Following cessation of ventilation, fish were weighed to the nearest gram, measured (total length in mm), and blood was drawn from the caudal vasculature along the spine of the fish using a 22-gauge needle and a 1 mL syringe rinsed with lithium heparin. Immediately after collection, the whole blood was centrifuged at 2000 xgravity blood for 2 min to separate erythrocytes from plasma. Erythrocytes were transferred to 1.5 ml. microcentrifuge tubes and immediately placed in liquid nitrogen until later storage at -80 °C. Samples of gill filaments and cardiac muscle, hereafter referred to as gill and heart tissue were excised and stored in 1.5 ml. microcentrifuge tubes filled with 1 mL of ice-cold RNAlater