Seasonal changes in the plasma levels of glycoprotein antifreeze, Na⁺, Cl⁻, and glucose in Newfoundland Atlantic cod (Gadus morhua)

A seasonal study was carried out on the hematocrits, plasma freezing point depression, and thermal hysteresis, and plasma Na + , Cl − , total protein, and glucose concentrations in laboratory maintained Atlantic cod. Significant thermal hysteresis was evident in the plasma during the months of January to May indicating the presence of antifreeze glycoproteins. Plasma freezing point depression and Na + and Cl − concentrations were highest during the winter months and lowest during the summer. Two peaks in glucose levels were evident; one in February and the other in July. No seasonal changes were evident in hematocrits and total plasma protein concentrations.