Recruitment of blue mussels, Mytilus edulis L., on suspended collectors in Finnmark, North Norway (70–71°N).

In order to investigate Mytilus edulis settlement in two North Norwegian fjords (70–71°N), short-term collectors were suspended at six different stations at intervals of 2–4 weeks during spring–autumn of 2002 and 2003. At the same stations, long-term collectors were deployed monthly from May to August 2002 and sampled the following autumn. Settlement occurred between early July and late October and peaked between mid-July and mid-September. Settlement peaked in inner Porsangerfjord, with the average mean daily settlement (MDS) up to 1408 m-1 day-1, and decreased towards the coast, where the maximum MDS was 3.8 m-1 day-1. In Altafjord, maximal mean MDS were between 47 and 168 m-1 day-1. Fjords apparently function as retention areas for larvae, whereas at the coast larvae are effectively dispersed. Eighty-nine per cent of the mussels recruited in October/November were <2 mm. Long-term collectors deployed in inner Porsangerfjord had the highest recruitment (mean density 47,537 m-1). Inner Altafjord had very low recruitment (mean density 46 m-1), perhaps due to freshwater discharge. Collectors deployed in late August had lower recruitment than those deployed earlier, but there was no evidence of recruitment differences between collectors deployed earlier. At densities above ca. 5000 m-1, intraspecific competition controlled the level of recruitment. [ABSTRACT FROM AUTHOR]