98 



Atomic Radiation and Oceanography and Fisheries 



ham and Palumbo (1951). Growth in length 

 and weight of fish exposed to radiation is re- 

 tarded as compared to control populations (We- 

 lander et al., 1949). 



"The growth increment during the fastest 

 growing period of the experiment was signifi- 

 cantly less in a fish irradiated with 750 r or more 

 of X-radiation and proved to be a very sensitive 

 measurement of radiation damage and directly 

 proportional to the amount of radiation given." 



The effects of X-radiation upon growth are 

 not confined to the exposed population. Foster 

 et al. (1949), reporting on the growth of rain- 

 bow trout fingerlings produced from parent 

 stock exposed to radiation prior to spawning, 

 comment : 



"The rate of growth of the young during 

 their first year of life was also found to be di- 

 rectly affected by the amount of irradiation re- 

 ceived by the parent fish. While variations in 

 mortality became less with increasing age of the 

 fish, variations in size became greater. Parents 

 treated with 100 r produced progeny in which 

 growth was slightly impeded, while parents 

 treated with 500 or more r units produced 

 progeny which grew appreciably more slowly 

 than normal." 



Damage to specific organs and tissues of sal- 

 monoid fish as a result of exposure to X-ra- 

 diation has been studied by the staff of the 

 Applied Fisheries Laboratory, University of 

 Washington. 



Adult rainbow trout exposed to X-radiation 

 prior to spawning were examined for gross ra- 

 diation damage (Welander et al., 1949). The 

 typical syndromes of radiation such as mass 

 hemorrhage, petechiae and ecchymosis have 

 been observed in all trout subjected to 1500 

 and 2500 roentgens. Gonadal hemorrhage was 

 observed in fish exposed to 500 r of total body 

 radiation. Exposures of 750 r resulted in hem- 

 orrhagic areas in the peritoneum, while all ex- 

 posures of 1000 r or more produced muscular 

 hemorrhage. 



The eggs of rainbow trout exposed to radia- 

 tion during early developmental stages (We- 

 lander, 1954) produced fish showing retarded 

 development. The eggs exposed during the 32- 

 cell, late germ ring and early eyed stages tended 

 to have a more juvenile appearance than the 

 controls, viz., a larger eye and head in propor- 

 tion to the size of the body. Other modifications 



evidenced in the young produced from radiated 

 eggs were as follows: 



"The number of parr marks was significantly 

 reduced in all stages after doses of 300 r or 

 more, with doses as low as 25 r significantly 

 altering the number in embryos irradiated dur- 

 ing the 32-cell stage. 



"Reduction in number of dorsal and anal fin 

 rays was general after irradiation of 32-ceIl, late 

 germ ring and early eyed embryos. Doses from 

 75 to 100 r were significantly effective in re- 

 ducing the fin ray number in these stages. 



"Gross superficial abnormalities observed in 

 X-rayed trout were similar, though usually more 

 numerous, to those found in the controls, with 

 the exceptions of anomalies of dorsal and adi- 

 pose fin produced by 200 and 400 r X-rays of 

 32-cell embryos." 



The eggs of chinook salmon {Oncorhynchus 

 tshaivytscha) exposed to X-radiation during the 

 eyed stage with the results reported by We- 

 lander et al. (1948), show somatic damage pro- 

 portional to the amount of exposure. 



Histopathological studies on serial sections of 

 the kidneys, with included hemopoietic tissue, 

 the interrenal bodies, the spleen, the gonads 

 and other organs of chinook salmon embryos 

 and larvae revealed first the gonads, then the 

 hemopoietic tissue as most radiosensitive. 



Exposure of the eyed eggs to 250 r greatly 

 reduced the number of primordial germ cells in 

 the gonads of the chinook salmon. This sharp 

 reduction (Table 4) in number of cells at 250 r 

 would indicate a measurable reduction at a 

 much lower radiation exposure. 



The hemopoietic tissue of the anterior por- 

 tion of the kidney of the chinook salmon pro- 

 duced from eggs exposed to 250, 500 and 1000 

 r showed a reduction in number of cells and a 

 temporary retardation in development, roughly 

 proportional to the dose. Temporary cessation 

 of mitosis at 1000 r and permanent cessation at 

 higher radiations was noted. 



Counts of the glomeruli in the kidneys of 

 young fish indicated a slight reduction in num- 

 bers at 500 r with definite damage at exposures 

 of 1000 r (Table 5). 



In general, it is observed that the tissues most 

 sensitive to radiation damage are those in rapid 

 division and growth. Gonadal and hemopoietic 

 tissues that are in rapid division are many times 

 more sensitive than those growing less rapidly. 

 The very early embryonic stages of an organism 



