THE REFISH (RESTORING ENDANGERED FISH IN STRESSED HABITATS) PROJECT, 1988-1994

The REFISH (Restoring Endangered Fish In Stressed Habitats) Project wa s established in 1988 to assess acid-tolerance among indigenous Norweg ian strains of brown trout. The work, comprising both laboratory and f ield studies, has involved the restocking and subsequent test-fishing of thirteen lakes with five brown trout strains. There was considerabl e variation in the ability of individual lakes to support adult trout. This did not appear related to ANC (acid neutralising capacity) or an y single chemical factor. One strain, Bygland, was found to be relativ ely acid-tolerant, accounting for more than 60% of all fish recaptured by test-fishing over 1990-1994. This is consistent with better surviv al of young life-stages of the Bygland strain, compared with that of t he other strains, in laboratory experiments employing acidic condition s. Strain-specific differences in calcium metabolism may be the physio logical basis for acid tolerance.