The impact of solar ultraviolet radiation upon the skin of rainbow trout, Salmo gairdneri Richardson, farmed at high altitude in Bolivia

The damaging effect of solar ultraviolet (UV) light upon the skin of hroodstock rainbow trout held on a high altitude fish farm in Bolivia is described. Both clinical observations and histoputhological findings confirm the lesions to be of a UV aetiology. An irradiation trial, on the same site, using juvenile rainbow trout was conducted over a 3‐month period and the sequential pathogencsis of the UV‐induced dorsal fin lesions paralleled those found in the broodstock fish. These findings are discussed in relation to the importance of recognizing sunlight as an environmental stress factor.