Restoration of a brown trout (Salmo trutta L.) population to Loch Enoch, an acified Loch in Galloway, South-West Scotland

The authors present the findings of a restoration project in Loch Enoch in Scotland. There are historical references that brown trout was present in Loch Enoch up to the 1920s but it is believed the acidity of loch triggered the disappearance of Salmo trutta. The recent observed reduction in the acidity of L. Enoch to a level close to that found in nearby lochs with trout populations, suggested that trout might now survive in L. Enoch. For a population to survive, all stages in the life-cycle of a species must be able to develop. Accordingly, tests were undertaken, first with eggs and fry. The availability of food was also studied. In October 1994, 3,000 yearling trout of L. Grannoch origin which had been reared in a local hatchery were distributed throughout the loch. The fish population was studied from 1995-98. The authors conclude that survival of the trout population is possible if the acidity of the loch water remains low

Restoration of a brown trout (Salmo trutta L.) population to Loch Enoch, an acidified Loch in Galloway, south-west Scotland

The decline and, in some waters, the disappearance of brown trout Salmotrutta populations in south-west Scotland have been attributed to surface wateracidification (Harriman et al. 1987; Maitland et al. 1987). From changesin the diatom flora and levels of heavy metals in sediment cores, Flower et al.(1987) have calculated water quality changes over the past 200 years for lochsin this area. For Loch Enoch (Fig. 1, and front cover illustration) theyconcluded that the pH of the loch water had decreased from 5.4 around 1840,to 4.8 in c. 1930, then more rapidly to 4.4 in 1982