The Influences of Addition of Minerals to Rearing Water and Smoltification on Selected Blood Parameters of Juvenile Steelhead Trout, Salmo gairdneri Richardson

Experiments were conducted to determine the influences addition of minerals to rearing water had on selected blood parameters of juvenile steelhead trout, Salmo gairdneri Richardson. Fish that were maintained in water with low mineral concentrations exhibited significant increases in plasma {aastex} {amsbsy} {amsfonts} {amssymb} {bm} {mathrsfs} {pifont} {stmaryrd} {textcomp} {portland,xspace} {amsmath,amsxtra} {wasysym} {empty} {10}{9}{7}{6} {document}NH₄⁺{document} and concomitant decreases in plasma Na+ concentrations. The alterations in the levels of these ions coincided with severe gill swelling and increased mortality. The changes in blood parameters, gill structure, and mortality probably are coincident with early changes associated with smoltification. Fish reared in water supplemented with minerals did not display such changes. It is hypothesized that the low environmental Na+ levels reduced {aastex} {amsbsy} {amsfonts} {amssymb} {bm} {mathrsfs} {pifont} {stmaryrd} {textcomp} {portland,xspace} {amsmath,amsxtra} {wasysym} {empty} {10}{9}{7}{6} {document}NH₄⁺{document} excretion by a Na+/{aastex} {amsbsy} {amsfonts} {amssymb} {bm} {mathrsfs} {pifont} {stmaryrd} {textcomp} {portland,xspace} {amsmath,amsxtra} {wasysym} {empty} {10}{9}{7}{6} {document}NH₄⁺{document} exchange mechanism.