Porcupine Newsletter Number 25, Winter 2008/09.

PORCUPINE PIECESNorthward spread of theimmigrant barnacle Elminiusmodestus on the British North SeacoastFrank Evans15 Thirlmere Avenue, North Shields NE30 3UQfrankevans@zooplankton.co.ukFollowing its discovery on test plates inChichester Harbour in 1946 (Bishop, 1947),the immigrant barnacle Elminius modestusspread rapidly along the south and east coastsof England, being recorded by 1948 in suitablelocations between Norfolk and Dorset (Crispand Chipperfield, 1948). Its first arrival inEngland from Australasia was clearly by shipand this type of remote dispersal resulted,as Crisp observed, in the species appearingat first in isolated places, in Holland, theIrish Sea and on the French coast. Later, in1977 a healthy but isolated population wasdiscovered by Hiscock et al. in Vidlin Voe inShetland (Hiscock et al., 1978). At the sametime, spreading up the east coast of England,it had reached the Humber by 1950, where itappeared for a time to halt (Crisp, 1958).But the advance of Elminius was not longinterrupted at the Humber for by 1960 Crisphad reported its presence at Saltburn (54º35’N) near the mouth of the Tees (Crisp, 1960).Following what was clearly a remote dispersalby ship, Elminius was found in the Firth ofForth, supposedly arriving at Rosyth around1958 (Jones, 1961). From there it appearsto have spread rapidly round the Fife coast,reaching Tayport (56º 27’N) on the southside of the Tay by 1961 but south eastwardsextending only as far as Dunbar (56º 00’N).Meanwhile, in 1958 I had discovered asingle colony at Newton-by-the-Sea (55º 31’N)in north Northumberland (Evans, 1958). Atthis time Elminius was present from Dunbarnorthwards and from Saltburn southwardsbut with this single discovery in between.On finding this colony I made a search at adozen sites along the Border coast for furtherexamples but specimens were found only asfar north of Saltburn as West Hartlepool andSeaham (54º 50’N). Apart from at Newton noother animals were discovered as far north asEyemouth (55º 52’N).However, by 1979 the coast betweenSeaham and Dunbar was widely colonised (seeEvans (2000) for Northumberland records)although my return visits from 1970 onwardsshowed that the species was by no means secureat individual sites, Elminius having almostdisappeared, for instance, at Newton. The siteof commonest occurrence in Northumberlandis on the causeway to Holy Island (55º 41’N),where it has been constantly found.In 1981 a visit to the Fife coast found thespecies to be common at a number of sitesbetween Aberdour (56º 03’N) and Tayport. Thebarnacle had by now succeeded in crossing theTay and in this year a few were to be found atBroughty Ferry (56º 28’N) on the north side.Further north, at Arbroath and at Montrose(56º 43’N) it appeared entirely absent.In 2008 a further examination of thecoastline north of the Tay showed a smallextension of the species range. Elminiuswas now present in very small numbers atMontrose. However, visits to Johnshaven (56º48’N) and Gourdon (56º 50’N), a little furthernorth, revealed no examples.Clearly, given its slow advance, the speciesis proceeding northwards under difficultyin the northern North Sea at what may benear the limit of its mainland range, but thefact that it continues to make slow progressindicates some adaptability. There are few sitesin eastern Scotland and northeast Englandwhere it is sufficiently common for significantreproduction to take place but its orderlymovement up the British North Sea coastsuggests nevertheless that new settlement islargely by development although ship dispersal8PMNHS Newsletter No.25 Winterer 2008/09