Leading Journal of the Irish & UK Fishing Industries

“like the native oyster, the farmed oyster is not without his own human challenges. However, it is our politics, not our overindulging appetites that he suffers.”

By Alec Reid, Oyster Farmer, Donegal 

This article tells the story of a few remarkable oysters doing some incredibly important environmental conservation on the other side of the Atlantic as part of the New York City Billion Oyster Project. It is hoped this article can shed some light on the invaluable contribution oysters provide to the coastal environment as a remarkably effective mollusc filter feeder. Accordingly, this article is meant for the fish, not the farmer, and it serves as an appreciation for all the good work the little oyster does to maintain the pristine coastal environment that both human and fish so greatly rely on.

Alec Reid

The Billion Oyster Project

The Billion Oyster Project is an ongoing community effort in New York Harbour to restore the harbour’s natural reef system and marine ecology, by placing a billion oysters back into the city’s estuary. In the face of the insanely complex challenge of trying to improve water quality and restore marine ecology in an estuary so industrial and concentrated in human activity as New York Harbour, New Yorkers have identified the reintroduction of oysters as being essential for achieving the desired healthy marine environment.

New Yorkers have done this is because the oyster is an indispensable species for achieving effective nutrient recycling in the coastal environment. An oyster can filter as many as fifty litres of water daily, and in doing so grazes on microscopic marine algae which exist in huge quantities in the coastal environment. These microscopic plants form the base of the food chain on which all marine life ultimately depend on. Having oysters take the nutrients from the algae and turn it into flesh that can then be consumed by other marine life is essential in ensuring the nutrients from these phytoplankton are effectively recycled into the coastal environment.

The nutrients the oyster doesn’t put into his flesh he puts into his completely biodegradable calcium carbonate shell, and using this resourceful shell the oyster actively engineers the environment that coastal marine communities live in. After the oyster dies, his shell becomes a fixed structure for spawning mollusc bivalves and seaweeds to attach to. Over time, the accumulation of many oyster shells becomes a solid natural reef supporting a diverse and rich community of marine life. Everything the oyster takes from the marine environment he gives back tenfold, and this is why he is so deservingly titled a ‘championed crustacean’ for sustaining marine ecology and ensuring coastal conservation.

The Irish Perspective

In New York City, the aptly named Concrete Jungle, they have skyscrapers for forestry, gutters for rivers, drain pipes for waterfalls, subways for caves, and 8.6 million humans living in an area smaller than County Louth. Within this artificial landscape they have managed to find space for a billion oysters, and overtly acknowledge the invaluable contribution the oyster makes to the city’s harbour as an indispensable nutrient recycler and natural reef creator. The blunt question to ask now is why, in Ireland, can we not share the coast with the oyster in the same way?

Unlike our distant Atlantic neighbours, who are endlessly grateful for the championed crustacean, in Ireland, the oyster is regularly persecuted and routinely insulted. The first Irish assault on the oyster came in the form of gluttony and greed. There once existed native oyster reefs in great quantities on the Irish coast, however, crude overfishing caused the native oyster population to dwindle dangerously low, and the covering of his nurseries in sludge arising from human waste and agricultural activities, effected the native oyster’s almost complete extinction.

Some non-profit organisations such as the Irish Native Oyster Fisheries ForumTralee Oyster Fisheries Society and Cuan Beo are actively working to restore and sustain the native oyster reefs in Ireland, however, the sad reality is that for the extensive majority of the country’s coast, oysters exist only as a farmed species on cultivating trestles. And like the native oyster, the farmed oyster is not without his own human challenges. However, it is our politics, not our overindulging appetites that he suffers.

Oyster Trestles, An Rinn, Co Waterford (Credit: David Clynch Photography)

The farmed oyster’s residence along the Irish foreshore is repeatedly condemned as a public nuisance. His antagonists argue that his trestle beds require too much of the shore to house, his coarse shell is too hazardous to the human foot, his black bags are too irritating to the tourist’s eye. Sadly, the great affection that exists in the Irish public for sustainable food production and farming, does not extend as far as the regularly ridiculed farmed oyster.

Appreciation for the little oyster in Ireland, be he a wild oyster or a farmed one, is limited. The recovery of the native oyster beds back to their former size is an enormous endeavour and will likely require a substantial amount of time and a serious change in human behaviour to rectify. And against the lingering negative public perspective of the farmed oyster, it is unlikely any significant area of the foreshore will be allocated to him any time soon. Accordingly, the Irish coast is currently suffering a significant oyster deficit.

This bleak reality raises the serious question as to whether that important practice of nutrient recycling in the Irish coastal environment is being achieved? The need for Ireland to ensure proper nutrient recycling in the coastal environment is perhaps even greater than that of the New Yorkers, as Ireland has the added challenge of limiting the amount of pollutants ending up in our coastal waters arising from the substantial agricultural fertilizing that the country engages in. Irish Naturalist Dr Cillian Roden provides the best arguments for why the lack of filter-feeding molluscs on the Irish coast is of particular concern to an agricultural Ireland in his article ‘Disrupting what we do not see, human impacts on coastal plankton communities’.

Dr Roden outlines “in the last thirty years, the single greatest change in our understanding of the sea has been the realisation that the sea is not uniform, instead it is divided into sharply defined and separate regions, each with a distinct ecology”. This revelation is quite alarming as it disproves the popular belief that nutrient runoff originating from agricultural fertilization and sewage treatment are washed away from the coast and are diluted into the open Atlantic.

What in reality occurs, is the nutrients from these activities stay in the immediate coastal environment for a considerable period of time, and in substantial quantities. This excessive nutrient enrichment feeds huge algae blooms, which greatly disproportions nutrient recycling in the coastal environment. It is here where the little oyster with his ravenous hunger for plant-based algae could play a vital role in ensuring these nutrients are naturally recycled back into the marine environment.

The impact of excessive nutrient enrichment of the coastal environment arising from human activities could be significantly reduced if we had dedicated oyster beds in place to control the exponential growth in algae populations through grazing, and to naturally recycle the nutrients absorbed from these algae back into the coastal environment. As Dr Roden notes; “The most radical improvement in the health of our coastal ecosystem would be the restoration of the once vast populations of bivalve molluscs. The re-introduction of a massive filtering and grazing capacity would return the whole ecosystem, including the algae, to the state that appears to have existed before the destruction of the shellfish beds began. It is at least possible that such a functioning ecosystem could more easily absorb the increased nutrient loading now placed on coastal waters”.

If anything is to be learnt from the Billion Oyster Project, it is that the oyster does far more for the world than simply acting as an up-market appetiser. He goes further to provide indispensable services in nutrient recycling, coastal conservation, natural reef creating and algae bloom eliminating – services that we in Ireland are slow to realise that we cannot afford to do without.

Respecting Genuine Concerns

This is not to argue that oyster farming is completely without harmful effects on the marine environment. We, as an industry, have to acknowledge there are scenarios when oyster farming should rightly be restricted when it can be proven it will have a harmful effect on the coastal environment. In this sense, the public debate on oyster farming should be one of mutual recognition, where alongside the benefits of oyster farming we also accept genuine concerns. Perhaps through this mutual recognition, we can start to change the negative public perception of oyster farming, and foster a public debate on aquaculture based on reasoned arguments, as oppose to the sensationalist claims argued by two vehemently opposed sides.


Response from Dr Cillian Roden 

Dr Cillian Roden

I agree and don’t agree with Mr Reid! That we need more oysters to balance our coastal ecosystems is beyond question. The debate is how we achieve it. The first approach should be the native oyster. For years this was a non-starter because of Bonamia disease but something is changing. I am seeing more and more native oysters in Galway Bay and spatting ponds built in the ’80s being dusted down and put back to work, so it is possible that we could rebuild our native oysters. One problem will be persuading people not to overfish once a few tonnes are found. I can see no way of doing this except real no fish zones. And no-nonsense about maybe just taking a few!!

That brings me to my basic worry – we lack most of the data we need to know where to place oyster farms or regenerate old beds. We also lack the political or social will to make the hard decisions, just as in climate change and so on. At present, I am appalled at the existing aquaculture licensing system as it first failed to give any licences and now is handing out licences like confetti, without adequate site surveys. To take two examples I know of; in one case it is proposed to allow trestling on an area of native spat fall, in the other to allow trestling on sea grass beds which act as fish nurseries. This is happening because no one is obliged—as one is on land—to do adequate ecological site surveys and inspections before a development proceeds.

There is a role for Gigas production – especially if they use triploids to prevent breeding and farms are sited carefully (and the farms are closed down if they dare buy cheap untested spat which introduces disease or alien invaders like the “sea vomit” sea squirt we have in Kinvara!). But, do we have the will or budget to do that? If we don’t, I suppose we will follow the French with overstocking followed by habitat destruction and introduced diseases, and end up doing more harm than good.

The American project is wonderful, but the scale needed far exceeds anything a Gigas farm could contribute so the connection between the two approaches isn’t very strong. I think we need to separate out ecological objectives of habitat restoration and economic objectives of creating wealth and employment. They need not clash but often do, because either debt or, if you want, greed pressurise people into decisions which are disastrous. After all, it was an oyster farmer who succeeded in bringing Bonamia into Ireland, thereby destroying the role of native oysters in our coastal ecology. (How’s that for smart business sense?)

In the US it is prohibited to use Gigas on the east coast in order to protect the Virginia oyster. What I am getting at is we need very tough enforced laws to allow both ecological restoration of oyster beds and commercial aquaculture. Consequently, I don’t really think that a general complaint that people don’t like oyster farming works – oyster farming, if not regulated, will destroy itself and the environment by disease and introduced species, not to mention tonnes of waste plastic! I have no problem with well-sited well-managed trestle farms with penalties for those which are badly managed, but oyster farming has already introduced the Saragassum weed, Bonamia disease and the sea vomit. Farmers can’t be surprised that they encounter opposition. It is interesting that native mussel farming appears to cause very little ecological impact – mainly because it uses a common native species.


Main Image: Oysters from Meitheal Trá an Rinne Teo (Credit: David Clynch Photography)