the marine malacofauna of skokholm lslandnofth haven (fig. 2) is one of the two coves which provide...
TRANSCRIPT
F.J.A. Sl ieker, A.F. de Jongr, H.L. Strack & E.J.O. Kompanjel' Natuurmuseum Rotterdam
The mar ine malacofauna o f Skokho lmls land
Slieker, F.J.A., de Jong, A.F., Strack, H.L., & Kompanje, E.J.O., 1994 - The marine malacofauna ofSkokhohn Island - DEINSE A l, 57 - 75 ISSN 0923-9308]. Published 15 April 1994.
With the aim of sludying the local malacofauna, the authors visited Skokholm_Island (Pembrokeshire,Wales, UK) in 1990 and 1991. hr this paper, known data are supplemented by the results of theauthon'fieldrvork. Atotal of l14 species were recorded;49 are new records for Skokholm Island,ofwhich four are also new for the Bristol Channel region. On the basis ofthe current results a marinereserve stalus for Skokholm is reconrmended.
De mariene nnlacofauna van Skokhohtr eiland - De auteurs bezoclrten in 1990 en l99l SkokholmIsland (Pernbrokeshire, Wales, UK) teneinde een beeld te krijgen van de locale malacofauna" Be-staande gegevens werden aangevuld met veldwaarnerningen van de auteurs. In totaal werden l14soorlen geregistreerd, waarvan 49 nieuw voor het eiland, vier hiervan bleken tevens nieuw voor deBristol Chamel regio te zijn. De auteurs concluderen op basis van de resultaten van het onderzoek,dat Skokholm voor de status 'marien reservaat' in aanmerkine dient te komen.
Correspondence: c/o Natuunnuseurtr Rotterdarn, P.O.Box 23452, NL-3001 KL Rotterdam, theNetherlands
Keyrvords: malacology, tnariue fauna, Polyplacophora, Gastropoda, Bivalvia, Cephalopoda, Skok-holm lsland, Great Britain
INTRODUCTION AND METHODSIn I 987 E. J.O.Kompanje conducted biornetricalstudies on seabird populations on Skokholm Is-land. On his recommendation the authors visitedthe island between 16th and 23rd June 1990 and10th and lTth August 1991 to study the malaco-fauna. The following localities were investi-gated: North Haveq Peters Bay, South HaverlHog Bay and Crab Bay (Fig. l). An inventorywas made of all available data on marine mol-luscs in tlre cardfile system, stored in the Labor-atory of the Bird observatory on Skokholm ls-land (see Table l). Marry of these early recordswere previously published by Crothers (1966).This inventory gave us a good impression of thecollecting sites and ofthe species recorded fromthe island before our survey. All previous rec-ords of marine molluscs were taken behl,een1947 and 1971 ; no later records could be traced.
Apart from the five localities shrdied, the follo-wing sites were occasionally mentioned in thecardfile system: Tlre Stack, Little Bay, HeadBay, Wild Goose Bay, Dumbell Bay, RavensGully, Mad Bay Point, East Bay, Fnnk's Bayand The Quarry. Most of these localities arc veryexposed, not easily accessible, and according tothe available data, not very interesting; thereforewe did not sample these localities ourselves.Collecting was done by searching the solid rocksurface and by turning stones embedded in san4or in rockpools. In addition algae werc collectedand rvashed in fresh water in search for livingmicromolluscs. Collecting methods did not in-clude snorkeling, SCUBA-diving or dredgingtherefore the search-range was limited from thesupra-littoral zone down to just beneath the lo-west low rvater mark.
The results of our research on the different siteswere influenced by tide level, windforce and di-rection. In North Haven and Crab Bay shell gritwas collected in which many dead micromol-luscs and juvenile specimers of larger specieswere found. Many of these species occur in theshallow subtidal zone. In 1991 a low water ofspring tides enabled us to extend our search-range by approximately 0.65 m compared to theprevious year.Systernatics and nomenclature were used ac-cording to Fretter & Graham (1977), Graham(1988), Jones & Baxter (1987), Tebble (19'76)and Thompson (1988). Some material waspreserved for definite identification and is nowstored in the Nafirurmuseum Rotterdam and inthe private collections ofthe authors.
TOPOGRAPHYSkokholm (Fig. 1) is a flat-topped island of OldRed Sandstone, lying 3 kilometers south ofSkomer Island and 3 kilometen west of themainland cliffs of Marloes in Pembrokeshire,Wales, United Kingdom (51'42'N, 05"16'W).
DEINSEA I, 1994
Skokholm lies within sea area boundary 21
@ristol Channel) as defined by Seaward (1982,1990). The island is 800 m wide with a mzx-imum length of 1.9 km and has about 9.6 km ofrugged coastline. Skokholm slopes very gentlyfrom an altitude of 50 m at the westem end to 20mattheclifftops inthe east. Mostofthe circum-ference is precipitous but access to the shorelineis possible in several places and two coves pro-vide sheltered landings.
DESCRIPTION OF LOCALITIESNofth Haven (Fig. 2) is one of the two coveswhich provide sheltered landings and featuresthe only sandy beach on Skokholm. This beaclusurrounded by steep cliffs, cornists of coarsesand and boulders and is only accessible at lowtide.Peters Bay (Fig. 3), south of The Neck, is theleast accessible locality we have studied. In thelittoral mne large boulders dominate. Thesplashzone contains a relatively large cave(Spider Cave).
Figure I Skokholm lsland; the five investigated localities are indicated by arrows
o loofr Soon!
SLIEKER et ol: malacofauna ofSkokholm lsland
South Haven (Fig. a) is the other cove that pro-vides sheltered landings, and is the landing-stage forthe service boatfromthe mainland. Thelittle harbour, with its concrete landing, is sur-rounded by sheltering cliffs. The bottom con-sists of a reddish layer of sandstone, derived par-ticles and small stones.Hog Bay (Fig. 5) is the smallest of the five lo-calities studied. It has a boulder beach with fewsmall stones.Crab Bay (Fig. 6) is the most sheltered locality,mainly because of a group of large rocks (CrabRocks) in front of the bay. The channel betweenthe island and Crab Rocks is only accessible atLWST and scattered with many small to me-dium sized stones, overgrown with Laminariaand Saccorhiza.
ABBREVIATIONSIn the systematic survey the records may befollowed by abbreviations (between brackeG) ofthe recorders who preceded us. Their rurmes arclisted in Tabel l. The years refer to the period(s)the persons and institutions made their observa-tions.
Tabel I Abbreviations of earlier recorders used in thesystematic survey, and of tide indications (below)
ADBSBBWCMCRTHAGSHJMHJMBH]T
J u
JHBJRPKSTMEBMJAMPHNDPPDBRBSSUHW
A. Davies (1955)
B.S. Brookes (1965)B.K. Whitaker (1948 -1949)
C. Metam (1977)C.R. Thorne ( 1956)High Arcal Grammar School ( 1966- 1969)HJ. Moore (1954)HJ.M. Bowen (1948 & 1950)HJ. Thiel ( lesT)
J. Green (1955)
J.H. Barret (1948)
J.R. Povey ( 1965)K.S.Thomson ( 1955)M.E. Blytheway (1955)MJ. Askew (1969 & t972-1973)M.P. Harris (1964)N.D. Purcher (197 l -97 2)P. de Brant ( | 952)R.B. Slone School ( | 963)U.H. Wil l iams (1950)
LWM
LWST
Low water mark
Low water of spring tides
Figure 2 Beach at North Haven with large boulders; only accessible at low tide
DEINSEA I , I 994
Figure 3 Peters Bay, the least accessible locality
SLIEKER et ol: malacofauna of Skokholm lsland I
Figure 5 Hog Bay, the smallest locality studied, at low tide
SYSTEMATICAL SURVEY OFRECORDED SPECIES
The following classification of abundancy is
used to indicate the 1990 and 1991 recordings:
rare < l0 specimens
scarce l0 - 25 specimens
common 25 - 100 sPecimens
abundant > 100 soeci
If less than l0 specimens were recorded, theexact number is given in most cases.Habitat notes are only given when live spe-cimens were observed and are strictly related toconditions on Skokholm Island. The authors'sobservations arel{ceded by an asterisk (*).
Class Po l yp lacopho ra
Order Neoloricata
Suborder Lepidopleurina
Family Leptochitonidae
Genus Le ptochi ton Gr ay, 1847
Leptochiton asellus (Gmelin, 179 1)No previous records from Skokholm. * North
Haven, 1990, I valve in shell-grit; NothHaven, 1991, I valve in shell-grit.
Snborder Ischnochitoniua
Family Ischnochitonidae
Genus Lepidochitona Gtay, l82l
Lepidochiton a cin erea (Linnaeus, 1767)Hog Bay, 9.VII.1968, 1 specimen (HAGS);
North Haverl 10.VIL 1969, 1 specimen(HAGS). * Crab Bay, 1991, I juvenile speci-men; Peters Bay, 1991, 3 sPecimers.
Habitat: LWM under stones embedded in sand.
Gerus T on i c ella Carpenler, I 873
Tonicella rubra Q,imraeus, 1767)No previous records from Skokholm. * Peters
Bay, 1991, 1 specimen.Habitat: LWM on solid roch sheltered by over-
hanging cliffs.
Suborder Acarrthochitonina
Farnily Acanthochitonidae
Genrs Acanthochitona Ctrav. 1821
DEINSEA I, I994
Acanthochitona crinita (P errnrfi. L'7'7'7 )North Haven, 29.V11.1963,1 specimeq South
Haven, 29.VII. 1963, I specimen; SouthHaven, 9.VI[.1964, 2 specimers; NorthHaveq 8.VII.1968, occasional specimens(HAGS); North Haven, 10.VII.1969, I spe-cimen (HAGS). * South Haverq 1990, 5specimens; North Haveq 1990, I specimen;Crab Bay, 1991, I specimen; Peters BaY,1991, I juvenile specimer
Habital Intertidal on solid rock, occasionallyunder stones.
Acanthochitona fascicularis (Linnaeus, 1767)Soulh Haver! 2.V11.I961,1 specimen (HAGS);
North Haven" 23.V11.197 l, 3 specimens.Remarks: Most likely these records represenl
misidentified A. crinita as they were found onoverhanging rocks; a habitat prefered by l.crinita but not by.4. /ascicalaris.
Class GastropodaSubclass Prosobranchia
Order Archaeogastropoda
Family Fissurellidae
Genvs Emarginula Lamarck, 1801
Emarginula ftssura (Linnaeus, 1758)No previous records from Skokholm. * North
Haveq 1990, I specimen in shell-grit; CrabBay, 1991, 4 specimens in shell-grit.
GensDiodora Gray, 1821
Diodora graeca (Linnaeus, 1758)SouthHaveq 3.VIII.1950, I specimen onLami'
naria-roots(HJMB); Crab Bay, 18.IV.1965, Ispecimen under rock at LWST (BSB); CrabBay, 12.MI.1968, I specimen under stone(HAGS); North Haven, 28.VI[.1969, 1 spe-cimen at LWST. * North Haven, 1990, I spe-cimen in shell-grit.
Farnily Acnraeidae
Genus A cm a e a Eschscholtz, I 833
Acmaea virgin ea Miiller, 1776)
Crab Bay, 2.VIII.l950, 1 dead specimen SIJMB& UHW); Peters Bay, 2.VI[.1950, I dead
E
SLIEKER et ol: malacofauna ofSkokholm lsland
sp€cimen (IIJNA & UHW). * North Haverq1990, I specimen in shell-grit; Crab Bay,1991, I live specimen.
Habitat: Underwell embedded stone atLWST.
Family Palellidae
Genus Patella Linnaeus, 1758
Patella vulgata Linnaeus, 1758Regularly recorded between 1947 and 1973. *
Abundant at all localities in 1990 and 1991.Habitat: On solid rock and large stones in inter-
tidal zone.
Patell a depr e s s a P enmrg 17 1 7Regularly recorde*between 1947 and 1969. *
Abundant at all localities in 1990 and 1991.Habitat: As P. vulgata but rarely above mid-tide
level.
Patella aspera Rdding, 1798North Haven, Peters Bay, South Haven and Hog
Buy, 1949-1968, frequent-common; CrabBay , Y .1962, few specimens. * North HaverlPeters Bay, South Haven and Hog Bay, 1990-1991, abundant; Crab Bay, 1990-1991,scarce.
Habitat: As P. depressa but in more exposedareas around low-tide level.
Genx Helcion Montfort 18 10
Helcion pellucidunt (Linnaeus, 1758)North Haven, SouthHaven, Crab Bay, Hog Bay
and Peters Bay, 1947-1969, abundant. *North Haven, South Haven, Crab Bay andHog Bay, 1990-1991, abundant; Peters Bay,1990, scarce; Peters Bay, 1991, common.
Habitat: Mainly on Laminaria and other largebrown algae. Often fowrd in Laminaria-hold-fasts (forma laevis). Rarely living under sto-nes.
Family Trochidae
Gems Gibbula Risso, 1826
Gibbula cin eraria (Linnaeus, 1758)North Haven, South Haven, Crab Bay, Hog Bay
and Peters Bay,1941-1968, common. * North
Haveq South Haverl Crab Bay, Hog Bay andPeters Bay, 1990-1991, abundant.
Habitat Always at or near LWM or in pools.Remarks: Absent in Head Bay, Frank's Bay,
Mad Bay Point and Ravens Gully accordingto observations from 23 to 30.WII.1969.Probably these localities are too exposed fortlis species.
Gibbula umbilicalis (Da Costa 1778)North Haveq South Haverq Crab Bay, Hog Bay
and Peters Bay, 1948-1969, commorl * NorthHaveq South Haven, Crab Bay, Hog Bay andPeters Bay, 1990-199l, abundant.
Habitat: From mid-tide to low-tide levelt some-times higher in rock pools.
Remarks: Absent in the same localities as thepreceding species.
Gibbula tumida (Montagu, 1803)No previous records from Skokholm. * North
Haver4 1990, 5 specimens in shell-grit; CrabBay, 1991, 2 specimens in shell-grit.
Gents Monodonta Lanarck, 1799
Monodonta lineata (Da Costa, 1778)No(h Haverq South Haven, Crab Bay, Hog Bay
and Peten Bay, 1947-1968, scarce; SouthHaveq 6.VII.1950, n:urow zone of large spe-cimens in mid-tide region (CM); SouthHaveq 1959-1962, conrmon (Stanbury,19141. * South Haverq 1990, scarce; PetersBay, 1990, 1 specimen; Hog Bay, 1991, 2specimens; South Haverl L99I,7 specimens;Peters Bay, 1991, 3 specimens; NorthHaven,1991,3 specimens.
Habitat: Prefers sheltered areas around mid-lit-toral level.
Remarks: Absent in the same localities as G.cineraria and G. umbilicalis. An extensivestudy on a population of M. lineata in SouthHaven was conducted bv D.J. Stanburv(re74).
Genx Calliostoma Swairrson. 1840
Cal liostoma zizyp hin um (Liruraeus, I 758)Hog Bay, Crab Bay, Peters Bay, Little Neck
Point and The Stack, 194'l-1969, only I or 2
d
specimens. * Crab Bay, 1990, I juvenile spe-cimen; Cnb Bay, 1991, 2 juvenile specimens;SouthHaven, 1991, I juvenile specimen.
Habitat: Normally, adult specimens occur in thelowest littoral zone on rocks. The juvenileswere found under stones.
Family Skeneidae
Genus,S/cenea Fleming 1825
Skenea serpuloides (Montagu, 1808)Plate l, fig. l.No previous records from Skokholm and the
Bristol Channel Area. * NorthHaven, 1990, Ispecinren in shell-grit.
Remarks: The species is e4si'foverlooked be-cause of its small size, or regarded as a ju-venile of another trochoid species.
Skenea nilens (Phtlipp| 1844)Plate l, fig. 2.No previous records from Skokholm. No live
records from the Bristol Channel Area. * CrabBay, 1990, 3 live specimens; North Haver;1990, I specimen in shell-grit.
Habitat: Under stones at LWST.Remarks: Like the former species S. nitens is
also easily overlooked.
Farnily Tricoliidae
Gens Tricolia Risso, 1826
Tricolia pullus (Linnaeus, 1758)Peters Bay, Crab Bay and South HaverL 1949-
1969, occasional records; North Haven,3l.VII.1950, cornmon on Enteromorpha justbelow LWST (IIJMB & UHW). * NorthHaven, South Haven and Crab Bay, 1991,abundant; Hog Bay and Peters Bay, 1991,scarce.
Habitat: Mainly on Gigartina stellata and Ce-ramium sp. near LWST; occasionally underrocks.
Order Caenogastropoda
Farnily lacunidae
Gents Lacuna Tunton, 1827
DEINSEA I , I 994
Lacun a vinda (Montagt 1 803)No previous records from Skokholm. * South
Haveq 1991, common; Peters Bay, 1991,scarce, Crab Bay and Hog Bay, 1991, rare.
Habitat: Near LWST, mainly on Gigartina stel-lata andCeramium sp.
Locuna palhdula @a Costa, 11 78)Crab Bay and Peters Bay, 5-12.IV.1948, few
specimens (BW); Peten Bay, 1.MII.1950,not uncommon (HJMB & UHW). * Crab Bay,1991, 8 specimens; Hog lay and NorthHaveq 1991, common; South Haven andPeters Bay, 1991, abundant.
Habitat: Near LWST, mainly onGigartina stel-lata.
Family Littorinidae
Gewx Littorina F6russac, 1822
Littorin a liflorea (Linnaeus, 1758)Hog Bay and Peters Bay,1941-1969, rare; Crab
Bay and North Haverl 1955-1977, scarce;South Haveq 1962, abundant. * Hog Bay,1990-1991, scarce; Peters Bay, 1991, scarce;South Haven, 1990-1991, common; NorthHaven, 1991, common.
Habitat Mid-littoral on rocks and stones.
Littorina neritoides (Linnaeus, 1758)Peters Bay, 11.IX.1949, abundant (GO);Peters
Bay, VII.1968, common (HAGS); Hog Bay,26.IX.I951, conrmon (CED); North Havenand South Haveq 1966-1968, frequenttom-mon (IIAGS); Crab Bay, 1966-1968, abun-dant (HAGS). * North Haven, South Have4Crab Bay, Peters Bay and Hog Bay, 1990-1991, abundant.
Habitat: Upper littoral and splash zone.
Littorinq obtusata (Linnaeus, I 758)North Haveq South Haven, Crab Bay, Peters
Bay and Hog Bay, 1950-1973, few spe-cimens. * Crab Bay, 1991, scarce; Hog Bay,1991, common; South Haverl, 1990, 3 spe-cimens;Peters Bay, 1990, 3 specimens;PetersBay, 1991, 8 specimens; North Haven, 1990,I specimen; North Haven, 1991, abundant.
SLIEKER ec ol: malacofauna of Skokholm lsland
Remarks: Only small specimens of the olivegreen variety were found in the littoral zone,particularly onFucus.
Liltorina nigrolineata Gray, I839North Haveq VII.|9'77, generally common in
the P elveti a-zone, especially common :rmongupper Fucoids (CM). + North Haveq SouthHaverq Crab Bay, Peters Bay and Hog Bay,1990-1991. abundant.
Habitat: On rocks in the high littoral zone.
Littorinq negleda Bearl 1844North Haven, South Haven, Crab Bay, Peten
Bay and \OgBay , VIl.l9'77 , abundant in theBalanus-zone, often extending beyond theChthamalus-zone (CM). * South Haver;1991,7 specimens; Peters Bay, 1991, com-mon; NorthHaverU 1991, abundant.
Habitat: High littoral zone, often in empty bar-nacle shells.
Liltorin a s qxatilis (Olivi, 17 92)North Haven" South Haven" Peters Bay, Crab
Bay and Hog Bay, 1950-1973, common toabundant. * This was confirmed by our find-ings in 1990 and 1991.
Habitat: In high littoral zone.
Farnily Hydrobiidae
Genus Hydrobia Hartmann, 1821
Hydrobia ulvae (Pennant I'777)South Haveq l2.VlIJ.1969, 2 specimens
(MJA); Hog Bay, 26.VI[.1969, 1 specimen(MJA).
Remarks: We did not find it in both 1990 and1991. As there is no suitable habitat for thisspecies on Skokholm, we believe these tworecords to be very doubtrul.
Family Rissoidae
Genus Rissoa Desmarest 1814
Rissoa parva (Da Cost4 1778)North Haven, 3I.VII. 1950, not uncommon
(HJMB & UHW); Peters Bay, I.VIII.1950,not uncommon at LWM (HJI\A & UHW). *
Crab Bay, 1991, scarce; Hog Bay, 1991, 2specimens; South Haven, 1990, 2 specimens;
South Haven and North Have4 1991, com-mon; PetersBay, 1991, abundant.
Habitat R. parva as well as the smooth-shelledR. parvaformainterrupta (Adams, 1798) liveamong red algae in the lower littoral zone.
Genus Alvania Nsso. I 826
Alvanio semistrista (Montagu, 1808)North Haven and Peters Bay, 1-3.MII.1950, not
uncornmon below LWM ((HJNA & UHW);Crab Bay, 2.VI[.1950, 1 specimen (HJMB &UHW). * North HaveiL South Haveq PetenBay and Hog Bay, 1990-1991, rare to scarce;Crab Bay, 1990, abundant; Crab Bay, 1991,scarce; North Haven, 1990-1991, dead spe-cimern cornmon in shell-grit.
Habitat: Lower littoral zone, under stones.
Alvania pundura (Montagu, 1803)No previous records from Skokholm. * North
Haveq 1990, 9 specimens in shell-grit; CrabBay, 1991, 18 specimens in shell-grit; NorthHaveq 1991, 3 specimens in shell-grit.
Alvania cancellata (Da Cost4 1778)No previous records from Skokholm. * North
Haverl 1990, 1 specimen in shell-grit; CrabBay, 1991, 2 specimens in shell-grit.
Genx Manzonia Brusirn, 1870
Munzonia crassa Kanmacher, 1798)No previous records from Skokholm. * North
Haver; 1990, common in shell-grit; CrabBay, 1991, 6 specimens in shell-grit; NorthHaverl 1991,6 specimens in shell-grit.
Genu Clngala Fleming, 1828
Cin g ula trifasciata (J.Adams, I 800)Peten Bay, I.VIII. 1950, I live specimen (HJMB
& UHW); South Haverl 3.VIII.I950, I deadspecimen (HJMB & [IHW). * Crab Bay,1990, 3 specimens; Crab Bay, 1991, common;Hog Bay, 1990, common; Hog Bay, 1991,abundan[ South Haveq 1990,7 specimens;Peters Bay, 1990, 4 specimers; North HaverL1991, I specimen; North Haven, 1990, 2 deadspecimens in shell-grit.
specimens. * Crab Bay, 1990, I juvenile spe'cimen; Crab Bay, 1991, 2 juvenile specimens;SouthHaverl 1991, I juvenile specimen.
Habitat: Normally, adult specimens occur in thelowest littoral zone on rocks. The juveniles
were found under stones. I
Family Skeneidae
Genus S/cenea Fleming 1825
Skenea serpuloides (Montagu, I 808)Plate l, fig. l.No previous records from Skokholm and the
Bristol Channel Area. * No(hHaven, 1990, 1specimen in shell-grit.
Remarks: The species is easily overlooked be-cause of its small size, or regarded as a ju-
venile of another trochoid species.
Skenea nitens (Ptnlippi, 1844)Plate l, fig. 2.No previous records from Skokholm. No live
records from the Bristol Chamel Area. * CrabBay, 1990, 3 live specimens; North Haven,1990, I specimen in shell-grit.
Habitat: Under stones at LWST.Remarks: Like the former species S. nitens is
also easily overlooked.
Farnily Tricoliidae
Genus Tricolia Risso, 1826
Tricolia pullus (Linnaeus, 1758)Peters Bay, Crab Bay and South Haveq 1949-
1969, occasional records; North Haven,31.VII. 1950, common on Enteromorpha }ustbelow LWST (HJMB & UHW). * NorthHaven, South Haven and Crab BaY, 1991,abundant; Hog Bay and Peters Bay, 1991,scarce.
Habitat: Mainly on Gigartina stellata and Ce-rantium sp. near LWST; occasionally underrocks.
Order Caenogastropoda
Family L,acunidae
Genrx Lacuna Turton, I 827
DEINSEA I, I994
Lacuna vincta (Moftagu, 1803)No previous records from Skokholm. * South
Have4 1991, common; Peters BaY, 1991,scarce; Cnb Bay and Hog Bay, 1991, rare.
Habitat: Near LWST, mainly on Gigartina stel-lata and Ceramium sP.
L acun a pallidula (D a Cosa, 11 7 8)Crab Bay and Peters Bay, 5-12.IV.1948, few
specimens (BW); Peten Bay, 1.MII.1950,not uncommon (HJMB & UHW). * Crab Bay,1991, 8 specimens; Hog BaY, and NorthHave& 1991, commoq South Haven andPeters Bay, 1991, abundant.
Habitat NearLWST, mainly onGigartina stel-lata.
Family Littorirridae
Gentss Littorina F6russac, I 822
Littorin a liltorea (Linnaeus, 1758)Hog Bay and Peters Bay,194'1-1969, rare; Crab
Bay and North Haveq 1955'1977, scarce;South Haveq 1962, abundant. * Hog Bay,1990-1991, scarce; Peters Bay, 1991, scarce;South Haverq 1990-1991, common; NorthHaven. 1991. common.
Habitat Mid-littoral on rocks and stones.
Littorina neritoides (Linnaeus, 1758)Peters Bay, ll.IX.1949, abundant (GO);Peters
Bay, VII.1968, common (HAGS); Hog BaY,26.IX.1951. common (CED); North Havenand South Haveq 1966'1968, frequent<om-mon (HAGS); Cmb BaY, 1966-1968, abun-dant (HAGS). * North Haven, South Have&Crab Bay, Peters Bay and Hog Bay, 1990-1991, abundant.
Habitat Upper littoral and splash zone.
Littorina obtusota (Linrneus, 1758)North Haven, South Haven, Crab Bay, Peters
Bay and Hog Bay, 1950-1973, few sPe-cimens. * Crab Bay, 1991, scarce; Hog Bay,1991, common; South Haven, 1990, 3 sPe-cimens; Peters Bay, 1990, 3 specimers; PetersBay, 1991, 8 specimens; NorthHaver; 1990,I specimen; NorthHaven, 1991, abundant.
I
I
iI
SLIEKER ec ol: malacofauna of Skokholm lsland
Remarks: Only small specimens of the olivegreen variety were found in the littoral zone,particularly onFucus.
Liltorina nigrolineata Gray, I839North Haveq VII.|9'77, generally common in
the P elveti a-zone, especially common :rmongupper Fucoids (CM). + North Haveq SouthHaverq Crab Bay, Peters Bay and Hog Bay,1990-1991. abundant.
Habitat: On rocks in the high littoral zone.
Littorinq negleda Bearl 1844North Haven, South Haven, Crab Bay, Peten
Bay and \OgBay , VIl.l9'77 , abundant in theBalanus-zone, often extending beyond theChthamalus-zone (CM). * South Haver;1991,7 specimens; Peters Bay, 1991, com-mon; NorthHaverU 1991, abundant.
Habitat: High littoral zone, often in empty bar-nacle shells.
Liltorin a s qxatilis (Olivi, 17 92)North Haven" South Haven" Peters Bay, Crab
Bay and Hog Bay, 1950-1973, common toabundant. * This was confirmed by our find-ings in 1990 and 1991.
Habitat: In high littoral zone.
Farnily Hydrobiidae
Genus Hydrobia Hartmann, 1821
Hydrobia ulvae (Pennant I'777)South Haveq l2.VlIJ.1969, 2 specimens
(MJA); Hog Bay, 26.VI[.1969, 1 specimen(MJA).
Remarks: We did not find it in both 1990 and1991. As there is no suitable habitat for thisspecies on Skokholm, we believe these tworecords to be very doubtrul.
Family Rissoidae
Genus Rissoa Desmarest 1814
Rissoa parva (Da Cost4 1778)North Haven, 3I.VII. 1950, not uncommon
(HJMB & UHW); Peters Bay, I.VIII.1950,not uncommon at LWM (HJI\A & UHW). *
Crab Bay, 1991, scarce; Hog Bay, 1991, 2specimens; South Haven, 1990, 2 specimens;
South Haven and North Have4 1991, com-mon; PetersBay, 1991, abundant.
Habitat R. parva as well as the smooth-shelledR. parvaformainterrupta (Adams, 1798) liveamong red algae in the lower littoral zone.
Genus Alvania Nsso. I 826
Alvanio semistrista (Montagu, 1808)North Haven and Peters Bay, 1-3.MII.1950, not
uncornmon below LWM ((HJNA & UHW);Crab Bay, 2.VI[.1950, 1 specimen (HJMB &UHW). * North HaveiL South Haveq PetenBay and Hog Bay, 1990-1991, rare to scarce;Crab Bay, 1990, abundant; Crab Bay, 1991,scarce; North Haven, 1990-1991, dead spe-cimern cornmon in shell-grit.
Habitat: Lower littoral zone, under stones.
Alvania pundura (Montagu, 1803)No previous records from Skokholm. * North
Haveq 1990, 9 specimens in shell-grit; CrabBay, 1991, 18 specimens in shell-grit; NorthHaveq 1991, 3 specimens in shell-grit.
Alvania cancellata (Da Cost4 1778)No previous records from Skokholm. * North
Haverl 1990, 1 specimen in shell-grit; CrabBay, 1991, 2 specimens in shell-grit.
Genx Manzonia Brusirn, 1870
Munzonia crassa Kanmacher, 1798)No previous records from Skokholm. * North
Haver; 1990, common in shell-grit; CrabBay, 1991, 6 specimens in shell-grit; NorthHaverl 1991,6 specimens in shell-grit.
Genu Clngala Fleming, 1828
Cin g ula trifasciata (J.Adams, I 800)Peten Bay, I.VIII. 1950, I live specimen (HJMB
& UHW); South Haverl 3.VIII.I950, I deadspecimen (HJMB & [IHW). * Crab Bay,1990, 3 specimens; Crab Bay, 1991, common;Hog Bay, 1990, common; Hog Bay, 1991,abundan[ South Haveq 1990,7 specimens;Peters Bay, 1990, 4 specimers; North HaverL1991, I specimen; North Haven, 1990, 2 deadspecimens in shell-grit.
Habitat: Mid to low littoral zone, under stones.
Gews Onoba H.& A.Adams. 1852
Onobe semicostata (Montagu, 1803)North Haver\ 31.VII.1950, I live specimen
(HJMB & IJHW); Crab Bay, 2$IL 1950, notuncommon in muddy plEles (HJMB &[IHW). * Crab Bay, 1990, Scarce; Cnb Bay1991, common; Hog Bay, 1990, I specimen;HogBay, 1991, common; SouthHaveq 1990,common; North HaverL 1991, 8 specimens;North Haveru 1990, dead specimens commonin shell-grit; Crab Bay, 1991, abundant inshell-grit; North Haven, 1991, 16 specimensin shell-grit.
Habitat: Under stones, on t€d algae and some-times in rock pools. Lower littoral zone.
Onoba aculeus (Gould, 1841)No previous records from Skokholm. * Crab
Bay, 1991, 2 specimern; Hog Bay, 1990, 9specimers; Hog Bay, 1991, 4 specimens;South Haven, 1991, I specimen; Peters Bay,1991, 3 specimens; North Haven, 1990, 2 spe-cimens in shell-grit; Crab Bay, 1991, 9 spe-cimens in shell-grit.
Habitat: As O. semicostata.
Family Barleeidae
Genus B arleeia W.Clark 1855
Barleeiq unifasciata (Montagu" I 803)No previous records from Skokholm. * Hog
Bay, 1990, I specimen; SouthHaven, 1990, Ispecimen; Peters Bay, 1990, 8 specimens.
Habitat: Living on Ceramium sp. and other rcdalgae in the lower littoral zone.
Family Cingulopsidae
Genss Cingulopsis Fretter & Patil, 1958
Cingulopsis fulgida (J.Adams, L'7 97)Peters Bay, l7.VIII.l948, rare (JHB); Peters
Bay, 1.WIL 1950, a small specimen (HJMB &UHW). * Peters Bay and Hog Bay, 1991,common; South Haven, 1991, 8 specimens.
Habitat: On red algae in the lower liftoral zone.
DEINSEA I , 1994
Family Rissoellidae
Genus Rlssoella Gny, 1847
Rissoelln diaphana (Alder, 1848)Plate l, figs. 3 & 4No previous records from Skokholm. * Crab
Bay, Hog Bay, South Haven and Peters Bay,1991, abundant; North Haverl 1991, scarce.
Habitat: On red algae in the lower littoral zone.
Family Ornalogyidae
Genvs Omalogyro Jefreys, I 860
Omalogtra atomus @hilippi, 1841)No previous records from Skokholm. * Hog
Bay, 1991,4 specimens.Habitat: On red algae in the lower littoral zone.
Family Skeneopsidae
Genvs Skeneopsis lredale, I9I 5
Skeneopsis planorbis (Fabricius, 1780)North Haven, 2O.VIII.1955, abundant on Coral-
lina and frequent but less abundarx on Lomen-taria articulata (JG); North Haven"17 .V11.1972, I specimen in bamacle (NDP). *
Crab Bay, 1990, 3 specimens; Crab BaY,1991, abundan! Hog Bay 1990, 5 specimens;Hog Bay, 1991, abundant; South Haver;1990,5 specimeq SouthHaveq 1991, l spe-cimen; Peters Bay, 1990,'7 specimens; PetersBay, 1991, abundant; North Haven, 1991,abundant.
Habitat: Mostly on red algae in mid and low lit-toral zone.
Family Tornidae
Genus Tornrs Turton & Kingston, 1830
Torn us subcarinatrs (Montagu, 1803)No previous records from Skokholm. * North
Haver; 1990, 2 specimens in shell-grit; CrabBay, 1991, I specimen in shell-grit.
Family Caecidae
Genus Caecam Fleming 18 13
C a ecu m gla b r u m Qvlontaga, I 803)No previous records from Skokholm. * North
Haverq 1991,6 specimens in shell-grit.
SLIEKER et ol: malacofauna ofSkokholm lsland
Family Cerithiidae
Gewts B ittium Inach, 1847
Bifrium rdiculatum @a Costa, 1778)South Have4 31.VII.1950, live specimens on
Halichondria GIJNC & llHW); Crab Bay,18.IV.1965, at LWST (JRP); Peters Bay,27 .Vll.lg7 I, 1 specimen. * Crap Bay, 1991, 4specimens in shell-grit.
Remarks: Previous live records probably refertoCerithiopsis tubercularis (Montagu, 1803) asthis species feeds on the sponge Halichon-dria.
Family Capulidae
Genus Capulus Montfo( l8l0
Copu lus un garicu s (Linnaeus, 1758)No previous records from Skokholm. *
Haverg 1990, I juvenile specimen ingrit.
Family Eratoidae
Genus ?rivlaGray, 1837
Trivio monacha (Da CostA 1778)Crab Bay, 12.VII.1968, 2 specimens under
stones at LWST (HAGS); North HaverL2.VIII.L969, I specimen (MJA); Crab Bay,I4.VIII.1969, I specimen (MJA); NorthHaverl 28-29.VIII.1969, several under over-hanging boulders (MJA). * Crab Bay, 1990, 1specimen; Crab Bay, 1991, I juvenile spe-cimen.
Habitat: Lower littoral zone, under stones and indeep rock pools.
Trivia arctica (Pulteney, 1799)Hog Bay, 27 .lll.l952,l specimen in Laminaria-
zone; South Haven, IV.1955, I specimen onrocks below quay (AD); Crab Bay,2l.VII.l955, at low tide KST).
Family Muricidae
Genus Nrcella Rdding 1798
Nucella lapillus (Linnaeus, 1758)Previous as well as prcsent records indicate the
abundant occunence ofthis species on all lo-calities studied.
Habitat: On rocks in the mid-littonlznne.
Genx Ocenebra Gray, 1847
Ocenebra erinaceu (Linnaeus, 1758)Crab Bay, 2.VI[.1950, l juvenile specimen at
LWST(HJMB &rrH!V).
Family Nassariidae
Geux HiniaLeach, 1852
Hinia rdiculala (Linnaeus, 1758)SouthHave4 31.VII.1950, I very wornwashed
up specimen (HJNA & UHW).
Hinia incrassala (Str<im, 1768)Crab Bay, 14.IX.1954, 8 specimens under one
boulder (HJM); North Haven, 28.VIII.I97 2, 2North specimens amongst stones atLWST (MJA). *
shell- Peters Bay, 1990, 2 specimens; Crab Bay,1991, 3 specimens in shell-grit.
Habitat: Under overhanging boulders in lowerlittoral zone.
Family Cerithiopsidae
Gents Cerithiopsls Forbes & Hanlev. 1849
Cerithiopsis tuberculsris (Montagu, 1803)No previous records from Skokhohq although
we assume this species has been erroneouslyidentified as Bittium reticulatum. * Crab Bay,1990, I specimen; Hog Bay, 1991, 1 spe-cimen; Peters Bay, L99I,I specime&
Habitat: Lower littoral zone, on rocks andboulders covered with sponges.
Family Triphoridae
Genx Triphora Blainville, 1828
Triphora sdversa (Montagu, 1803)No previous records from Skokholm. * Crab
Bay, 1991, 3 specimern in shell-grit.
Farnily Epitoniidae
Gents Epitonium R6ding 1798
Epitonium clathratulum (Kanmacher, 1798)
No previous records from Skokholm. * NorthHaveq 1990, 3 specimens in shell-grit; Crab
ir
I
Bay, 1991, 2 specimens in shell-grit; NorthHaven, 1991, I specimen in shell-grit.
Family Janthinidae
Gen;s J anthina Plbding, 1798
Janthina janthina (Limneus, 1758)SkokholnL 18.VI.1964, I specimen with dried
up animal in gull-nest (NPH). ..-
Family Eulimidae
Genrs Vitreolina Monterosato, 1884
Vitreolina philippii @ayneval & Ponzi, 1854)No previous records from Skokholm. * Crab
Bay, 1991, 2 specimens in shell-grit.
Family Pyrarnidellidae
Genvs C hry s allida Carparter, 1 85 7
Chrysallida obtusa @rown, 1827)No previous records from Skokholm. * Crab
Bay, 1991, 4 specimens in shell-grit; NorthHaverl 1991, 3 specimens in shell-grit.
Chrysallida indistinda Montagu, 1808)No previous records from Skokholm. * Crab
Bay, 1991, 5 specimens in shell-grit.
Genvs Brachystomia Monterosato, 1884
Br achy stomia lakisi (J effreys, I 858)Plate l, figs. 5 & 6No previous records from Skokholm. * Crab
Bay, 1990, rare; Crab Bay, 1991, rare; HogBay, 1990, I specimen; Hog Bay, 1991, 3specimens; North Haverl 1990, 3 specimensin shell-grit; North Haverq L991,4 specimensin shell-grit; Crab Bay, 1991, 8 specimens inshell-grit.
Habitat: Under stones at LWST.
Gel:l.s Odostomla Fleming, l8l3
Odostomia unidentata (Montagu, I 803)No previous records from Skokholm. * Peters
Bay, 1991, I specimeq Crab Bay, 1991, 8specimens in shell-grit.
Habitat: In Laminaria-holdfast at LWST.
DEINSEA I , I994
Subclass Opisthobranchia
Order Bullomorpha
Family Retusidae
Genus Relasa Brown, 1887
Rdusa truncatuln @ruguidre, 1792)No previous records from Skokholm. * Crab
Bay, 1991, 3 specimens in shell-grit.
Family Rrmcinidae
GenvsRuncina Forbes & Hanlev. 1853
Runcina coronata (Quatrefages, 1844)Crab Bay, 22.V1I.1955,1 specimen at low tide
(KST); Crab Bay, 27.Y1.1956,1 specimen inrock pool (CRT). * Crab Bay, 1990, abun-dant; Hog Bay, 1990, 1 specimen; Crab Bay,1991, I specimeq Hog Bay, 1991, I sPe-cimen.
Habital Under stones in pools in the lower litto-ral zone.
Order Aplysiomorpha
Family Aplysiidae
Gents Aplysia Linnaeus, 1767
Aplysia pundata Cuvier, 1803Peters Bay, 24.IV.1952,1 specimen attached to
a rock at low tide level.
Order Sacoglossa
Farnily Stilligeridae
Genns Hermaea l,ov64 18,{4
Hermaea dendritica (Alder & Hancock, 1843)No previous records from Skokholm. * Crab
Bay, 1990, 3 specimens.Habitat Under stones in rock pools at LWST.
Family Limapontiidae
Genus Limapontia Johnston, 1836
Limapontia copitata Miiller, 1774)Crab Bay, 22.VII.I955,1 specimen at low tide
(NEB). * Crab Bay, 1990, common; HogBay, 1990, cornmon.
Habitat: Under stones, often in pools, at low tidelevel.
t 'SLIEKER et oL: malacofauna ofSkokholm lsland
Order Nudibranchia
Family Dotidae
Genus Doto Oken, 1815
D oto millb o y an u Lemche, I97 6No previous records from Skokholm. *
Bay, 1991, 2 specimens on Hydroids.Habitat At low water level under stone.
Family Goniodorididae
Genus Goniodoris Forbes & Goodsir, 1845
Crab
Goniodoris nodosa (Montagu 1808)Crab Bay, 14.IX.1954, I specimen (IIJM); Crab
Bay, 18.V. 1969, 2 specimens in rock pool.
Genus Ancula Lov6n, I 846
Ancula gibbosa (Risso, 1818)Crab Bay, 24.III.I952,1 specimen (PDB).
Family Polyceridae
Gerls Polycera Cuvier, l8l7
Po ly c er a fa er o en si s Lemche, | 929No previous records from Skokholm. * Crab
Bay, 1990, I specimenHabitat: Under stone in rockpool, lower littoral
zone.
Polycera qu adrilineata (Miiller, 1776)South Have& 19.VII. 1955, I specimen on weed
(KST); South Haveq 17.VII.1966, 7 spe-cimens on lower shore (HAGS); SouthHaven, 7.VII.1968, I specimen (HAGS). *
Crab Bay, 1991, scarce; SouthHaver; 1991,4specimens; Peters Bay, 199I,4 specimens.
Habitat: On rocks among red algae in the lowerlittoral zone.
Genus Palio Gray, 1857
Palio dubiq M.Sars, 1829)No previous records from Skokholm. * Crab
Bay, 1990, 2 egg-laying specimens; SouthHaverl 1990. 2 eggJaying specimens.
Habitat: Under stones inpools inthe lower litto-ral zone.
Remarks: According to the Invertebrate CardFile System on Skokholm, P. dubia has not
been recorded. We suspect ttnt the single rec-ord of Palio nothus (Johnsto41838) wasmisidentified ard actually refers to the presentspecies.
PaEo nothus (JohnstorL I 838)Hog Bay, 6.Vtr.196'7,2 specimens under a rock
atlow tide (HAGS).Remarks: Seewder P. dubia.
Gerns Limacia Miiller, 178 I
Limacin clavigera Miiller, 1776)No previous records from Skokholm. * Crab
Bay, 1990, 2 specimens; Crab Bay, 1991, 5specimens; Hog Bay, 1991, I sPecimen
Habitat: In rock pools under stones at LWST.
Family Archidorididae
Genrs Archidoris Berch 1878
Archidoris pseudoargus @app, 1827)Crab Bay, 1948-197I, scarce; Hog Bay, 23-
30.VIII.1969, I specimen; South Haverl22.X.1957, a specimen of 2" (H.f-D; SouthHaveq 23-30.VI[.1969, under overhangs onsponge (MJA); Peters Bay, 1962, a male andfemale in copulation together with strips ofeggs; Peters Bay, 20.VII.I97I, I specimenNorth Haven, 23-30.VI[.1969, I specimen(MJA); North Haven" 2.VIil.1969, I spe-cimen under overhang (HAGS); NorthHaveq 20.VII. 1971, 2 specimens (NDP).
Family Kentrodorididae
Genrs Jorunna Berch, 1876
Jorunna tommtosa (Cuvier, 1804)Crab Bay, 1960-1968, rare; North Haveq
2.VI[.1969, I specimen (MJA); SouthHaveq I2.VIlI.l969, I specimen (MJA).
Family Facelinidae
Genvs Facelina Alder & Hancock 1855
Facelinq coronda (Forbes & Goodsir, 1839)There are only two known records fnom Skok-
holm. LittleBay, 16.VIII.1950, I specimeninrock pool at LWST; Little Bay, 1S.VIII.1969,I specimen in rock face in shade.
Remarks: This species has neverbeen recordedfrom the localities we examined.
Family Aeolidiidae
Genx Aeolidia Cuvier, 1798
AeolfuIia papillosa Q-iruneus, I 76 I )South Haver; 12.VIII. 1969, I specimen in crack
at low tide (MJA). * Crab Bay, 1990, 2 spe-cimens; Hog Bay, 1990, I specimen.
Habitat: In pools under stones, lower littoralzone.
Gents A eoli di e lla Berch. I 867
Aeolidiella glauca (Alder & Hancock, 1845)Crab Bay, 22.VII.I955,1 specimen at low tide
(KST).
Subclass Pulmonala
Order Basomnatophora
Family Ellobiidae
Gents Leucophyda Winckworth, 1949
Leucophytia bfuIentata (Montagu, I 808)No previous records from Skokholm. * Crab
Bay, 1990, 4 specimens; South Haven, 1990,I dead specimen;HogBay, 1991, I specimen.
Habital Mid-littonl to LWST in dark. wet rockcrevices.
Gems Phyia Gray, 1828
Phytia myosotis @raparnaud, I 80 l)No previous records from Skokholm. * Crab
Bay, 1991, 1 specimen in shell-grit.
Family Otinidae
Genss Otina Gray, 1847
Otina ovata (Browq 1827)No previous records from Skokholm. South
Haven, 1990, commoq Hog Bay, 1990,scarce; Crab Bay, 1990, 3 specimens; PetersBay, 1990, I specimen; HogBay, 1991, abun-dant.
Habitat: As L. bidentata
DEINSEA I , I994
Class BivalviaSubclass Protobranchia
Order Nuculoida
Family Nuculidae
Genus Nncala l,amarc$ 1799
gdcula nucleus (Linnaeus, 1767)South Have4 3.VIII.1950, one valve (IIJMB &
UHW). * Crab Bay, 1990-1991, ll valves inshell-grit; North Haven, 1990, 5 valves inshell-grit.
Subclass l,amellibranchia
Order Taxodonta
Family Arcidae
Genus lrca Linnaeus. 1758
Ar c a tetr a g on a P oli, l7 9 5According to Crothers (1966) I specimen was
dredged at 12 fathoms dept[ 100 yards offNorth Point in 1960. Raven's Gully,25.VI[.1969, I live specimen onLithotham-nioninapool MJA). * NorthHaverq 1990, Ivalve in shell-grit; Crab Bay, 1991, I valve inshell-grit.
Family Glycymeridae
Genus Glycymeris Da Costa, 1778
G lycy meris glycymeris (Linnaeus, I 758)No previous records from Skokholm. * North
Haveq 1990, I valve in shell-griq NorthHaven, 1991, I valve in slrcll-grit.
Order Anisomyaria
Family My'tilidae
Gentss Rhomboidella Monterosato. 1884
Rhomboidells prideauxi (Leacb I 815)
No previous records from Skokholm and theBristol Channel Area. * NorthHaven. 1990" Ivalve in shell-grit.
Gews Modiolus Lamarch 1799
Modialus modialus (Lirrlaeus, 1758)South Haven, 2-I6.VI[.I969, occasional small
specimens (MJA). * North Haven, 1990, 1ju-venile valve in shell-grit.
SLIEKER et ol.: malacofauna of Skokholm lsland
Modiolus barbalus (Linnaeus, 1758)Peters Bay, North Haven and South Haverl
VIII.1969, occasiond specimens (Mln). *
Peters Bay, 1991, scarce; Crab Bay, 1991, Ispecimen; North Haver; 1991, I specimen;Hog Bay, 199I,2 specimens.
Habitat: At LWM:rmong red algae.
Modiolus phaseolinus @hilippi, I 844)Crothers (1966) claims this species dredged off
North Point at 12 fathoms depth where it ap-pears to be abundant (1960). Crab Bay,2.VIII.1950, smallvalves (HJMB & IJHW).
Genus Musculus Riiding, 1798
Musculus discors (Linnaeus, 1758)No previous records from Skokholm. * North
Haveq 1990, 3 valves in shell-grit; Crab Bay,199I, 2 specimens; Hog Bay, 1991, 1 spe-cimeq North Haven, 199I, I specimen
Habitat: At LWM among red algae.
Ganus Mytilus Linnaets, 1758
Mytilus edu Es Lirul.aleus, 1758Commonly distributed throughout the Skok-
holm coastline according to records from1947-1969. We recorded the species from allfive localities inboth 1990 and 1991.
Remarks: Probably due to the large populationsof breeding gulls on the island, only smallspecimens were found.
Family Pectinidae
Genx Camptonectes MeeE 1864
Camptonedes tigrin us (Miiller, 1776)No previous records from Skokholm. * Crab
Bay, 1991, I valve in shell-grit.
Gewx Aequipeclen P.Fischer, 1887
Aequipeden opercu laris (Linnaeus, 1758)Dredged off Skokholm Island at 5-10 fathoms
(Crothers 1966). One doubtful record fromPeters Bay [Pectin chlamys (sic)], 2l.VI-I.1955, I specimen at low tide (KST). * CrabBay, 1991, 4 valves in shell-grit; NorthHaverl 1991,3 valves in shell-grit.
Genx Chlamys Roding, 1798
Chlomys varin (Limneus, 1758)Dredged offthe north coast of Skokholm at 7-10, fathoms (Crothers). Peters Bay, Crab Bay and/ North Haverq VII-VI[-1950, I small valveI and fragments (IIJMB & IJHUD; Crab Bay,
14.IX.1954, I white juvenile specimen(HItvt). + Crab Bay, 1991, 2 juvenile spe-cimers; North Haverl 1990-1991, 8 valves inshell-grit.
Habitat: Under stones at LWST.
Genus Hinnites Defrance, 1821
Hinnites distortus (Da Costa, 1778)No previous records from Skokholm. * Crab
Bay, 1991, 4 valves in shell-grit.
Family Limidae
Genvs Mantellum Rii'ding, 1784
Mantellum ftrans (Gmelin, 1790)Stack Bay, 30.VII. 1963, I specimen under hold-
fast of Laminarla (RB SS).
Family Anomiidae
Gents Anomia Linnaeus, 1758
Anontia ephippium Linnaeus, 1758Peters Bay, 1I.MII.1949; Peters Bay,
l.VIII.1950 (HJIVIB & UHW); North Haverl29.VII.1950, common GIJNB & UHW);Crab Bay, 2.VI[.1950 (HJNA & UHW);Crab Bay, l4.Ix.l954,frequent (HJM); SouthHaveg North Haverq Hog Bay, 6-13.Vrr.1968 (HAGS).
Remarks: Most likely the records of A. ephip-pium from all five localities (1949-1969)represent misidentified H. squ amu la.
Gents Heteranonla Winckworth. 1922
Hderanomin squamula (Linnaeus, 1758)Crab Bay, 2.VIII.1950 (HJMB & UHW);North
Haveq 23.VII.1950, not uncommon (HJMB& UHW). * Crab Bay, 1990-1991, abundant;Hog Bay, 1990,4 specimens, Hog Bay, 1991,3 specimens; South Haveq 1990, 4 spe-cimens;Peten Bay, 1990,2 specimens; Peters
t -
b l |
hnJ Remarks: This species has neverbeen recorded
I from the localities we examined.
II
Family Aeolidiidaej Gens Aeolidia Cuvier, 1198lri Aeolidia papillasa(Liruraeus, 1761)
South Have4 l2.VI[. 1969, 1 specimen in crackat low tide (MJA). * Crab Bay, 1990, 2 spe-cimens; Hog Bay, 1990, 1 specimen.
Habitat: In pools under stones, lower littoralznne.
Genss AeolidiellaBerch, I 867
AeolidieUa glauca (Alder & Hancock, 1845)Crab Bay, 22.V1I.1955,1 specimen at low tide
(KST).
Subclass Pulmonala
Order Basommatophora
Family Ellobiidae
Gents Leucophyia Winckworth, 1949
Leucophytia bidentata (Montagu" 1 808)No previous records from Skokholm. * Crab
Bay, 1990,4 specimens; SouthHaven, 1990,I dead specimen; Hog Bay, 1991, I specimen.
Habitat: Mid-littoral to LWST in dark, wet rockcrevices.
Genus Phytia Gtuy,1828
Phytia myosotis @raparnaud, I 80 l)No previous records from Skokholm. * Crab
Bay, 1991, I specimen in shell-grit.
Family Otinidae
Genus Orina Gray, 1847
Otina ovata @rorvrl 1827)No previous records from Skokholm. South
Haven, 1990, commoq Hog Bay, 1990,scarce; Crab Bay, 1990, 3 specimens; PetersBay, 1990, I specimen; HogBay, 1991, abun-dant.
Habitat: As L. bidentata.
DEINSEA I , I994
Class BivalviaSubclass hotobranchia
Order Nuculoida
Family Nuculidae
Genrss Nucula l-amarck- 1799
Naculo nucleus (Linnaeus, 1767)South Haveq 3.VI[.1950, one valve G{JMB &
[IHW). * Crab Qay, 1990-1991, ll valves inshell-grit; North H4verL 1990, 5 valves inshell-grit.
Subclass t amellibranchia
Order Taxodonla
Family Arcidae
Gents Arca Linnaeus. 1758
Arca tetr agona P oli, l7 9 5According to Crothers (1966) I specimen was
dredged at 12 fathoms depttq 100 yards offNorth Point in 1960. Raven's Gully,25.VItr.1969, I live specimen onLithotham-nion inapol (MJA). * North Haverl 1990, Ivalve in shell-grit; Crab Bay, 1991, 1 valve inshell-grit.
Farnily Glycymeridae
Gents Glycymeris Da Costa, 1778
G ly cy m eris g I y cy m eris (Linnaeus, I 758)No previous records from Skokholm. * North
Haven, 1990, I valve in shell-gri! NorthHaveq 1991, I valve in shell-grit.
Order Anisomyaria
Family Mytilidae
Genvs Rhomboidella Monterosato. I 884
Rhomboidella prideouxi (Leacb I 815)No previous records from Skokholm and the
Bristol Channel Area. * NorthHaven 1990. Ivalve in shell-grit.
G enss M odi o lu s Lanarck, I7 99
M o dio Iu s mo dio lus (Limaeus, I 75 8)South Haven, 2-l6.Vll[.l969, occasional small
specimens (MJA). * North Haven, 1990, l ju-venile valve in shell-grit.
q
SLIEKER er ol: malacofauna of Skokholm lsiand
Modiolus barbalzs (Linnaeus, 1758)Peten Bay, North Haven and South Haverl
VIII.I969, occasiond specimens (MJA). '*
Peters Bay, 1991, scarce; Crab Bay, 1991, Ispecimeq North Haven, 1991, I specimen;Hog Bay, 1991,2 specimens.
Habitat At LWM among red algae.
Modiolus phaseolinus @hilippi, I 844)Crothen (1966) claims this species dredged off
North Point at 12 fathoms depth where it ap*pears to be abundant (1960). Crab Bay,2.VI[.1950, smallvalves (HJMB & IIHUD.
Gert.x Musculus Roding, 1798
Musculus discors (Liruneus, 1758)No previous records from Skokholm. * North
Haverl 1990, 3 valves in shell-grit; Crab Bay,199I, 2 specimens; Hog Bay, 1991, I spe-cimen; North Have4 1991, 1 specimen
Habitat: At LWM among red algae.
Genx Mytilus Linnaeus, 1758
My,tilus eduhs Linnaeus, 1758Commonly distributed throughout the Skok-
holm coastline according to records from1947-1969. We recorded the species from allfive localities inboth 1990 and 1991.
Remarks: Probably due to the large populationsof breeding gulls on the island, only smallspecimens were found.
Family Pectinidae
Gerus Camptonectes Meek 1864
Camptonedes tigrinus (Miiller, 1776)No previous records from Skokholm. * Crab
Bay, 1991, I valve in shell-grit.
Gents Aequi pe clen P.Fischer, I 887
Aequipedm opercularis (Linnaeus, 1758)Drcdged off Skokholm Island at 5-10 fathoms
(Crothers 1966). One doubtful record fromPeters Bay fPectin chlamys (sic)1, 2l.VI-I.1955, I specimen at low tide (KST). * CrabBay, 1991, 4 valves in shell-grit; NorthHaveq 1991, 3 valves in shell-grit.
Genus ChLamys R0ding, 1798
Chlamys varin (Lint:oLeus, 1758)Drcdged offthe rprthcoast of Skokholmat 7-10
fathoms (Crothers). Peten Bay, Crab Bay andNorth Have4 VII-VIII-1950, I small valveand fragments (IIJMB & IJHW); Crab Bay,14.IX.1954, 1 white juvenile specimen(HJlvf). * Crab Bay, 1991, 2 juvenile spe-cimens, North Have4 1990-1991, 8 valves inshell-grit.
Habitat Under stones at LWST.
Genus .F/irnites Defrance, l82l
Hinnites distortus (Da Costa 1778)No previous records from Skokholm. * Crab
Bay, 1991, 4 valves in shell-grit.
Family Limidae
Genrx Mantellum Rciding, 1784
Mantellum hians (Gmelirl 1790)Stack Bay, 30.VII. I 963, I specimen under hold-
fast of Laminarla (RB SS).
Family Anomiidae
Genvs Anomia Linnaeus, 1758
Anomia ephtppium Linnaeus, 1758Peten Buy, 1I.MII.1949; Peters Bay,
1.VI[.1950 (HJMB & UHW); North Haverl29.VII.1950, common (IIJI\{B & UHW);Crab Bay, 2.VI[.1950 (]IJMB & UHW);Crab Bay, 14.IX.1954, frequent (HJM); SouthHaverl North Haveq Hog Buy, 6-13.Vrr.1968 (HAGS).
Remarks: Most likely the records of A. ephip-pium from all five localities (1949-1969\represent misidentified H. squamu la.
Gentss Heteranonia Winckworth- 1922
Hderanomia squamula (Linnaeus, 1758)Crab Bay, 2.V1I.1950 (HJMB & UHW); North
Haveq 23.VII.1950, not uncommon (HJMB& UHW). * Crab Bay, 1990-1991, abundant;Hog Bay, L990,4 specimens; Hog Bay, 1991,3 specimens; South Have4 1990, 4 spe-cimers; Peters Bay, 1990,2 specimens; Peten
il
Bay, 1991, common; North Haven" 1991,abundant. Valves are abundant in shell gritfrom both Crab Bay (1991) and North Haven(1990 and 1991).
Habital Under stones at LWST.
Order Eulamellibranchia
Family Astartidae
Gems Godallia Turton, I 822
Goodalliq bian gularis (Montagu, 1803)No previous records from Skokholm. * North
Haven, 1990-1991, valves, common in shell-grit.
Family l,eptonidae
Genus lasaea Brown" 1827
L as ae a r u b r a (Montagu, I 803 )Crab Bay, 13.IX.1954, I specimen collected,
'likely to be numerous' (HIM). * Crab Bay,1990, 3 specimens; Crab Bay, 1991, common;Hog Bay, 1990, 4 specimens; Hog Bay, 1991,scarce; South Haverl 1990, 2 specimens;North Haveg 1991, 3 specimens.
Habitat: On rccks and under stones among algaeat LWM.
G ents K e I I i a Turton. | 822
Kelha sub orbicularis (MontagU 1803)No previous records from Skokholm. * Hog
Bay, 1990, 2 live specimens; North Haven,1990,2 valves in shell-grit.
Habitat: Under stones at LWST.
Gents Lepton Turton, 1822
Lepton nitidum TurtorU 1822No previous records from Skokholm and the
Bristol Channel Area. * NorthHaven 1991.2valves in shell-grit.
Family Montacutidae
Gents Mysella Angas, 1877
My sella bfuIentata (Montagu, I 803)No previous records from Skokholm. * North
Haverl 1990,2 valves in shell-grit.
DEINSEA l, 1994
Family Cardiidae
Gen:s P amicardinrn Monterosato, 1884
Purvicatdium orale (Sowerby, 184 l)No previous records from Skokholm. * Crab
Bay,.1991, valves scarce in shell-grit; NorthHaveN990-1991, valves common in shell-grit.
Panicardium exiguum (Gmelin, 179 1)Crab Bay, 2.VIU.1950, valves (HJMB &
uHw).
Genus Cerastoderma Mdrclr. 1853
Cersstoderma edule (Lirnaeus, 1767)South Haven" 3I.VII.1950, I freshly washed up
specimenG{JNB &UHW).
Family Veneridae
Gents GouM i a C.B.Adams, I 847
Gouldiq minima (Montagu, 1803)No previous records from Skokholm. * North
Haveq 1990-1991, 6 valves in shell-grit;Crab Bay, 1991, 3 valves in shell-grit.
Genrx Chione Megerle von Miihlfeld, l8l I
Chione ovata (Penmnt" 1777)No previous records from Skokholm. * North
Haven, 1990-1991, 8 valves in shell-grit.
Gents Venerupis t amarclg I 81 8
Ven er u pis pu ll a str a (Montagu, I 803)No previous records fiom Skokholm. * Crab
Bay, 1991, I dead specimen; South Haveq1991,2 dead specimens.
Family San guinolariidae
Genus Psammocola Blainville. 1824
Psammocola depressa (Pennant, 1777)No previous records from Skokholm. * Crab
Bay, 1991, I dead specimen
@
SLIEKER et ol: malacofauna of Skokholm lsland
Family Hiatellidae
Genus Hiatella (Daudin in) Bosc, l80l
HfuteAa qrdica (Linnaeus, 1767)Various records from all localities from 1949-
1969. * Crab Bay, 1990, 3 specimens; CrabBay, 1991, abundant; Hog Bay, 1990, I spe-cimen; Hog Bay, 1991, I specimen; NorthHaverL 1991, common
Habitat Understones or inLaminaria holdfastsAtLWST.
Hiatella rugosa (Pennant, 1777)No previous records from Skokholm. * Crab
Bay, 1990, l specimen.Habitat Boring in stone at LWM.Remarks: H. rugosa is often considered only a
form of fL arctica. We preferto retain its spe-cific status.
Class CephalopodaOrder Decapoda
Family Sepiidae
Genus ̂ Sepla Linnaeus, 1758
Sepia ofricinalis Linnaeus, 1758One record, 2.VIII.1950, conceming 2 'borrcs'
of this species by a gullery at Bread Rock(HJMB & UHW). * No(h Haveq 1991, I'bone'.
Order Octopoda
Family Octopodidae
Genus Eledone Lnacll 18 17
Eledone cirrhosa (Lamarck, I 798)North Haver! 20.IX. 1955, I specimen caught by
a limpet and held to the rock surface by orrctentacle. The animal was released and keptalive for several days.
coNcLUstoNsIn total, 114 species of marine molluscs are nowrecorded from Skokholm. Of this amounl 49species were newly recorded during our survey.The following species werc new records or newlive records for the Bristol Chanrrl area (Sea-war{ 1982 & 1990): Skenea serpuloides, Ske-ne dt, n i t e n s, Rh o; mb oi de I I a pri de auxi atfr Le p to nnitidvm. Four of the earlier recorded species areprobably based on misidentified specimens:Acanthoch i tona fasci cu lari s, Hydrobi a ulvae,Palio nothus andAnomia ephippium.As might be expected from an island with arocky coastline, bivalves are poorly represented.Even the few bivalve species inhabiting this typeof ervironment occur in relatively small num-ben. Although predation by gulls was regularlyobserved, in our opinion this carmot be the solecause of this phenomenon.Skokholm proves a suitable habitat for opisto-branch molluscs of which 18 species are hithertorecorded.In our opinion the rich gastropod faunajustifiesa marine reserve status for Skokholm Island, andinclusion in the recently designated SkomerMarine Nature Reserve should be considered.
ACKNO\^/LEDGEMENTSThe authon would like to express their gratitudeto warden Michael Betts and his wife Susan Bar-clay for their hospitality and inspiring enthusi-asm during the visits to Skokholm Island, aswell as to the Dyfed Wildlife Trust for enablingus to conduct our malacological survey. Ac-knowledgements arc also due to Mr. J. Goud(Nationaal Natuurhistorisch Museunl LeideqThe Netherlands) for the SEM photographs usedin this paper, as well as to Mrs. J. Light (Go-dalming, Surrey, England) and Michael Betts forcritically reading the text. We also like to thankMr. H.P.M.G. Menkhont (Natuurmuseum Rot-terdanL The Netherlands) for identification ofseveral micromolluscs.
E
DETNSEA l , 1994
REFERENCESCrothers, J.H., 1966 - Dale Fort Marine Fauna - Supplement
to Field Studies 2
Fretter, V. & A. Graham, 1977 -'Ilne prosobranch molluscs
of Britain and Denmark, Part 2 - Trochace4 Supplement
3 - The Joumal of Molluscan Studies 8l-87.
Graharn, A., 1988 - Synopses of the British Fauna No.2;
Molluscs: Prosobranch and Plramidellid Gastropods -
l,ondon.
Jones, A.M. & J.M. Baxter, 1987 - Synopses of the British
Fauna No.37; Molluscs: Caudofoveata" Solenogastres,
Polyplacophoraand Scaphopoda- London
Seaward, D.R., 1982 - Sea area atlas ofthe marine molluscs
of Britain and lreland.- Nature Conservancy Council.
Shrewsbury
Seaward, D.R., 190 - Distribution ofthe marine molluscs of
north west Europe - \ature Conservanry Council. Peter'\
borough \Stanbury, D.J., 1974 - Some marking e4periments on a
population of Monodonta kneata (Da Costa), South
Haven, Skokholnr, Pembrokeshire - Skokholm Bird
Observatory Repott 197 4: 27 -3 4.
Tebble, N., 1975 - British bivalve seashells. A handbook for
identificalion - london.
Thompson, T.E., 1988 - Synopses of the British Fauna No.8;
Molluscs: Benthic Opisthobranchs (Mollusca: Gastro'
poda) - Leiden.
received 27 Oclober 1992acceoted l5 December 1992updated l2 October 1993
PLATE I (scale bars are loo mu)
Figure I Skeneo serpuloides (Montagu, lB0B), Skokholm lsl., North Haven, FJAS 4923;
Figure 2 Skeneo nitens (Philippi, lB44), Skokholm lsl., Nofth Haven, FjAS 4922;
Figure 3 Rissoe/lo diophono (Alder, lB4B), Skokholm lsl., Hog Bay, FJAS 6597;Figure 4 Aperture with operculum, same species as Fig. 3;
Figure 5 Brochystomio /ukrsi (Jeffreys, lB5B), Skokholm lsl., Hog Bay, FJAS 6601;
Flgure 6 Aperture with operculum, same specimen as Fig.S;(FJAS = collection F.J.A. Slieker, Schiedam)
SLIEKER et o/.: ma.lacofauna of Skokholm lsland
PLATE I