From small sea-lice do great problems grow

ANOTHER LIFE: IN MANY CHILLY, rattling streams of the west, two little black dots have appeared in golden eggs, the size of peas, lodged among the gravel. The wild salmon babies now have their eyes. They will hatch in March or April, as alevin or fry, and go on, if they are lucky, to be parr, and then smolts, silvered and ready for the sea.

Such talk seems remote from the noisy canyons of Dublin’s inner city, and the late and heroic Tony Gregory TD had, sadly, other things to think about in his final months. But his service to environmental groups continued right to the end. Even in December, prompted by Friends of the Irish Environment, he tabled probing Dáil questions, about – of all exurban topics – controlling sea-lice levels at salmon farms. The ministerial answers reflected another crisis in the industry: despite all the efforts, the sea-lice problem has been getting much worse. Sea lice are among thousands of species of copepods – minute crustaceans, mostly no bigger than a grain of rice – that form the bulk of the zooplankton. They feed on plant plankton and then go on to be eaten by everything from cod to whales. Some, however, have a parasitic lifestyle, attaching themselves to fish and feeding on their tissue. Wild salmon returning from the Atlantic to their home rivers often carry a sprinkle of lice with no harm, but infestation in high numbers, especially of young fish, can check growth, cause infections or worse.

It is some 20 years since the concentration of sea lice at salmon farms – chiefly Lepeophtheirus salmonis, specific to the salmonid family – was linked to dramatic local declines in sea trout roaming out into the same bays. Anglers’ catches of 10,000 a year in Connemara dwindled to some 200 in 1990. “Prove it!” was the challenge of the salmon industry, knowing the impossibility of tracking individual copepods between farm cages and the trout.

The circumstantial evidence has long been accepted by independent scientists, and, if reluctantly, by most salmon farmers. Recent studies have strengthened the case – estimating, for example, that up to 95 per cent of salmon lice eggs and larvae produced on the west coasts of Ireland and Scotland are of farm origin. An Irish project funded by the Fisheries Board and the EU, which fed anti-lice chemicals to hatchery-bred salmon, has shown that the treated smolts survive better than those left without. This is the first hard evidence of the threat, not only to sea trout, but to wild salmon smolts, which travel out with no such doses in their systems.

The answers to Tony Gregory from Minister for Agriculture, Fisheries and Food Brendan Smith promised action this year on the failure to control the lice. The breakdown has happened despite inspection by the Marine Institute 14 times a year and stricter threshold for treatments. A department “strategy” group reported last year that the lice have rapidly developed resistance to available veterinary chemicals, and rising sea temperatures have helped their populations survive and increase year by year since 2002. Outbreaks of pancreatic disease in farmed salmon, and the increase in toxic plankton blooms, have made the fish even more vulnerable to attack.

Briefing Tony Gregory, Friends of the Irish Environment charged that control has never been adequate and has worsened steadily since the industry began. The group has now made a formal submission to the European Commission arguing that Ireland is failing to protect wild salmon in bays conserved for them as Natura sites under the EU’s Habitats Directive. Also, that it has broken European law again – by granting fish farm licences without proper environmental impact assessments.

There is still plenty remaining to be done in controlling the lice, as the strategy report has made clear – more fallowing and separation of farms between generations of the copepod, more co-operation in managing bays as a whole. There are now big peripatetic “well boats” coming into service (otherwise known as Very Large Live Fish Carriers), which can dunk whole cages of salmon into insecticide.

Most Irish farms bath the fish on a much smaller scale, with cypermethrin, or add emamectin benzoate in food. There are “organic” feed alternatives, meant to boost the salmon immune systems to withstand lice infection, rather than to kill the copepods. Ecoboost, I’m fascinated to learn, blends garlic and rosemary.

Lepeophtheirus salmonis is not the only sea louse in prospect as Irish aquaculture expands to other species. The smaller Caligus elongatus parasitises more than 80 kinds of fish, farmed salmon ­ and cod – among them. The evolving resistance of marine invertebrates to pesticides is simply a repeat of what has happened to intensive farming ashore, and likely to grow more problematic as the ocean warms.

• Ireland's Ocean: A Natural Historyby Michael and Ethna Viney is published by the Collins Press, Cork

EYE ON NATURE

Can birds see colour? I have been watching a stretch of pyracantha hedging since early December. Part had red berries while the rest were yellow. All the red berries have disappeared while the yellows are barely touched.

Martin Crotty, Blackrock, Co Louth

Birds have colour vision, but it varies among individual species, which also have features of their eyes adapted to specific visual tasks or conditions.

I regularly drive a particular stretch of road from Bantry towards Cork city. Self-propagated patches of bright orange-flowered montbretia/ crocosmia are springing up along the roadside. There were none in 2005, I counted two in 2006, four in 2007, and 12 in 2008.

Jim Dixon, Beara, Co Cork

I was hiking in the Mourne Mountains over the Christmas holidays and noticed a lone crow-like bird wheeling above me and emitting an unusual call. Was it a raven? I also noticed the complete absence of sheep on the mountainside.

Ollie Burke, Kilcullen, Co Kildare

It was a raven. Sheep are taken off the mountains in winter.

On New Year’s Day the beach at Portmarnock was strewn with dead man’s fingers, Alcyonium digitata, which were gone a few days later.

Brian Graham, Baldoyle, Dublin, 13

• Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo. Include a postal address.