five species produced in Ireland 2002
|Mussels (bottom and rope reared)
| Atlantic Salmon
| Rainbow Trout (sea reared)
| Native Oyster
Source: ICES 2003b
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.
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