86 



Atomic Radiation and Oceanography and Fisheries 



and temperature influence the uptake of ele- 

 ments in solution. One group was kept at 

 20-22° C in sea water containing Sr*^^, and 

 another group at 8-12° C. The fish in both 

 groups averaged 0.02 g. each. Figure 8 shows 



Figure 8. Uptake of Sr*" by Larval Flatfish. 



that strontium was taken up more rapidly at 

 the higher temperature. Thus at one day, the 

 fish at the lower temperature had less than one 

 third of the radioactivity of the fish at the 

 higher temperature. The graph also shows that 

 very young fish continue to take up strontium 

 from solution very rapidly at 14 days, while at 

 14 days the Tilapia had reached an apparent 

 steady state condition. 



The uptake of zinc^^ by croakers was studied 

 at the R.L.F.W.S. These fish were fed the iso- 

 tope in hardened gelatine. After 12 hours only 

 about 27 per cent of the dose remained in the 

 fish (Table 8). The distribution of zinc is 

 quite different from that of strontium. About 

 90 per cent of the strontium retained by the 

 various fishes used at the H.M.L. was found in 

 the gills, bones, and integument. Zinc, how- 

 ever, is concentrated mainly in the liver and 

 spleen. The muscle and bone, because of their 

 bulk accounted for a large part of the total 

 zinc^^ of the body. The turnover times of the 

 zinc-containing compounds of the skin, muscle 

 and bone were slow, whereas those of the in- 

 ternal organs were relatively rapid. 



The uptake of radiocesium by fish was studied 

 at the R.L.F.W.S. Table 9 shows the distribu- 

 tion of cesium^^'^ which was fed to little tuna. 

 It can be seen that the liver, heart, spleen, and 

 kidney rapidly take up the cesium, but these 

 organs also lose the cesium during the following 

 week. Muscle, gonad, brain, and skin, on the 



TABLE 8 ZiNc"^ Distribution in Croakers 



{Micro pogon undulatus) 12 HouRS After 



Oral Administration 



^ S -S g a. 3 C O"^ 



1 issue or u,-^ «ju; cP'C'Ut^'-io.is 



rgan a."" ^°" NNfi. 



Muscle 80 48.80 1.6 78.1 44.7 



Bone 11 6.71 5.5 36.9 21.1 



Gills 2 1.22 10.9 13.3 7.6 



Liver 0.8 0.49 40.7 19.9 11.4 



Gonads 0.4 0.24 17.6 4.2 2.4 



Kidney 0.3 0.18 41.5 7.5 4.3 



Heart 0.2 0.12 14.0 1.7 1.0 



Spleen 0.1 0.06 25.3 1.5 0.9 



Remainder . . 5.2 3.17 3.7i 11.7 6.7 



Skin, scales 



G I tract 60.99 174.8 



Blood 



Brain 



Eyes 



etc. 



1 Based on skin and scales 



Dose per fish — 6,100 myuc 

 Distribution after 12 hours 



Tissues 3 percent 



G I tract 24 percent 



Loss 73 percent (mostly excreted) 



Other hand, continue to accumulate the cesium 

 faster than they lose it. 



The accumulation of cesium in solution was 

 demonstrated by keeping croakers in Cs^^" en- 

 riched sea water. The water was changed daily 

 to maintain a relatively constant concentration. 

 Figure 9 indicates that during the 29 days, the 

 heart, spleen, liver, brain, and muscle con- 

 tinued to accumulate the cesium. The concen- 

 tration factor for the heart, spleen, and liver, 

 was about 10, but this value is far below an 

 equilibrium value. 



TABLE 9 The Distribution of Cesium^^^ in the 



Tissues of the Little Tuna as a 



Function of Time 



Cs^^' content in /ic/g. wet wt. 



Days after the dose 



Organ 1 



Spleen 3-46 



Liver 9.07 



Kidney 3.13 



Heart 6.17 



Bone 0.41 



Eye 0.30 



Muscle 0.46 



Gonad 0.54 



Brain 0.30 



Skin 0.29 



0.46 



0.41 



1.01 



