Blue mussel in feed for rainbow trout

Rainbow trout ( Salmo gairdneri Richardson) with a mean weight of 240 g were fed diets containing 0, 15, 30 and 45% of undersized, ground, whole blue mussel ( Mytilus edulis L.) for 9 weeks. Chemical analyses showed that meat of blue mussel may be a good source of protein and has a favourable fat composition. The shell fraction causes high ash content and low energy density in the whole blue mussel. There was a tendency towards poorer growth and lower digestibility of protein with increasing level of blue mussel in the diet. Total dry matter digestibility decreased with increasing amounts of blue mussel in the diet, and the livers of the fish became enlarged. Negative effects of the high calcium content were not observed. Visual evaluation of flesh pigmentation showed that trout fed the diets with blue mussel were inferior to those fed the reference diet. The experiment showed that it is possible to use blue mussel as an ingredient in diets for rainbow trout.