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 (T-3) 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 T-3 were measured beginning at 5 and 16 days after hatching. Body content of T-3 was measured by radioimmunoassay. T-3 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, T-3 at 100 ng ml(-1) and 50 ng ml(-1) retarded the growth of larval striped bass and caused a lower survival rate than T-3 at 25 ng ml(-1) or the control treatment. At 16 days after hatching, T-3 at 100 ng ml(-1) retarded the growth of larval fish and caused a higher mortality. T-3 at 10 ng ml(-1) and 1 ng ml(-1) did not show any effect on either survival or growth. Body content of T-3 returns to control levels within days following end of treatment. The results indicate that exogenous T-3 can be detrimental to the growth and survival of larval striped bass.