W&M ScholarWorks

VIMS Articles Virginia Institute of Marine Science

2002

Rapa Venosa (Valenciennes, 1846) Rates On Hard Clams Mercenaria Mercenaria (Linnaeus, 1758)

D Savini

JM Harding

Roger L. Mann Virginia Institute of Marine Science

Follow this and additional works at: https://scholarworks.wm.edu/vimsarticles

Part of the Marine Biology Commons

Recommended Citation Savini, D; Harding, JM; and Mann, Roger L., "Rapa Whelk Rapana Venosa (Valenciennes, 1846) Predation Rates On Hard Clams Mercenaria Mercenaria (Linnaeus, 1758)" (2002). VIMS Articles. 470. https://scholarworks.wm.edu/vimsarticles/470

This Article is brought to you for free and open access by the Virginia Institute of Marine Science at W&M ScholarWorks. It has been accepted for inclusion in VIMS Articles by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. Jo11r11al of Shellfish Re.,earch, V,>I. 21. No. 2. 777- 779. 2002.

RAPA WHELK RA PANA VENOSA (VALENCIENNES, 1846) PREDATION RA'fES ON HARD CLAMS 1l1ERCENARJA MERCENARIA (LINNAEUS, 1758)

1 3 2 DARIO SAVINI, • JULlANA M. HARDING/'-' AND ROGER l\i1ANN 1 School of· Sciences, Unive rsity of ~Va/es-Bangor, Menai Bridge. A11glesey. LL59 5EY. Wales. U11i1ed Kingdon,: 2 Virginia /11 stit11re of 1\lfari11 e Science, Depart111ent of Fisheries Science, P.O. Box 1346. Glouces1er Poi111. Virginia 23062; 3 Unirersirci degli Studi di Pavi(I. Depar1i1ne11to di Gene1ica e Microbiologica. Via Sa,11 'Epefanio, 14. 1-2 7100 Po1 1ia. !1aly

ABSTRACT The recent discovery of adul1 vei ned rapa whelk, Rapl11u1 1•e 110.10 (Valencienne,. 1846) in the Lciwer . U.S.A. offers cause for both ecological and econo1nic concern. Adult rapa are large predutory gastropods that consume bivalves including co1n111erc1ally val uable ,pecics such a, hare.I clams. A1ercenaria 111erce11an,1 (Linnae us. 1758). Laboratory feed ing experi­ ments were used 10 eM imate daily con,u1nption rates of two ,i, e, of whelks feedi ng on 1wo size clas,es or hard clams. Large rapa whelks (shell lengLh. SL >10 1 111111 ) are capable of con,uming up to 2.7 g wet weight of clam tissue daily. e4u1valcnt lo 0.817~ of Lheir body weight. Small whelks (60-100 mm SL) inge,l an average or 3.6% of their body weight per day.

KEY \il'ORDS: rapa whelk. Napana 1·e11usa. , J\llerce1wna 111erce11ana. prcdaLion. ChesapeaJ..e Bay

INTROD UCTlON height. SH) and five large (7 1- 100 1n rn SHJ hard cla1n s as poten­ tial prey. Clams were arranged in the experirnental cages so that The veined rapa \vhelk. Rapana venosa, (Valenciennes 1846; whelks initially had the same probability of encountering each size Gasrropoda: J\tTu ricidae) was discovered in the H arnpton Roads of prey (i.e., ,vhelh.s at the center of a circle with clan,, of alter­ region of the Chesapeake Bay, USA, in the sun1n1er of 1998 (Har­ nating size classes spaced evenly around the circun1ference). ding & M ann L999). The is native 10 lhe . The experimental flu111e \vas covered with a fixed plastic net to . and the (Tsi et al. 1983) bu t prevent escape of the whelks and n1ainta.ined on a 14/ IO h natural ,vas introduced LO the in the l 940's (Drapkin 1953) and light/dark sched ule. \.\later ten1perature and sa linity data \Ve re col­ has since spread to the (Koucsoubas & Voult.s iaclou­ lected daily from the flun1e for the 38 clay duration of the experi­ Koukou ra 1990) and the (Ghisoui l 974). Recen tly a n1enl (June 11 10 July 18. 2000). Experin1ental cages were exam­ fen1a le specin1en together with egg masse, \vas found in the Rio ined dai ly and the en1pty shells of all prey were re1noved and del Plata, an estuary between and U ru guay in South 1n eas ured. Cla1ns that were cons u1ned were replaced dai ly 1vi1h America (Pastorino et al. 2000). clan1s of si1n i lar cl in1 ensions thus n1 aintaining constant prey avai l­ T he predatory acti vity of rapa whelks in the Black Sea is con­ abi Ii Ly. sidered by Zolotarev ( 1996) 10 be the pri1ne reason for lhe deci­ A size range (30-l 00 mn1 SH) of fifty hard clams was selected n1a1ion of native Black Sea . scallop anu n1ussel populations. fron1 the pool of potential prey ite1ns and used to create ~ize- Gi ven this history. there is both ecological and econo,njc concern 1,veigh1 relationships for the prey. lndividuaJ hard clan,s were mea­ for the fu ture of shellfish stocks in the Hampton Roads region of sured (SH. 111111) and \veighed (g) prior LO the ren1oval of soft ti ssue. the Chesapeake Bay. Hard clarn. Merce11aria 111erce11aria. popula­ Ciani so ft ti ss ue was ,ve ighed (wet weight. g) 10 Lh e nearest 0. 1 g. tions are of particular concern in that the H an,pton Roads region supports a substantial local co1nn1ercial hard cla1n fishery. Labo­ Data Analyses ratory feeding experin1ents were used 10 quantify daily feedi ng Significance levels for all statistical tests \Vere established at rates for 11vo size classes of ad ult rapa whelks offered hard clan1s. P = 0.05 a priori. Bartlett's test for hon1ogeneity of va riance and MATERIALS AND lVillTHODS the Ryan-Joiner test for norrn ali ty \Vere used prior 10 analyses. When appropriate, Fisher's test was used for post-hoc rnulLiple T wel ve adult rapa 1vhelks. collected fron1 the lo1ver Chesa­ con1parisons. peake Bay. USA. between M arch and M ay 2000. were sepa rated into l\VO different size classes: s1n all (60-100 111 111 shell length Feeding Rates tSL), the maxirnun1 di 111ension fron1 the apex of the to the end The nun,bers of clan1s consumed by each size class of whelks of the siphonal canal) and large ( 101 - 160 n1 m SL). Rapa whelks during the entire experin1en1al period were con1pared using a one­ were n1 aintained individually in 60 x 40 x 30 c 1n plastic neL cages way ANOVA with indi vidual whelk as a factor. The nun1ber of subnlerged in a hallow flun1e (250 x 70 x 30 en, ) with a constant clams consun1ed satisfied the assun1ptions of ho111ogeneity of vari­ flo1v of unfilte red York River water as described in Savini (200 I). ance and norn1ali1y without transfonnation. Dai ly feeding rates The bottom of each cage ,vas covered \vith 15 cm of clean hard were ca lculated for each whelk by dividing the total nun1ber of' sand subsrra te. Rapa whelks \vere starved for 48 hours prior to the clan1s consun1ecl during the experi1nental period by the duration of addition of hard clams (prey) to each enclosure. Each 1vhelk \vas the experin,ent (38 clays). given five small (50-70 mm n1axin1u1n cl in1ension, hereafter shell Consun1ption on a \.Veight-\.\leight Bas is

*Corresponding author. E-mail: jharding@vim,.edu: Tel: + l -804-684- Clan1 wet and dry tissue eq uivalents consurned by whelks were 7302: Fax: + J -804-684-7045 compared using a two-way ANOV A ,vith 1,v helk size class and

777 778 SAVJ'Nl F.T AL. indi vidual \Vhelk as factor~. Tissue equivalent data ~ati5fied the as~u rnptions of homogent!llY or variance and non11ality \vithoul • Small rapa whelks (60-100 mm SL) transforn1a1iun. C L.1rge rapa whelks (101 -160 mm SL) KESU LTS 100 Average water temperature during the experi111en1 al period \vas ~ CJ) 26°C (+ I °C). Average salinity \Vas 2 1 ppl (+ I ppt). During the 38 ~ .c: -CJ) day experin1en1, the six srnall \V helks ate a total of 19 clan1s while ·;; lhe ,ix large ,vhelk~ consumed a total of I 5 clam~. There was no "- significant difference in the total nun1ber of clan1s eaten by small " t () ~ "<: and large ,vhelks (ANOVA. F = 0.67: P > 0.05). Sn1all rapa "'0 whelks did not shO\V any clear size preference ,vhen offered hard ""<.) - 0 clan1s as prey (Fig. I) although sn1all whelks con~u 111ed a Lota I of "'0 ..C: I I srn al I clain~ and 8 large cla,ns. lt should be noted tha t 5 of the • • o® 11 ~n,all clan1s ,vere con~u mecl by one individual. Large rapa •• 0 whelk~ consu rned large clarns n1ore frequently than i;n1all cla111s (4 • 0 sn1all clan1s vs. I I large- cla111 s: see Fie-. I J. C lan, Size-\>Veighl Relationships 0. 1 Cl::un tissue wet and dry weights \Vere ploued in re lation 10 0. 1 10 100 1000 she I I height and used to ca lculate ~hell heigh1-wet tissue ,,.,eight Ra1>a whelk body wet weight (g) relationships for hard clan, prey. The~e relari on~hips \Vere used to Figure 2. Daily ingested clam wet weight (g) in relation to rapa wet ca lculate wel tissue equi valen1s for each clan1 consu111ed by an weight (g) obsen ·ed in laboratory feeding cxperin1ents during June individual whelk and were desc ribed with the follo,¥ing equa tions: a nd July, 2000. T he solid diagonal line represents cla111 consu,nption Log (CW\.Vgt) = -3.93 + '2.77 * (Log SH ): R-' = 0.96 equal to the body weight of the predator (whelk) or a I: I consurnption relations hip on a prey WC't weight: pred ator wet weight bas is . Points ,vhere CWWgt is clan, tissue \Ve t weight (g) and SH is clan, i.hell above the line indicate prey cons u.rnption at a rate greater than one ~ - ~ height. while points below the line indicate daily consun1ption rates less than the bod y weight of lhc predator. Rapa \>Vhclk Size-\Veight Relationships

Rapa whelk tiss ue •.vet ,¥eight \vas plotted in relation to shell lationship for whelk predators. T his relationship is based on 150 length and used to calculate a ~hell length-\ve l tissue \veight re- ani111ah (80-165 n1n1 SL) collec1ed fron1 lo,ver Chesa pea ke Bay. USA bet,veen Oc tober 1999 and July 2000 (Harding and 1\1ann. unpublished data): A. I WWWgt = 6.4908 * e(0.0229 * SL ), R2 = 0.69 2 - ~ \Vhere WWWgt is whelk tissue wet ,.veight (g) and SL is \vhel k J she II length ( 111111 ). On the basis of tissue \Vet ,¥eight, large \Vhe l ks consun1ed .i significantly n1 ore prey fle~h tissue than small \vhelks (ANOVA. s F = 4.45. P < 0.05). Indi vidual small •.vhelks ate proportionately n1ore hard clan, tissue on a clan, ,,.,et weight: whelk wet weight 6 basi~ than large \v helks (Fig. 2). Maxi1nun1 daily clan, consu mp- B. ~ 1ion rates of 5.61'.)f, or body wet \veight were recorded for s,nall 7 \v helks as cornpared to I .6o/" of body wet weight for large whe lks . 8 DJSCUSSION 9 Large rapa whelks ( 101 - 160 mm SL) are ab le tocon~u me up 10 10 2.7 gran1s of clan, tissue (we1 weight) per day or 0.8o/o of their body ,.veighl per clay at ,,.,a,er ten1per:nures of approx in1ately 11 26°C. In contrast. sn1all rapa 1vhelks (60-100 111 111 SL) ingested an average 3.6% of their body \\'eight every day. \vhich is n1ore than J 12===== four tirne5 tha1 observed for larger rapa whelks at sin1 ilar \¥ater 100 80 60 40 20 0 0 20 40 60 80 100 1 Percemage of small clams consumed Percentage of large clams consumed ten1per;1tures on a \Veight-specific basis. Ed\\ards and Huebner ( 1977) sugges t that ten1 pera tu re affects feedi ng rate in the moon Figure I. Percentage of s n1all (50-70 111111 SH ) and la rge (71- 100 111m snai l Po/i11ices by increas ing predators' 111e1a bolic rate. and th us SH ) hard clam s eaten in each experirnenta l cage by eacb rapa whelk the requiren1en t for a larger an1 ou n1 of food. The present investi­ during the whole exp erin1cntal period (June 11 to July 18. 2000). AJ N. gation \¥3S conducted during wanner n10111hs and is probably in­ 1-6 = s,nall whelks (60-100 111111 SL). B) N. 7- 12 = la rge whelks (101- 160 mn1 SL ). dicative of the n1axin1un1 feeding activity of rapa whelks. There is RAPA WHELK PRtDATION ON H ARD CLA!VIS 779 considerable vanat1on 1n reported ingestion rates for predatory pahann ock Ri ver in the orth. to the Chesa pea ke Bay Bridge gastropods with va lues up to 25% of its body weight per clay tunnel in the southeas t and to the Lafayelte River in Lhe south reported for the moon snail, Poli11ices dupliccuus (Thorson 197 1). ( Harding & Mann 1999. Mann & Hru·ding 2000). is ,vithin the The hard cla111 fishery in the lower Chesapeake Bay is already historic distribution of M. 111erce11aria (Roegner & Mann 1991 ). in decline. Hard clan1 landings during 1999 were less than lOo/" of The 1999 sun11ner fishing season for hard cla1ns in the lo\ver landings during 1973 (Virginia Marine Resources Comn1ission. Chesapeake Bay produced a harvest of 27388 kg or approxin1ately Newport Ne\vs. VA). The ob~erved decline in hard cla n1 ~tocks 3.040.000 indi vidual clan1s. Based on the preda tion rates obi,erved may be related to increased anthropogenic in1pacts on the Chesa­ in this study, a popL1lation of I 000 rapa whelk~ in the lower Bay peake Bay ecosysten1 in the past 20 years including ovc,fishing. could reduce this yield by bet\veen 0.3 to 0.9o/<' . water pollution and disea$e. Habitat changes arc considereJ the major threats to estuarine ecosysten1 (S1n ith el al. 1999 ). The su­ ACKN0\¥ LEDGNIENTS perin1position of a novel invad ing predator on this already stressed population has clear ecological and econon1ic in1plications. This \VOrk ,vas supported by funds fro111 the National Ocean ic Virnstein ( 1977). found that particularly in Chesapeake Bay, Atmospheric Adn1inistration, National Sea Grant Aquatic Nui­ densities of infaunaJ species are not controJJ ed by competitive sance Species Research and Outreach Progra111. Virginia Sea interactions for food or space but n1ainl y by the action or predators. Grant. the Virginia Saltwater Corn111ercial Fishj ng Developn1ent lf th e introduction of Rapa11a 1·e11osa into the lo\ver Chesapeake Fund. and the Commonweal th of Virginia. It \Va!; completed by the Bay results in a large scale successful invasion. rapa whelks could senior au thor during study for a M.S. degree :n the University of have a seriou1> negative impac t on the density and disrribution of Wa les, Bangor. UK. Financial support for the senior au thor's visit the native hard cla111 population in the lo~1er Chesapeake Bay. A t co the Virginia Institute of Marine Science \vas provided by the this tin1e \Ve do not have a good estirnate of the resident population Drapers Con1pany. London. The authors thank Melissa South­ of rapa \vhelks in the Chesapeake Bay bu t is poss ible to use our ,vorth, Erica Westcott. Stephanie H:iywood. Rl1oncla Howlett, data for a hypothetical calcul ation to es tin1ace potential in1pacl of D. Bryn Jones. and Catherine Ware for assistance in general labo­ the \Vhel k on the clan1 population. The rapa whelk distribution in ratory procedure~ during the study. This is contribution nu1nber the Chesapeake Bay, which extends from the n1 outh of the Rap- 2487 fron1 the Virginia [nstitute of Marine Science.

LITERATURE CITED Drapkin , E. I. I 953. Nov ii molliusc v Cernom more. Priroda 8:92- 95. Habi1at requucmcnts for Chesapeake Bay living resources. Solomons. Edwards. D. C. & J. D. Huebner. 1977. Feeding and growth rate, of 1'1aryland: Chap1er 5: 1- 17. Chesapeake Research Con;ortium. Inc. Poli11ices d11plicat11$ preying on P.1ya c11·e11aria at Barnstable Harbor. Savini. 0. 200 I Predation strmegies and feeding raies of the introduced J\1assachusens. 58: 12 18-1236. gastropod Rapano ve11osa (Valencienncs. I 846) in Chesapeake Bay Ghison i, F. 1974. Rapc111a renosa (Valencicnne>) nuova ospite adriatica? (Virginia. U.S.A.). WI.Sc. Thesis. School of Ocean Sciences, University Co11chiglie Nlila110 I0 : 125- L26. of \:Vale; Bangor. Nlcnai Bridge. Anglesey. \.Vales, UK. 62 pp. Harding, J. M. & R. Mann. 1999. Obscrvauons on the biology of the Smith, L. D .. M. J. \.Vonham. L. D. McCann , G. M. Ru iz. A. H. Hines & Veined Rapa whelk. Rapana ve11osa (Valenciennes. 18-16) in the J. T. Carlton. 1999. In vasion pressure 10 a ball as1-nooded estuary and Chesapeake Bay. J. Shellfish Res. 18. 9-17. an asse;sn1ent of inoc ulant survival. Bi"log. 1111·. I :67- 87. Kou1soubas. D. & E. Voultsiadou-Koukoura. 1990. The occurrence of Thorson, G. 1971. Life in the Sea. New York: 1'1cGraw-Hill. 256 pp. l?apa11a venosa (Valenciennes. 18-16) (. Thaididae) 111 the Tsi. C .. X. 1\ila. z. Lou & F. Zhang. 1983. Illustrations of the fauna of Aegean Sea. Bo/le11i110 Malacologico. Mi lano. 26:201 - 204. China (Nlollusca). vol. 2. Beij ing: Science Press. pp. l- 150. pla1es Mann. R . & J. M. Hardmg. 2000. Invasion of the North An1eri can Atlantic I- IV . by a large predatory as1an mollusc. Biological Invasions 2:7- 22. Pastorino, G., P. E. Penchaszadeh, L. Schej1er & C. Bremec. 2000. Rap(l11a Vimstein, R. W. 1977. The importanr of pre