Dr. Paddy Gargan:

On Deputy Ó Cuív's point regarding the availability of information which suggests that finfish farming has damaged wild salmon stocks, most of the information we have suggests it definitely damages sea trout stocks because sea trout live in the sea close to the shore and in the estuaries. This information, which is based on experiments involving one batch of salmon going to sea being treated with a chemical to protect them against sea lice and another batch not being treated, points to serious impacts on salmon in particular years. Most of the research carried out in Ireland is based on the impact on sea trout. In regard to the point about Jackson et al, a number of studies have been carried out in Ireland and Norway on the treatment of hatchery fish going to sea, with one batch being treated and another batch not being treated. These fish are examined when they return the following year as adults to determine whether having gone through a salmon farming area they were impacted or not by the salmon farm. The evidence from all of those studies, including the Jackson study, shows that there is some impact, which in some years may be 10% or 20%. Dr. Jackson concluded that the impact was minor and that there was a 1% loss in marine survival.

We believe that, generally, only 5% of salmon return. If that is reduced to 4%, it equates to a 20% reduction. All of the studies have found varying degrees of impact, with the impact in some years being greater, which is understandable. Not all salmon smolts migrating to sea will face the same level of potential lice infestation, as farms may have their lice under control, there may only be smolts on the farm, or there may be a big freshwater influence in some years. All of the studies reviewed in the document to which we made reference indicate that, on average, the impact on salmon returning is between 12% and 29%. It may be lower in certain circumstances but it has been higher. Those studies show that salmon, as well as sea trout, need to be considered. There is a large amount of information to support this. In some areas, there is no impact because of the location of farms and the control of lice. However, this is not the case in all areas, particularly on the west coast.

Juvenile salmon are put into the bays in March each year. As these fish are quite small, they do not have sea lice, which means there will be good survival of salmon and sea trout that year. It is in the following year, when those fish have increased in size to approximately two or three kilos and lice are difficult to control, that a problem arises. Generally, the problem arises in the second year. This is the biggest issue that we believe needs to be addressed. As the fish in many of the bays are small in year one, it is possible to predict that we will not have a problem that year. However, the following year, if the lice are not brought under control at the time when the wild fish are going to sea in late March, April and May, there will be a problem. The challenge is to ensure that the bigger fish do not catch lice. Quite often, fish are harvested over the May-June period, at which time they may not have been treated for lice and, therefore, it is difficult to control the lice.

The other issue is resistance to the chemical used to treat sea lice. There are what is known as treatment failures, which is when fish are treated but it does not have the desired effect.