The main marine finfish species currently farmed in Ireland are the salmonids, the Atlantic salmon (Salmo salar) and, to a lesser extent, the rainbow or sea trout (Oncorhynchus mykiss). Meanwhile, the shellfish farming sector is dominated by extensive cultivation of native blue mussels (Mytilus edulis), native/flat oysters (Ostrea edulis), and non-native Pacific oysters (Crassostrea gigas).
In recent years there has been a growing interest in the culturing of non-salmonid marine finfish species and alternative shellfish species (including molluscs, crustaceans and echinoderms), as well as exotics such as seahorses. Whether native or non-native, such species are known as novel or new species in marine aquaculture.
Considerable research and development effort has been expended on extending the range of marine finfish species that can be farmed commercially. For example, small quantities of turbot (Scophthalmus maximus) [1] and halibut (Hippoglossus hippoglossus) have been produced in land-based facilities on Cape Clear Island, Co Cork.
Trials conducted in Norway, Scotland, Canada and the USA to cultivate novel temperate water species such as Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and hake (Merluccius merluccius) are poised to spread to Ireland. The high level of interest in the commercial production of cod means it is likely to soon become a reality.
The culture of such species brings with it the risk of unforeseen problems. Experience from salmon farming shows how many unexpected impacts, such as diseases and negative interactions with natural populations, can arise. It is noticeable that in reviewing the published literature concerning the commercial farming of these "new" marine fish species, much is known about the husbandry, economic and marketing aspects of their culture — but limited consideration seems to have been given to the relative sustainability and likely environmental footprint of these developments. Detailed environmental assessments should be regarded as absolutely vital before commercial production units are licensed.
Berry and Davison 2001
Some potential novel marine species are non-native. While the intentional introduction of non-breeding "alien" species such as the Pacific oyster (Crassostrea gigas) from Japan has been relatively benign — at least directly — there is a risk of accidentally introducing and transferring associated non-target "hitchhiker" species. The cultivation of the Pacific oyster, for example, has resulted in the introduction of the invasive Sargassum muticum seaweed into many parts of Europe and North America. (See Introduced Species for more details on introductions and transfers of marine organisms).
Projects aimed promoting species diversification in marine aquaculture are supported and subsidised at both the EU level, under the umbrella of the Common Fisheries Policy (see EU policy on introductions), and the national level by the Irish Government.
It is Irish Government policy to support the "diversification into novel species" by funding marine aquaculture projects — particularly small-scale projects in a pilot development phase prior to full-scale commercial development — under the Aquaculture Development Measure of the National Development Plan (NDP) 2000-2006. The grant aid is administered through Bord Iascaigh Mhara/Irish Sea Fisheries Board (BIM), apart from in Gaeltacht areas where Údarás na Gaeltachta has funding responsibility, with technical assistance provided by the Marine Institute, often via university research institutes.
In 2001, the then Minister for the Marine and Natural Resources, Frank Fahey TD, made available an extra 5% funding under the Aquaculture Development Measure as an incentive to projects concerning novel species developments. The Minister also established the Irish Aquaculture Working Group on New Species Development (NSD). The NSD Group was tasked with identifying suitable new species for fish farming and with drawing-up an integrated plan of action for the Irish aquaculture industry to facilitate and accelerate the commercial cultivation of novel species in the short-term, within the framework of the EU co-funded aquaculture grants scheme. In May 2002, the NSD Group's report identified turbot (Psetta maxima), halibut (Hippoglossus hippoglossus) and Atlantic cod (Gadus morhua) as key species with potential for development by the industry (IntraFish 2002).
The most recent round of grant aid for aquaculture projects — including projects concerning development of new species — under the Aquaculture Development Measure, totalling €13.3 million, was announced in July 2006. Minister of State at the Department of Communications, Marine and Natural Resources, John Browne TD, stressed the importance of diversifying into new species to underpin future growth in Irish aquaculture (NDP 2006).
In September 2001, BIM held a conference to discuss the potential for cod farming in Ireland given the gap between demand and supply created by falling wild catches due to overfishing. The conference heard from a number of international speakers with a track record in farming Atlantic cod (Gadus morhua) and other whitefish species. Delegates heard that in Newfoundland, intensive mass production of cod fry is now a reality, enabling development of industrial scale cod farming, and that most of the current salmon farming technology is directly transferable to cod farming. Dr Reid Hole, head of the Nutreco Aquaculture Research Centre in Norway, predicted that the annual production of intensively farmed cod in Irish waters could be between 5,000 and 10,000 tonnes within a decade, with haddock and halibut to follow. Dr Hole introduced the concept of "dedicated industrial marine aquaculture parks", instead of separate production operations far removed from one another (IntraFish 2001a).
In Norway, and to a lesser extent Scotland, there has been substantial investment put in fast-tracking the development of cod farming. In its 2003 analysis, BIM points to the cost of juveniles and reliability of stock performance as being major hindrances to development in Ireland. "Given the head start that our competitors already have, our studies indicate that production costs will have to be significantly reduced to make the cod farming sector commercially viable in the longer term, particularly if there is any recovery in the volume of the wild catch" (BIM 2003).
Cod farmers may find it more difficult to keep production costs down initially as juvenile production is still a technical bottleneck (problems include early survival, physiology, nutrition and aggression) and is costly. However, one must assume that these problems will be overcome with increasing knowledge and economies of scale.
BIM 2003
Ireland's first cod hatchery
Between 2002-2005 a research project entitled "Investigations into the
hatchery rearing of cod (Gadus morhua) in Irish conditions" was undertaken
at the Martin Ryan Institute (National University of Ireland, Galway) marine
research laboratories in Carna, Connemara. The specific objective was to "identify
and harness potentially exploitable research and technology so as to enable
the establishment of a commercially viable cod hatchery in Ireland". With
€600,000 of State grant aid delivered through Údarás na Gaeltachta,
the project to pilot the commercial scale production of juvenile cod resulted
in the establishment of Ireland's first custom-built hatchery to rear juvenile
cod and other whitefish species including haddock, hake and halibut (Galway.Net
2003).
Can cod farming impact wild cod stocks?
In contrast to salmonid farming, with cod farming the whole lifecycle takes place in seawater. This will in most cases increase the environmental effects of cod farming compared to that of salmon and trout farming. Potential environmental impacts arise particularly from diseases and parasites, with possible transfer to wild fish, and from genetic and ecological interactions between farmed cod and wild stocks.
In Norway there has been some conflict between fishermen and fish farmers concerning whether or not a cod farm can have an impact on local coastal cod stocks. Theoretically, there are several ways in which this can happen, including the release of nutrients and chemicals, and use of artificial light, which could have a potential impact on local wild cod stocks. Experiments conducted in 2003 indicate that cod actually avoid seawater that has been "used" by farmed fish.
Escaped farmed cod
Experience from cod farming in Norway shows that cod exhibit a different behavior when in the cage, and are much more adaptive to escaping than are salmon or trout (Fiskeriforskning 2004). Research reveals that the chances of caged cod escaping are ten times higher than that of salmon. This is because a cod stays close to the net where it will quickly see any hole that forms and then escape. In addition, cod have been shown to chew on the net, and can actually make holes through which to escape.
WWF-Norway 2005 (edited)
Like farmed salmon, farmed cod are fed with large amounts of pellets. As with salmon feed, much of this is likely to be made from fish meal and, to a lesser extent, fish oil sourced from unsustainable "industrial" fishing on wild stocks.
From the mid-1990s until 2005, turbot (Scophthalmus maximus) was farmed commercially at Cape Clear Island, County Cork, in an onshore tank facility with seawater pumped into it and re-circulated. The reported 2003 production was 60 tonnes. The Cape Clear farm is now producing non-native abalone shellfish instead. In 1999, Heffernan reported that there were three other experimental and small-scale turbot ongrowing trials: two in Cork and one at Tarbert in County Kerry.
Abalone are marine gastropods (sea snails) introduced from abroad. These molluscan shellfish are a premium-priced luxury product, and a particularly prized seafood delicacy in Japan. Many wild populations are subject to overfishing and poaching, and commercial landings have shown significant reductions worldwide since the mid-1990s. Hence there is a high level of interest in Ireland in farming them for export to Asia and ethnic markets in Europe (BIM 2003).
Abalone are macrophagous, i.e. they are grazers which feed on seaweed. They occur naturally along exposed coastlines and show preference for areas with clear oceanic water. Clear water is essential as their elaborate gills are unsuited to turbid waters where high silt loads could clog their gills. Abalone in culture require either a very sheltered environment or cultivation on sub-surface longlines as they show poor growth rates with excessive disturbance of their cages. Proper exchange of water is essential to remove waste products, as build up of waste products can also lead to reduced growth.
Heffernan 1999
There are two non-native species of interest to the Irish aquaculture industry; these are the European abalone (Haliotis tuberculata) and the Japanese or Pacific abalone (Haliotis discus hannai) [2].
The European abalone (Haliotis tuberculata), commonly called ormer, was introduced into Ireland in 1976 and 1977 from Guernsey. After a one-year quarantine period of the imported broodstock at the NUI Galway Martin Ryan Institute shellfish laboratory at Carna, the spat was released for ongrowing trials. Due to the species' preference for red seaweeds, "and the fact that the species does not particularly like the more common Irish brown seaweeds or kelps" (BIM 2003), a decision was taken to introduce the Japanese cold-water abalone Haliotis discus hannai, also called ezo awabi, to Ireland in 1986.
The Japanese species prefers kelps and can withstand lower sea temperatures than the European abalone. It has been found to grow 10% faster than the European abalone in Irish ongrowing trials. The Japanese abalone is much sought after by Japanese communities in Europe. This market-led introduction was to offer a great opportunity to Irish abalone farmers to supply this market.
BIM 2003
About 20kg (wet weight) of seaweed is required to produce 1kg of abalone (Hensey 1995 cited in Heffernan 1999). Viana et al. (1996 cited in Heffernan 1999) looked at the possibility of using silage made from fish and abalone viscera as an ingredient of abalone feed. "This proved to increase growth rates compared to a kelp based diet. However, the dangers of feeding animals their own offal is well documented for example in the transmission of BSE (Bovine spongiform encephalopathy) in cattle" (Heffernan 1999).
Due to their non-native species status, abalone spat must be supplied by hatcheries where they are grown in tanks and fed on algae. In 2003 there were three abalone hatcheries in Ireland, with more at the planning stage, employing a variety of advanced techniques to produce abalone (BIM 2003). Once grown to 10-15mm size, the spat are ready to be transferred into ongrowing units where the juveniles are grown to market size, which takes about three years.
In 2003, there were six ongrowing units (i.e. abalone farms) on the west coast of Ireland, three of which include hatchery facilities. In 2004-2005, the Cape Clear Island hatchery/land-based production unit was turned over to abalone farming following the commercial cessation of turbot farming (RTÉ 2005). BIM (2003) states:
"The units are land-based, coastal and offer little visual impact. Due to the high value of the species the volumes cultivated are small and so facilities in turn can be small. Abalone prefer warm water in the region of 15-20°C so the ongrowing units are housed in a specially insulated building with animals growing optimally at elevated temperatures using recirculation technology… The discharge or waste from a farm of this nature is also limited and unlikely to cause any impact on local ecology or habitat. As both species do not occur here naturally due to temperature limitations, there is no risk of populations establishing in the wild." [3]
However, Heffernan (1999) states that the main ecological implications of growing abalone are likely to be:
In considering the sustainable development of marine aquaculture, the Secretariat of the Convention on Biological Diversity (2004) states that: "In the case of land-based abalone culture, artificial food is used as supplement to natural feed. This requires treatment of effluents in order to reduce impacts on the natural ecosystem."
The importation of abalone for aquaculture in California in the 1980’s is believed to have resulted in the introduction of a parasitic worm, posing a significant risk to native abalone and other mollusks. The worm quickly spread among the state’s abalone farms and became established in the wild. After several years the worm was successfully eradicated, and a disease-free culture environment is currently maintained through a strict program of hatchery and interfacility transfer regulation, including inspections and periodic certification of disease free status.
SeaWeb Aquaculture Issues: Diseases and Parasites
There are two native species of sea urchin (an echinoderm) present in Ireland, the purple sea urchin (Paracentrotus lividus) and the green sea urchin (Psammechinus miliaris). Sea urchins are macrophages, i.e. they graze on algae with a preference for kelp. To survive, sea urchins require a hard solid surface, usually a rock crevice or holes, which they bore themselves, especially in limestone. In the wild they occupy sublittoral habitats from permanent rock pools at the low-tide level down to boulder strewn seabed at 30m (Heffernan 1999).
Sea urchin roe has long been considered a delicacy and urchins have been extensively fished for decades. The world production of urchins comes essentially from the wild, and Japan consumes 80% of the world's sea urchin roe production.
The sea urchin is considered a delicacy and has a high commercial value. The edible part of the animal are its gonads, and urchins are sold either live or the gonads are removed and sold separately for instance as vacuum packed or canned product. It is estimated that 80% of the world’s supply of urchins is consumed in Japan, and Japan imports from at least 13 countries on five continents. France is the main market for sea urchins in Europe… In France, urchins are considered a luxury and are not widely consumed by the public.
BIM 2003
In Ireland, research into the feasibility of culturing purple sea urchins on a commercial scale has been conducted, with support from BIM, since the late 1980s at the NUI Galway Martin Ryan Institute shellfish laboratory at Carna, Connemara.
The first commercial purple sea urchin hatchery in Ireland was established in Dunmanus, County Cork during the early 1990s. The hatchery expanded rapidly with its main focus being on the production of about 1 million juveniles per year [4]. In tandem with the development of hatchery, aquaculture licenses were acquired by several individuals for the purpose of ongrowing these juveniles in intertidal and subtidal rock pools in the south-west. The urchins grow for four years before reaching market size. In 2001, some 5 tonnes of urchins were harvested. In 2003, some 73,000 individual urchin juveniles were sold by the hatchery. Mature specimens amounting to 320kg were also sold at €3,850 per tonne. This annual harvest is expected to rise to between 50 and 80 tonnes by 2006 (BIM 2003).
BIM has stated that this will help to replenish (and otherwise remove exploitation pressure from) Ireland's wild purple sea urchin fishery, which has effectively collapsed due to overfishing and mismanagement. A reported 500 tonnes of urchins were exported annually in the 1970s, principally to the Paris restaurant market; in 2001, just five tonnes of urchins were landed. (See Purple sea urchin fishery).
Heffernan (1999) believes that the main ecological concern with sea urchin farming would be the harvesting of kelp. "As they are an overfished native species, ranching could be considered a form of restocking. This is provided the spat is sourced in Ireland from native wild stocks."
There are other concerns. BIM (2003) states: "disease identification and treatment is a particularly difficult area with little work done to determine prevention methods and possible treatments."
Understanding the mechanism of disease transfer between species is likely to be one of the main headaches for fish farmers as diversification into novel species grows, according to a top fisheries scientist Dr Ron Stagg, deputy director of the Fisheries Research Service (FRS) Marine Lab in Aberdeen, Scotland.
In August 2001, he told IntraFish news agency: "We have to be careful how we manage diversification in terms of interactions between different species. A lot of producers would like to kick-start the cod industry by growing cod alongside salmon, but we don't really understand at this point in time what the disease risks are between these two species, whether there would be the ability of some pathogens to jump between them, and what the consequences of that would be. We should be thinking about how we can proceed safely, and what sort of physical separation we should be looking for. I believe that if we anticipate problems, we're able to be strategic in our approach and deal with them sooner and more effectively."
Dr Stagg said that much of the current work in the FRS and other centres is based on looking at the area of inter-species disease transfer. "One of the big issues we're dealing with is the problem of VHS [Viral Haemorrhagic Septicaemia]. There's a very nasty strain which affects rainbow trout, which we most certainly want to control, because we have freedom from VHS in our rainbow trout industry. There are restrictions on trade with some parts of Europe that have the disease, but of course we've also discovered in recent years that there's some VHS in the marine environment. This could possibly result in infections in marine fish farms, for example in turbot, where we experienced problems in Scotland and Ireland a few years ago. There have been some recent outbreaks of VHS in the Baltic, in rainbow trout farms, so the whole question of how we manage VHS is getting difficult."
"One of the research areas we're looking at is whether there are different strains that can be distinguished," said Dr Stagg. "We know that there are pathogenic differences between strains, and that the turbot type of VHS doesn't really cause problems in rainbow trout, for example, so there seem to be different genotypes of VHS and there seem to be different levels of pathogenicity. It would be very useful to have a tool to distinguish these genotypes of VHS which cause any problems in rainbow trout but don't cause any problems in marine species and vice versa, then we may be able to have separate management regimes for them, that's one area we're quite active in" (IntraFish 2001b).
Footnotes
1. Turbot production ceased in 2005. [Back]
2. There are approximately 75 species of abalone in the world of which 22 are either currently farmed or have potential for cultivation. [Back]
3. Heffernan (1999) describes a different type of abalone ongrowing unit comprising sea-cages made from modified 250 litre barrels. The barrels are suspended from longlines, rafts or submerged longlines. The juveniles are fed seaweed through a porthole and on reaching 26mm they are ready for ongrowing in bottom-laid cages. "The cages are made from modified lobster pots and are laid in strings on the sea floor in suitable areas and are hauled to the surface for feeding and cleaning. Each string consists of 8-10 pots connected to each other by 4m lengths of leaded rope. The cages are stocked with abalone of mean size not less than 30mm as survival of smaller sized ones is lower" (Heffernan 1999). [Back]
4. Adult urchins are collected from the wild and held in tanks in the hatchery prior to spawning, which is induced by chemical or thermal stimulus in the hatchery with the aim of having simultaneous release of eggs and spermatozoids (BIM 2003). [Back]
References
Berry C. and Davison A. 2001. Bitter Harvest: A call for reform in Scottish aquaculture. Report for WWF-UK, Panda House, Weyside Park Godalming, Surrey GU7 1XR, England.
BIM. 2003. Seahorses to Sea Urchins - The next big splash in Irish aquaculture. BIM Aquaculture Development Division. (pdf 1.6Mb)
Secretariat of the Convention on Biological Diversity. 2004. Solutions for sustainable mariculture - avoiding the adverse effects of mariculture on biological diversity. CBD Technical Series No.12
DCMNR. 2006. Department of Communications, Marine and Natural Resources, Ireland. Accessed 28-08-2006.
Galway.Net. 2003. Ireland's first marine finfish hatchery established. 28-07-2003.
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.
IntraFish. 2002. Report identifies 'real potential' of cod, halibut & turbot for Ireland. IntraFish 10-05-2002.
IntraFish. 2001a. Irish to set up cod farming working group. IntraFish 13-09-2001.
IntraFish. 2001b. Disease transfer problems need to be identified. IntraFish 23-08-2001.
NDP. 2006. Funding of €13.3 million announced for aquaculture industry. Ireland's National Development Plan (NDP), 2000-2006.
RTÉ. 2005. Seascapes News Summary - 7 April 2005. RTÉ Radio 1.
WWF-Norway. 2005. On the run – Escaped farmed fish in Norwegian waters. Report 2/2005. WWF-Norway, Oslo. (pdf 2.1Mb)