Saving The Torgogh

Issues facing the Torgogh in North Wales

The Arctic charr is a sensitive cold-adapted species vulnerable to a range of anthropogenic pressures. In a review of the species conservation status, Maitland et al., (2007) highlight the following concerns:

Climate Change - Warming waters

The UK lies towards the southernmost distribution limit of the circumpolar Arctic charr, and native populations of high national conservation value occur in all four component countries. However, given the temperature requirements of this species and the already relatively mild UK climate, there is strong reason to expect a significant negative impact of climate change on local populations. Some supporting evidence has been provided by analysis of long-term monitoring data by (Winfield et al., (2010), who found a significant positive relationship between the observed rate of population decline in 11 UK lakes and vulnerability to climate change based on lake latitude, altitude, and depth.

Pollution

Most point-source pollution is discharged to running waters, usually after treatment of some kind, and so there are relatively few Arctic charr lakes in Britain which have been seriously affected by domestic or industrial pollution (though see eutrophication below). However, stocks of Arctic charr have been directly affected by pollution and the loss of this species from Ullswater is attributed to discharges from local mines. In Ireland, Loughs Leane, Keel, Conn, Caragh, Currane, Corrib, Mask, Ennel and Clare have all been affected to a greater or lesser degree by polluting discharges.

Eutrophication

The process of eutrophication (nutrient enrichment) may have both direct and indirect effects on fish populations and the latter may be particularly dramatic when combined with the introduction of alien species. Arctic charr populations are usually directly impacted through the reduction of dissolved oxygen levels in deep-water thermal refugia habitat, which itself results from the decomposition of increased algal populations produced by elevated nutrient availability. In such situations, Arctic charr can only be effectively conserved by the restoration of their habitat and Windermere provides an excellent example of how this can be done through the introduction of phosphorus stripping. 

Acidification

Arctic charr have disappeared from at least two lochs in Scotland, apparently as a result of acidification. The extinction of Arctic charr in three Irish loughs has also been attributed to acidification.

One of the most characteristic effects of acidification on fish populations is the failure of recruitment of new age classes into the population. This is manifest in an altered age-structure and reduction in population size, with decreased intraspecific competition for food and increased growth or condition of survivors. To anglers, the fish stock then appears to ‘improve’ because larger fish are caught albeit in lower numbers. However, with no recruitment the population contains fewer and fewer fish until eventually there are none. 

Afforestation

The impact of coniferous afforestation and forestry practice on freshwater habitats in Britain and Ireland has caused much concern in recent decades. The effects of each stage of the forestry cycle – ground preparation, tree planting to canopy closure, the maturing crop and felling – may have an impact on local fresh waters.

It seems highly likely that extensive afforestation in the catchments of Loch Grannoch, and to a lesser extent Loch Dungeon, exacerbated the acidification which had already taken place in their headwaters and caused the extinction of Arctic charr in these two waters. Land use changes may also be involved in the apparent decline of Arctic charr in Ennerdale Water. Conifer plantations near to Llyn Cwellyn are perhaps a concern for the lakes’ Arctic charr.

Engineering

It is well known that hydroelectric schemes can have deleterious effects on local fisheries. The Arctic charr population in Llyn Peris in Wales is now extinct due to the development of a pumped storage scheme. Arctic charr at neighbouring Llyn Padarn have survived but their spawning areas are greatly impacted by the power station. Water supply schemes may also have significant effects on fish populations, especially where no account is taken of local fish ecology when the engineering works are being designed. This can lead to damage to fish stocks as, for example, at Loch Lee, where substantial numbers of adult fish are washed out of the loch each year at spawning time, due to construction of a spillway near charr spawning grounds. Water abstraction for drinking water may cause spawning areas to dry out, resulting in egg mortality.

Introduction of alien species

The deliberate or accidental introduction of new fish species is considered to pose one of the most insidious threats to fish conservation around the world and specifically in Britain and Ireland, where new fish species may act as predators, competitors or environmental degraders. The fish communities of water bodies containing Arctic charr in Britain and Ireland are particularly at risk from this threat because they are relatively species-poor and often have pools of potential invader species in close geographical proximity. The roach is one such species which has increased in distribution greatly in recent years as a result of live-baiting practices, with resulting concerns over potential competitive effects on native planktivorous fish species including Arctic charr. This problem is considered to be of such magnitude in England that the use of live bait has recently been banned in 14 lakes of high conservation value, including all those which contain native populations of Arctic charr. In Ireland, the extinction of Arctic charr in Lough Corrib was closely associated with the rapidly expanding and recently introduced roach population. Perch is also increasingly appearing in Arctic charr lakes, including at Llyn Padarn, and are potential predators of juveniles.