Fisheries and Aquaculture: Eutrophication (Algal Blooms)


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Eutrophication occurs due to nutrient loading which can arise from a number of different sources both natural and *anthropogenic. The increase in nutrients (in particular phosphates, and in the case of salt water environments, nitrogen) lead to the overgrowth of aquatic plants and algae. The subsequent decomposition of those plants and algae consumes oxygen and depletes dissolved oxygen levels within localized environments overall. Algal blooms also reduce sunlight access which is necessary to regulate oxygen levels through photosynthesis. These depletions in available oxygen can have adverse effects on biodiversity as it can lead potentially hypoxic or anoxic ‘dead zones’ causing die-offs of plants in littoral zones (Chislock et al. 2013) and increased mortality in marine organisms. Algal blooms therefore impact on localized marine environment food-webs as well as water visibility and quality.


While eutrophication occurs naturally over centuries as bodies of water age, human activity has accelerated this process due to:

  • Soil retention (nutrient loading cased by human activity)
  • Industrial run-off (chemicals may enter water)
  • Domestic run-off (use of detergents)
  • Agricultural run-off (leaching of nutrients from fertilizers)



Fertiliser and water run-off (WWW1)

Algal blooms are of particular danger to sessile, benthic organisms, such as anemones and corals, which do not have the ability to move to an area with higher oxygen levels. Also known as red tides, these blooms occur almost annually around the Irish coast, even in areas free from industrial influence like Lough Hyne Marine Reserve (Jessopp et al., 2007). Many of these red tides also contain harmful toxins that can become airborne, causing health complications in humans and animals alike (Watkins et al., 2008). These toxins can also bio-accumulate in filter feeding organisms, like mussels, which is what causes neurotoxic shellfish poisoning, a disease caused by the consumption of contaminated shellfish.


Localised eutrophication is also a cause for concern when it comes to fish farms in shallow bays and estuaries, especially when it comes to sensitive habitats like the maerl beds located in Casteltown Bearhaven (Hession et al., 1998). With aquaculture facilities, of both finfish and molluscs being found in Bantry Bay, Dunamanus Bay, Roaringwater Bay, Baltimore Harbour, and in the areas around Sherkin Island, this has the potential to become a major threat to the marine ecosystem. However, due to the EC’s Water Framework Directive (WFD), this issue is becoming less prevalent.

Seán & Orla-Peach





*Anthropogenic: environmental pollution and pollutants originating in human activity (i.e. agricultural/domestic/inductrial run-off of detergents and fertilizers)

** Sessile Organisms: Organisms that are fixed in one place; immobile.

*** Benthic Organisms: Organisms that occur in the lowest level of a body of water


Chislock, M. F., Doster, E., Zitomer, R. A. & Wilson, A. E. (2013) Eutrophication: Causes, Consequences, and Controls in Aquatic EcosystemsNature Education Knowledge 4(4):10

WWW1 – Fertiliser run-off 

Siltflux Literature Review


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New EPA Research Report: SILTFLUX Literature Review has been released as part of the EPA Research Programme 2014–2020. The programme was financed by the Irish Government and administered by the Environmental Protection Agency, which has the statutory function of co-ordinating and promoting environmental research. This report focuses on the key issues that affect the role of fine sediment in bodies of water  in areas of Northern Europe, the UK and Ireland. It provides a comprehensive explanation of fine sediment morphology, routes of entry, and potential environmental impacts.

As part of our Deep Maps Pollution Series we discussed the role of resuspended sediments and water turbidity in the mortality of marine organisms. To learn more, visit:

Pollution Series: Resuspension of Sediments 


Fisheries and Aquaculture: Seaweed/Algae Mariculture


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Initially focused in Asia, this industry has been increasingly more prevalent in Western Europe, including Ireland. Currently 44% of all aquaculture is algal aquaculture (FAO, 2002). At present, algae is used in the food, cosmetics, pharmaceuticals, fertiliser, filtration, and animal fodder industries, with 90% of all commercial algae sourced via aquaculture (Walsh and Watson, 2011). However, Ireland has a long history of harvesting algae for use in fertiliser (Verling 1990, 40), food and the production of pottery and glass as far back as the 12th Century (Guiry, 2010).

Evidence for gathering and consumption of seaweed is present in historical texts, literature, art-historic sources, and in the Irish oral tradition (see O’Murchu 2002; Verling 1986, 40; Irish Folklore Commission). One of the earliest textual references we have for the harvesting of seaweed in the Irish tradition comes from the poem ‘Buain Duilsigh’ which was written by an anonymous Irish monk in the 12th century.

Buain Duilisg

Seal ag buain duilisg do charraig
seal ag aclaidh
seal ag tabhairt bhidh do bhoctaibh
seal i gcaracair.

A while gathering dillisk from the rock
a while fishing
a while giving food to the poor
a while in a cell.

Once harvested seaweed could be eaten as food or taken in folk tonics and cures. Sleabhac (Porphyra dioica) for example was believed to be an aphrodisiac and a treatment for gout, while dilisk was ingested to eliminate worms and to remedy ‘women’s longing’ (WWW1). Seaweeds such as kelp were also burned in features known as kelp kilns to reduce the organic material to ash containing potash and soda. This material could then be be used in the glazing of pottery, and the production of glass and soap (ibid). Evidence also exists for the harvesting of seaweed for consumption during the famine and as a source of fertiliser when no manure was to be had (Verling 1986, 40).

Currently, with over 500 species of seaweed identified along Ireland’s coastline, the Irish algae industry has a value of €18 million per annum (Morrissey et al., 2011), and is expected to reach €30 million per annum by 2020 according to the Sea Change Strategy (2006). Despite being under similar constraints as fish farming, the industry continues to boom. Annually, Ireland produces over 36,000 tonnes of algae (Walsh and Watson, 2011) through culturing facilities, such as the Roaringwater Bay Sea Vegetable Company.

In 2004, BIM set up a pilot scale hatchery to develop techniques in growing various kelp species as part of a broader bord of works investigating the potential of farming seaweed in Ireland, with a preliminary focus on Atlantic Wakame (Alaria esculenta). This work was based at the Daithi O Murchu Marine Research Station on Sheeps Head Peninsula in West Cork. Advances in the techniques for the hatchery and ongrowing, particularly of kelp and dulce (Palmaria palmata), will lend to a further increase in this industry in Ireland, providing, not only additional income and employment, but also a whole range of new marine based products.

To learn more about the different types of seaweed along Ireland’s coastline see the Irish ‘Macroalgae Factsheet‘, or watch last weeks episode of EcoEye, where Anja Murray investigates the potential pressures the recently awarded licence for mechanised seaweed harvesting in Bantry Bay may have on coastal marine ecosystems and their importance to ocean life.

Seán & Orla-Peach


*Mariculture: Branch of aquaculture involving the cultivation of marine organisms for food and other products in the ocean, tanks, ponds or raceways which are filled with seawater.


FAO (2002) The state of world fisheries and aquaculture, FAO, Sofia.

Indergaard, M. and Minsaas, J. 1991 2. Animal and Human Nutrition. in Guiry, M.D. and Blunden, G. 1991. Seaweed Resources in Europe : Uses and Potential. John Wiley & Sons.

Guiry, M (2010). ‘History of Seaweed in Ireland’. In ‘World Seaweed Resources’, UNESCO. Ed. A.T. Critchley, M. Ohno. D.B. Largo.

O’Murchu, T. (2003) Beara woman talking : the lore of Peig Minahane, folklore from the Beara Peninsula, Co. Cork /Collected by Liam Ó Murchú ; edited, arranged and translated by Martin Verlag. Mercier Press, Cork.

Morrissey, K., O’Donoghue, C., & Hynes, S. (2011). Quantifying the value of multisectoral marine commercial activity in Ireland. Marine Policy, 35(5), 721–727.

Sea Change (2006). A Marine Knowledge, Research and Innovation Strategy for Ireland, 2007-2013. Marine Institute. 172pp.

Walsh, M., & Watson, L. (2011). A market analysis towards the further development of seaweed aquaculture in Ireland. Irish Sea Fisheries Board, Dublin, Part 1, 1– 48

WWW1 – Heritage Council Seaweed Poster 

WWW2 – Irish Folklore Comission: Seaweed – Wexford

WWW3 – Irish folklore Comission : Seaweed – Donegal

Fisheries and Aquaculture : Need for Space


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With the growing pressures on the global fisheries to provide more and more product than is readily available, the aquaculture or mariculture industry has become more and more prominent in recent years. However, there are many constraints placed upon aquaculture that can become issues for the coastal communities involved in aquaculture production. One such constraint is the need for space, which in turn is effected by an  understanding of the life-cycles and processes of the organisms in question and also public perception.

The Real Map of Ireland.jpg

‘The Real Map of Ireland’ outlines the extent of  Ireland’s marine territory (WWW1)

The Need For Space

Marine organisms require the water in which they live to have the proper physical and chemical parameters to yield large, healthy individuals. Such conditions are very difficult to maintain in ponds or tanks due to the requirement for complex water treatment systems and filtering devices to remove potentially toxic materials and natural wastes. Most attempts to raise marine organisms on a large scale involve significant economic investment to maintain water quality. For example, in Co. Cork, the largest finfish species to be farmed is salmon, with 3,467 tonnes produced annually. This demands for a high usage of physical space, be it in cages, tanks or ponds, where regulations and biological information, constrains the number of individual fish per until area, in order to produce commercially viable product (Theodouru, 2002). Further to this, these sites may require zoning in close proximity to freshwater resources for the treatment of diseases such as Amoebic Gill Disease as we discussed in last week’s blog post.


AGD present in gills of Atlantic Salmon (WWW2)

Complexity of Life Cycles

Many marine organisms go through a complex series of larval stages, each requiring different surrounding conditions and food requirements prior to reaching marketable size. To rear each form successfully is often costly, challenging and even not currently possible in captivity. This has led to the importing of young fish into the aquaculture industry, which brings with it, its own potential dangers. This introduction of “foreign” individuals is seen to be one of the primary threats to native biodiversity around the world (Bax et al., 2003). Invasive species can take the form of microbial life, fish pathogens, juvenile invertebrates, molluscs, crustaceans, and fish, each of which is capable of creating immense damage through biofouling cages and other structures. An example of this can be seen in the intentional distribution of the Pacific oyster (Crassostrea gigas) which can dominate native species and destroy local habitats (Molnar et al. 2008; WWW3). With the developing understanding, stemming from scientific research, these risks are being minimised, but are still a long way off from being totally closed cycles with the aquaculture industry.


Map of harmful invasive species by ecoregion (Molnar et al. 2008, 488)

Public Perception

One issue facing the aquaculture industry is that of public perception. Anecdotally, fish cages and mussel/algae lines have been described as “unsightly” and can affect the aesthetic beauty of an area. Complaints have also been made about unpleasant odours and water contamination arising from aquaculture practices, which can all have a detrimental effect on tourism and for the local community. Artisanal and recreational fishermen have also registered complaints with groups like “Save Bantry Bay”, about infringement on traditional fishing grounds (WWW4).


Marine Harvest salmon farm in Northern Ireland (WWW5)

Ireland’s coastline, which has been traditionally interpreted or perceived as a common property resource, plays host to several competing industries and sectors both commercial and recreational. Because of this, Ireland’s waterways are put under increasing pressures which has lead the European Union (EU) and its member states to move towards ‘Ecosystem Based Fisheries Management to balance food production and security with wider ecosystem concerns”(Tidd et al. 2015). Since 2008, the EU has placed the responsibility on member states to establilsh a set of common principles, referred to as ‘Maritime Spatial Planning’ which operate withing the  Marine Strategy Framework Directive, in order to to (ibid.):

  • manage *anthropogenic activities in space and time
  • preclude an minimise conflicts between competing sectors without negatively impacting the ecosystem

It is hoped that these spatial strategies will mitigate many of the issues surrounding the aquaculture industry and zonal allocations.

Seán & Orla-Peach

*Anthropogenic – (chiefly of environmental pollution and pollutants) originating in human activity


Bax, N., Williamson, A., Aguero, M., Gonzalez, E., & Geeves, W. (2003). Marine invasive alien species: A threat to global biodiversity. Marine Policy, 27(4), 313–

Clarke, M., Farrell, E.D., Roche, W., Murray, T.E., Foster, S. and Marnell, F. (2016) Ireland Red List No. 11: Cartilaginous fish [sharks, skates, rays and chimaeras]. National Parks and Wildlife Service, Department of Arts, Heritage, Regional, Rural and Gaeltacht Affairs. Dublin, Ireland.

FAO (2002) The state of world fisheries and aquaculture, FAO, Sofia.

Molnar, J.L., Gamboa, R.L. Revenga, C. & Spalding, M.D. (2008) Assessing the global threat of invasive species to marine biodiversity. Frontiers in Ecology and Environment 6(9): 485–492,

Theodorou, J.A. (2002). Current and future technological trends of European seabass– seabream culture. Reviews in Fisheries Science, 10, 529–543.

Tidd, A.N., Vermard, Y., Marchal, P., Pinnegar, J., Blanchard, J.L.&  Milner-Gulland, E.J. (2015) Fishing for Space: Fine-Scale Multi-Sector Maritime Activities Influence Fisher Location Choice. PLoS ONE 10(1)

WWW1 – INFOMAR – Marine Institute

WWW2 – Amoebic Gill Disease

WWW3  – Pacific Oyster (Crassostrea gigas)

WWW4 – Save Bantry Bay 

WWW5 – Marine Harvest

Fisheries and Aquaculture: Spread of Disease


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One major constraint is the spread of disease within an aquaculture facility. Pathogens can be introduced from natural sources or through the introduction of new individuals to farm stocks. These animals have also been known to escape, spreading disease to wild populations. When animals are confined to a relatively small space, it is common for diseases and parasites to proliferate and spread rapidly. In Irish salmon farms, outbreaks of Amoebic Gill Disease (AGD) have become more and more frequent in recent years (Palmer et al., 1997). AGD is caused by Neoparamoeba perurans, and attacks the gills of farm raised salmonoid fish, eventually drowning them, and has led to mass mortality across the industry (Ruane and Jones, 2013). Most notably its effects have been recorded in Tazmania, Australia, and Washington, USA, however it has also been recorded in Chile, Norway, Scotland and Ireland.


Marine Harvest salmon farm in Northern Ireland (WWW1)

AGD is identified in commercial farms by utilising a ‘gross gill score’ field evaluation methodology which established the presence and severity of the disease in farmed fish stocks. AGD appears in the early stages of growth at sea subsequent to being moved from freshwater hatcheries to open net sea cages, with symptoms presenting as (WWW2 & 3):

  • Mucoid patches
  • Hyper-plastic lesions
  • Flared operculae and gasping
  • Fish may also appear higher in water column

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Once identified, infected fish stocks can be treated with 2-3hr freshwater bath. Access to freshwater resources may therefore be a key consideration in the planning and development of farmed fishing facilities and may be hindered by restrictions that will be discussed in next week’s blog post “Aquaculture: Need for Space”. Hydrogen peroxide has also been effective in treating symptoms and is a common method used in Ireland (Adams et al., 2012).

Additional environmental impacts have been observed due to fish farming facilities in the form of sea lice infestations on trout stocks. Current research conducted by Inland Fisheries Ireland and Argyll Fisheries Trust (Scotland) suggest that trout caught in close proximity to farmed salmon stock have a higher incidence of sea lice than those caught elsewhere. These results were based on an assessment of lice infestation of 20,000 trout over a 25 year period across  94 river and lake systems in both Ireland and Scotland. Increased levels of sea lice lead to:

  1. increased mortality
  2. reduced body condition
  3. changed migratory behavior

Lice infested sea trout (Shephard et al. 2016, 597)

Salmon farming facilities operate in Bantry Bay, Co. Cork, Roancarrig, Bantry Bay, Co. Cork, with an additional site proposed by Marine Harvest for Shot Head (near Trafrask, Adrigole), Bantry Bay, Co Cork. The licence for this development was approved in 2016 however the Aquaculture Licence Appeals Board (ALAB) will be holding an open discussion on the proposed developments in the coming months (date TBC) in West Cork to address any concerns or queries.

Influence of pathogen spread is also seen in the culture of the Pacific oyster in Co. Cork. This species has shown an increase in production (7%) since 2014 (WWW3), but has the potential to crash due to the spread of disease, which has been shown to give rise to mass mortalities across the UK, France, Spain and Ireland (EFSA, 2009). Financial losses due to these mortalities can have profound effects on the dozens of aquaculture employees in Co. Cork alone, not least the value of the product to the Irish economy as a whole.

Seán & Orla-Peach


Adams, M. B., Crosbie, P. B. B., & Nowak, B. F. (2012) Preliminary success using hydrogen peroxide to treat Atlantic salmon, Salmo salar L., affected with experimentally induced amoebic gill disease (AGD). Journal of Fish Diseases, 35: 839–848.

EFSA (2009) Scientific Opinion of the Panel on Contaminants in the Food Chain on a request from the European Commission on Marine Biotoxins in Shellfish – Summary on regulated marine biotoxins. The EFSA Journal of Agricultural and Food Chemistry, 1306, 1-23.

Palmer, R., Carson, J., Ruttledge, M., Drinan, E., & Wagner, T. (1997). Gill disease associated with Paramoeba, in sea reared Atlantic salmon in Ireland. Bulletin of the European Association of Fish Pathologists, 17: 112–114

Ruane, N. M., & Jones, S. R. M. (2013). Amoebic Gill Disease (AGD) of farmed Atlantic salmon (Salmo salar L.). ICES Identification Leaflets for Diseases and Parasites of Fish and Shellfish, (Leaflet No.60), 6pp.

Shephard S., MacIntyre, C. & Gargan, P.(2016) Aquaculture and environmental drivers of salmon lice infestation and body condition in sea trout.Aquaculture Environment Interactions. Vol. 8: 597–610

WWW1 – Marine Harvest

WWW2 – Gill diseases in seawater-farmed salmon have multiple causes and lead to substantial losses.

WWW3 – Amoebic Gill Disease 

WWW4 – Inland Fisheries Ireland

Ireland Red List No. 11 Cartilaginous Fish


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A complete list of the sharks in Irish waters has just been published. ‘Ireland Red List No. 11 Cartilaginous fish [Sharks, skates, rays and chimaeras]’ presents spatial distribution and biological information pertaining to 71 species in Irish waters.


Scope of red List assessment (Clarke et al. 2016, 8)

Of those species discussed, research indicated that 6 species are ‘critically endangered’, with a further 5 assessed as ‘endangered’.


Number of Species in each of the ICUN categories following assessment (Clarke et. al 2016, 14)



Clarke, M., Farrell, E.D., Roche, W., Murray, T.E., Foster, S. and Marnell, F. (2016) Ireland Red List No. 11: Cartilaginous fish [sharks, skates, rays and chimaeras]. National Parks and Wildlife Service, Department of Arts, Heritage, Regional, Rural and Gaeltacht Affairs. Dublin, Ireland.

Fisheries and Aquaculture Series : Aquaculture


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With the growing pressures on the global fisheries to provide more and more product than is readily available, the aquaculture or *mariculture industry has become more and more prominent in recent years. Between 2002 and 2012, the farming of finfish and shellfish has been expanding at a rate of 6.1% annually, with the global industry having an estimated value of $137.7 billion (FAO, 2012). The Irish industry alone accounts for €115 million as of 2014 (BIM, 2014). This increase allows for human demand not to be limited by ocean productivity. However, there are many constraints placed upon aquaculture that can become issues for the coastal communities involved in aquaculture production. These constraints include.

The information contained in these blog series was researched and compiled by Seán MacGabhann  as part of a larger literature review looking at West Cork’s coastline, and has been edited and contributed to by Orla-Peach Power unless otherwise stated.

* Mariculture involves the cultivation of marine organisms for food in the open water (i.e. farming of oysters/salmon)


FAO (2002) The state of world fisheries and aquaculture, FAO, Sofia.

BIM (2014) Bord Iascaigh Mhara Aquaculture Survey.

Decommissioning Schemes


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Decommissioning schemes are aimed at “reducing fishing capacity, through removing vessels and licences and relieving pressures on resource stocks, allow vessel profits and resource rents to rebound, fish stocks to recover and income and wealth distribution to change through redistribution of access and compensation and transfer payments” (Holland et al. 1999). This was a well established policy tool within the Common Fisheries Policy with similar methods being applied in the preceding decade to whitefish industries in EU member states including Spain, France, the UK, Belgium and Holland (WWW1). Some of the benefits observed in implementing this policy tool are (ibid.):

  • Directly increasing economic efficiency/profitability of the remaining fleet.
  • Modernising fleets and adjusting their structure to improve competitiveness.
  • Conserving common resources or fish stocks underlying a fishery.
  • Conserving biodiversity and ecological public good.


In 2005, the Minister for the Marine commissioned a review to examine the scope and cost of the decommissioning requirements for Irish demersal and shellfish fleets in order to establish a balance between the number of fishing vessels in operation in Ireland and the available fishing stocks (White 2005). The results of the White report lead to ‘a realisation that there is no real economic future for some of the participants in these sectors unless a large proportion of the fishing capacity can be taken out so that those remaining can look forward to working in a fishing industry with good economic prospects and not dogged by one crisis after another’ (WWW2). In this regard, the report continued to highlight the need for immediate intervention in order to effect significant changes in the economic viability of Irish fishing industry.

The report indicated that many issues compounded the situation facing Ireland’s fishing industry at the time which contributed to the decision to pursue a plan for decommissioning vessels. These factors included:

  • Decline in fish stocks
  • Rising fuel costs
  • Availability of crews
  • Age of vessels
  • Safety standards
  • Technology creep

Gradual annual reduction in quotas reflective of decline in biological status of many stock (White 2002, 8)

Subsequent to this report, the Department of Agriculture, Food and the Marine introduced financial incentives for fishermen to voluntarily decommission their vessels (ibid.) and to help encourage confidence in the future of the industry. Primarily aimed at whitefish fishery vessels older than 15 years and greater than 18m, where upgrading of equipment to adhere to the new legislation was proving too costly, €11.8 million was allocated as reimbursement for participation in this scheme. In this initial scheme 25 of the 1,861 Irish vessels were removed from service, giving the crew of said vessels enough financial support to seek further training in a new field. In 2008, a second scheme was launched with a budget of €36.6 million, allowing for a further 46 of 2,022 vessels to be decommissioned. This second scheme included 1 vessel from Union Hall, 3 from Castletownbere, and 3 from Schull. These decommissions allow ships that remain in service to fish a higher quota without exceeding national Total Allowable Catch, thus making the endeavour more fiscally valuable to those reliant upon the industry. The removal of these ships from service, despite the cost of public funds, is hoped to help alleviate the biological pressures of commercial fishing the world’s oceans.

Seán  and Orla-Peach


Holland, D., Gudmundsson, E. & Gates, J. 1999. Do fishing vessel buyback programs work: a survey of the evidence. Mar. Policy, 23 (1): 47-69.

Squires, D., Joseph, J. & Groves, T. (2010)  Buybacks in Fisheries. In  R. Allen, J.A. Joseph &  D. Squires (eds.) Conservation and Management of Transnational Tuna Fisheries. Wiley-Blackwell.

White, P. (2005) Decommissioning requirements for Ireland’s Demersal and Shellfish Fleets. A report to Marine Minister, Pat the Cope Gallagher T.D.

WWW1 – Value for Money Review. Fisheries Decommissioning Schemes 2005-2008

WWW2 – Bord Iascaigh Mhara Building a Sustainable Future for Ireland’s Fleet. A Scheme to Permanently Withdraw Capacity from the Demersal and Shellfish Sectors of the Irish Fishing Fleet.

Lough Hyne – RTE Radio Documentary


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Listen into an RTE radio documentary about Lough Hyne broadcast over Christmas at:

This  broadcast featuring Neily Bohane (Dromadoon), Terri Kearney (Skibbereen Heritage Centre), Jim Kennedy (Atlantic Sea Kayaking), and our very own Deep Maps Cork Principal Investigator, Rob McAllen (UCC).

This documentary was first broadcast in 2006 and was made Nuala Hayes.

Fisheries and Aquaculture: Ghost Fishing


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Another factor that is proving financially costly to fishermen and a danger to the marine environment, is loss of, or damage to fishing gear, which can lead to ghost fishing. “Ghost fishing” can be defined as the capture of any marine organism once control of the gear has been lost by the fisherman (Brown and Macfayden, 2007).


Ghost Fishing Cycle (WWW3)

Previous studies carried out on the impact of ghost nets in deep-water gillnet fisheries suggest that it may be a significant source of unaccounted mortality for both target and by-catch species (WWW1, Part 1, 1). This was explored in the EC-funded Pilot Project “Recuperation of Fishing Nets Lost or Abandoned at Sea” that was designed to (WWW1, Part 1, 1):

  • to conduct targeted retrieval exercises of lost, discarded and abandoned nets in deep-water gillnet fisheries > 200m
  • to conduct structured surveys in order to estimate the quantity and range of ghost nets in these fisheries.

It is important to note that ghost nets are not always present due to abandonment or negligence. Lost Nets can occur due to factors and conditions otherwise outside the control of the fisherman such as adverse weather conditions and gear malfunctions. Similarly these factors and conditions can result in the abandonment of operational netting in the short-term with the intention of later recovery. Nets may also be abandoned with no intention of retrieval. According to the Food and Agricultural Organization of the United Nations (Macfayden et al., 2009) adverse weather, operational fishing factors (e.g. the cost of gear retrieval), illegal, unregulated and unreported fishing, vandalism/theft, and access to, and, cost and availability of onshore collection facilities are all factors in the loss and damage of fishing gear.


Grey seal entangles in fishing net on the North Sea Coast (WWW4)

In this comprehensive report, Macfayden et al. (2009) go on to mention that *gillnets, **trammell nets and pots/traps have a high ghost fishing potential (Macfayden et al. 2009, 55) while other gear, such as trawls and longlines, are more likely to cause entanglement, and habitat damage. This means that lost nets or traps can continue to catch and kill a wide range of marine life. Incidents of ghost fishing in Irish waters are relatively low due to disciplined maintenance of gear by Irish fishermen (Brown and Macfayden, 2007). However, there have been reports of damage being done to nets, particularly by seals, which can put further financial pressures on the Irish commercial fishing industry (Cronin et al., 2014).


*Gillnet – is a wall of netting that hangs in the water column and is typically made of monofilament or multifilament nylon. Mesh sizes are designed to allow fish to get only their head through the netting,thus trapping the fish’s gills in the mesh as it tries to back out of the net (Image credit – Macfayden et al. 2009, 16 – 17) .

**Trammel Net – is a variation on the gillnet. It consists of three layers; two outer large mesh layers and a central net with finer mesh size. when caught, a fish pulls the smaller net through the larger outer nets trapping it (Image credit – Macfayden et al. 2009, 17-18).

Seán  and Orla-Peach


Brown, J., & Macfadyen, G. (2007). Ghost fishing in European waters: Impacts and management responses. Marine Policy, 31(4), 488–504.

Macfayden, G., Huntington, T., & Cappell, R. (2009). Abandoned, lost or otherwise discarded fishing gear. FAO Fisheries and Aquaculture Technical Paper, 115

WWW1 – Deep Clean Survey Part 1 and Part 2

WWW2 – Deepwater Ghost-Fishing problem Eases. Marine Institute

WWW3 – Olive Ridley Project

WWW4 – Ghost Nets Threaten Marine Wildlife