OPINION: Radical rethink of fish farming needed

Time for a rethink.
Seventy years ago, entrepreneurial individuals started experimenting with the concept of farming one of this country’s greatest natural assets, wild salmon and trout.
Early efforts were focused on trout production, but attention soon turned to the more desirable and eminently more profitable Atlantic salmon.
Almost from the off, the industry was not without controversy. For instance, the use of the chemical malachite green as a means of parasite control was once widespread, until the true nature of that particular substance became more widely acknowledged.
For many hoteliers and tourist operators, catering for visitors come to angle for the world-renowned wild Irish sea trout was once a mainstay of their trade.
When the sea trout population collapsed in the late 1980s, anglers stayed away while the sea-cage fish-farming industry went from strength to strength. The disappearance of these once prolific and sought-after fish coincided with the expansion of salmon farming in affected areas.
To many, the evidence was overwhelming: parasitic sea-lice infestation on the farms was spilling into the wild fish population. So virulent was the problem, wild fish were literally being eaten to death. While the matter was fiercely debated at great length, the greater leverage of the aquaculture industry held sway, and fishery owners and anglers were left holding the bare bones of what had been a national treasure.
Some kind of rethink was required. Modern lice-control methods include the use of so called ‘cleaner fish’, such as wrasse and lumpfish, that pick lice from the skin of caged fish. While this practice is far more environmentally friendly, it has not entirely solved the problem.
Another issue facing coastal communities and the local environment is the vast amount of excrement produced by farmed fish. While strong tidal currents might remove this from the vicinity of fish farms, the same material, containing varying amounts of antibiotics and other chemicals used to treat a variety of diseases, is nonetheless absorbed into the greater environment. Again, some kind of rethink is required.
Yet another problem is the matter of accidental release of farmed salmon into the ocean, as happened last week in Killary Harbour, leaving them to mingle with wild fish and ultimately dilute the wild gene pool.
It has taken geological periods of time for wild salmon to become the creatures that they are. It might take only days for aeons of survival-of-the-fittest to be undone. The results of gene pool contamination might not ever be readily evident, but by undermining natural selection we are playing with the very existence of natural order.
But we do have an answer at hand.
Before we discuss that, we might mention mass-mortality events that are affecting fish farms around the world. Climate change leading to warmer waters has been blamed for blooms of toxic algae and hypoxic conditions that have caused the deaths of countless millions of farmed fish.
To get a scale of the problem, the journal Scientific Reports recorded 865 million premature farmed-salmon deaths over a ten-year period, in five countries alone.
Diseases on salmon farms include heart and skeletal muscular inflammation, infectious salmon anaemia, piscine orthoreovirus, pancreas disease, and many more proving difficult to control.
The accidental release of an unknown number of farmed salmon into Killary Harbour should have focused media attention on sea-cage fish farming. In this instance, the number of escapees is reported somewhere between 10,000 and 30,000 fish, averaging 1.5 to 2kg. While it ought not be difficult to round up the majority, this is a severe blow to the environmental integrity of Killary and all rivers that flow into it.
All of this is unnecessary. The answer to all of the foregoing is quite simple. Open cage fish farming could become a land-based operation.
Water-treatment plans could remove excrement and waste food from seawater pumped through the farm. A Norwegian project named Nutricycle is already working on this, with the resulting organic matter being sold for use as fertiliser.
Onshore aquaculture also negates the need for boats, minimising the potential for accidents (including accidental release). Outbreaks of disease could be monitored more effectively, water temperature could be easily controlled, the loss of expensive feed prevented, the slaughter of fish performed onsite.
Had the onshore option been properly explored, the catastrophic relationship between sea lice and sea trout would never have developed.
It is even possible, more than possible, that our sea trout population could be properly restored. We could have again what we had before.
Yes, it is time for a rethink.