Effect on Rainbow Trout and Chum Salmon of Deletion of Trace Elements from Fish Meal Diet

Abstract

Feeding experiments were conducted in order to investigate the effect on rainbow trout and chum salmon of the total deletion of trace elements from the mineral mixture in fish meal diets. In long-term feeding trials of 18 and 54 weeks of the rainbow trout, feeding it with a diet without a supplement of trace elements resulted in reduced growth and low feed effciency. The fish on the deficient diet revealed by the 14th week of the feeding, lens cataracts and short body dwarfism as the most noticeable gross external signs. The abnormalities of the eyes and body attained 86% and 31% at the end of 18th week of the feeding.
In a short-term feeding of 13 weeks the total deletion of trace elements from the diets caused cataracts together with exophthalmus and deperessed growth in both chum salmon and ranbow trout fry, and also a high mortality in the former fish, but short body dwarfism was not observed in the short-term feeding of these fish.
These results have demonstrated that even though white fish meal containing various kinds of minerals is used as a used as protein source, a supplement of dietary trace elements is essential for ranbow trout and chum salmon. The deficiency of trace elements exerts ill effects on normal growth, morphology, and eye health.