Radioactivity in the Reef Fishes of Belle Island Eniwetok Atoll April 1954 to November 1955

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UNITED STATES ATOMIC ENERGY’ COMMISSION RADIOACTIVITY IN THE REEF FISHES OF BELLE ISLAND ENIWETOK ATOLL APRIL Applied Fisheries Laboratory University of Washington Technical Information Sorvico Extension, Oak Ridge, term.

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Thie report wae prepared ae aa account of Government epoaeored work. Netther the Vatted Statee, nor the COUUXI~JJ~Q,nor any perron acting on behalf d the Coumhto~~ A. blakor my mrmaty or repremntJtlaa, elrpreu or Implled, wtth reepect to the not infrtnge prtwtely owned r*& or AJ UJJ~ in the We, “perroa acting on behalf d the Commi~akm” includes soy employee or contractor d the Coauntmioa to th extent that such employee or contractor prepare+ handler or dietrtbute8, or prodder acce8J to, my taformatloa pursuant ta hia employment or contract with the Commleeion. Thir report haa been reproduced directly from the beet available copy. Prlated in USA. Price 61.25. Available from the Office d Technical Servicee, Department of Commerce, Wubgton 25, D. C.

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RADIOACTIVITYIN THEREEFFISHES OF BELLEISLAND ENIWETOKATOLL APRIL 1954 TO NUVEMWt 1955 Applied Fisheries Laboratory University of Washington . Operated by the University of Washington under Contract No. AT(45-1)540with the UMted States Atomic Energy Comrnlssion

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Studies of the radioactivity In reef fishes of13elle (Bogombogo) Island, Eniwetok Atoll, were made durm a period of about one year !'ollowlngthe atomic detonations Ln 1954. Thirty-four different collections were made and 693 specimens were analyzed to determine the trend or decline of radloactivity. The deollne of radloactlvlty during the perlod under study vat! generally similar In all species, The relative amount of radioactivity per gram of tl8aue war iveatest ln the alimentary tract, with the llvcr, rkln, bone and muscle vailed throughout the period. The rate of decline wab greate8t during the first 100 days, wlta a 1088 of 90 per cent of the radloactlvlty during the period. Studle8 were tie on the varlatlon of total radioactivity In the tissues and bpecleb, on comparison8 of the amount of radioactivity Fn the 8pecles and In their food, and on comparisons of the decline of radloactlvlty during the period with the decay of radioactivity ln

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Materials and Methods Trends or Decline in the Levels of Radioactivity Variation In the Samples Co;;;;~n of the Decline of Radioactivity by Comparison of the Decline of Radioactivity In Olsh with that of their Food and with Other Factors Compmlson of Decline with Decay of Radioactivity

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RADIOACTIVITYIll TRY REEFFISHES OF BELLE Previou8 studies of the radioactivity In the fishes in the Marshall Islands have been confined to single surveys made soon after an atomic detonation, occasionally followed by one to three reaurvey8 a few month8 up to three years later (WFL-7, Trend8 ia the level8 or decline of radioaotlvity in the fish population8 could only be estimated by basing assumptions on The purpore of thir i.nv8StigatlOn was to measure the trend or decliae of radioactivity in the flrh, to compare the decline in different speolea, in some of the organs or tlsaue8, and in the environment and to compare the decline with the physical decay of radioactivity. lty Lo tbr, reef fl8b68 of Belle (Bogombogo) Islend, Enlwetok Atoll, were made from April 14, 1954, through November 1, 1955, during and after the weapons testing program at Eniwetok and Bikini Atolls. The leatar shot of May 14, 1954, was the mo8t important in these studies, since the detonation occurred but

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2.7 mile3 eagt-northeast of Belle Igland, and thus contributed the greatest amount of radioactivity to the Belle area. There was however, residual radioactivity present from previous atomic weapons detonated at Bikini Atoll and at EnLwetok. Reef fishes were collected in the viclnltg of Belle Island by using rotenone, hook and line, or spear in depth3 ranging from a few i.nche3 to about 12 feet. Almost all of the collections were made on the seaward side of the island in Area F coral and sand. The area is typical of the reef of the northern portton of the atoll except that It sustained a certain amount of physical damage because of its proximity to the shot. Attempts wepe made to confine the specimens analyzed to those fish which were typical residents of the Belle area, but such efforts were not entirely 3uccedaful. The flab collected during the first month after Nectar shot consisted mainly of goatflah and mullet, species which move along the north reef from island to island. Typical reef residents such a3 grouper, damselfl3h and aurgeonfl3h appeared to be scarce during this period. In all, 34 different collection3 were made in 1954 and 1955 whloh included 693 apcclmens, these representing 57 species lies were conalatentl~ present in the collections (Table 1 and The collections and treatment of data were similar to those in earlier lnveatigationa by the Applied Fisheries Laboratory, For complete details see WT.616 (UWFL-33).The specimens were

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SOUNOINGS IN FATHOMS l-w Fig. 1. Plap of th8 north reef and Islands of EniW8tOk Atoll (top) with an enlarged map of Belle Island (bottom) showing typical current patterns. The wind rose Indicates lffevaillng

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Table 1. I&tea of collection with number of specil~bnsof the principal famllles of fish listed in order of approximate omum~~~ In the rramples. Species lo. of

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a freezer on being returned to the laboratory. Tirsue8 were dissected, weighed, and dried at *the Enlwetok laboratory. The tirrsuertaken were skin, mudcle, bone, liver and vl8cera (dlgesentire fish were USOd. At the University of Washington 540' C, cooled, slumled,, dried and counted In an internal gasAll oouat8 r0r radioactlvlty were corrected to the date 0r oollectlon, the deaay factor8 for all gnlwtok sampler being bared on a 8011 8azuplScollected at Belle ISland my 15, 199. geometry and oolncidenm. The radioactivity i8 expressed in mlcrocurles per kilogram 0r wet tisrue. blslntegrationr per minute per gram can be converted to microcurl.es per kilogram Trend8 or Decline in the Level8 or Radioaetlvltg General trend8 oi the radloactivity in the fish collected at Belle f8m am 8hOVn In Figure 2, L-08 conaectlng the

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Fig. 2. Trends In the levels of radloaatlvltyIn tlssuee of fish from Belle feland. Preehot levels are plotted to the left of zero days.

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to there in othm tlsruea. Differences are greatest In vlscera in which the amount of radioaCtiVity i8 much greater than ~a liver tisrue the first 100 days; after this period the two tissue8 decline at about the lame rate. Bone and skin fluctuate about a commonintermedisto rmge betveen musole and liver, radioactivity 0r more than 90 pes cent from emly port-shot 018, which, at Ealvetok, vere higher tbaa aormal beoaure of another duru the decline of radloactlvlty msy Indicate oompasrtively alight difierenoes in selective uptake In the five dividing the total amount Of radiofmtlvit~ in al]. the 8ample8. age amount premmt on a per--am-vet-weight basis for the period of April 199 to November 1955. The iOiiOWlng result8 Percent of total The relationship varle8 depending on the tim after

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on the rpeoier of flrh. For emmple, a halfbeak caught the day after mhot bed oomparatlvelyhigh concentration8of redloactlvlty ME due to both adsorptionaad absorption,whorear it had not yet reaohed the bone 80 boon after the rhot. The average counts for vlroera were higher la mart fish for the first 100 daya than rubrequeatly. Dlffereaceria 8peoler la which there were 10 or more rampler are to be 8eea in the lov concentration of total radioactivity, for example, in the liver of wra88e, and the moderately high coaoeatratloasia bone aml skin of goatflrh (aete Correotingthe percent of total aotlvity per tlsrue fPom the above table for the tlraue weight by using the percentage8 8, 63, 18, 2, and 9 ar relative value8 of the total weight of radioactivitywould be distributeda8 follows: Variation in the 3amle8 The tread or decline la radloaotivltyfluctuatesrather widely, due, in part, to iaadequatesampling and In part to aatual fluctuatloa8ia the amount of radloa~tlvltyin the Belle Island area. The downwind,dowacurreatposltloa of the island relative to the t8rget area would undoubtedlyaubjeot the Belle region to varying mounts of effluent from the tsrgetarea.

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The amount of oo&mlnatlon would, in turn, be subject to 8uah variable8 aa tlder, w2ndr and currenta. Biological varlableu, such a8 migration of the fish, mortality, iafltur and outflow of breed- populat2oas and their young also could contribute to In order to determine the extent of the variat2on, calculatlonr of the coeffl~lent of varlatlon (V) were made (1) by fam212e8, using four or more specimens for the oalculations (Table 2) and (2) by date, wing murole tissue from all famfthe ooefflclent of variation between famlllea, I.e., distbctly high In gontflsh and mullet, and between tla8ue8, averag2ng all fam212e8 and all tissues comb2ned wa8 56 per cent. By omltt2ng the goatflsh and mullet 2n th4 calculations the average 28 lowered to 37 per cent. The latter value 2s s2milar to that found for algae (37%) (Palumbo, 1357) and far hwertetrates The fact that goatflsh and mullet prefer the open sandy bottom area8 of the reef, moving in schools f?om island to island may actount for the higher coefflclent of var2ation in these fishes. The average coeffloient of varistioa Is much greater when aamples of mixed fam21Les or species are used. Table 3, In which the data for muaole tissue are 8ummarlted, indicate8 that the cosffic2ent verier from 16 to 209 per coat. The coefficient of variatloa of muscle in all the collections average8 97 per Cent,

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ape bared on row or mope ri8h with the name Skin Musele Bone Liver Viscera Entire Av.

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ples with and without goatfish and mullet and with and wfthout combined samples.

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but when goatfishand mullet are excluded the average La Comparison of the Decline of Radloactlvits by SPeclea A com~~laon of the decline of radioactivity ti two apeclea with different feeding habits la made ln Figures 3 a 4. Surgeonflsh, with herbivorous habltq and grouper, vith capnlvop probably prevailed ln the fish in the vlclnlty of Belle Ialan& For comparisons of other species, reference may be made to Figureta 7 through 10, which depict the decline ln goatfish and mullet tlaawa. As has been polnted out, goatf Iah and mullet, beoauae of their movement along the reef from island to island, are not atrlctly comparable to Belle Island “resident” fish, and the decline trends apparently refleot these differences. Surgeonfish and poupera were obtalned fairly regularly throughout the period of lnveatlgatloa. The former feed principally oa fllameatoua algae (Davaon, a a., 195% vhereaa the grouper8 feed principally oa fishes. The radloactlvlty in the surgeonfish, Flgurs 3, declines at a greater rate than that of the groupers, Figwe 4, for all tissues for the first 50 to 100 days after the shot. For example, muscle tissue of aurgeonflah cdatalned approximately four times as much rediaactivity as that of the grouper lmmedlately after the shot, but by 125 days the two apeclea coatalned similar amounta, Comparlaon of the Decline of Radloactivltsin Fish with that of In Figure 5 the radlocretlvity ia surgeonfish viscera la

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Fig. 5. Trend8 In the levela of cera compared with those of algae and sea water, all fran Belle

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compared vith that in algae and found to be quite similar,a8 would be expwted in a rpecles vhlah is principallyherbivoron a dliferent scale to Indicate the dependenceor similarity in the trenda. Algae are dependent on beb water for their radioactivity, which they concentrateup to 8everal thousand tilllO of radioactivematerial by feeding on the algae. The data Prom curie of radiosotlve Iwrterial lnge8ted into the alimentarytract, about 0.55 mim?ocuriea are dirtrlbutedto the skin, musole, bone In Figure 6,the decline of radioactivityin the liver tlsappear to be marked during the early period of decline, with lng greater amountr 0r radioactivity than algae at 531 days. Sea cucumber gut oontent 18 m&de up mortly of coral detriCoral fsagaentr are alro found abundantly In the alimentary tract of the mullet, a detritu8 feeder, along with plant and animal material. HOVeVOC, comparison8 of the deeline In these tvo orof radioaetlvlty. It ~$11 also be noted that the decline of radloactlvity ln mullet tl88ue8 18 conrldersbly different from

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fig. 6. Wends in the levels of radloactlvlty of liver tissue of omnivorous fish compared with those of algae and sea cucumber gut from

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that of other fish tissues. Goatfish viscera (Fig. 7), oa the other haad, deell.aer slmllarly to that of 8ea cucumber gut, the liver of aa omnivore, aad to some degree, algae. Qoatfleh feed largely on braohywan crabs, vhloh, in tura, iced on algae, dead fl8h, etc., 80 that the diet of goatfish 18, to a certain degree, comparable to that of omnlvorou8 fishes. Com~rlson of Decline with Decay of Radioactlvltx Flgwes 7 through 13 8hov certain marked differences betveea deallne and decay of radloaatlvlty In the rame tissues for both goatflsh aad mullet. In goatflsh the differences are evideat la the first 100 day8 after ahot, while in mullet the dlffereaces are greateat f’or the first 150 to 200 days. Varlatlons due to sampling and other causer, which have been dlscussed in a previous seation, might explain 8ome of the differeaces. Also they might be due to the dlffereatlal affinity of various 8pecler for shorter-lived isotopes. Ia goatfish the radiation varier to around 50 to 170 UC/‘& for liver, about 20 50 uc/kg for bone end 3 to 7 uc/kg for muscle. Slmilaritlea in the decay wrves are shown ln Figures 7, 9, 10, and 11. For example, liver decay In goatflsh (Fig.8) similar to that of mullet liver after 100 days; muscle decay goatfhh ir rlmilar to surgeoafish liver and surgeonfish boae after 200 days; while bone decay of goatflsh is similar to bone decay of mulletand 8urgeonflsh after 100 to 250 day8. Dlsaimllarities In the decay curves appear to be greatest during the first 100 to 200 days after the shot, the curve8 tending to

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DAYS AFTER NECTAR Fig. 8. Decline of radioactivity in goatflsh liver and muscle tlsaues compared

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Fig. 9. Decline of radioactivity In mullet liver and muscle tissues compared

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lug. 11. RadioactIvedecay in various tiasuea of several species of fish from

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approach each other In pattern with pasrage of time. During the early period after the shot there is, of course, a greater variety of radioactiveIsotopespresent than later, and there 1s some Lndlcatlon that aeleCtive uptake mlght be more marked or relectlveexclusionle8s marked during this period, As The data presenteddo not permit exact di8tlnctions betvsen tissue8 or between different specie8 on the basis of dlffemnCe8 In the uptake of radioaatlvo materials. It appear8 tl88Ue8 differ mainly in Order8 Of I=gPitUde rather than ia quality after the flmt 100 days, although there is the posslblllty of different leotopeswith similar half llver being Flab collectedwithin one month after the 1954 shots and analyzed (Lowman,Palumbo and South, 1957) contributedthe remainderof the mdloactlvlty. There may be fl88lOA product8 In the fl8h the first few week8 or month8 after the shot, but after four or

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Blologlc8l decline of radioactivity ln the fishes of Belle Irrlsnd, Ealvetok Atoll, 18 generally similar in all species. Differences which are evident my be attributed to differences fn feddlng habits and, these differences, which appear greatest during the first 100 to 200 days after shot, may be attrlbuted to dlffmences ln the uptake and retention …