Daily variation in plasma growth hormone of juvenile coho salmon, Oncorhynchus kisutch

Abstract

Circulating levels of plasma growth hormone were measured in juvenile coho salmon (Oncorhynchus kisutch) over a 24-h period. Growth hormone followed a circadian rhythm, peaking three times during 24 h. Peaks occurred at 10:00, 16:00, and 24:00, with the largest peak (24:00) representing a 575% increase in plasma growth hormone over a 2-h period (22:00–24:00).