Radiobiological Studies of the Fish Collected at Rongelap and Ailinginae Atolls, July 1957

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IUDIOBIOIJXHCAL STUDIES OF THE FISH COLLECTED AT RONGELAP AND AILINGINAE ATOLLS, JULY 1957 Applied Fisheries Laboratory University of Washington Twhnicol Information Servico Extension, Oak Ridga, Tonn.

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I Radmbtologtcal anaiycm of the rod fishes M Rongehp and I ALlingtnae Atolls lnd~cated that a recontamination curred in 1956 Gross levels of bets lctivity in of the lrea OCI ranged from O 016 to O 038 uc/kg wet weight. The \eveLe of radioactivity in bone and muscle ttesues of fish collected during 1957 were abo~t the same as the levels for similar tissues collected in 1955 Gamma spectra analysis and ion-exchange methods wet weight) in the bone of fish from Kabelle Island, Rongela,p Atoll Approximately 40 per cent of the total radioactivity in the reef fishes was due to Zn65, 28 per cent to cobalt, 26 per cent to Fe55, and 6 per cent to other radtonuclides

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RACKJB1OLOGICAL STUDIES OF THl? FISH COLLECTED AT During Ju\y 195? collections of fish for radlobiological lnalysts were made lt Ailinginae and Rongelap Atolls. The data from theoe collections represent part of the information from a continuing program of radiobiological studies which was begun on March 26, 1954, .oon after the first radiological contamination of Rongelap and Ailinginae Atolls. Subsequent collections were made on July 16, 1954, January 29, 1955, and October 10, 1955 All of these investigations have been reported by Donaldson, et ai. ( 1955). Data from the investigations in the Rongelap area by this—— Laboratory and other organizations have been summarized lnd coordinated by Dunn~ng (1957). Results of the analyses of additional material collected August 3, 1956 are included in this report. F~sh were collected at Enlbuk Island, Ailing~nae Atoll, on July 11, 1957, by no~son~ng an area of the Lnner reef One large grouper also was taken by hook and ilne In ?vlogtrl Pass On July 17, 1Y57, l collection was made in the lagoon in front of the .iila~ on ftongelap Island. Rongeiap Atoll, and

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date of collection. com=oa nasr. es. genera, s~t~o aad number of lpectmena for tha 1956 ld 195? collections lre listed in the appecd~x. ‘f?w ftsh were placed on Ice m insulated containers within two hours of capture and transported to the Eniwetok Marhw Biolo@cal Laboratory where they were frozen. except m the case of fish ‘Iltere the fish were identified and dissected, collected in 1956 when the frozen fish were shipped to the base Laboratory lt the University of Washington for dissection and Subsequent radiological analysis. Tissues used for analysis were muscle, bone, liver and stomach contents or viscera. Specimens which were too small to dissect were processed as whole fish. Partly because of the omnivorous food habits of the Marahallese natives and partly because of variations in the samples, it is advisable to analyze many specimens of a variety of species to obtain reliable estimates of levels of radioact~vity (We lander, 1957). Consequently, twogram aampie. of muscle tiseue were ta~en from each fish and the aggregate was homogenized in a Waring Blender. Plates were made of allquots of this homogenate and the remainder dried for radiochemlcal

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internal methane gas- flow counttng chamtirs at ttw Laboratory of grations per mmute per gram of wet tissue by corrcctt~ for samoh Other ttssues were treated similarly. with the lxception of liver, in whtch case the whole organ was removed from each lpectmen. u a lfficient number of specimens of a single species was obtained, the tissues were treated separately ls in the case of goatfish and halfbeak from Kabelle Island (see Table 1). Decay rates for radioactivity of tissues of fi~h collected in 1956 were calculated because there were indicatlone that Rongelap Atoll was contaminated during the Redwing operation. Gamma spectra and total gamma counts were made on dried or ashea samples In a single channel, 50-position, automatic advance, gamma specanalvses were made by ion-exchange resin column and radio chemical precipitation techniques l%e radioactive isotopes contained in the separate fractions were Ldentliied by determination of the gamma lnerg~es, and by beta mass absorption st~dies using aluminum foil Correction factors for ronvertlng beta and gamma counts to d.stntegrations per minute were calcuused are given by Lowman et al (~gs?)

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T-k 1 show gross Levds of beta radcmetivtty W ttIO floheo duriu Islad. Radtoactiti ty in muscle tioouc of fish fmm Enibuk Islan& Ailinginae Atoll, w8* ati great or greater than that of KabeUe Island. Comparatively minor differences lre seen in the levels of radioactivity in similar tissues of omnivorous and carnivorous fishes from Rongelap Island, except for stomach contents. l%e presence of alga. in the stomachs of many omnivorous fish would account for the higher levels in these fishes. Two species, the goatfish and the halfbeak, were taken in sufficient quantities for separate analyses me goat.fish feeds on small invertebrates, prlnctpally cruatacea, of the sandy bottom areas. Levels of radioactivity in the stomach contents and liver of these fish were much higher than in ot~er fish of the same area; however, rwiioactivity in muscle tissue was not much higher The hslfbeaks from KabelAe Xnland had about the same amount of radioactivity as fish from Rongehp, reflectMand. The ha~ak normally feeds lt the surfsce on macrqhnkton ,

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which icwiudes smali ftsh, invertebrates and llgae. I Table 2 contains data on the rate of decimeofthekta radioactivity in reef fish collected at Rongelap and Ailmgmae Atolls betwe*n March 26, 1954 and July 18, 1957. The rates of decline h Uver, bone and muscle tissue of fish from Kabelle Island are given in Figur@ :. The decline rates are similar for all three tissues, lspecially during the first two years. Recontamination by other nuclear devices during the 1 summer of 1956 is indicated by the increase of radioactivity in muscle and bone and a temporary decrease in rate of decline in liver tissue. I At present, the radioactivity in liver tissue appears to be declining at I viscera or stomach contents has decl~ned more rapidly than that of other I tissues (Table 2) It has been suggested (Welander, 1957) that some of the long-lived Isotopes may bc accumulating in the bone and muscle of fish, whereas the radioactivity in liver tissue is similar to that in the stomach, bearing out the fact that the liver is an organ for the temporary storage and passage of food and waste products It ia of interest to note that the levels of radioactivity in the bone and muscle are about the same as those of the 1955 samples. Data on rad~oactlve decay were obtained from bone and liver tissue of groupem (Epinephalus merra) from Kabeile and Rongelap Islands, ard fmm homog~nlzed muscle tissues from 13 species of reef fish The decay rates of muscle and bone wi~re 1) are more rapid than declkr,e rates for the

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same period, however, llver tlseue decay and decline rate- lre limilar. radioactive materials in Rortgelap Island between the rate of decline in the ttssues of fish from January 25, 1955 and July 17, 1957. Again it will be noted that the rate of Jecline ~ radioactivity is somewhat greater in the liver tissue than in bone or muscle. All tissueo show l deftnttc increase in radioactivity after the summer of 1S56, reach~ng a relatively higher level than for the same tissues in fish from Kabelle Island, but declining at a more rapid rate after 1956, Decay and decline ratee of radioactivity of muscle and bone ttsoue from fish from Rongelap Island are approximately the same, decay being slightly mole rapid. The radioactivity in liver tissue decline- at a more rapid rate than Lt decays. Gross Gamma Radioactivity, 1!357 Table 3 contains data on gross levels of gamma radioactivity In the homogenate of many reef fishes collected at Rongelap and Ailinginae Atolls. AS with the beta radioactivity, Rongelap Island fish generally had leas gamm radioactivity than fioh from either En~buk or Kabeiie Islands. Also dtffer - l rices were not great between sirr. iiar species from dtiferent Lsiands. A markedly higher amount of radioactivity was noted again in the Liver of

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was &neralAv aboJt the same in Kabe\le and Enibuk reef fish. Gamma radioactivity in the rtlu.cle lveraged about 26 per cent that of the ltver wtth variation of from 7 io 48 per cent. Beta actlvtty waa slightly iower, the rr. uscle to liver ratio averaging about 10 cr cent, with a range of from 5 to 27 per cent. me greatest difference in the amounts of both gamma and beta radioactivity between liver and muscle Gamma spectra were made on dried sample- of tissue to detcrm~ne if gamma peaks other than those from expected fission products were present. The gamma spectrum curves obtained from various fish tissues are compared w~th Sptkea of radioactive cobalt and radio act~ve The gamma spectra (made in October i9S7) on whole samplee exh(b; ted certain common characteristics with peaks at several positions as follows O. 12 MEV considered to be from C057

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The Zn65 peak at 1 12 MEV occurred In lvery tissue sample tested, b! many authcrs, as sun; rtlar!zed by Lowman et al. (1957). Additional—— data from this Laboratory are given tn Table 4. The C057 peak of O. 12 MEV was present in the liver of all fish tested, however, Lt ~ppears to be rather low in the liver t~ssue of omnivorous fish taken at Rongelap Island. This radioisotope was not detected tn goatfish gut or goatfish bone, but occurred in small amounts I in go~tftsh muscle No dlst]nct peak at ttssue of reef fish or ~n halfbeaks 0 81 MEV One or both of these O. 12 MEV appeared in the taken at Kabelle Island. partially obscured by the C058 radioisotopes appeared to be in the muscle and liver of reef fish from Enlbuk Island, and liver of hal.fbeaks from Kabelle Island, and possibly An the muscle of reef fish from Kabelle Island, Ver\ficatlon of the presence of both of these isotopes in Enibuk reef fish liver was later obtained by ion-exchange resin column analysis (see below) The C060 peak at 1 17 MEV was obscured by the Zn65 peak at 1.12 MEV; however, the CoGo peak at 1.33 MEV was obeerved in the liver and muscle of Kabelle goatfish and in the liver of Rongelap ommvorous fish The presence of Co6° was also later verified by ion-exchange analysts of Enlbuk reef ftsh liver.

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[n general. the gm. rra spectra of the fish tlssuea from d~fferent areas hav~ defmlte s~m~larlt[es. l ven when compared to results ob - spectra appear to be greater between different organs of the same fish than between the same organs of fish from different islanda or atolls. To identtfy the varioua radionuclides contained in the reef fish liver samples collected at Embuk island, Ailinginae Atoll, July 11, ld57, the samples were pooled and the ash (O. 384 grams) dissolved in O. 2 N HC1. of the sample were combined and later passed through an ion-exchange colurrln of Dowex 1 antonlc resin to further separate the fractions and to obtain the excess of the nu~lldes resulting from overloading the catlonic restn The radloassay of the fract~ons obtained from both columns ~s gurr. marlzed Ln Table 5. Details of these procedures have been reported by Lowman et al (1957) The methads generally follow those developed.— by Tompkins et al. (1947), Kraus and Moore (1953), Kimura et al (1956),—— —— Takanobu et al. (1956), and Ish~bashi et al. (1956). , The ~dentlftcation of Fe55 In the oxalate fractions was made by mass absorption technique in a windowless methane gas-flow beta counter One-ml plates of several fract~ons totaled 39 c/m after drytng under an

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Practton9 in order ash wet If It It 1+ II l Ash weight of sample ).3811grams. “*These fractions contained considerable amounts of manganese, cobalt, and zinc, :ndicatlw an Overlwduig of the Dowex 59 catlonlc reslna

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with dsainum foal 4 7 m8/czB2 in weight. A total correction famr of 112 wae used (based on l secondary ?es$ staadud obtemed fmm grations per minute. ‘I%e rsdiohotopes of zinc, cobalt and manganeee were identified by their gamma lnergies and the disintegrations per mmute were calculated from the gamma spectrum curves of the different fractions. Radioctrontium was not detected m the citrate fractiona where it would be expected to occur. Radiochemical precipitation determinations revealed the presence of small amounts of radiostrontl~m in the bone of fish collected at Kabelle Island. No radiostrontium was detected either in the liver or muscle of any of the fish taken at Aiiinginae or Rongelap the bone of fish from Enibuk Island or Rongelap Island. Atolls or in tains data on the Sr90 content Ln fish tissues collected during and since 1954 at Rongelap Atoll by this Laboratory. Except for traces of SrgO in goatfish and reef fish bone frGm the Kabelle Island 1957 collections and in bonito bone from the 1955 collections at Labaredj, no radiostrontium has been detected in the fish tiseues. A summary of the data on the radioisotopes obtained from the liver tissue sample of reef fish from Enibuk Island is contained in Table 7. In total radioactivity, Zn65 contributed about 40 per cent, C057, COS8.

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l Beta+ activity for ZnG5 fs 2.5 per cent of the total radioactivity. Self-absorption corrections for beta actlvlty in cobalt ver~ wide by ualng etandards and splk~s in 5 per cent citrate dried on 1~-lath plates rnd counted in the methane gas-flow Ifucleometer jo O from the beta activity (314 d/m/g vet weight)

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t~ Ma* was detected in only minor amoun~ and unidentified hotopes amounted to about 6 per cent of tha total radiosctivtty. pre~mmd that the unidentified radkmcttvity was dtm to beta particles which penetrated the duminuxn lhiehl of the sodium i~de cryotal. However, these totals may be conoervattvc. dus tn part to lamplo MS and partly because all of the gamma lctivity was It will be observed that almost all, if not all, not lccounted for. of the radiosctivtty I is due to non- fisston products (Table 7). It i. Q- of htmest to ride 1 that since the discovery of Zn65 in tissues of fish from the Pacific area by Kawabata ( 1954), this in fish tissues, usually as the radioisotope has consistently been found i Mori, 1955; Mori and Saiki, 1956; Yoshii, 1956; Nagasawa lt ll. 19S6;—— Lowman et al., 19S7).—— There are additional similarities in the kinds and lmounts of radioisotopes found in fish tissues. Most Investigators have found little or no have been found even in the bones of fiaheo. Radioisotopes of cobalt well as in activity in the fish tissues of fish from Bikini and Entwetok Atolls (Lawman fish of the open sea (Kawabata, 1954). COST, comprise aa much as 28 per cent of the radio-

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in fish tiaww but onAy in small contatt & certain orgsna in tb. same fish have become lviolent. Bone, for aampk, differs from mO@t other tissues in lacking C057, Co5~, and CO*, although considerable amounts may be present h the muscle and liv~r & the same fish. U the radioisotopes in Table 7 lre ueed ad the half UV*S wei~ted by lither …