Fig. 4. Seasonal changes in reproductive parameters correlated with changes in photoperiod and water temperature. Changes in GSI are negatively correlated with daylength (A) but
not water temperature (B). Plasma T levels are negatively correlated with both daylength (C) and water temperature (D). Plasma 11-kT levels are negatively correlated with daylength
(E) but not with water temperature (F).