Effect of triiodothyronine on the growth and survival of larval striped bass (Morone saxatilis).

This study was carried out to test the effect of triiodothyronine (T3) on the growth and survival of larval striped bass (Morone saxatilis). Growth and survival of striped bass held in 5 ppt seawater and treated with various doses of T3 were measured beginning at 5 and 16 days after hatching. Body content of T3 was measured by radioimmunoassay. T3 dissolved in the 5 ppt seawater was taken up by larval striped bass in a dose-dependent manner, and affected the growth and survival of the fish. At 5 days after hatching, T3 at 100 ng ml(-1) and 50 ng ml(-1) retarded the growth of larval striped bass and caused a lower survival rate than T3 at 25 ng ml(-1) or the control treatment. At 16 days after hatching, T3 at 100 ng ml(-1) retarded the growth of larval fish and caused a higher mortality. T3 at 10 ng ml(-1) and 1 ng ml(-1) did not show any effect on either survival or growth. Body content of T3 returns to control levels within days following end of treatment. The results indicate that exogenous T3 can be detrimental to the growth and survival of larval striped bass.