No abstract

The crab Carcinus maenas (L.) has an endemic distribution along the European Atlantic coastline but has been accidentally introduced into intertidal habitats in several parts of the world. Its discovery al the Cape Peninsula in South Africa is recorded here. The crab is well established in Table Bay harbour and the population is at least seven years old. From here it has spread 117 km north and 10 km south. Populations on the open coast are more recently established. The crab feeds on a wide range of intertidal animals, particularly the isopod Paridotea ungulaw, limpets and polychaetes, but it is too early to make quantitative assessments of its impact on local intertidal communities.Initial predation experiments suggest that the barnacle Notomegabalanus algieola and the whelks o.l)'stele I'l/riegata and O. tigrina have no refuge in size or zonation from the crab. O. sinensis, of similar size to O. tigrina, is less vulnerable by virtue of its stronger shell. Its critical size (above which it is too large to be attacked) is correlated with crab size. Larger species, such as the mussels Chorom)'lilus meridionalis and Aulacomya ateI' and the periwinkle Turbo sarmatieus, clearly achieve a refuge in size, but predation on their recruits may influence their abundance and size structure. C. maenas rejected only the urchin Pareehinus angulosus as a source of food. While it is conceivable that shifts in community structure, selection for thicker shells in molluscs and localized extinction of certain species may occur at high crab densities, it is predicted that C. maenas will only have a significant impact in areas protected from wave action.Die krap Carcinus maenas (L.) kom endemics langs die Atlantiese kuslyn van Europa voor, maar is per ongeluk in lussengetyse habitatte van etlike werelddele ingebring. Sy ontdekking langs dic Kaapse Skiereiland in Suid-Afrika word hiermee geboekstaaf. Die krap is goed gevestig in Tafelbaai, en die bevolking is ten minste sewe jaar oud. Hiervandaan het dit 117 km noord en 10 km suid versprei. Bevolkings aan die onbeskutte kus is meer onlangs gevestig. Die krap teer op 'n wye verskeidenheid tussengelyse diere, veral die isopode ParidOiea ungulata, klipmossels en borselwurms, maar dit is te vroeg om nou al kwantitatiewe ramings van sy invloed op plaaslike tussengetyse gemeenskappe te maak. Voorlopige voedingstoetse dui daarop dat die scepok NOlomegabalanlls algicola en die wulke Ox)'slele variegara en O. ligrina geen ontvlugting in Of grootte of sonering van die krap vind nie. O. sinensis, van soortgelyke grootle as O. ligrina, is minder kwesbaar van wee sy sterker skulp. Sy kritieke grootte (waarbo hy te groot is om aangevalte word) hou verband met krapgrootte. Groter spesies, soos die mossels Choromyti/llS meridionalis en Aulacom)'a aler en die alikreukel Turbo sarmalieus, verwerf wei deeglik beskerming wanneer hul groot word, maar roofbedrywighede op hul rekrute kan die talrykheid en groottesamestelling be'invloed. C. maenas het net die seekastaiing Parechinl/s angulosus as 'n voedse...

No abstract

No abstract

No abstract