』,θgでOgrα″乃ジ 10・ 17-22. Aug.20,2008

Unusual Heavy lnfection with Acα れす乃οcttθ乃材月力PHttcαれす乃'(COpepoda,Chondra― canthidae)On Adult Sailfln Sandnsh ArcroscOP"syaPθれた″s from the Pacinc Ocean ott Southwestern Hokkaido

Kazuya Nagasawal*and Yoshiyuki Takaya2 l Graduate School of Blosphere Science,Hiroshima University,

1-4-4 Kagalmyama,IIigashi― Hiroshilna,IIiroshima,739-8528 Japan

2 Hokkaido Mariculture Fishe五 es Expeiment Station,

1-156-3 FunaIIll,Muroran,IIokkaido,051-0013 Japan

Abstract.Adult sおlin sandflsh Arcゎscqルsittθれた,s salnpled in thc coastal Pacinc Occan orF southwestern Hokkaido were found to be heavily infcctcd with the chondracanthid Acα沌″力οcんθれJriα Pr,αcαれ″乃J Shiino, 1964 in Dcccmber 2007. This flnding is completely difFerent from prevlous obsettations that rlsh frorn the salne reglon were ostalI■ free from thc parasite, Mean abundancc ofthe copepod in 2007 was up to 770-fold highcr than that recordcd in 1999,and a current sharp increase in the copepod population is suggest― ed for the occan surveyed.

Key words: Parasite,copepod,Acα れ筋θcんθれ″ria prttcαれ筋j,sailfln sandnsh,Arcヵsc?″,sittο力'c″s,heavy infection.

Introduction For experilnental scedling production at the Hokkaido Mariculture Experirnent Station,Muroran,

The sallin sandish Arcす οscθP功ざブαPοれ'C″S we collected adult sallin sandish in the North (Steindachner, 1881)is diStributed in the Sea of Paciflc Ocean ofF southwestern Hokkaido in 2007 Japan,Sea of Okhotsk and western North Paciflc but unexpectedly found that these flsh were very Ocean(Okiyama,1970,1990)and iS One ofthe most heavily infected with the chondracanthid copepod important commercial nsh in northem Japan(Ochiai Acαれすんθcんθれ冴r,αノrJαcα乃″ん,Shiino, 1964. This &Tanaka,1986).The flSh are caught as adults using inding was completely different froHl prevlous set nets and glll nets in coastal waters and as iIIma― infomation that rlsh in this reglon were quite rarely ture flsh with bottoln trawls in offshore waters. infected with the copepod(Yanagimoto&Konishi, Since the stock abundance of the species has been 2004).ThuS,We made detailed obsettations on the extremely reduced in Japanese waters,various activ― occurrence of the copepod on sallfln sandflsh from ities,including flsheries management,seedling pro― coastal Pacinc waters of southwestern Hokkaido. duction,and release of hatchery― reared juvenlles, The results are reported herein. have been conducted in order to recover the flsh resource(夕.g,Sugiyama夕 ″α′.,2002;Tomoda夕 ″α′., Materials andコ 販ethods 2006). A total of 239 ArcrοscOp″ざブαβοれ'C″ざWere sam― pled at three locations(Noboribetsu,Muroran,and *Corresponding author omatus@hiroshima― u.acjp Shikabe)in the North Pacinc ocean ofF southwestem

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43。N

ガ 令 Ｎ 付 ん

North Pacific ocean

1410E 1430E

Fig,1.A map ofsouthem Hokkaido,showing locations where scηsailfln冴ざブηοれ 'C″sandashざ Arcゎ were collected. |`: locations in the present study;: locations● off which Yanagimoto& Konishi(2004)sampled the FIsh in 1999;▲ :locations oIF which the nsheHnen captured the nsh infected with Acαれれοcんθれ冴ガαP/協cαれれ,in 2007.

Hokkaido on December 6-16,2007(Fig.1).The the wall of the branchial cavity,the gill arches,and flsh were caught using set nets and gill nets installed the chin(Fig。 2), Both prevalence and inean abun― in coastal waters. They were broughtto the laboratory dance of thc copcpod wcrc constantly high,ranging within a day of capture and individually examined from 79.9-100%and from 7.87-15。 40,respectively, for total length(TL,mm),bOdy weight(g)and the at three locations(Table l),There was a IIlarked presence of Acαれ″力οcんοれ冴r,α Pr,αcαれ′ん,. C)toliths difFerence in infection level bet、veen age-O flsh and were removed frotln the flsh for subsequent age the older flsh(age…l tO age-3):age-O flSh showed the deterlnination. The copepods found、 vere flxed and lowest prevalence and mean abundance.The maxl― presenred in 70%ethanol. Voucher specllnens are mum number of copepods(47)per infected host was deposited in the crustacean(Cr)c01lection at the recorded from an age-2 female nsh(207 mm TL). National Science Museum,Tokyo,Japan(NSMT―Cr 17988). The terms,prevalence(the prOportion of Discusslon infected ish of a given species in a sample as a per― centage),mean abundance(the mean number of par― Acα″″んθcんοれar,αP/サαcαれ″ん,had been a rare para― asites per host exaElined in a sample),and habitat(a site of sallfln sandflsh in the ocean where we sam― typical local environment in which parasites occur) pled the nsh。(Yamagimoto&Konishl,2004)。 Just are used according to the deinitions of Bush夕″α″. eight years before our research(November 1999), (1997). infection levels ofA.Priacαれすん,on adult sallfln sand― nsh remained quite low at two sites(Kttyohama and Results Yakumo,sce Fig。 1)near Our sampling locations, being 8.00%and 2.35ワ うin prevalence and O.09 and

Acα乃″んθcんοれ冴rliα Pr,αcα″″ん,was found in varlous O.02 in mean abundance,respectively(Yanagimoto parts of the host,including the inner surface of the &Konishi,2004)。 When We cOmpare these infec― opercululn,the n。。r and roof of the buccal cavity, tion data with the data from our study,Inean abun―

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Fig.2.Sailan sandish Aκ 皮パc?βttSブα″οれた材ざ(A,B)infected with Acα れれθcんθれ冴rJα prJαcαれれサ (C).ThC nsh werc collected in the coastal North Pacinc ocean orF Muroran,Hokkaido,on December 6,2007. A:part of the left operculuma、vas removed to sho、v the infection with A. priαcαれすんサin the buccal and branchial cavities and on the gill arches;Bi the chin infected 、vith A.pr,αcαれすんど;C: a gravid female、vith a pair of egg sacs,whole body,ventral vie、v. Scale bars:101nm in A and B;21nm in C.

danccs(9.99 at Noboribetsu, 15.40 at Muroran, found by asherlnen working at Toyoura and Muro― 14.48 at Shikabe)On adult flsh(agc-l tO agc-3 11sh ran(See Fig.1)in early December 2007.It is,thus, combined)werc lll― to 770-fold highcr than those very likely that the infection level or population size rccorded for 1999. Further,IIshermen who had been of A.β /Jαcαれ″ん,changed markedly in 2007 off engagcd in coltnlnercial flshing of sallfln sandflsh atsouthwesterll Hokkaido, and if this is the case,the Sawara(scc Fig。1)diSCOvercd ish hcavily infcctcdcopcpod must havc incrcascd cnomously in number 、vith A.Pr,αCα乃″ん,for the flrst tilne in their catch inthere. Junc 2007(Dr Teruhiko Awakura,クタパ.cο初初.). At present,it is very dittcult to clarify what fac― SiHlilarly,IIsh infected with many copepods were tors contributed to the observed,sudden heavy infec―

Tablc l. Occurrcncc of Acαれすんοcんθ乃冴rJα P/Jαcαれすん,on sailfln sandflsh Arcrθscθ― ク″Sブ々βοれ'C″s collected at three locations in the coastal Paciflc Ocean off southwcsterll l=okkaido in Dccember 2007. C糧 MC警 NC 挽mpling 射tte聡盛鮮 濫銚棚 技券ド 器好 Noboribetsu 0 40 8は 101 (91) 30,0 0.50(い 4) 1 36 142-193 (158) 83.3 11.22(0 39) 2 102 162-245 (213) 98,0 9.63(0-47) 3 1 224 (224) 100 2.00(2) Subtotal 179 80L245 (175) 79.9 7.87 (0-47) Muroran 20 178-233 (197) 100 15,40(1-42) Shikabc 13 138-180 (152) 92.3 13.15 (0-30) 27 169-234 (200) 100 15.11(2-45) Subtotal 40 138-234 (184) 97.5 14.48(0-45) Total 239 80-245 (178) 87.0 9.60(0-47) *l Percentage of infected flsh. 米2 Attcan number of copcpods per ash examined. *3 Age was not deterlnined,but thc flsh exaIIuned、vere all adults.

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tion of sailfln sandish with A.PrげαCαれ″ん,,because reported again by Ho&Kim(1996)。SallIIn sandllsh various host and environmental factors must have from northerll Honshu and Hokkaido were infected been connected direcdy or indirecdy with ito Some with A.Prttcα れれ,(Yanagimoto&Konishi,2004), infomation,however,is avallable to thro、v light on and the present study conimed infection of the flsh our observations. According to Yanagimoto&Ko― with A.Pr,α Cαれ物げor southwestern Hokkaido.In nishi(2004),in the Pacinc Ocean off southern Korea,the copepod was found on the tongue sole Hokkaido,infection levels of A.〃 rJαcαzすん,were の れοgわSざ″ざS夕初JあタソJs Gunther,1873(PleurOnccti― high in 1999 on flsh froln areas ofF southcentral and formes,Cynoglossidae)(Kim,1998).TheSe past southeastern Hokkaido(夕 .ge prevalence: 78,97%, and present records suggest that A.Prliαごαれすん'OCCurs mean abundance:3.53,ofF Erimo,see Fig。1).MOre_ on various teleosts in direrent orders and fanlllies over,based on the current molecular analysis,the but shows a limited host preference foriapθ A.」ttc″s. sallan sandish is known to form one stock in thc In additionラYanagilnoto&Konishi(2004)sug― Pacinc waters ofF southerll Hokkaido(Yanagimoto, gested that A.ノ/サαCαれすん,prefers cold、vatcrs,be― 2004;Shirai夕すα′.,2006,2007). TherefOre,in addi― cause the species infected A.プαβθれ'C″S from waters tion to a sharp9 enormous increase in the copepod aIFected by the cold Oyashio current rnore frequently population itself ofF southwestem Hokkaido in 2007, and heavily than those frorn waters by the、 varm another possibly contributing factor could be that Tsushima current.Arcゎsc?β″sブqβθガC″s is mainly ish froln other Paciflc rcglons(夕.g.thOse ofF Ettlno) distributed in cold subarctic waters(Okiyama,1990) have expanded their distribution. and C)れθg′θss″ss夕″,冴αタソ′s also occurs in cold shal― A silnilar sudden increase in infectlon level has low waters ott Korea and China(Yamada夕 ″α′., been reported for the pennellld copepod P夕 乃れ夕J′α 2007). On the Other hand,since Cο οた夕οJ″s」icPθ″j― sp.,a parasite of the Paciflc saury Co″ο″αう,s sα,rα c″sis a wan圧卜Water species occurrlng in tropical and (BreV00rt,1856),in the westem North Pacincsubtropical ocean rcgions(Starlles, 1988),its diStribution and attacent Seas(Nagasawa,1984;Nagasawa夕 すα′., area does not overlap with those ofA.pr,αcαれすんメand 1985,1988).In thiS Case,the parasite appeared sud… thc other known hosts. Based on these considera― denly in 1981,kept infection levcls high for three tions, C.プαβοれ,c″s llight be an accidental host for years from 1982-1984,but almost disappeared in the copepod. 1985(Nagasawa夕 ″α′.,1988)。 SinCe we have as yet Prevlously A.prJαcαれすん'was recorded only from little infomation on the population blology of para… the inncr surface of the of the nsh(shil― sitic copcpods in wild flsh populatlons,continuous no,1964;Ho&Kim,1995).In thiS Study,however, monitodng of the infection level of A.Pガαcαれすん'on the species was found in the buccal and branchial sailan sandish is desirable to clarify the change in cavities and on the gill arches and chin,as well(Fig. population size and geographical distnbution of the 1)。 SOme Other copepods(夕 .g.Sa力 物けれcο′α spp.in copepod ofFthe coastal Pacinc waters of Hokkaido. the Lerllaeopodidae)parasitic on ishes are known to Acαれすんθcんοれ冴/サα Pr,αcαれ″ん,was originally de― change their habitats with increase in their number scribed as a new species by Shiino(1964)from ttle on a host(Bltack夕″α″.,1983;NagasawaタチαJ.,1995). longrlnned bullseye Cθθた夕θJ″s」り θれ'C″S(Cuvier, Thus,it appears that A.P/Jα Cαれすん,exhibits such 1829)(as P/JαCα乃筋″sう拘?ps,Perciforlnes,Pttacan― habitat changes as well,in cases of heavy infectlon, thidac:see Stttes,1988,for the nomenclature of the species)collected in thc Sca of Japan near Sado Acknowledgements lsland. The copepod was latcr redesc五 bed by Hot免 Kim(1995)from the sallin sandflsh A/cす θsc?β″s We thank the star of the Hokkaido Mariculture 」iCβθれ'C″S(PercifOrlnes,Trichodontidac)c01lected at Fisheries Expe五rnent Station for their assistance dur― Kushiro,Hokkaldo. Specllnens froln Kushiro were ing the study. We also acknowledge Dr Teruhiko

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Awakura,Hokkaisuiko Consultant Corporatlon,Sap― (COpepoda)on the saury,Cθ ′θ筋うな sα'陶,in dle poro,for his provislon of useful inforlnation on the westem North Pacinc ocean and attacent Seas. parasite. Part of the present study was supported by ル aFOう'θ′θg'α,167/168:571-577. a Grant―in―Aid for Scientinc Research(B)(No. Nagasawa,K。 ,Yamamoto,M.,Kumagai,A.& 18380116)from the Japan Society for the Promodon ,1995。Sakurai,Y。Rediscovery in Japan and host of Science. association of Sα ′初ブ乃cοtt cα/Piοれどs(Copepoda: Lernacopodidac),a parasite of wild and reared Literature Cited freshwater salmonids.Cα 乃.ユ FJsん。α?″α′.SCJ・, 52(Suppl.1):178-185.

Black,G.A.,MontogoHlery,W.L.&Whoriskey,F. Ochiai,A. &Tanaka,M,, 1986. rc乃 ″乃メ。′。gy,2 G,,1983. Abundance and distnbution of SaL陶 げ乃― (New Edn)。 1,140 pp.Koseisha― Koseikaku, cο挽″夕冴予夕α/Js所(COpepoda)on anadromous brook Tokyo。 (In Japanese). trout,Sα′ッタ′,れ″s ybれす,れα〃,s(MitChill),in theC)kiyama,M.,1970。 Studies on the population biol― M【oisie River system,QuebeC.プ.FJsんβげο″.,22: ogy of the sand flsh,Arcす οscop″ざ」iαβοれ,c″s 567-575。 (Steindachner).II.POpulation analysis(prelinll_ Bush,A.O.,LarFerty,K.D.,Lotz,J.M.&Shostak, nary report).β″冴.J々βαれS夕α″g.Fisん.R夕s.助 み., A.W., 1997. Parasitology meets ecology on its 22:59-69(in Japanese with Enghsh absttact). own terlnsi Margolis夕 才α′.rcvisited. J.Pattαsげ″., ― , 1990。 COntrast in reproductive style betぃ 83:575-583. wecn two species of sandishes(famlly Tricho― Ho,J.― S.&Klln,I.― ]H., 1995。 Acα れすんοc力οれ冴/Jα dontidae). ‰ ん。β″″J.,88:543-549, (COpepoda:Chondracanthidae)paraSitic on flshes Shiino,S.M., 1964. On two new species of the of Sado lsland in the ,with a prelinli― genus Acα乃筋θcんο乃か,α Oakley(CttStacea Cope― nary review of the genus. R夕 βo Sαao初 αr.ぅザθJ. pOda)fOund in Japan. Zθθ′.Mc冴 夕ac′.,34:30L36. S″らPV,,gα″αUれげソ.,25:45-67, Shiral,S.,Kuranaga,R.,Sugiyama,H.&Higuchi, 一 ,1996. Copepods parasitic on flshes of west― M.,2006。 Populatlon structure of the sallfln sand― erll North Paciflc.P″うなざ夕ゎ れαr.うJο′.駒 う.,37: flsh,Arcゎ sc?β″sブCPο″JC″ざ(),in 275-303. thc Sea of Japan.rcん協り。′。R夕s.,53:357-368. Kim,I.―】H., 1998. Cindpedia, symbiotic Copepoda, Shiral,S.,Goto,T.&Hirose,T.,2007.Sall― fln

and Pycnogonida. "′ ″srrα″夕冴E■cノc″?β夕冴Jαザ sandish“ rcわSC響 ″貯 ?θ れ'C″S)C01lected ofF the 月α″乃αα乃冴F″θ阿 ザ Kθ″α,38.1,038 ppo Min― lwatc area in Febttary to March,2004:evidence istry of Education,Seoul.(In Korean). that they came from the Sca of Japano乃.プ Jレ. Nagasawa,K., 1984, The flnding of P夕 れれ夕J′α sp. rc乃″乃メθ′.,54:47-58(in Japanese with Engllsh (COpepoda:Pcnncllidae)on the saury, CO″ θ″αう,s abstract). sαげrα, in the western and central North Paciflc Starnes,W.C.,1988. Revision,phylogeny and blo― Ocean and the Okhotsk Sea. F,sん Pα′んο′., 18: geographic colninents on the circulntropical 205-208. marinc percoid flsh fanlily Priacanthidae, β ″″J. Nagasawa,K。 ,Imal,Y.&Ishida,K.,1985.Distri― 初αre ScJ.,43:117-203. bution, abundance and effects of」 P夕″″夕J′α sp, Sugiyama,H.,Morioka,T.,Furunaka,H.,Sugishita, (COpepoda:Pennellidac),parasitic on the saury, S.&Nagakura,Y.,2002. Blological Characteis― Cθわわう,s sα′陶 (BreV00rt),in thC Westem North tics and Seedling Production Techniques of ― Pacinc ocean and attacent Seas,1984.β″冴。みサθ― Sailfln Sandnsh,ブ ″βαれ夕s夕Sゼα rαれcん'乃g冨 夕cん g夕θgre Sθc.ル pαれ,40:35-42. れげ?″夕S夕rテタs,(8). 113 pp. Japanese Sea F倒 郎ning ― ,1988. Long― tem changes in the population Association,Tokyo。(In Japanese). size and geographical distribution of れP夕れ夕″Jα sp. Tomoda,T.,Hotta,K.&Morioka,T.,2006.

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Growth,spawning and IIligration of hatchery― ヽ韓 θttC″S,inferred from PCR― RFLP analysis on reared Japanese sandnsh ざc印Arcゎルsンフοれ'C″ざ mtDNA.物 ο″S″′髭じれCαえ'協な海,70:583-591 released in Nanao Bay and Toyama Bay.2w″″οれ (in Japanese with Engllsh abstract). S″Jsαれ6た】桝乾ガざ所,72: 1039-1045(in Japanese Yanagimoto,T.&Konishi,K.,2皿 .Acα 乃筋οc力οれ― witt Engllsh abstract). ar↓αPriacαれ協,(COpepodai Chondracanthidae)aS Yamada,U.,Tokimura,M.,Horikawa,H.& a blological indicator for stock identiflcation of Nakabo,T.,2007.炉 材ざん夕ざα″冴riざ乃夕ri夕ざザ れタ sandflsh Arcゎsc?″ざブηο乃げC″ざ(Steindachner). EaざすCh,72●αZtt FCL″οw S夕αざ. 1,262 pp. Tokai Fisん。Sc,.,70:336■338. Universiけ Press,Hadano。 (In Japanese). Yanagimoto,T.,2004.Geographic population sub― (Accepted Febmary 4,2008) divislon of the Japanese sandnsh,Arc′ οざcop″s

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