Spatial variation in the recruitment of the intertidal barnacles Chthamalus montagui Southward and Chthamalus stellatus (Poli) (Crustacea: Cirripedia) over an European scale

Spatial variation in the recruitment of the intertidal barnacles Chthamalus montagui and Chthamalus stellatus was examined over an European scale. The study was carried out using 0022-0981/$ see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jembe.2003.12.005 * Corresponding author. Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, 117543 Singapore, Singapore. Tel.: +65-687-41034; fax: +65-67792486. E-mail addresses: [email protected], [email protected] (R.M. O’Riordan). 1 Present address: Dove Marine Laboratory, University of Newcastle, Cullercoats, North Shields, Tyne and Wear NE30 4PZ, England. 2 Present address: Marine Environment Research Centre, ENEA-Santa Teresa, P.O. Box 224, Pozzuolo di Lerici, 19100 La Spezia, Italy. R.M. O’Riordan et al. / J. Exp. Mar. Biol. Ecol. 304 (2004) 243–264 244 standardised protocols at a series of locations. The five locations chosen (SW Ireland, NW Spain, SW Portugal and NW and NE Italy) span a large part of the range of these species in Europe. The spatial scales were location (hundreds of kilometres) and shore (thousands of metres). Estimates of total cumulative recruitment (cyprids and metamorphs) summed over the year (April 1997 to March 1998) showed substantial variation between locations which was dependent on the species. Recruitment was highest in SW Portugal for C. montagui and in SW Ireland and NW Spain for C. stellatus. Overall recruitment of C. montagui was higher than that of C. stellatus at all locations except SW Ireland, where recruitment of the two species was not significantly different. There were significant differences among shores in each location. The recruitment period of both species varied with location, with recruitment beginning earlier further south. In general, recruitment of C. montagui and C. stellatus was recorded in 8 months in NW Spain and NE Italy, while only in 7 months in SW Ireland. Recruitment of C. montagui occurred in 10 months in SW Portugal, but no recruits of C. stellatus were found. In all locations there was at least one distinct peak of recruitment. In SW Ireland both species showed only one peak of recruitment, a month after initiation. At the more southerly Atlantic locations, as well as in the Mediterranean, two unequal peaks of recruitment were generally seen. During recruit census, the number of cyprids, in comparison to metamorphs, found at any location was very low. In SW Ireland and NW Spain cyprids of both species were found, while in SW Portugal and in the Mediterranean, only cyprids of C. montagui were found. D 2004 Elsevier B.V. All rights reserved.