The growth rate of Elminius modestus (Crust., Cirripedia) in Scotland
The Australasian barnacle, Elminius modestus, is now common in Europe, often competing very successfully with a number of indigenous species (CRISP, 1958).
The Clyde Sea Area and the Firth of Forth represent the most northerly points yet reached by the immigrant in Britain (BARNES and BARNES, 1960; CRISP, 1960;JONES, 1961). Although the species shows a considerable degree of eurythermy throughout its life cycle, it is evident that moderately high temperatures, of the order of 15-20 "C, favour both growth and breeding. Temperatures in the Clyde are lower ( 6 1 5 "C) and information regarding the growth rate of the species a t such temperatures is desirable. Further, information on the effect of intertidal exposure and that of suspended matter is needed. Growth rates have, therefore, been measured a t three places, namely; Stranraer harbour wall a t two tidal levels ; Kirkcolm, further out in Loch Ryan, also a t two levels; Millport, where both high intertidal (+EL9 ft) and raft (continuous submersion) exposures were made under partially controlled conditions. The upper tidal heights used a t Stanraer and Kirkcolm were chosen so as to give the same immersion times as the + 8.9 f t level a t
Millport (BARNES and POWELL, 1953). The results allow of a comparison between 6he growth rates at different (extreme) tidal levels and also between those of muddy and relatively open water conditions.