cesium'" in marine fishes 



185 



The retention data were expressed as a composite 

 curve consisting of two rate functions wliicli wore 

 extremely different from eacli other. The first 

 component liad a <w of 13.4 days, representing 

 86 percent of the Cs'" at zero time. The second 

 component had a <uj of 911.0 days, representing 

 only 3 percent of the Cs"" at zero time. The 

 sum of both components indicated a deficit of 

 11 percent which (h'noted either a tiiird rate 

 function not detectable front the data or a masking 

 effect by variation. During the summer months 

 it was noted that the gonads of both males and 

 females discharged ripe sex products. Differences 

 in retention between males and females were not 

 evident from the data. Retention of Cs'" bj^ 

 rat ovaries was considerably different from croaker 

 gonads. Ballou and Thompson (1958) reported 

 a 3-component ciu-ve with <^'s of 1.5, 7, and 17 

 days. 



The concentration of Cs'" in fiver at zero time 

 was much higher than that of the other tissues. 

 However, elimination from fiver occiuTed at a 

 rapid rate, resulting in a lower concentration 

 than that of gonad and muscle after 219 days. 

 The retention curve consisted of four rate func- 

 tions with ij^'s of 0.7, 4.2, 24.0 and infinite days. 

 The individual components represented 61, 37, 

 2, and 0.4 percent of the Cs'" at zero time. 

 Ballou and Thompson (1958) reported the reten- 

 tion curve for Cs''^ in rat liver as having three 

 components with t^^'s of 2, 7, and 16 days, repre- 

 senting 69, 19, and 12 percent of the Cs''^ at 

 zero time. 



DISCUSSION 



In the present experiments an attempt has been 

 made to reproduce conditions that occur in the 

 natural environment. This approach was used 

 especially in the long-term accumulation experi- 

 ment with flounder and in both retention 

 experiments. 



Accumulation of Cs'" by flounder was followed 

 through a temperature range which conformed 

 to the gradual change from winter to spring 

 temperatures in the local estuary. Although the 

 reduction of food at certain times nuiy have 

 produced less than optimum conditions, it is 

 conceivable that fish in their natural environment 

 also tolerate periods of inadequate food supply. 

 The fact that flounder had a higiier concentration 

 factor during the period in which tiiey did not 



increase in weight than during the period in which 

 they did increase may be contrary to what might 

 be expected. However, if Cs is not essential for 

 growth, the amount accumulated would not be 

 proportional, necessarily, to the rate of weight 

 increase. 



According to the present results and published 

 reports, Cs concentration factors for most fishes 

 range approximately from 10 to 20, depending 

 upon growth rate, water temperature, and other 

 conditions. Young spot (Leiostomus xanthurus) 

 had a concentration factor of 12 for the whole- 

 body, 17 for viscera, and 23 for muscle (George 

 H. Rees, U.S. Bureau of Commercial Fisheries, 

 Beaufort, N.C.; unpublished data). Krundiolz 

 and others (1957) gave an approximate factor of 

 10 for soft tissues of marine vertebrates. Pendle- 

 ton and Hanson (1958) reported concentration 

 factors of 9,500 and 3,000 for muscle of sunfish 

 {Lepomisgibhosus) and carp {Cyprinus carpio) in an 

 aquatic community. These factors were based 

 on the amount of Cs"' in the water after it had 

 become stabifized at 5 percent of its original 

 concentration, 95 percent having been removed 

 in 50 hours by the ecosystem, including inanimate 

 sm-faces. If the same data on sunfish muscle 

 were related to the initial Cs'" concentration of 

 the water, they would yield a factor of 8-|- 

 which is in closer agreement with the present data. 



Accunmlation of Cs"' from sea water and 

 from ingested material has been followed inde- 

 pendently in the present investigation. In cer- 

 tain situations in the marine environment both of 

 these pathways might be utifized simultaneously. 

 In other situations, fish might absorb radio- 

 activity mostly from food due to differences in 

 migratory patterns between fish and their prey. 

 In noncontaminated water, the rate of accumula- 

 tion of radioactive Cs by fish depends upon the 

 nature of the contaminated food ingested. For 

 example, Pendleton and Hanson (1958) reported 

 higher Cs"' concentration factors for carnivorous 

 vertebrates tlian for omnivores. Fish feeding 

 entirely on phytoplankton might be expected to 

 have even lower concentration factors than 

 omnivorous fish. This is based on data indicating 

 that nine species of algae had concentration 

 factors ranging from 1.2 for Nitzschia dosterium 

 to 3.1 for Nannochloris atomus (Boroughs and 

 others, 1957). 



