Immigration, dissemination and ecology of Elminius modestus Darwin in the North Sea, especially along the Dutch Coast

In 1947, Bishop was the first to pay attention to the occurrence of the barnacle Elminius modestus Darwin in British waters. This barnacle, which is a native of the coasts of southern and eastern Australia and New Zealand, i.e. of the temperate seas of the southern hemisphere, had been found by him in great quantities on test-panels in Chichester Harbour in July 1945. Soon after, several other records were published. Crisp and Chipperfield (1948) mentioned a number of localities; Elminius modestus appeared to be already widely distributed along the British coast (see fig. 1). Stubbings (1950) had the disposal of data of 1944 and from the size of the collected specimens he concluded, that Elminius must have occurred in Portsmouth as early as 1943. According to Knight-Jones (1948), Elminius had by then become a pest in the oysterbeds off Essex. Boschma (1948) recorded the barnacle from the Dutch coast where it had first been found in 1946. Meanwhile, Elminius modestus has enlarged its area considerably, in the British waters as well as along the continental coast. This paper will chiefly deal with the immigration, the dissemination and the habitat of Elminius modestus along the continental coast.