Abstract
The effect of deletion of various trace elements from the mineral mixture in the fish meal diets on mineral composition of gonads was examined by feeding fingerling of both rainbow trout and carp with various diets for 93 and 83 weeks, respectively. Deletion of one of each trace element or total deletion of trace metals from the mineral mixture in fish meal diets greatly affected the mineral compositions of both ovary and testis in rainbow trout and carp. Especially mineral compositions in gonads were found to be significantly affected by Zn or Mn deletion. The content of Zn in both testis and ovary of carp was three to four times higher than that of the rainbow trout. A similar result of Zn was also obtained in the concentration of Mn in testis, being higher in carp than in rainbow trout. However, the content of Mn in ovary of carp was much less that of rainbow trout. Thus, it is suggested that quality of eggs in terms of rate of eyed eggs and hatchability is affected by mineral status in broodstock and eggs through diets.
These results have also demonstrated that although white fish meal containing various kinds of minerals is used as a protein source, a supplement of dietary trace elements is essential for normal growth and reproduction of both rainbow trout and carp.
