Effects of Hyperoxic Rearing Water on Blood Hemoglobin and Hematocrit Levels of Rainbow Trout

Abstract

Rainbow trout Oncorhynchus mykiss cultured under hatchery conditions were exposed to hyperoxia by injection of oxygen into the rearing water. In two separate studies of 67 and 73 d, mean hemoglobin of experimental fish reared at oxygen levels averaging 147–220% saturation was 7.8–8.7% lower than that of control fish reared at mean oxygen saturations of 66–74%. Mean hematocrit of experimental fish was also 3.1–5.7% lower than that of control fish. Fish reared in hyperoxic conditions did not differ in growth, survival, or behavior from control fish. Fish exposed to hyperoxia rapidly adjusted hemoglobin and hematocrit to levels similar to those of control fish after oxygen injection was stopped.