EFFECTS OF CHRONIC EXPOSURE OF CHINOOK SALMON EGGS AND ALEVINS TO GAMMA IRRADIATION.

Abstract Chinook salmon (Oncorhynchus tshawytscha) eggs and alevins were exposed continuously to low levels of gamma radiation from a 60Co source, from the instant of fertilization until the yolk sac was completely absorbed. The irradiated fish were compared with a similar stock that was not exposed to irradiation. The level of irradiation exposure was gradually increased from 0.5 roentgen/day for the 1960 brood year, to 1.3 roentgens/day in 1965, 2.8 roentgens/day in 1966, 5.0 roentgens/day in 1967 and to 10.0 roentgens/day, a total of 820 roentgens, for the 1968 brood year. At a level of 0.5 roentgen/day no damaging effects were found. The data for the higher levels of exposure will be evaluated as the adults return from the sea. Studies are carried on during the entire life span of the fish.