tntroduced Species Page42

San FranciscoBay in the San Pablo Channel by 1954 and from the Delta-Mendota Canal, in fresh water, in 1973 Light, 1977;Carlton, 1979a,p. 30S!.It was also collected from freshwaterin the New River and the Alamo River in Imperial County in southeasternCalifornia in 1979,and from a canalin Mar Chiquita, Argentina with the Australian serpulid worm Ficopomatusertigmaticus Kudenov, 1983!. Boccardiellaligerica may have been introduced with ships' ballast water, perhaps during World War II or the Korean War. Spionid larvae are among the most abundant and frequently encountered groups of organisms in ballast water Carlton k Geller, 1993!. B. tigericawas one of the most common benthic organisms collected by CDFG near Martinez in 1975-1981,and was found upstream as far as Collinsville in the western Delta Markman, 1986!.In 1976,a dry year, Siegfried et al. 980! found B. ligerica to be a dominant species at their upstream stations near Collinsville in the late summer and fall, with peak densities of around 20,000individuals/m2, and Markman 986! similarly reported an increase in B. ligericaupstream in the dry year of 1981.Light 978, p. 201! summarizing recent studies showed 8. 1igerica collected only from the ends of the Bay: at the southern end of the South Bay and from Martinez to the Antioch bridge in the northern Bay.

Ficopomatusenigmaticus Fauvel, 1923! [SERPULTDAE]

AUSTRALIAN TUBEWORM

SYNONYMS:MercieretIa enigrnatica

Ficopomatusenigmaticus is an Australian worm that builds and lives in a white, calcareoustube, the tubes forming large agglomerate masseswhen the worm is abundant. Reported from ships' hulls WHOI, 1952! and probably transported as hull fouling, it has becomeestablished in many parts of the world including the Black, Caspian and Mediterranean seas,northern Europe, Uruguay, Argentina, Hawaii, Japan and the Gulf of Mexico. It was first reported in San FranciscoBay from Lake Merritt, a tidal lagoon on the East Bay shore, in a 1921article in the Oakland Tribune headlined "Coral Reefs Spreading in Lake Merritt." The "reefs" had been first noticed by park officials about a year earlier. It was also in 1921that F. enigmaticuswas discovered and described in France, and discovered at the London docks Carlton, 1979a!. F. enigmaticus apparently requires water temperatures of at least 18'C to breed Obenat k Pezzani, 1994!, and in Europe it frequently lives in water heated by the cooling water effluent from power plants Vaas; 1978!. In the Netherlands its colonies have interfered with lock operations Vaas; 1978!. F. enigmaticushas beencollected from many sitesin the South,Central and San Pablo bays, sometimes in densemasses, especially from enclosedlagoons or protected waters. Thesesites include Aquatic Park Lagoon in Berkeley first appeared between 1942and 1946,and still abundant!, Alameda Lagoons abundant in 1971, scarcein the 1990s!,Berkeley Yacht Harbor 969!, San Rafael and Corte Madera Page43 Introduced Species Creek970!, Palo Alto Yacht Harbor and China Camp 974!, Foste Ci y Lgoons andBelvedere I.agoons before 1979!, and the Petaluma River Turning Bsin abundantin 1993' see Carlton, 1979a, p,331., for references onthe other records!. It is lessabundant now in LakeMerritt than it wasin the1920s and the 1960s-70s. Newman's963! report of a serpulidworm "comparable toMerciere/ta enigmatica"inthe seawater system ofa navalvessel docked inSan Francisco Bay suggeststhat it mayhave been introduced more than once.

Heteromastusfilifonnis Claparede, 1864! [CAPITELUDAE] Heteromastusfiliforrnis isnative to the Atlantic coast ofthe United States fromNew England tothe Gulf of Mexico, and has also been reported from Greenland,Sweden, theMediterranean, Morocco, South Africa, the Persian Gulf, NewZealand, Japan, and the Bering and Chukchi Seas. The wide temperature range coveredbythese locations suggests thatmore than one species maybe involved. In CaliforniaHeterornasfus wascollected from San Francisco Bay in 1936,from Morro Bayin1960, possibly fromsouthern California by1961, and from Bolinas Lagoon by 1969.It was collected from Vancouver Island in 1962,from Coos Bay, Oregon in 1970 pers.obs.!, and from Grays Harbor, Washington by1977 Carlton, 1979a, p.322!. Aswith other polychaetes firstcollected onthe Padfic Coast inthe 1930s by QlgaHartman including Polydora ligniand Sfrebfospio benedicti inSan Francisco Bay!,Heterornastus fitiformis may have been. present but undetected formany decadesdue to the lack of earlier investigations ofintertidal polychaetes onthis coast.Thus this mud-dwelling capitellid worm may have been introduced toSan FranciscoBayin the late nineteenth orearly twentieth century with Atlantic oysters, withwhich it occurs;Wells, 1961!, ormay have been an early ballast water introduction.Heteromastusfiliformis is commonlycollected from the far South Bay to the westernhalf of Suisun Bay at concentrations of 10to 4000 per square meter, and has beencollected upstream toPittsburg Hopkins, 1986; Markmann, 1986!. It is one of themost common benthic organisms in the shallows of SanPablo Bay and the channelsof the SouthBay Nichols& Thompson,1985a!.

Manayunkr'aspeciosa Leidy, 1858 [SABBLLIDAEJ SYNONYMS;Manayunkia eriensis Krecker, 1939! Manayunkiaspeciosa is a freshwaterpolychaete native to eastern North Americafrom the westernmost Great Lakes, New York and Lake Champlain in Vermontsouth to theSavannah River in SouthCarolina Klemm, 1985!. It was collectedfrom two small, shallow lakes in northern Alaska in1961 and 1964, and fromSevenmile Canal in Klarnath County, Oregon in 1964 Hazel, 1966; Holmquist, 1967;Croskery, 1978!. It was first collected inCalifornia from the Mokelumne River nearNew Hope Landing inthe eastern Delta in 1963 Hazel, 1966! Hartrnan's 969! Introduced Species Pttge 44

report of this speciesfrom SanPablo and Suisunbays appears to be basedon a misreading of earlier reports. Thistube-dwelling, colonial worm has neither a restingstage nor a planktonicor swimmingstage that mightaid dispersalor transportin water youngworms mature within the parentaltube and emerge as small, crawling adults to build tubesnearby Holmquist, 1967; Croskery, 1978!. However, transport in detrituscarried in watermay be possible.Hazel 966! suggestedthat M. speciosa arrived in the Delta in the water in which freshwatergamefish from the eastern UnitedStates were transported. Hazel 966!, citingSmith 896!, notedas pertinent the fact that white catfish Ictalurtts now Ameittrus! catus introduced to the Delta in 1874were taken from the SchuylkillRiver, Pennsylvania, the type localityfor M. speciosa.However, although Smith 896! describesthese as "white catfish or Schuylkillcatfish," he clearlystates that the fish transportedto Californiawere taken from the RaritanRiver, New Jersey.Thus "Schuylkill" appears to bepart of a commonname for thesefish, ratherthan the site from whichthey werecollected Although most or all of the freshwater fish introduced to California from the northeasternUnited Statesappear to havebeen planted in the late nineteenthor early twentieth century Table 1! and Manayunkiawas not discoveredin California until 1963,it is possiblethat this smallpolychaete was present and overlookedfor a longtime Holmquist,1967; Mackie k Qadri,1971!. Alternatively, it may have been transported in detritus floating in freshwater ballast. Martayttnkiuis the fourthmost numerous benthic invertebrate collected by the California Departmentof Water Resourcesin the Delta,with densitiesin the interiorof theDelta of 2,000to 50,000individuals/m2. It apparentlyrequires fresh waterand silty substrates,and is foundin theeastern portions of theDelta downstreamto Frank'sTract and Rio Vista, with questionablerecords from * few stationsfurther downstream Markmann, 1986; Herbold k Moyle,1989; Hymanson et al., 1994!.

Marenzelleria viridis Verrill, 1873!tSPIONIDAE]

SYNONYMS:Scolecolepis viridis Scolecolepis ten@is Scolecolepides vi ri dis

Marenzelleria viridis is native to the northwestern Atlantic and was collected in Germanyin 1983,probably havingbeen introduced via ballast water Essink8c Kleef,1993!. It spreadthough western and northern Europe and into theBaltic Sea, where it is now extremely abundant. It was first collected on the Pacific coast in Nov. 1991 at Collinsville on the SacramentoRiver, at which station it has been found most consistentlyand abundantlyat up to 1700worms/m2. It has sincebeen collectedfrom Frank's Tract and the Old Riverin theDelta downstream to Grizzly Bayin 1992,in SanFablo Bay in 1995,and in thefar SouthBay M.Kellogg, pers. comm,1995; W. Fields,pers. comm., 1995; DWR, 1995!. It probablyarrived in ballast water. Page45 Introduced Species

Marphysasanguinea Montagu, 1815! tEUNICIDAE] Marphysasattgttinea isregarded asa singlecosmopolitan species,but likely consistsofseveral difficult-to-distinguish butdistinct taxa. It isreported from Europe from Great Britain tothe Mediterranean!, thewestern Atlantic Massachusettstothe West Indies, the Gulf of Mexico, Bermuda andthe Bahamas!, Japan,China, and from Australasia tothe Red Sea and Africa, Inthe eastern Pacific it hasbeen known from San Francisco Bay since 1969, and from various sites betweenLosAngeles andPanazna Carlton, 1979a, p.302!. The San Francisco Bay populationmayhave been introduced fromthe Atlantic with shipments ofoysters, withwhich it occurson the Atlantic coast Wells, 1961!, or it mayhave been introducedHopkins in ballast969! water.reported M.sattgttinea ascommon atconcentrations of10-200 persquare meter, but found only in the South Bay south ofHunters Point, and most commonlyin the channels.

Nereissttccirtea Frey & Leuckart,1847! [NEREIDAEj

PILE WORM

SYNONYMS: Nean thes sttccirtea Nereis saltorti Hartman, 1936 Nereis limbata Webster, 1879 Thiseuryhaline "pile worm" lives in a varietyofhabitats; under rocks, in mudand sand, in oysterbeds and in foulingcommunities. It isreported from locationsaround the world, including the eastern Atlantic and the Mediterranean; thewestern Atlantic from the Gulf of St.Lawrence to theWest Indies, Gulf of Mexicoand South America; West Africa and South Africa; and the tropical eastern Pacificfrom the Gulf of Californiato Colombia Carlton, 1979a, p. 295!.These reports mayinvolve a singlespecies transported synanthropically aboutthe globe, or multiple, closely-relatedspecies. In Californiait hasbeen collected from San Francisco Bay earliestrecords from1896!, the Salton Sea from 1935!, Tomales Bay 941!, several southern Californiabays from 1952!, and in Oregonfrom Netarts Bay 976! Carlton,1979a! andCoos Bay 986; pers. obs.!. The San Francisco Bay population probably originatedinthe western North Atlantic and arrived inshipments ofAtlantic oysters with which it occurs onthe Atlantic coast; Wells, 1961; Maurer k Watling, 1973!or in shipfouling. It may have been independently introduced tosouthern Californiabays in baUast water or as fouling, or secondarily introduced from San FranciscoBay by coastalshipping. Nereissttccinea is commonin SanFrancisco Bay in watersof lessthan two metersdepth, generally atconcentrations of 10-400 individuals/m>. It has mainly beencollected in the northern Bay from San Pablo Bay to Antioch,and in thefar SouthBay below the Durnbarton Bridge Hopkins, 1986!. It is one of thedominant Introduced Species Page 46 benthicorganisms in SuisunBay Nichols k Thompson,1985a!. As discussedby Oglesby 965!, the native worm Nereis vexillasaoccupies more marine waters in the Central Bay and the native Nereis limnicola occupies fresher waters in the Delta. Nereissuccirtea may thus have squeezedin betweentwo existing pile worm populations,with eachpopulation restrictedby a combinationof physiological limitations and competition with its neighbors. Recher 966! noted Nereis succirtea in the diet of shorebirds in the South Bay, and Oglesby965b! reportedon infectionby the trematodeparasite Parvatrerrta borealisalong the East Bay shore. Carlton 979a! summarizes other research on the worm's physiology and ecology.

Polydoraligrti Webster, 1879 [SPIONIDAE]

MUD WORM

SYNONYMS:Polydora amarincola Hartman, 1936

Polydora ligrti is native to the northern Atlantic where it is found in mudflats,fouling including ship fouling; Hartman,1961! and oysterbeds, sometimesforming thick mud bedsthat causeextensive oyster mortalities.In the Pacific it was first collected in Ladysmith Harbor, British Columbia in 1932 " on [oyster]cultch sacks"!,in SanFrancisco Bay in 1933 redescribedas Polydora amarincola!,and in False Bay on San Juan Island, Washington in 1937.It has since beenreported from otherbays and harbors in BritishColumbia, Washington and Oregon,and from DrakesEstero, Bolinas Lagoon, Elkhorn Slough, Morro Bay, Mugu Lagoon,Santa Monica Bay,Los Angeles/LongBeach Harbors, Alamitos Bay, Anaheim Bay, SantaCatalina Island, Mission Bay and the SaltonSea in California seeCarlton, 1979a, p. 306,for references!.There are a fewrecords, questioned by Carlton 979a!, from Mexico, As with Heteromastttsfiliformis, Polydoraligrti could have been transported to the Pacific coast with Atlantic oysters decadesearlier and overlooked, or transportedin ballast water larvaeof Polydoraspecies have been found to survive transportin ballasttanks; Carlton, 1985,p. 345!,or possiblyin ship fouling. Considerablemovement between embayments along the coast may have occurred with shellfishtransplants or coastalshipping. In SanFrancisco Bay it hasbeen collectedfrom the far SouthBay to CarquinezStrait Light, 1977,1978!, and is oneof the more commonbenthic organisms in the shallowsof SanPablo Bay and the channelsof the SouthBay {Nichols & Thompson,1985a!.

Potamilla sp. [SABELLIDAE] This worm was first collected in June 1989at ShermanLake in the western Delta by the California Department of Water Resources.It has been found from Frank'sTract and the Old River in the Deltadownstream to Grizzly Bay,and is most commonat or just upstreamof the confluenceof the Sacramentoand SanJoaquin Page47 Introduced Species

Rivers,where it hasreached densities of over 16,000/m2 W. Fields, pers. comm., 1995;DWR, 1995!. Its absencefrom Delta samplings in previousdecades suggest a relativelyrecent introduction. It was probably introduced inballast water.

Pseudopolydorakempi Southern, 1921! [SPIONIDAE] SYNONYMS:Neopygospio laminifera Berkeley & Berkeley,1954 Pseudopolydorakempi californica Light, 1969 PseudopoIydorakempijaponica Imajima & Hartman,1964 Thisspionid worm has been reported from Mozambique, India,Japan and the KurileIslands, in watersranging from marine salinities down to 6 ppt Light,1969!. It wasfirst collected in the eastern Pacific in 1951at Nanaimo, British Columbia, and laterfrom False Bay, San Juan Island 968! in WashingtonandYaquina Bay 974!, NetartsBay 976! and Coos Bay 977; JTC, pers. obs.! in Oregon.InCalifornia it appearedinMorro Bay 960!, Bolinas Lagoon 967!, San Francisco Bay972!, and BodegaHarbor, Tomales Bayand Anaheim Bay 975! references inCarlton, 1979a, p.310!. Many of these sites have received shipments ofthe oyster Crassosfrea gigas fromJapan, possibly containing thisworm. Alternatively it couM have been transportedin ballast water or shipfouling. Light969! found that the California specimens more closely resembled Indianthan japanese P.kempi. In CaliforniaP. kempi occurs intertidally and subtidallyonmud and sand. It has been collected inSan Francisco Bayfrom the far SouthBay to thewestern end of CarquinezStrait Light, 1977, 1978!.

Pseudopolydorapaucibranchia$a Okuda, 1937! [SPIONIDAE]

SYNONYMS:Polydora paucibranchiata P,paucibranchiata wasdescribed from Japan. It was first reported from Australiain 1973 Carlton, 1985! may also be present in NewZealand. It was reportedfrom Los Angeles Harbor in 1950and thereafter from other southern Californiasites: Newport Bay in 1951,San Diego Bay in 1952,Alamitos Bay in 1958, AnaheimBay and Santa Barbara in 1975,and Mission Bay indensities up to 60,000 individuals/m2!by1981 Carlton, 1979a; Levin, 1981!. It was collected in South San FranciscoBay Hunters Point and Oakland Inner Harbor! in 1973,Elkhorn Slough, BodegaHarbor and Tomales Bay in 1975 where it "may be the dominant spionid polychaeteonmany sand flats," Blake, 1975!, and Netarts Bay, Oregon in 1976 Light, 1977;Carlton, 1979a,p. 312!. Summarizingrecent studies, Light 978, p. 200!showed P. paucibranchiata collectedfrom the South Bay to thewestern end of CarquinezStrait. It mayhave beenintroduced to the northeasternPacific in ballastwater or in fouling on ships, possiblyrelated to increasedship traffic during or afterthe Korean War, or with japanese oysters, Introduced Species Page 48

Sabacoelongatus Verrill, 1873! [MAI.DANIDAEj

BAMBOO WORM

SYNONYMS:Asychis elongata Asychisarnphiglypta Ehlers! Maldane elongata Maldanopsiselongata Brachioasychis colmani Brachioasychis americana

This common"bamboo worm" is native to the westernAtlantic from Maine toFlorida, the Gulf of Mexicoand British Honduras Light, 1974!. It wasfirst reportedfrom south San Francisco Bay in 1960 Berkeley & Berkeley, 1960! and probablycollected in the 1950s Carlton, 1979a, p. 324!.It isnow extremely common, typicallyfound in concentrationsof 10-1,000individuals/m~ at moststations from the far SouthBay to mid-SanPablo Bay, and in concentrationsof 1,000-5,000 individuals/m2alongthe eastern shore of the Central Bay. It isnot found upstream of SanPablo Bay Hopkins,1986!. Light974! suggested that Sabaco was introduced with Atlantic oysters. As therehad been no systematic subtidal benthic sampling inSan Francisco Baysince the 1912-13Albatross survey, it is conceivablethat it wasa lateintroduction with oystersin the 1920s or 1930sand overlooked for 30 years. Alternatively, it may have been introduced with ballast water.

Streblospiobenedicti Webster, 1879 [SPIONIDAEj

SYNONYMS:Streblospio lutincola Hartman, 1936 Sfreblospiobenedicti is common in thewestern Atlantic, ranging from the Gulfof St.Lawrence to theGulf of Mexicoand Venezuela, and is alsofound in northernEurope and the Mediterranean andBlack seas. It was collected atBerkeley in SanFrancisco Bay in 1932,in Tomales Bay and Bodega Harbor by 1936,and in subsequentyears in severalother estuaries south to Newport Bay and north to Grays Harbor,Washington records in Carlton, 1979a, p. 314!.As with Polydora ligni, the otherspionid discovered inSan Francisco Bayin the1930s, Streblospio could have beenintroduced with Atlantic oysters with which it occurson the Atlantic coast; Wells,1961; Maurer & Watling,1973!, in ballastwater, or possibly in shipfouling, andmoved along the Pacific coast with shellfish transplants or coastal shipping. In SanFrancisco Bay Streblospiobenedicti has been collected from the far SouthBay to Antioch,commonly at densitiesof 1-10,000individuals/m in the channelsand up to 50,000or moreindividuals/m2 in near shore areas, especially in constrictedcmbayments Light, 1978; Hopkins, 1986!. It is oneof themost common benthicorganisms inthe shallows ofSan Pablo Bay and the channels ofthe South Bay Nichols & Thompson,1985a!.

MOLI.VSCPa GASmar OD Busycotypuscanaliculatus Linnaeus, 1758! [MELONGENIDAE]

CHANNELED WHELK SYNONYMS:Busycon canalicutatum Busycon pyrum Thechanneled whelk, a nativeof thewestern Atlantic from Massachusetts to Florida,isnow by far the largest snail inSan Francisco Bay.As discussed byCarlton 979a!,Stohler 962! stated that the whelk was first collected inthe Bay at Alameda in1948, but specimens from Berkeley atthe California Academy ofSciences may havebeen collected asearly as 1938. There are records and frequent observations of thewhelk on the eastern shore of theBay from Alameda and Bay Farm Island to Berkeley,andon the western shore from Belmont Slough toCandlestick Point.One specimenwascollected in1953 from the Tiburon Peninsula inMarin County Stoh]er,1962, Carlton, 1979a, p. 397!. Thechanneled whelk feeds on bivalves, It produces distinctive strings of egg casesthat release crawling nonplanktonic! snails. Natural dispersal may be achievedby floating egg cases, one string of which was collected atBolinas Lagoon. Thewhelk may have been introduced toSan Francisco Baywith some of the later andsmaller shipments ofAtlantic oysters with which it occurson the Atlantic coast;Wells, 1961; Maurer & Watling1973!, but could also have been released from a private or schoolaquarium.

Cipangopatudinachinensis matteata Reeve, 1863! [VIVIPARIDAE]

CHINESE MYSTERY SNAIL

SYNONYMS;Vivi parus malleatus Cipangopaludina matteafa V ivipar us stelmap hor us Bourgui gnat A longhistory ofrevisions anddisagreements overidentification, reviewed herewith regard to Bay and Delta area specimens, leaves it unclear whether one or two or possibly more! species ofJapanese orChinese viviparids have been introduced into California. In 1S92Wood reported buying live snails from Japan ata Chinesemarket in SanFrancisco, ata priceof tencents per dozen, and found "that each specimen containedinside, from twelve to eighteen young shells." The snails were identified Introduced Species Page50

by W. J. Raymondas Palttdina japonica Martens. Wood's specimens were later separatedby Tien-ChienYen at theCalifornia Academy of Sciencesinto threelots identified as Vivipttrus japonictts,Viviparus japorticus inakarva and Viviparus stelrrtaphorus.The last of theseis accomparuedby Wood'sbusiness card with the notation:"Bought alive for 10cents a dozenat a Chinesevegetable store on Wed. morning, Nov 18/91- Camefrom China."Stearns 901! describedWood's snails as "being part of the first lot brought alive from Japan,where they arecollected in the rice-fields near Yokohama, and are sold for a few cents a quart." Sorenson950! recalled purchasingViviparus tnalleaftts in Fresno's Chinatownin 1895which "had beenimported from Chineserice fields to Fresnofor the thousands of Chinese vineyard workers there." In 1901Stearns reported receivinga few snailsfrom the SanJose or Mt. Hamilton area"a year or more ago." One living specimenwas examinedand identifiedby Pilsbry as "Vivipara steltrtaphoraBgt. =V. malleataRve.!." Later Hannibal 908! found no viviparids in the Mt. Hamilton area, but between San Joseand San FranciscoBay collected snails identified by Dali as Viviparalecythoides Bensen. He reported theseas "introduced by the Chinesefifteen or twenty yearsago" and "cornrnonwhere planted,but spreadsslowly." A few yearslater, Hannibal 911! reportedthat on re-examination both these snails and Wood's snails in Raymond's collection were Viviparrts rnalleatusReeve, which he said were "brought from Yokohama and originally plantedbetween Alameda and Centervilleta small town 18 miles eastof Fresno]to supply the markets of San FranciscoBay...whence colonies have been distributed to a numberof points in the Sacramento-SanJoaquin Valley as well. This is verified by specimensfrom an irrigating ditch near Fresno."However, Hannibal reported that he also found Vivipara japonica, "readily distinguished from malleafus," in an irrigation ditch at Hanford, about 30 miles southeastof Fresno. The first record of introduced viviparids within the study zone consists of five shells at the California Academy of Sciences,labeled as malleata,collected from a sloughnear Holt in the Delta in 1938.Other specimensfrom within or near the Delta include eight snails collected from a canal north of Stockton in 1933,three snails from Victoria Island in 1941,eight snails from SycamoreSlough in 1946, and two undated snails from a slough near Stockton, all labeled as rnalleata.Greg 948! reported finding a few live and many broken shells of Vivipara malleatain irrigation ditches near Stockton, speculating that muskrat may have been eating the snails. Sorenson 9SO! reported collecting Viviparus rttalleatusfrom an irrigation canal 60 miles northwest of Fresno in 1948. Also, the wet collections at the California Academy of Sciencesinclude two viviparid snails labeled Bellamya japo»ica that were collected at Stockton in 1968. Hanna 966!, referred all existing western North America records to Viviparus stelmaphorus,based on finding enoughvariation in shell morphology in specimensfrom a singlelocality to encompassrecords that had beenreported as rnaileata,japonica, irvakawa or lecythoides.He reported that the snailswere still for sale in San Franciscomarkets and very abundant throughout the Delta and in irrigation canals, and in Mountain Lake and Stow Lake in San Francisco. Taylor 981! assignedthese various California records to two species, Bellamyajaponica including Wood's1891 market specimens,Hannibal's 1911 Page51 Introduced Species Hanfordrecord, and records from Mountain Lake! and Cipangopaludina chinensis rnalleata apparently including allother California records known tohim!, which helisted as occurring in irrigation ditches, sloughs and ponds from the Central Valleyand San Francisco Bayarea to southern California. Hereported both species presentin Californiasince 1891. Basedupon these records, weconclude thatthe Chinese mystery snail is establishedin the study region. The current distribution and status of theJapanese mysterysnail placed inBellamya byTaylor 981! and in Cipangopaludina by Turgeonetal, 988!! remains tobe determined in the Bay area. Viviparidsnails from these one or more species have been reported from manyother North American locations, including: theChinese market atVictoria, BritishColumbia Pilsbry k Johnson,1894!; Muddy River in Boston'sFenway from 1914to at least1942!; Worcester, Massachusetts 917!; Philadelphia 925!, at St. Petersburg,Florida and near Niagara Falls 942!; Ottawa, Sioux City, Iowa and Seattle943!; near Agassiz, British Columbia collected by1948, but reportedly plantedin1908!; Lake Erie 940s!; Jefferson County, Washington 964!;and Hawaii by1976! La Rocque, 1948; Abbott, 1950; Mills et al., 1993; and specimens atthe CaliforniaAcademy ofSciences!. These snails are both used as food items and commonlysoldby dealers ofaquarium fish, which has Undoubtedly helped to spreadthem La Rocque, 1948; Abbott, 1950!. They were reportedly introduced to SanduskyBay, Lake Erie to feed channel catfish in the 1940s, and became so abundantbythe 1960s that they were a nuisancetocommercial seine fisherman, whoreported sometimes catching two tons in a singleseine haul Wolfert & Hiltunen, 1968!.

Crepidttlaconvexa Say, 1822 [CALYPTRAEIDAE]

CONVEX SLIPPER SHELL

SYNONYM[:Crepidula glauca Say, 1822 Thisslipper shell is native to the western Atlantic, where it isfound from NovaScotia to Floridaand Puerto Rico. It wasfirst collectedin SanFrancisco in 1898,from oyster beds, and was almost certainly introduced inshipments ofAtlantic oysters with which it occurs onthe Atlantic coast; Wells, 1961!. InSan Francisco Bay Hopkins986! reported Crepidula spp. mainly from the South Bay, where C. canvexais commonly found on shells of thenative oyster Ostrea Iurida and the Atlanticmudsnail Ilyanassa obsaleta. It is notknown from any other Pacific coast site Carlton, 1979a,p. 370!.

Crepidulaplana Say, 1822 [CAI.YPTRAEIDAE]

EASTERN WHITE SLIPPER SHELL introducedSpecies Page52

Crepidulaplana is nativeto the western Atlantic with a recordedrange from PrinceEdward Island to SouthAmerica. It wasfirst reported on the PacificCoast fromthe eastern shore of San Francisco Bay in 1901,where it wasprobably introducedwith shipmentsof Atlantic oysters with which it occurson the Atlantic coast;Wells, 1961!, and was found in WillapaBay and Puget Sound in the 1930sand 1940s Carlton, 1979a, p. 376!.C. plana is similar to and may be mistaken for the nativeflat slipper shells C. perforansand C. nummaria,and in factwent unreported in theBay, though occasionally collected and misidentified or unnoticed,for many decadesafter its initialsighting. It is foundconsiderably further into the estuary than thenative slipper shells which are restricted tothe outer, more marine portions of theCentral Bay. On boththe Atlantic coast and in SanFrancisco Bay, C. plana is commonon the insideof hermitcrab-occupied snail shells,

Ilyartassaobsoleta Say, 1822! [NASSARIIDAE]

EASTERN MUDSNAIL

SYNONYMS: Rassarius obsolefus

This mudsnail is native to the westernAtlantic from the Gulf of St. Lawrence toFlorida, It wasintroduced tothe Pacific Coast with shipmentsof Atlantic oysters it isreported from oyster beds on the Atlantic coast; Wells, 1961!, and was first collectedin SanFrancisco Bay in 1907from beds of Atlanticoysters at Alameda. Carlton979a! suggeststhat it wasprobably introduced between 1901 and 1907, as its presencein the Baywas unlikely to have been missed for very long due to the intensiveactivities of shellcollectors in thearea beginning in the1890s. Ilyartassahas also established breeding populations in Willapa Bay, Washingtonand Boundary Bay, British Columbia, first reported in 1945and '1952 respectivelybut possiblypresent for a considerabletime earlier,It hasalso been reportedfrom but apparentlynot established populations in five additionalPacific Coastsites, as discussed byCarlton 979a, p. 404!:Tomales Bay 920s-1930s?!, "BolinasBay" 920s or earlier!, Humboldt Bay 930!, Birch Bay, British Columbia 950s!,and one specimen from Bodega Bay 968!. Ilyanassaistoday the dominant mudflat gastropod inSan Francisco Bay Nichols& Thompson,1985b!, and is also sometimesabundant m salt marshesand marshsloughs and on pilings. Hopkins 986! reported it mainlyfrom the southern partof theSouth Bay and from San Pablo Bay, and we havealso seen it abundantat Alameda.Although intensively studied in theAtlantic with, for example,studies demonstratingsignificant effects on mudflat community structure and sediment composition Grant, 1965; Sibert, 1968!!, there has been relatively little work on the PacificCoast. Ilyanassa is listed or mentionedin many faunal surveys and checklists andbird diet studies e. g. Painter 966! lists it an important food of diving ducks, butWilliams 929! and Moffitt 941! found it tobe a minorornegligible food for Californiaclapper rail!, and a fewstudies contain brief notes on its ecology Carpelan,1957; Filice, 1959a; Quayle, 1964a; Vassallo, 1969!. Itsdistributional ecology Page53 Introduced Species inLake Merritt is the subject ofan unpublished master s thesis Gilmore, 1935!. GrodhausandKeh 959! found it to harbor five species oftrematode flatworms, includingtheschistosome Austrobilharria variglandis whichis responsible for "swimmers'itch." Race 979, 1982! demonstrated competitive displacernent and predationofthe native hornsnail Cerithidea califorrtica, asdiscussed inChapter 6.

Lit farinasaxati lis Olivi,1792! [LITTQRINIDAE]

ROUGH PERIWINKLE Thiscommon north Atlantic snail was first collected inSan Francisco Bayby J.Carlton inMay of 1993 onthe shore ofthe Emeryville Marina. Thissite is adjacent toa publicboatramp and dock, and L.saxatiIt's waslikely introduced inthe seaweed usedtopack live marine baitworms shipped fromMaine and discarded byanglers. Wehave repeatedly found live L. saxatitis inthe seaweed Ascophyllum rtodosum andoccasionally otherfucoid seaweeds! packing baitworms shipped toNewport Bay andSan Francisco Bay Carlton, 1979a; Lau, 1995; ANC, pers. obs.!. As many as over a millionMaine baitworms areshipped tothe Bay Area each year Lau, 1995! packed inseaweed containing many millions ofliving invertebrates frommany phyla, so thatthis may be a transportvectorof some significance alsosee Miller, 1969!. Wehave irregularly visited and collected a total ofabout 100 live Littorina saxatifisfrom the shore ofthe Emeryville Marina, where the snails were abundant intertidallyin1993 and 1994, andscarce in1995, inthe crevices ofrocky debris along about10 meters ofshoreline. They have not been observed. elsewhere in the Marina orthe Bay. They produce "crawl away" larvae, andcould spread aseggs orsnails on rafting seaweed.

Melanoidestuberculata Miiller, 1774! [THIARIDAE]

RED-RIM MELANIA

SYNONYMS:Thiara tuberculata Melanoidestuberculata is a freshwatersnail native to theregion from Africa tothe East Indies. It was introduced tothe United States through theaquarium trade andwas first reported from California in1972 from adrainage ditch in Riverside County Taylor, 1981!, TheCalifornia Department ofWater Resources hascollected it fromseveral sites in theDelta since December 1988, atdensities ofup to 754 snails/m2 DWR, 1995!.

Urosalpinxcinerea Say, 1822! [MURICIDAE!

ATLANTIC OYSTER DRILL IntroducedSpecies Page54

Urosalpinxcirterea is nativeto the northwesternAtlantic from the ;ul f of St. Lawrenceto Florida.It was introducedin shipmentsof Atlanticoysters to San FranciscoBay, where it wasfirst collected from oyster beds at Belmontm 189p Steams,1894!. It hasbeen collected from many other bays in thenortheastern Pacific,and is currentlyestablished in BoundaryBay, British Columbia first record 1931!,southern Puget Sound 929!, WillapaBay 948!, TamalesBay 935! and NewportBay pre-1940s?! Carlton, 1979a, p. 384!.As Urosa/pirtx's larvae are not pelagic,most of thesesites represent either independent introductions from the Atlanticor intracoastal,human-aided transfers from other bays, including commercialshipments of oystersand other bivalves along the coast.Within San FranciscoBay, Hopkins 986! reportedUrosalpinx only from the SouthBay. Urosalpirtxeats barnacles, mussels and bryozoans as well as oysters.Although in some studies the drill has apparently preferred barnaclesor musselsto oysters Haydock,1964; Carlton, 1979a!, its impactson oysters,especially on oysterspat, can be substantial Haydock, 1964!.

Booneabisufuralis Say, 1821![PYRAM!DElLIDA]

TWO-GROOVE ODOSTOME

SYNONYMS: Merjesfho bisufuralis Odostomia bisufuralis Odostomia fetella

Boo@ca bisufuralis is native to the western Atlantic from the Gulf of St. La~ rence to Delaware,where it is an ectoparasiteboth of the Atlantic oyster Crassosfreavirginica and of a number of bivalvesand gastropodsthat were transported to San FranciscoBay with shipmentsof Atlanticoysters. It was reported in San FranciscoBay in 1977associated with the Atlantic rnudsnailIlyanassa obsoletaand the native hornsnailCerithidea californica on the Fremont shore Race,pers. comm.!, and reportedas commonon a far SouthBay mudflat Nichols & Thompson, 1985b!. Odosfomiafetella reported from SanPablo Bay Filice, 1959! and Suisun Bay Markman, 1986!may also be this species,Carlton 979a, p. 435! arguesthat Bootteabisuturalis was probablyintroduced with oystershipments in the 19th or early 20th century, and remainedunreported because of incomplete systematic work on the Odosfomiacomplex in the northeasternPacific. He predicts that early collections of Bootteabisuturalis and possiblyother speciesof Atlantic odostomids will be found when unsorted, unidentified or misidentified material in museum collectionsis systematicallyworked up by specialists. Although, basedon its associations,Boonea was probably an introduction with oyster shipments that remained unrecognizedfor many year's, it might possibly have been a later introduction in ballast water. Introduced Species Poge55

Catriortarickettsi Behrens, 19S4 [TERGIPEDIDAE] SYNONYMS:Trinchesia sp. Behrensh Tuel, 1977 Catrionarickettsi was first collectedin SanFrancisco Bay from Pete's Harbor, SanMateo County in 1974,where it isassociated with and presumably feeds on the hydroidTubularia crocea Behrens iceTuel, 1977; Behrens, 1984!, and was subsequentlycollected from La Jolla Behrens, 1980!. In1995 it was collected on Tubulariamarina on the oceanside of theUmpcIua River jetty in Oregon0. Goddard,pers, comm., 1995!, The most likely means introduction isin ballastwater or transportedaseggs on ship fouling. Its origin is unknown.

Cuthonaperca Marcus, 1958! [TERGIPEDIDAE]

LAKE MERRITT CUTHONA In California,Cuthona perca is knownonly from Lake Merritt, where it feeds onthe introduced Japanese anemone Hatiptarteita lineata Carlton, 1979a, p. 431,as Trinches~'asp.!It is reported from Brazil, Jamaica, Miami, Barbados, NewZealand andHawaii Behrens, 1991!, The most likely mechanisms of transport are either in ballast water or as eggson ship fouling,

Eubra<1chusmisakiensis Baba, 1960 [EUBRANCHIDAE]

MISAKI BALLON AEOLIS Eubra>fichusmisakensis was describedfrom Japanin 1960and collected at the SanFrancisco Municipal Marina in !962 Behrens, !97!; Gosliner, 1985!. It occurs on boatfloats and docks and silty-clay bottoms throughout the Bay, where it isfound withand apparently feeds on the hydroid Obelia, Carlton, !979a, p.433; Behrens, 1971,1991!. It tnay have been introduced inballast water or as eggs on ship fouling, orpossibly with shipments ofJapanese oysters and overlooked fora few decades.

Okeniapla~ia Baba, 1960 [GONIODORIDIDAE]

FLAT OKEIVIA Page56 Introduced Species

Okeniawas f'rst ~eported from San Francisco Bay by Jom Steinberg in 1960 thes meye r itwas described from Japan!, based on coi}ectior in the195ps. It has ahobeen rePorted from San Qnofre, Qrange County Goslmer, 1995!. It occurson floatsand pilings among fouling and with egg cases on a membraniporidbryozoan tentativelyide tifiedas Conopeumterruissimum!, on rock on mudflats,an ubtidallyinSan Francisco Bay,where it hasbeen reported f om the South Bay palo AltoYa&t Harbor, Crown Beach in Alameda!,Central Bay Berkeley pier anc} Yacht Harbor,San Francisco Yacht Harbor! and San pablo Bay Pont Richmond and China Camp! Carlton, 1979a, p.425' ANC, pers. obs.!. Carlton 979a! suggests that it was Probab}ymtro«~ withshiPPing from Japan, either in ballast water or as eggs on fouling,PehaPs related toincreased trans-Pacific shiptraffic during and after the KoreanWar. Alternativelyit coulcihave been introduced with shipmentso japaneseoysters and overlooked for a coupleof decades

Philirte auriformis Suter, 1909 [PHII INIDAE]

TORTELLINI SNAIL Philirteauriformis is native to NewZealand and possibly southern Australia, and was first identified from San FranciscoBay in july, 1993.It had beencollected fromthe South Bay for about a yearprior to itsrecognition as an introduced species i.e.since about the summer of 1992!in trawlsby theMarine Science Institute of RedwoodCity, USGS and CDFG K. Grimmer,J.Thompson and K. Hieb,pers. comm,!,By 1994 it wasregularly collected in ottertrawls and benthic samples from theCentral Bay P,Donald, pers comm.;ANC, pers. obs.!, and snails and. egg masses whichsuccessfully hatched in the laboratory!were collected from intertidal mudflatsin BodegaHarbor, 120 km northof theentrance to SanFrancisco Bay, in April,1994. As it isnot known from fouling, Philine was probably introduced to California via ballast water Gosliner, 1995!. All specir.;enswere taken from fine,silty mud, Stomachs contained fragmentsof bivalveshells, Nutricula =Transennella!tarttilla artd N. confusein BodegaHarbor and possibly the introducedbivalve Gemma gemma in San FranciscoBay Gosliner,1995!.

Sakuraeolisenosimertsis Baba, 1930! [FACELINIDAE]

WHITE-TENTACLEDJAPANESE AEOLIS SYNONYMS:Coryphella sp. Behrens,1980 Sakuraeolisertosimertsis is native to japan and was first collectedin FranciscoBay in 1972,It is commonand widespread in the southern portions of San FranciscoBay Gosliner,1995!, where it feedson thehydroid Tubularia crocea Introduced Species Page57 growingon boat docks Behrens, 1991!. It couM have been introduced in ballast wateror as eggson fouling.

Tenelliaadspersa Nordmann, 1845! ]TERGIPEDIDAE]

MINIATURE AEOLIS

SYNONYMS:Tenellia pallida Alder & Hancock,1854! Fmbletoniasp. Alder & Hancock,1851 Tenelliaadspersa is widespread in Europeanand Mediterranean waters and recentlyreported from Chesapeake Bayand Brazil, with a single2 mm specimen reportedfrom Japan Carlton, 1979a!. Itwas first collected from the Pacific Coast of NorthAmerica at PointRichmond in SanFrancisco Bay in 1953,and laterfrom the Richmondand Berkeley Yacht Harbors, Lake Merritt, San Leandro Bay, Sausalito andSouth Beach Harbor, San Francisco Carlton, 1979a, p. 428;Jaeckle, 1983; ANC, pers.obs.!. It is now known from Coos Bay to Long Beach Gosliner, 1995!. In Europeit is reported torange from waters ofocean salinity to"quite fresh water"and feedsvoraciously on a varietyof hydroidsincluding the freshwater hydroidCordylophora caspia Roginskaya, 1970!, which is introduced toand commonin theDelta. In SanFrancisco Bay Tenellia adspersa apparently feeds on theintroduced hydroids Tubularia crocea Carlton, 1979a; Behrens, 1991! and Obelia dichotoma Jaeckle, 1983!. Carlton 979b! suggested that it wasprobably introduced fromEurope by shipping,either in ballast water or as eggs on fouling.

~ulmonata Ovatellamyosatis Draparnaud, 1801! [MELAMPIDAE]

SYNONYMS:Alexia sefifer Cooper, 1872 Alexiasetrfer var. tenuis Cooper,1872 Phytia myosotis Ovatellamyosotis occurs on both coasts ofthe north Atlantic, but may have beenintroduced to the westernAtlantic in the late18th or early19th century Berrnan& Carlton,1991!. It wasfirst collected from San Francisco Bay in 1871, probablyintroduced with Atlantic oysters, although possibly carried inwet ballast or wedgedinto holes or cracks in the wooden hulls of sailing vessels. Failure tofind it earlierin SanFrancisco Baydespite intensive prior sheU collecting in the area, plus theinitiation of Atlanticoyster shipments with the completion ofthe transcontinentalrailway in 1869, suggests that Q. myosotis wasintroduced notlong beforeits discovery,probably in 1869-1871. 0, myosotiswas collected inHumboMt Bay in 1876, in San Pedro Harbor in southernCalifornia in 1915,and in Washingtonstate in 1927.It hasnow been Introduced Species Pnge58 recordedfrom numerous Pacific coast bays and estuaries horn Boundary Bay, Britis ColumbiatoScammons Lagoon, Baja California Carlton, 1979a, p. 414!-Since 0 osotislac s planktoruclarvae. theseadditional sites resulted from transport eitheron coastalshipping or in replantingsof oysters,or fromseparate introductions from the Atlantic. 0 myosotisis absent from Pacificcoast Pleistocene deposits but thereis one anomalous report by Gifford916! of thissnail in anaboriginal shellmound on the shoreof SanFrancisco Bay. Carlton 979a!doubts this is pvatella,and Gifford's material has been lost. 0, myosotisis euryhalineand livesunder boards and debris near the high- tideline of saltmarshes and protectedbeaches in lagoonsand bays. The snail has beenstudied in Europebut largely ignored in NorthAmerica. On thePacific coast it hasbeen reported from the stomachsof willets Catoptrophorussemjpalmatus! Stenzelet al., 1976!.Carlton 979a! notedthat its co-occurrence in variousPacific coastsites with severalspecies of nativeand introduced snails provided suitable systemsfor the study of competitiveinteractions between native and introduced species.Herman and Carlton991! founddietary overlap with the nativesnails Assimirteacalifornica and Littorina subrotundatain CoosBay, Oregon, but no evidenceof competitivesuperiority by O. myosotis,and concluded that its establishment was not at the expense of the nativesnails,

MOLLUSCA: BIVALVIA Arcuafulademissa Dillwyn, 1817! [MYTILIDAEf

RIBBED MUSSEL, RIBBED HORSE MUSSEL

SYNONYMS: lschadium demissum Modiolus demissus Geukensia demissa Volsella demiss us Brachidontes dernissus Modiolus plicatulus Lamarck, 1819

Arcuatula demissa more commonlyknown as Ischadjumdemjssum on the Pacific coast and as Geukensia demissaon the Atlantic coast! is native to the northwestAtlantic, commonly found in saltmarshes from the Gulf of St. Lawrence to North Carolina, Southward it is replacedby a subspecies,Arcuatula demissa granossisjmum.It wasfirst collected in the Pacificfrom south San Francisco Bay in 1894 Stearns, 1899!, probably introduced with Atlantic oysters small Arcuatula are commonlyfound on oystersm the Atlantic;Wells, 1961; Maurer 8z Watling, 1973!. It has sincebeen collected from four othersites: Newport Bay first collectedin 1949!, AlamitosBay 957! andAnaheim Bay 972! Reish,1968, 1972; Carlton, 1.979a, p. 440!.Questionable or probably adventitious specimens from other Pacific coast bays arediscussed by Carlton979a!- Introduced Species Page 59

Arcuatulahas becomeone of the most abundantbivalves in San Francisco Bay.De t root927! reported that "countless millions of thesesmall mussels cover theedges and sometimes theentire bottoms ofthe gutters and creeks ofthe west Bay marshes."Pestrong 965! found in thePalo Alto area that they "effectively rip-rap channelbanks when they form in largecolonies, as is oftenthe case."Carlton 979a,b!found Arcuatula lining the base of concreteretairung walls at LakeMerritt, a brackishlagoon in Oakland.Arcuatmla is common and often abundant in salt marshesfrom the South Bay to San Pablo Bay, where it frequentlylies embedded withits posterior margin protruding above the mud. This"endobyssate" habithas resulted in a curiousreported effect on the endangeredCalifornia clapper rail Rallieslongirostris obsoletus!. UeGroot 927! reportedthatthe toes orprobing beaks ofrails are caught and clamped between the exposed,slightly gaping valves ofthe mussel. Hereported thatalmost every rail examinedover the preceding twenty years was missing one or moretoes, presumablyfromthis cause, that others had had their beaks clamped shutand died of starvation,and estimated that an average of oneor two chicks per brood were caughtby mussels and drowned bythe incoming tide. More recent observers note thatclapper rails in SanFrancisco Bay are frequently missing one or more toes Moffitt,1941; Josselyn, 1983; Takekawa, 1993!, and Takekawa 993! reported that a railcaptured inthe Palo Alto marshes with a musselclamped onto its bill subsequentlylostpart of its bill, On the other hand, Moffitt 941! found that Arcuafala formed 57 percent byvolume ofthe total food in 18 clapper rail stomachs thathe examinedin 1939,and Recher 966! andAnderson 970! recorded Arcr~afulafrom the stomachs of willet anddunlin in the SouthBay.

Corbicnlafluminea Muller, 1774! [CQRBICULIDAE]

ASIAN CLAM, ASIATIC CLAM

SYNONYMS:Carbicula fluviafalis Muller, 1774! Corbicularnanilensis Philippi, 1841!, Corbicula leana Prima, 1864! and Corbiculasinensis as reportedin NorthAmerica, and many other namesin Asia;see Prashad 929!, Morton979!, Britton& Morton 979!, andWoodruff et al.993! for extensive synonymies This freshwaterclam is nativeto China,Korea and the UssuriBasin in southeasternSiberia Ingram, 1948!, with closely related and possibly conspecific populationsinJapan Britton & Morton, 1979!. The earliest North American record consistsof three shells collected on thebeach at Nanaimo,British Columbia in 1924, thoughno further specimens have been reported from Canada Counts, 1981!. Corbiculawas next collected from the mouth of theColumbia River in 1938 McMahon,1982!. It was reported from the Delta in 1945 Hanna, 1966! and v idespreadthereby 1948 Ingram, 1948!, and reached theImperial Valley in southeasternCalifornia by 1952 McMahon, 1982!. Introduced Species Page 60

From southernCalifornia Corbicula spread eastward to Arizona by 1954 Ingram,1959!, and to nearEl Pasoin westTexas by 1964 McMahon,1982!, Meanwhile,Corbicrtla was collected from the Ohio River near Paducah, Kentucky in 1957,which McMahon982! suggestsinitiated a secondzone of dispersalirt North America.By theend of the 1960sCorbicula had spread through the lower Mississippiand Ohio river valleys, into southeastTexas and Oklahoma, and along the Gulf coast from Louisiana to southern Florida, and by the mid-1970shad spread up theMississippi Valley to northernIowa andalong the Atlantic coast from Florida to New Jersey.By the early 1980s,Corbtcula was found in 35 of the United Statesand in northernMexico McMahon,1982!. Corbicrtla was reportedfrom South America,France and Portugalin 1981,and a specimenwas collectedfrom a stream in Oahu, Hawaii in 1992 Araujo et al., 1993;Burch, 1994!. Althoughfor many yearsthe Corbicttlain North Americawere describedas belongingto at leastthree different species, in 1979Britton 6 Morton argued that only one species is involved, the highly variable Corbicttlaflutrtirtea, a view that has generally been acceptedsince. Corbicuiafrom California, Texas, Arkansas, Tennesseeand South Carolina showed no genetic variation between populations at 18 loci, 14 of which were polymorphic in some Asian Corbicttla Smith et al., 1979!. SinceCorbicrtla are cultivatedand soldas food in many Asian countries, many researchershave suggestedthat it wasdeliberately introduced to establisha food resource e. g. Ingram, 1948;Hanna, 1966;Britton k Morton, 1979;McMahon, 1982!,or possiblyintroduced throughthe aquariumtrade Ingram et al., 1964!.Some researchershave suggestedthat it was introducedwith Japaneseoysters Burch, 1944; Hill, 1951;Filice, 1959!,but sinceCorbicrtla is mainly a freshwaterorganism, this seems unlikely. Corbicrtla'sspectacular spread within and betweenwatersheds in North America may have resultedfrom transportfor useas bait, food or aquariumpets, or in river gravels dredged for use as aggregate Ingram et al., 1964!,although McMahon 982! argues that natural meansof dispersalwere paramount,including passivedownstream transport of juvenilesin currents,upstream transport in fish stomachs,and upstream or between-watershedtransport on birds. Corbiculaare fairly hardy,tolerating several months without food Hanna,1966! and 7-27 days out of water McMahon,1979!. One specimen was mailed, dry, in an envelopefrom Pennsylvaniato Washingtonstate for identificationand mailed back without ill effect McBane,pers. comm., 1995!. The use of Corbiculain aquacultureor for wastewaterclarification, in either commercial or experimentalapplications as on St, Croix, Virgin Islands Haines, 1979!, may serveto introducethe clam to new locationsin the future. Corbiculais today the mostwidespread and abundantfreshwater clam in California, found throughoutlower elevationwaters, the dominantmollusk and the third most abundantbenthic organism in the Delta, and one of the most commonly identifiedbenthic organisms in fish stomachs Gleason, 1984; Herbold & Moyle,1989!. Densities of 2,000young clams/m2 are common, and range up to 20,000/m-'.Spring flows carry young Corbicrtla down to Suisun Bay where they are sometimescollected as far westas Martinez,but high fall salinitiesappear to prevent Page6I Introduced Species theestablishment oflarge adult populations evenin the western Delta Hazel & Keliey,Populations1966; Evans ofetCorbicttlaal., 1979; withMarkmann, typical 1986!.densities of10,000 to20,000 clams/m2 witha maximumof131,200/m ! trapped sediment andformed extensive barsin theCentral Valley Project's Delta-Mendota Canal,reducing delivery capacity and. requiringexpensive dewatering andthe dredging ofover 50,000 cubicyards ofclam- bearingmaterial. Onebar was described asfilling the bottom ofthe canal from 0.3-1.0 meterdeep for3 kilometers Hanna,1966; Eng, 1979!. Ingram 959! reported the clamasan economic pestofwater delivery systems inCalifornia, infesting and impairingoperation ofunderground pipes,turnout valves, laterals andagricultural sprinklersystemsin the Coachella andImperial valleys, andplugging thetubes of condenser-coolerunitsat the federal government's TracyPumping Plant in the Delta.Corbicula isfrequently citedas a significantproblem infouling irrigation systems,municipal watersystems, powerplant steam condensers, emergencyreactor coolingsystems andservice water systems elsewhere inthe country e.g. Ingram et al.,1964; Sinclair, 1964;Hanna, 1966; Goss k Cain, 1977; McMahon, 1977,1982; Mattice,1979; Goss et al., 1979; Parsons, 1980!. Corbiculaisalso reported torender river sand and gravel unfit for use as aggregate,andtooutcompete nativeunionid andsphaeriid clams McMahon, 1982!. Bluecatfish, Jctalurtts furcttttts, were introduced tosome California waters inpart to controlUpperCorbicu!a, salinity buttolerances without success forCorbicttla Gleason, flumittea1984!. havebeen reported at14 ppt Gainey,1978!, 13-17 ppt Morton h Tong, 1985!, andabout 10ppt without acclimationand22-24 ppt with acclimation Evanset al,, 1979!. Sparse populations of Corbictilahave been observed in the San Francisco Estuary near Martinez at17 ppt, andabundant populations inareas subjected todaily salinities of10 to 12 ppt Evans et a l1979!.Corbiculaflttmitrea areviviparous, releasing benthic pediveliger larvae or planktonicveligers thatbecome benthic within 48 hours Eng, 1979!. There are typicallytw;ospawning periods peryear, with one study reporting peakproduction ofover 300 larvae/clam/day andan average of1,140,820 larvae/m>/year. Biomass productivityrateswere the highest everrecorded fora freshwaterbivalve,and higherthan most marine bivalves Aldridge & McMahon, 1978!, InCalifornia there are modest market sales ofCorbicula both for bait and for food Gleason, 1984;commercial harvesting forfood isallowed only in Lake Isabella inKern County!. Itwas noncommercially harvestedfrom the Delta for food atleast asearly as 1946 Hanna, 1966!,

Gemmagemma Totten, 1834! [VENERIDAEj

AMETHYST GEM CLAM

SYNONYMS:Gemma purpttrea Lea, 1842! Page62 Introduced Species Thissmall, viviparous clam, native to thenorthwestern Atlantic from Nova Scotiato Floridaand Texas, was first reported from the Pacific coast as 42 specimens recoveredfrom the crop of a duckbought in a SanFrancisco market in 1893.It was collecteddirectly from the Bay in thelate 1890s, from Solinas Lagoon in 1918 and fromthree other nearby embayments Bodega Harbor, Tomales Bay and Elkhorn Slough in the1960s and 1970s Carlton, 1979a, p.490!. Earlierobservations of Gemmagemma in theseembayments could have goneunremarked because ofconfusion withthe small native venerid Transenttella tantilla.The early records from San Francisco Bay noted above were originally identifiedas Trartsertrtella, andmany later reports of Gemmagemma from various Pacificcoast embayrnents andoffshore sites were based on material that on re- examinationturn out to beTransettrtella or one of twoother native clams Carlton, 1979a!.Gemmagemma was probably introduced with Atlantic oysters, which it commonlyoccurs on the Atlantic coast Wells, 1961; Maurer & Watling,1973!. It is abundanton theintertidal mudflats from the far SouthBay through San Pablo Bay whereit is oneof themost common benthic species, in placesreaching rnidsumrner densitiesof over 400,000 individuals/m2 Nichols & Thompson,1985a, 1985b! and is occasionallyfound up through Suisun Bay Hopkins, 1986!. It has been found in the stomachsoften species ofshorebird in San Francisco Bay Recher, 1966!, ofwhite sturgeon McKechnie 8zFenner, 1971!, and possibly ofthe introduced nudibranch Philitteouriformis Gosliner, 1995!, isreported asan important food of diving ducks Painter,1966!, and is undoubtedly eaten by many other organisms. Oglesby 965! suggestedthatGemma gemma may be the first intermediate hostof the trematode Parvatremaborealis. The trematode makes characteristic pits in theshell of Gemma gemma,and such pits have been found in shellsfrom San Francisco Bay, Bolinas Lagoonand Tomales Bay Carlton,1979a!.

Lyrodttspedicella.'its Quatrefages, 1849! tTEREDINIDAEj

BLACKTIP SHIPWORM SYNONYMS:Teredo diegensis Bartsch, 1916 from SanDiego Teredotorortsertdi Bartsch, 1922 from San Francisco Bay manyother synonyms from other parts of the world Turner, 1966! Lyroduspedicellatus is a warm-temperate andsubtropical wood-boring shipwormthat requires temperatures of14 to 24'C and salinities ofat least 29 ppt to breed Eckelbarger & Reish, 1972!. It has been reported from many parts of the world the easternand western Atlantic, the Indo-Pacific region, Australasia, South Africa,Japan and Hawaii and its origin is unknown, having been early and widely distributedeither by drifting wood or in thehulls of ships.It hasrepeatedly been "discovered"and described asa newspecies: 12times in theAtlantic, and 21 times in the Pacific Turner, 1966;Carlton, 1979a,p, 551!. Page63 Introduced Species A shipworm,apparently Lyrodus, w~ reportedfrom Wil ingtonHarbor nowpart of the Los Angeles-Long BeachHarbor system! in1871 and following years,and Lyrodus wascollected fromSan Diego Harbor by1876. Itwas subsequently veryabundant inthese harbors Miller, 1926!. It was collected from San Bruno Sloughinsouth San Francisco Bayin 1920, from Klkhom Slough in1935, and from severalsouthern California bays and ports beginning in the 1940s Carlton, 1979a!.

Macomapetafum Valenciennes, in Humbold & Bonpland, 1821! [TELLINIDAE]

BALTIC CLAM SYNONYMS:Macoma balthica of SanFrancisco Bay authors Macomaincartspicua of SanFrancisco Bay authors ThisMacoma species in SanFrancisco Bay has heretofore been known as Macomabatthica. In recent decades, M balthicahas generally been regarded as a singlespecies with a circumboreal/arcticdistribution, withrecords from central Californianorth to Alaskaand the Bering Sea, the Okhotsk and Japan seas, the Beaufortand Siberian seas, the Barents and White seas, northern Europe, the mid- Atlanticstates north to westernGreenland, Hudson Strait, Hudson Bay, and BathurstInlet in theCanadian Archipelago. However, the analysis of shell characteristicsandgrowth rates Beukema & Meehan, 1985! and allozymes Meehan, 1985;Meehan et al., 1989! clearly indicates the existence of twospecies, one native to thenorthv estern Atlantic herecalled Macoma petalum!, the other native to the northeasternAtlantic and northern Pacific Macomabalthica!. Basedon recentstudies, the smallpink Macomaof SanFrancisco Bay, long thoughttobe native Macoma balthica, appears rather to be M. petalum introduced from the northwesternAtlantic. Tested at elevenloci, the allelefrequencies of San FranciscoBay specimens closely resembled those of northwestern Atlantic M. petalum Nei's 978! unbiased genetic identity of 0.943!,and differed sharply from thoseof M. balthicafrom Alsea Bay and Coos Bay, Oregon genetic identity of 0.394- 0,461! Meehan et al., 1989!. Genetic identities >0.9 are generally thought to occur amongconspecific populations, of0.5-0,8 among sibling species, and of <0.5among non-siblingspecies Meehan et al., 1989!. Theearly history of Macoma battbica and petalum in SanFrancisco Bay remainsto be workedout. Shells identified as M. balthicahave been recovered from 2,000-6,000year old sedimentsunder San Francisco Bay. It maybe that Macoma balthicathen died out in the Bay, as Meehan etal. 989} argued based on the lack of recordsfrom later sediments and aboriginal shell middens in theregion. Clams, apparentlyreferable toM, balthica orpetalttm, were collected inthe Bay by the UnitedStates Exploring Expedition in 1841and by variousparties in the1860s Carpenter,1857, 1864; E. Coan, pers. comm., 1995!. They were found to be common in all partsof theBay in theAlbatross survey of 1912-13 Packard, 1918}. Clamscollected prior to 1850could represent Macoma balthica native to the Bay,if an aboriginalpopulation persisted despite Meehan et al.'sarguments; or Page64 IntroducedSpecies couldrepresent M,balthica fromfurther northan the Pacific coastor M. pefalutrt fromthe northwestern Atlanticintroduced insolid ballast. Clams collected after 1850transplantscould inofadditionthe native representoyster OstreaM balthicacortchaphila from northern =lttrida!. baysClamsintroducedcollected with after 1869could inaddition represent M.petatttm introduced withshipments afthe AtlanticoysterCrassostrea virginica.Morphologic Beukmak Meehan, 1985!or geneticTheanalysiscurrent of museumdistributional specimenspatternmight ofMacorrtasort some balthica ofthese and possibilitiesMacorrta petalttrnout. inthe northwestern Pacific,particularly betweenSan Francisco Bayand Coos Bay, alsoremains tobe determined. SouthofSan Francisco Bay,there are records of shellsandpossibly livespecimens of"Macama batfhica" as far south asSan Diego, butthese appear tobe sporadic occurrences, probablyrelated toanthropogenic transport,Macomaratherpetatum than establishedor batthica haspopulations.been collected throughout SanFrancisco Bay upstreamtoCollinsville, especiallyinthe shallows wheredensities havereached over'1,000 individuals/m~ Siegfriedetal., 1980; Hopkins, 1986;Markmann, 1986!, and Nicholshas been& aThompson, dominant 1985a!.benthicItcan organismbe an importantin South Bayfood andof fish,Suisun divingBay ducksshallows and clapperrail Williams, 1929;Painter, 1966!,and formed 8percent ofthe volume of foodin18 clapper railstomachs Moffitt,1941!. In San Francisco BayMacorrta feeds onboth planktonic andbenthic rnicroalgae, andThompson & Nichols988! found supplythattheandtiming highand mud-flatrate of growthair! temperatures,of intertidal andpopulationsindependent wasofcontrolled salinity averby fooda 0-31 ppt range,Itwas recently determined thatMacotna balthicafrom both Vancouver Island andthe Baltic Seahost thesame three species ofdigenean flatworms Pekkarinen k Ching,1994!,It would beof interest todetermine whetherMacortta pefatumfrom SanFrancisco Bayand the northwestern Atlantichost the same ordifferent parasites.

Musctdistasenhousia Benson, 1842! [MYTIUDAE! SYNONYMS:Muscutus senhottsia Modiolusdemisstts of Filice 959! NativetoJapan andChina, thissmall mussel wasintroduced toWashington andcentral California withJapanese oysters Crassostrea gigas!,with which it has beenWashington,found inonincoming beds ofJapaneseseed Kincaid, oysters1949!.in1924, Itwas and collectedat Olympia inSamish in1959. Bay,In central Californiaitwas collected fromTomales Bayin1941, Bolinas I.agoon in1944, San FranciscoBayin1946, Elkhorn Slough in1965 and Bodega Harbor in1971. Itwas collectedfromMission, SanDiego andNewport baysin southern California, and PapiloteBay near Ensenada! m BajaCalifornia inthe 1960s and1970s Carlton, 1979a,p.449!, probably transported inballast water oron ship orboat fouling. Inthe Page65 introduced Species 1970sitappeared inNew Zealand andAustralia andin the 1980s m the Mediterranean,Inthe western paclfrc Mrrscrrtrsfa I s been reported atdensrtres ofUp to 28,650 juveniles/m~settledoneelgrass or2,500-2,800 adults/mjust buried inthe mud of thetidal flats, where theclams build nest about them ofbyssal thead, mucus and sediment.Musculista isused as food inChina and as fish bait and as feed for cultivatingshrimpand crab inJapan Morton, 1974;Carlton, 1979a!. Onthe bottom ofLake Merritt, a shallow, brackish Lagoon onSan Francisco Bay,Musculista occursindense byssal matsthat can bepulled from the bottom in sheets,andas individuals among thefouling onpilings and floats. AtAlameda individualsarefound nesting inthe sediment orattached tothe base of eelgrass plants.Mrrsculista hasbeen collected atdensities ofup to 1,000-2,000 clams/m~from theSouth Bay to San Pablo Bay, where it has frequently beenone of the most commonbenthic organisms, andoccasionally collected upstream toHonker Bay Nichols& Thompson, 1985a,Hopkins, 1986;Markrnann, 1986!.Crooks 996! has investigateditsecology andbiology inMission Bayin southern California.

Myaarenaria Linnaeus, 1758 [MYIDAE]

SOFT-SHELL CLAM SYNONYMS:Mya hemph ill ii Newcomb,1874 Myaarenaria isnative tothe American Atlantic coast and from Alaska north ofthe Aleutian Peninsula, although its distribution north of British Columbia isnot wellknown. It has been introduced into western and northern Europe. Although recordedfrom Miocene and Pliocene deposits on the Pacific coast, ithas not been foundin Pleistocenedeposits orin aboriginalshell middens south ofthe Bering Sea, andhad not been encountered bynumerous collectors on the Pacific coast prior to 1874 Stearns, 1881!. Inthat year itwas collected inSan Francisco Bay Newcomb, 1874!,almost certainly transported there in the transcontinental shipments of Atlantic oysters that began in 1869. Thislarge, edible clam was soon transplanted toother Pacific Coast sites e. g. CoosBay, Oregon by1880, Santa Cruz, California by1881, Willapa Bay and Puget Soundin Washington by1884 and 1888-89; also note Stearns' 881! exhortation that "itwould be a wise, public spirited act if thecaptains ofour coasting vessels would takethe trouble and incur the slight expense attending theplanting ofthis clam at suchpoints as their vessels touch atin the ordinary course ofbusiness"!, andmay havebeen distributed to others with transplantings ofoysters from these sites or withfresh introductions ofoysters from the Atlantic. It is less likely, though possible,thatMya arenaria's appearance insome locations resulted from deliberate introductionsfrom the Atlantic which Rathbun 892!, Heath 916! and Coe 956! claimwas attempted oroccurred!, orfrom the transport ofsmall clams in ship fouling.Although some workers have suggested thatsome orall of Mya arenaria's northwardmovement was due to natural dispersal e.g. Quayle,1960!, Carlton 1ntroducedSpecies Page 66

979a! concludesthat "there is littlehard data that Mya hasever spread naturally anywherealong the Pacific coast." Mya arenaria does not appearto havebecome establishedsouth of Monterey, despite a planting of about 2,000clams in Morro Bay in 19IS and occasional,probably erroneousreports of Mya arenariafrom southern California reviewed in Carlton, 1979a!. By the 1880sMya arenariawas reported as the mostcommon clam sold in San FranciscoBay area markets Stearns, 1881! But the commercialharvest declined from500-900 tons per year in 1889-1899,to generallyabove 100 tons per yearin 1916- 1926,to nothingafter 1948, possibly due to overharvesting,habitat loss,pollution or a decline in the market due to an increasing harvest of Verterupis phillipinarum Skinner,1962; Herbold et al,, 1992!.Today, noncommercial harvest of Mya continuesfor food and bait Sutton,1981; Herbold et al., 1992!.It hasbeen collected throughoutthe Bayas far upstreamas Collinsville and Sherman Lake, frequently at densitiesover 100 and sometimesover 1,000clams/m2, and hasbeen one of the dominantbenthic organisms in theshallows of the SouthBay and SuisunBay Nichols k Thompson, 1985a;Hopkins, 1986,Markrnann, 1986!. Severalworkers reported that Mya arenariareplaced populations of the native clam Macoma rtasutain San FranciscoBay, at least in regularly harvested clambeds e. g. Fisher,1916!. Clam beds encompassing from a few to hundredsof acreswere established from the SouthBay to theNapa Riverand Martinez, some of thempublic and someprivately owned, with some fenced to keepout batrays and fiounder Bonnot,1932!, Predators of Mya arertariaon the Pacificcoast include rays, sharks, flounder, ducksand shorebirds.Five speciesof nativepinnotherid crabs are recordedas living in Mya arenaria'smantle cavity referencesin Carlton, 1979a!.

Mytilus galloprovirtcialis Lamarck 1819 [MYTILIDAE]

MEDITERRANEAN MUSSEL

SYYONYMS;the taxonomy of the Mytilus "edulis" complexis reviewedby Koehn 991! and Seed 992!

The cosmopolitan Mytilus "edulis" speciescomplex was variously grouped into one or severalspecies by differentauthors until electrophoreticevidence published in the late 1980sand 1990sled to the generalrecognition of threespecies: M. edulis from northern Europe and easternNorth America;M. galloprovirtcialis from the Mediterranean Sea,various sites on the Atlantic coastof Europe,South Africa,California, Japan, Hong Kongand eastern China, Australia, Tasmania and New Zealand; and M. trossulus from the northwestern Pacific, Siberia, eastern Canadaand the BalticSea McDonaldet al., 1991;Koehn, 1991; Seed, 1992!, although frequenthybridization between these forms may raisedoubts about their specific status Seed,1992!. Mussels from Chile,Argentina, and the Falklandand Kerguelen islandscontain alleles characteristic of all threegenotypes but havebeen tentatively assignedto M. edulis McDonald et al., 1991!, Page67 IntroducedSpecies Thetwo species present inthe northwest Pacific have been differentiated on thebasis pf rnorphornetricanalysis Sarver & Foltz,1993; mussels from San FranciscoBaycollected in1990!, starched gelelectrophoresis at8-1S allozyme loci McDonald0 Koehn, 1988, using mussels collected in 1985-87; Sarver k Foltz, 1993!, andthe sequencing ofmitochondrial 16Sribosomal DNA Geller etal., 1993. 1994!. Allmethods agree in finding predominantly orpurely M trossulustype from Eureka,California north to Alaska; a hybridization zoneincluding Westport, TomalesBay, San Francisco Bayand Monterey Bay where sites contained various mixturesof M. frossulus,M. galloprovinciafis andtheir hybrids; and high proportionsofM. galloprovitrciafis atsites south ofMonterey toSan Diego. However,these methods differed in theirconclusions about how dominant M.galfoprovincialis issouth of Monterey, withallozyme analyses showing almost pureM. gafloprovitrciaiis genotype and DNA analysis showing a roughly equal mix ofM. galloprovincialis-M. trossulus genotypes. Geller et al. 994! suggest that this couldresult fram the introgression of the M. trossulusmitochondrial genome into individualswith M. gaOoprovincialisnucleic genome. Since mitochondrial DNA is mainlytransmitted maternally inMytilus species, such introgression could be producedby repeatedcrossings with M galloprovitrcilismaleswith a fernaleM. trossulusand her female descendants. Thepattern of occurrenceof these species suggests that M. Irossulus is a cold- ternperatespecies native to thenorthern Pacific, and that M. galfopravirtciahsisa warm-temperatespecies native to theMediterranean and introduced to California, Japan,China and South Africa Koehn, 1991; Seed, 1992!, as well as Australia, Tasmaniaand New Zealand.DNA analysisof rnuseurnspecimens indicates that M. galloprovincialisarrived in southernCalifornia between 1900 and 1947, probably as shipfouling or aslarvae in ballastwater, displacing M. trossulusg. Geller in Culotta, 1995!. DNA analysisalso showsthat viableM. galloprovincialislarvae are continuallydischarged in largenumbers into Coos Bay, Oregon in theballast water fromJapanese ships, though no adultM. galloprovincialisorhybrids were found in the bay Geller et al., 1994!. ln SanFrancisco Bay, bay mussels are found mainly from thenorthern South Bayto southernSan Pablo Bay, and occasionally as far upstreamas Martinez Hopkins, 1986!.Distribution af M, trossulusand galloprovincialis at four sitesas indicatedby allozymefrequencies show a heterogeneousmixof speciesand hybrids that follows no obvious environmental cline, with M. frossulusstrongly dominating at both the most upstreamand most seawardsite, andM. galioprovi~ciafisless strongly dominating at sitesbetween Sarver 5 Foltz,1993!. On the Pacificcoast these two difficult-tp-distinguishspecies have long been consideredone species and have been frequently used for thebiomonitoring of pollutantsin the CaliforniaMussel Watch program and other studies. Recent indicationsthat separate species in theMytilus "edulis"complex exhibit different growthrates anddifferent concentrations of various elements when grown in the samehabitat Labelet al., 1990!suggest that conclusions about the relative contaminationof varioussites based on comparativebioassays of baymussel specimensincorrectly assumed to belongto a singlespecies may be invalid.Other studiesha> e founddifferent species within thecomplex to havedifferent levels of Jntrpduced Species Page68

ectionby parasit~, spawning periods, fecundity and strength of byssal attachment Seed, 1992!.

Petrrcolar

FALSE ANGELWING

SYNONYMS:Petricola pholadtformfs

The false angelwing is native to the northwesternAtlantic, rangingfrom the Gulfof St.Lawrence to the Gulf of Mexicoand possibly to Uruguay, andhas been introducedto Europe Carlton, 1979a, p. 515!.It wascollected in southSan Francisco Bayin or before1927 Grant 8zGale, 1931!, from Willapa Bay in 1943 Kincaid,1947! andfrom Newport Bay in 1972,Reports of P. pholadtIormisRom "nearMonterey" andfrom Scammons Lagoon, Baja California are probably erroneous Carlton, 1979a!.It is a borerinto clay, peat,mud, sand and other soft sediments, and has been recordedfrom oysterbeds on the Atlanticcoast Wells,1961!. Though it was most likely introducedto the Pacific in shipmentsof Atlanticoysters, it is puzzling that it was reportedfrom the Pacific relativelylate. It is a strikingshell that would not likely havebeen overlooked by collectors.It is possiblyan early ballastwater introduction. In Willapa Bay a spionid polychaete,a Corophiumamphipod and a nereid polychaeteare often associatedwith P. pholadiformis.In San FranciscoBay, Bush 937! reportedthat about90 percentof theseclams collected from sandybeaches near the Oakland Airport host the ciliate Ancistruminakofoidi. This protozoan is knownonly fromP. pholadiform'rsfrom San Francisco Bay, and is presumedto be native to the Atlantic and introducedalong with the clam.

Potamocorbiilaamierensis Schrenck, 1867! [CORBULIDAE]

AMUR RIVER CORBULA, ASIAN CLAM

In October1986, a collegebiology class dredged three email and unfamiliar clamsfrom the bottom of SuisunBay, These were subsequently identified as Potamocorbulaamurensis, a native of estuariesfrom southern China 2 latitude!to southernSiberia 3' N! andJapan, which was likely transportedto Californiaas larvae in ballast water. By the summerof 1987 Potarnocorbulahad becomethe most abundant benthic organism in thenorthern part pf theBay, carpetingthe bottom at densitiesof over16,000 juvenile clams meanshell length of 1,7mm! per square meter Carlton e't al., 1990; Nichols et al-, 1990! It seemslikely thatPotamocorbula arrived in theBay very shortly before its discovery,because it v asnot collectedearlier despite regularbenthic sampling, encl becauseall specimenscollected through March 1987 were less than 11 ~rn long,and therefore probablyless than a yearold Carltonet al,, 1990!. Jn traducedSpecies Page 69

An intensivebenthic survey of thenorthern Bay in 1990found Potamocctrbrrlavery commonfrom San Pablo Bay through Suisun Bay, and most abundantin theSuisun Marsh region with mean concentrations of up to 19/00 clams/m2and a mediansize of 2-3 mm.Median sizewas 10-11mrn in SanPablo Bay,and S-6 mrn and 8-9 rnm in theshoals and channel ofSuisun Bay Hymanson, 1991!.Potamocorbtela isnow abundant in parts of theSouth and Central Bay, and hasoccasionally been collected in the western Delta as far upstream asRio Vista, overa rangeof salinities from 33 ppt to less than 1 ppt.At thesesites it wouldbe exposedtotemperatures ranging from 8' C onsubtidal bottoms in the winter to23' C onintertidal flats in the summer,within the temperaturerange of 0-28 C suggestedbyits latitudinal range in Asia. It livesboth subtidally and intertidally on all soft-bottomsubstrates, where it typicallysits with one-thirdto one-halfof its lengthexposed above the sediment surface Carlton et al., 1990!. Priorto 1986,the benthic species composition and abundance in the northern Baychanged markedly from year to year, with freshwater species declining during dryperiods and more numerous, higher-salinity species dominated bythe clam Mytrarertaria, theamphipods Corophittm acherusicum andAmpelisca abdita, and thepolychaete Streblospio benedictt, allintroduced organisms invading the area Nichols,1985!. Pofarrtocorbuta's arrivalin theBay followed a majorflood in the springof1986, and its increase andspread coincided with a multi-yeardryperiod thatbegan in mid-1986,The 1986 flood left the benthic community nearly depauperateinthe Suisun Bay area, probably facilitating Potatrtocorbula's establishment.Thiscornrnunity failed to return during the subsequent dryperiod, presumablydueto Potamocarbttla's presence. Themechanisms bywhich Potamocorbtelaexcluded these organisms arenot known, but could include the depletionoffood resources seebelow! orfeeding byPotamocorbula onthe larvae of theseorganisms Nichols etal., 1990!. Patamocorbula hasmaintained substantial populationsinthe northern Bayeven after the end of the drought andthe return of normalfiows 0, Thompson,pers. cornrn., 1994!, and thus appears tohave permanentlychanged benthic community dynamics inthis part of the Bay Nichols et al., 1990!. Examinationof fecesfrom specimens collected in the Bayshow Potamocorbrelaingesting both planktonic Coscirtodiscrts spp.and Skeletortema cosfatum!and benthic Navicula spp.! diatoms Carlton et al, 1990!.Werner k, Hollibaugh993! found that Potamocorbuta filtersbacterioplankton aswell as phytoplankton,thoughatlower efficiency, andassimilates bothwith high efficiency. Theycalculate thatat present densities inthe northern Bay >2,000 clams/rn2! Potttmocarbtelacouldfilter the entire water column over the channels more than onceper day and over the shallows almost 13times per day, a rateoffiltration whichexceeds thephytoplankton's specific growth rate and approaches orexceeds thebacterioplankton's specificgrowth rate, Thus Potamocorbrtla maypermanently reducethephytoplankton standingstock in the northern reachof the Bay. Alpine & Cloern992! described thepre-Potamocorbuta regimeasone in which phytoplanktonbiomassand production wereregulated byriver-driven transport whenbenthic grazers were few, but limited by grazing pressure when grazers were introduced Species Page70 ab~~dant.With Potamocorbulain the Bay,grazing pressure may be permanently h'gh, andphytop]ankton biomass and pmductlvie permanently low I" laboratoryexperiments Kirnmerer 991! found that potamocorbufareadily consumednauplii of the copepodEuryfemora afjinis, but not the introduced copepodPseudodiaptomus sp. Kimrnerer et a].994! arguedthat an observed declinein the abundanceof threedominant copepod taxa p. affinis,Sinoca]anus doer"'i,and Acartia spp. that coincidedwith the spreadof pofarrtocorbu]ain the northernreach of theBay resulted from direct predation on cppepods by Potamocorbula rather than from food limitation due to the decline in phytoplankton. Furthertrophic changes may be expected to resultfrom the reductionin zooplanktonand the build-up of potamocorbu]a,including declines in the organismsthat feedon zooplankton,and increases in organismscapable of feeding on Potamocorbula Carlton et al., 1990!.Potamocorbula has been found in the stomachsof diving ducksand sturgeonin theBay Nicholset al., 1990!,and in aquariais readily consumedby the introducedgreen crab Carcinus maenas Cohen et al., 1995!. Investigatinga]]e]e frequencies at eight ]oci, Duda 994! found high genetic diversity in the SanFrancisco Bay population polymorphicat 75 percentof sites with a meandirect-count heterozygosity of 0.295!,with little geneticdifferentiation between sites within the Bay.

Teredonavafis Linnaeus, 1758 [TEREDINIDAEJ

NAVAL SHIPWORM

SYNONYMS: Teredo beacbi Bartsch, 1921 Teredo diegensis in part! Teredojaponica Clessin, 1893 othersynonyms are reviewed by Turner966!, andthe historypf taxonomicdebate regardingSan Francisco Bay shipworrns is reviewed by Carlton 979a, pp. 558-S60! Theearliest northwest Pacific record of thisglobally-distributed, temperate water shipworm is from San Francisco Bay in 1913,and it has also estab]ished populationsin Willapa Bay, Washington first reportedin 1957!,in pendre]] Sond British Columbia 963!, and possibly in Los Ange]esHarbor 927! and other southernCalifornia bays Barrows,1917; Kofoid k Miller, 1927;Reish, 1972; Carlton, 1979a,p, 556!.It undoubtedly arrived in the hu]ls of ships. When CommodoreJohn Sloatarrived on the Pacificcoast in 1852in searchof a suitable location for the Navy Department's western shipyard, his orders directed him to pick a sitethat was "safe from attackby wind, wave,enemies, and marine worms" Lott, 19S4!.He chose the eastern shore of Mare Island in the northern upstreamreach of SanFrancisco Bay, where low salinities kept the regipnfree pf marinewood-boring organisms and where marinefacilities such as wharves and Introduced Species Page71 ferryslips could consequently be built on untreatedwooden pilings, It w» in wooden structures at Mare Island that Teredortavalis, which readily tolerated much fresher water than did the existing marine borers in the Bay thriving down to 9 ppt andsurviving indefinitely down to 5 ppt;Miller, 1926!,was first noticedin 1913.By 1919-1920,possibly aided by a dryspell that brought higher than average salinities, Teredonavahos was found from the South Bay to Suisun Bay and had grown so abundantas to destroyvirtually all thewooden structures in thenorthern part of theHay, with damageestimated at overhalf a billiondollars in currentdollars McNeily,1927; this paper, Chapter 6!. This destruction led to the formation of the SanFrancisco Bay Marine Filing Committeewhich produced a seriesof reports annualreports in 1921,1922 and 1923,and the FinalReport in 1927!covering the activitiesand management of a varietyof marinewood-borers in San Francisco Bay and elsewhere in the Pacific. Theparticipants in the Committee's investigations later published several additionalpapers on. the biology and morphology of Teredonavalis references in Carlton, 1979a!. The evidence that Teredorravafis is not native to San FranciscoBay is reviewedby Harrows917, p. 29!, Kofoid 921, pp. 43-44!, Kofoid & Miller922, pp. 81-82;1927, pp. 206-207, 246-247! and Carlton 979a, pp. 560-563!. This evidence includesthe absenceof anyknown damage from marineborers in the northernpart of theBay prior to 1913,the lack of anyprior record of Teredonavalis on the Pacific coastdespite extensive collecting by nineteenthcentury conchologists, and the failure to find Teredonavalis in an investigationof shipwormsconducted for the United States Forest Service in 1910-1911. Althoughthe specific source of theshipworms introduced to SanFrancisco Bayis unknown,Carlton 979a! suggests that Teredo navalis is nativeto the Atlantic.A shipworm,probably Teredo navafis but possiblyNotateredo rtrjrvegica Turner,1966!, was known. from Europe since at leastthe start of the 17thcentury andwas apparently mentioned by Pliny,Cicero, Theophrastus and others in ancient times Moll, 1914!.Teredo rtavalis was reported from Europe in 1731by a Dutch commissiondescribing a "horribleplague" of shipwormsthreatening to destroythe dikesthat protected the lowlands of Holland,and by Sellius in 1733Teredo navalis wasalso present in Japanat least since the 1890s, though it appearsto havebeen absent from Australia at that time Carlton, 1979a!. Althoughthere has been little noticetaken of shipwormsin SanFrancisco Bayin recentyears, New York City has apparently experience a resurgence of shipwormactivity reportedly resulting from a cleanerharbor or, less likely, from shipworrnsdeveloping a tolerance to creosote!. When city officials visited the BrooklynArmy Terminal in thespring of 1993to inspectshipworm damage they foundthat one of thepiers had collapsed the previous night. The city spent $100 millionto protectits piers against woodborer damage Gruson, 1993!.

Theorafragilis A. Adams,lSSS [SEMELIDAE]

ASIAN SEMELE Tntrad~eed species Page 72

SYNONYMS: Theora lubrica Gould, 1861 Theorafragilis is a small,mud-dwelling clam native to Japan,China, the Indo-West Pacific and New Zealand. It first appearedin the northeastern Pacific in southern California, where it was collected from Anaheim Bay in 1968-69,from Newport Bayin 1971-73,and in largenumbers from Los AngelesHarbor in 1973 Seapy,1974, Carlton, 1979a, p. 517!.It wasprobably introduced in ballastwater, possibly from ships returning from SoutheastAsia during the VietnamWar. Theorafragilis larvaehave been collected from the ballastwater of Japanesecargo shipsarriving at CoosBay, Oregon and rearedto juverulestages Carlton et al., 1990, p 85!. Theorawas first collected in San FranciscoBay in 1982at Islais Creek, San Francisco Carlton et al., 1990!.It occurs in small numbers through much of the Bay, the California Department of Water Resourceshas collected it at Point Pinole at densitiesof up to 127/m2since sampling began in 1991 DWR,1995!, and it was one of the most common benthic organisms collected at the Alameda Naval Air Station in 1993 G. Gillingham,pers, comm.!. It is absentfrom SuisunBay accordingto U. S. GeologicalSurvey sampling records Carltonet al., 1990!.

Venerupis philippinarum Adams & Reeve, 1850! [VENERIDAE]

JAPANESE LITTLENECK CLAM, MANILA CLAM

SYNONYMS:Tapes japonica Deshayes,1853! Tapes semidecussafaReeve, 1864 Tapes philippi naram Ruditapes philippinarum Paphiabifurcata Quayie, 1938

Ve»erripis philippinarum, known until recently as Tapesjaponica, is an Asian clam that was introduced with shipments of Japaneseoysters to the northeastern Pacific, where it has become establishedin numerous bays from British Columbia to central California and is the numerically dominant clam in many of them. It was first noticed in planted oyster beds in SamishBay, Washington in 1924 Kincaid, 1947!,and in a shipment of Japaneseoysters arriving at Elkhorn Slough in 1930 Bonnot, 19351!,However, the first record of an establishedpopulation on the North American coast is from Ladysmith Harbor on the eastern shore of Vancouver Island, British Columbia in 1936 Quayle, 1938!.Northward spread from that site, and later northward spread from Barkley Sound on the west side of Vancouver Island to Venerupis'northernmost record in HecateStrait, appearto have been due to the transport of larvae by currents, but the clam's spread southward to California is probably due in large part to new introductions in oyster shipments from Japan, to the transplanting of oysters along the coast, and to intentional transplants some probably not recorded! of Venerupis, Page73 introducedSpecies Verterupiswasfound inPuget Sound in1943, inWillapa Bay and San FranciscoBayin 1946, inBodega Harbor and Elkhorn Slough in1949, inTomales Bayin 1955, inHumboldt Bayand Grays Harbor in1964, and in Bolinas Lagoon in 1966.It had entered the commercial market by 1941, which encouraged laboratory aquacultureeffortsand reseeding andreplanting programs inthe Pacific northwest, someofwhich continue, Efforts were made to establish Venerupis inMorro Bay, NewportHarbor andthe Salton Seain 1953, inthe Queen Charlotte Islands in1962, andin Yaquina andTillamook baysin 1965, allof which failed. However, itwas successfullyestablished inNetarts Bay,Oregon inthe 1970s Carlton, 1979a, p.502!. InSan Francisco Bay, Verterupis iscommonly found at concentrations upto 2,000clams/m2 from the South Bay through SanPablo Bay, where itis one of the mostcommon benthic organisms, andhas on occasion been found as far upstream asChipps Island Nichols k Thompson, 1985a;Hopkins, 1986!. Inthe Bay itis collectednoncommercially bothfor food and bait Sutton, 1981; ANC, pers. obs.!. InSan Francisco Bayand elsewhere, Venerupis co-occurs withvarious native clams,including thesimilar native littleneck clamProtothaca starninea. Although a fewauthors have stated that Verterupis displaces thenative littleneck, others have seenlittle evidence ofcompetition between them, with Venerupis living higher in theintertidal zone or closer tothe surface than Protothaca seeCarlton, 1979a!. However,the question hasnot been effectively studied. A varietyoforganisms feedon Venerupis onthe Pacific coast, including the rnoonsnailPolinices tewisii, sturgeon, willet, gulls, ducks and raccoons Glude, 1964; Painter,1966; McKechnie & Fenner, 1971;Stenzel etal,, 1976; Carlton, 1979a!, and undoubtedlymany others.

ARTH ROPODA: CRUSTACEA

Erisarsietlazostericola Cushman, 1906!

SYt ONYttS: Sarsiella zostericola Sarsiefla fricosiata Jones, 1958 Thiswestern Atlantic ostracod occurs from Maine to Floridaand in the Gulf of Mexico.It is known on the Pacific coast only from San Francisco Bay, where it was firstcollected in 1953 at Point Richmond Carlton, 1979a, p.573!, It iswidely distributedinthe Bay on soft substrates inshallow water. It has also been introduced toEngland, where itoccurs onlyin regions where Atlantic oysters wereplanted. Thoughnotrecorded fromSan Francisco Bayuntil the 1950s, thisminute, ben.thic crustaceancouldhave been long present butgone unnoticed orunrecognized, and thusmay have been introduced withAtlantic oyster shipments. Sinceostracods otherthan holoplanktonic ostracods! haverarely been collected fromballast water samples e.g. Carlto~ k Geller, 1993!, ballast water seems a less likely transport mechanism, liitroduced Species Page74

~Coi~eisa Acarfiella sinensis

This copepod,native to the subtropicalto tropicalwaters of the China coast, wascollected in SuisunBay in 1993,1994 and 1995. It isfound in thevicinity of the entrapmentzone and doesnot extendupstream as far as the easternDelta Orsi, 1994,1995; J. Orsi, pers.comm., 1995!. It was probablyintroduced in ballastw-ter.

Limnoifhona sinensis Burkhardt, 1912!

SYNONYMS: Oithona sinensis

This copepodhas been collected from the brackishand freshwaters of the YangtzeRiver Changjiang!inland to at least300 km and fromnearby lakes and canalsin 1898,in 1906and prior to 1962.It wascollected from the SanFrancisco Estuaryfor firsttime in 1979,by CDFGfrom the San Joaquin River near Stockton Ferrari& Orsi,1984!. Herbold & Moyle989! suggest that a declinein zooplankton abundancein the Deltaprior to 1979may have facilitated L. sinensis'establishment. It has beencollected throughout the Delta where it is more abundantin the San- Joaquinthan in theSacramento River! and downstream to Suisun Bay, though apparentlyrestricted to watersof lessthan 1.2 ppt Herbold& Moyle,1989!. It has beenmost abundant in Oct./Nov.and scarcest in Mar./Apr., with a maximum recordedabundance of 71,176individuals/m2 in Aug., 1981near Stockton Ferrari & Orsi,1984!. In 1993-94it wasreplaced over its entire range by Limnoifhonafefraspina J, Orsi, pers. comm.,1995! The lack of any recordof thiscopepod in theeastern Pacific prior to 1979,and earlyrecords of it fromthe YangtzeRiver area, suggest that L. sinensisisa recent introductionto the San Francisco Estuary Ferrari & Orsi,1984!. It wasmost likely transportedacross the Pacificin ballastwater oithonidcopepods have been found to survive transportin ballasttanks; Carlton, 1985,p. 346!.

Li m noithcna f etraspi na Thiscopepod, native to theYangtze River, was first found in theEstuary in 1993at Chipps Island in SuisunBay and at Collinsvilleand Hood on the SacramentoRiver. By 1994 it hadreplaced Limnoithona sinensis and, reaching densitiesgreater than 40,000/m3, had become the mostabundant copepod ever seen in theEstuary Orsi, 1995; J. Orsi, pers, comm., 1995!. It wasprobably introduced in ballast water. Page75 1mtraduced Species

Mytilicolaorientalis Mori, 1935

PARASITICCOPEPOD SYNoNYMs:Mytilicola ostreae Wilson, 1938 Thissmall red copepod livesin the intestine orrectum, orrarely inthe digestived,iverticulae, ofoysters and other mollusks. Itis native tothe western Pacificandwas introduced tothe northeastern Pacificwith shipments ofthe JapaneseoysterCrassostrea gigas,ltwas first collected fromWillapa Bay, Washingtonin1938, and subsequently frommany bays and estuaries from VancouverIsland, British Columbia toMorro Bay, California, including San FranciscoBayin 1974 where it was discovered inthree out of 30 native oysters Ostreacortchaphi7a fromthe Berkeley Marina, Bradley k Siebert, 1978;Carlton, 1979a,p.577!. These various sitescould have received Mytilicola directlywith shipmentsofoysters fromJapan, withoysters transplanted fromother eastern Pacificbays, or with rnussels fouling coastal ships. Onthe Pacific coast Mytilicola hasbeen found in inaddition toJapanese oysters!theintroduced slippershell Crepidula fornicata one record fromPuget Sound!,andseveral native bivalves, including theoyster Ostrea conchaphila, the musselMytilus californiartus, andthe clams Protothaca staminea onerecord from PugetSound!, Saxidomus giganteusand Cfirtocardircm rtuttallii one record each fromBritish Columbia!. It hasalso been found inthe native mussel Mytifus trossulus northern records reported asM edttlis! and possibly theintroduced musselM.gal1aprovirtcialis orin hybrids San Francisco Bayrecord reported asM. edulis;see Sarver k Folz,1993! Carlton, 1979a!. Carlton979a! notes that the data for sites and for hosts may be selective as "allbays that have been searched, andmost if not all mollusks thathave been examined,havebeen found tohave Mytilicola." Healso notes that due to the copepod'sendoparasitic habitand a lackofexploration andearly collecting, Mytilicolacould have been inthese bays long before itwas first observed. Katanskyetal. 967! and Bradley 6 Siebert 978! summarize thebiological researchon Mytilicalain theeastern Pacific.

Oithona davisaeFerrari & Orsi, 1984 Thiscopepod wasfirst collected ineastern Suisun Bayin 1979, and described byFerrari &Orsi 984!. Ithas been collected fromthe South Bayto San Pablo Bay, andupstream toChipps Island inwaters of12 ppt. Copepods thatwere collected fromSan Pablo Bay in the winter, spring and fall of 1963 and identified asOithorta sp.may also have been Oitharta davisae Ferrari k Orsi, 1984!. Ambleret al. 985!found Oithorta davisae to be one of themost common copepodsinthe Bay in1980, InJune toDecember ofthat year, atsites from theSouth BaytoCarquinez Straititwas found in25-48 percent ofthe samples collected, and Jntrodueed Species Page76

reachedpeak abundances of 22,ppp-44,pppindividuals! m2 in theSouth Bay in October and November. Ferrarik Orsi984! argued that the lack of any record of this copepod in the Bayprior to 1979, and the fact thatsome distinctive morphological characters are sharedexclus'vely with Indo-WestPacific oithonid copepods, suggests that Oitporta davisaewas a recentintroduction to theSan Francisco Estuaqr from the western Pacific.It wassubsequently found in Japanesewaters, where it isfrequently abundantin eutrophicembayments Uye > Sano,1995!, and considered to be of Asianorigin Flerninger & Kramer, 1988!. It hasalso been reported from southern Chile Carlton,1987!. Oithona species have been found to survivetransport in ballasttanks Carlton, 1985, p. 346!,and this one was most likely transported across the Pacific in ballast water.

Pseudodiaptomusforbesi Poppe & Richard,1890!

Pseudodiaptomusforbesi is native to the fresh and brackish waters of the YangtzeRiver Changjiang!, China, usually restricted to waters of lessthan 8 ppt.It was first collected outside of China in 1987in fresh water in the eastern and southernDelta. By thefollowing year it wasfound throughout the Delta and downstreaminto Suisun Bay up toa salinityof 16ppt, in whichareas it wasthe most abundantcalanoid copepod in the fall of 1988and in 1989.The maximum abundancerecorded was 22,408 individuals/m~ in fresh water in theSan Joaquin Rivernear Stockton in earlyJune, 1988 Orsi, 1989; Orsi & Walter,1991!. Varioushypotheses have beenproposed to explainthe recentdramatic shifts in theabsolute and relative abundanceof Pseudodiaptomusforbesi and other copepodsin thenorthern reach of theEstuary, including competition between nativeand introducedcopepods, differential predation by introducedfish and clams ondifferent copepods, and predation by copepods on other copepods. Herbold et al. 992!, implying competitionas the relevantmechanism, reported that the "invasionsof the westernDelta and SuisunBay by Sinocalanusdoerrii in 1978and by Pseudodiaptomusforbesi in 1987were followed by declinesin abundanceof Eurytemoraaffinis and the almostcomplete elimination of Diaptomus spp." On the otherhand, Kimmerer 991! reportedthat the cryptogenic copepod Eurytemora affiniswas not food-limited irt theEstuary so that competition with recently introduced copepodscould not accountfor its decline. Orsi989! noted that striped bass appeared tobe more effective predators on Eurytemorathan on P. forbesi, and Meng & Orsi991! found that striped bass larvae in laboratoryfeeding experiments selected native copepods Cyclops sp, and cryptogenicEurytemora present in the Estuarysince at leastthe 1912-13Albatross survey;Esterly, 1924! over the recently introducedcopepods P. forbesi and Sirtocalanusdoerri, and suggested that differences incopepod swimming and escape behaviorscould account for the differentialpredation. Kimrnerer 991! reported that in laboratoryexperiments the introducedAsian clam Potamocorbula artturensis consumedEurytemora but not Pseudodiaptomusspecies, and Kirnmerer et al. ]994! arguedthat the decline in Ererptemorawas caused by Potamocorbula preying on its IntroducedSpecies IPagc77 nauplii.Orsi 995! suggestedthat, in additionto predationby Potamocorbula,the declinemay have been partly due to competitionwith P.forbesi, noting that Kurytemoracontinues to be seasonallypresent in winterand springwhen P. forbesi is scarce,both within and upstreamof Potamocorbula'srange. Orsi 995! also suggestedthat predation by theintroduced copepod Tortanus sp. may account for a declinein Pseudodiaptomusin westernSuisun Bay in 1994.

Pseudodiaptomusmarinus Sato, 1913!

Pseudodiaptomusmarinus is native to China, Japanand PacificRussia, and has beenintroduced to Hawaii and MauritiusO'ones, 1966; Grindley k Grice, 1969; Orsi et al., 1983!.It was collectednorth of SanDiego in MissionBay in 1986and in AquaHedionda Lagoon in May 1987 Flemingerk Kramer,1988!. It wasfirst collectedin the SanFrancisco Estuary from westernSuisun Bay in 1986,and has beencollected from there upstreamto Collinsvilleon the SacramentoRiver, in waters with surfacesalinities ranging from about 2 to 18 ppt. It hasalso been collectedfrom TomalesBay Orsi 8eWalter, 1991!. Pseudodiaptomusmarirtus may have been introducedto San FranciscoBay in ballast water, to the southernCalifornia bays or TomalesBay in oystershipments, and movedbetween bays by coastalcurrents Fleminger 8z Kramer, 1988; Orsi k Walter,1991!, Heminger & Krarner{19SS! suggested that the native copepod P. euryhalirtusmay havebeen displaced by P. marirtusin southernCalifornia embayments,and calledfor moresampling to determinewhether P. euryhalinus was in fact absent or confined to sites where P. marinus had not become established.

Siuocalauus doerrii Brehm, 1909!

SYNDNYMS:Sinocalartus mystrophorus Burckhardt, 1913

Thiscalanoid copepod is nativeto the riversof mainlandChina, and like the otherpelagic copepods described here was probably introduced in ballastwater. It wasfirst collectedfrom theEstuary near Pittsburg in 1978and soon became from 1979to the early1980s! the most abundant copepod in the Delta,with maximum densitiesof over10,000 individuals/m2 and greatest densities from June to September.It has been collected from throughout the Delta upstream to Hoodon the SacramentoRiver and Stocktonon the SanJoaquin River, and downstream to SanPablo Bay, generally at salinitiesbelow 5 or6 pptbut on occasion up tonearly 15 ppt.Its downstream limit xnay be regulated by both salinity and the location of the entrapmentzone Orsi et al.,1983; Ambler et al.,1985; Herbold & Moyle,1989; Orsi, 1995}.It wasnot collected in 1994,but reappearedin 1995Q. Orsi, pers- comm, 199'!- Five speciesare recognizedin the genusSittocalarrus, all from the northwestern Pacific. As 5. doerrii had not been collectedin regularplankton surveysin theEstuary in 1963and from 1972-78, it was probably introduced shortly before1978 via ballastwater Orsiet al,,1983!. Orsi et al.suggest, based on the Introduced Species Page 78

apparentpattern of spreadin 1978-79,that thesite of introductionwas in the Pittsburg-Antiocharea near where S. doerrii was first collected.They further suggest that waterpumped out of the Deltainto the CaliforniaAqueduct will carryS. doerrii to waterproject reservoirs near Los Angeles, and that theColumbia River and Puget Soundare likely sitesfor secondaryintroductions via the ballastwater carried by coastal ships. Several researchers have considered interactions between Sinocalanus doerrii and other copepodsin the northernestuary someof which are discussedabove under PseudodiaptomusIorbesi!. Orsi et al. 983! noted that competition between Sinocalanusand the cryptogenic copepod EurytemoraafPnis was unlikely because their preferredsalinity rangesdiffered, and suggestedthat competitionand/or predationbetween Sinocalanus and the freshwatercopepods Cyclops and Diaptomuswas a stronger possibility and should be investigated. Ambler et al. 985! questionedwhether there is competitionfor food, at leastin yearswith average river dischargeand diatom blooms in Suisun Bay. Meng & Orsi 991! found that striped basslarvae in laboratory feeding experimentsselected Cyclops sp. and Euryfemora over Sirtocalartus. Herbold et al, 992! reported that the introduction of Sinocalanusand of Pseudodiaptomusforbesi in 1987 was followed by declines in Euryfemora and the almost complete elimination of Diaptomusspp., although Herbold & Moyle 989! had earlier suggestedthat declines in Delta zooplankton prior to 1979may have facilitated Sinocalartus'establishment. Kimmerer 991! reported laboratory studies indicating that although Sinocalartusmay be food limited in the estuary in some years, Eurytemorais not and so competition with recently introduced copepods could not account for Eurytemora'sdecline. Orsi 995! suggestedthat Sirtocalanus had "apparently slipped into an unoccupied niche" between Euryfemora downstream and Diaptomus speciesupstream in the San Joaquin River, but noted that Diaptomus abundance fell when Sirtocalanusspread upstream. Herbold k Moyle 989! had noted that the invasion of the SacramentoRiver by Sirtocalanus coincided with a reduction in the relative abundanceof chlorophyll in the north Delta.

Tor tan us sp.

This large calanoid copepod of unknown origin was collected in Suisun Bay in the fall of 1993and in 1994 Orsi, 1994,1995; J. Orsi, pers. comm., 1995!.It preys on other copepodsand Orsi 995! suggeststhat it may have causeda decline in Pseudodiaptomusin western Suisun Bay in 1994.Its prior absencein this well- studied region of the Bay suggeststhat it was introduced in ballast water.