Settling, growth and mortality of young bivalves in the Øresund

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Abstract
The quantitative aspects of the settling of 11 bivalve species were registered in the Øresund, based on bottom samples from two localities. The time of spatfall and the numbers of settling specimens were related to existing data on occurrence of larvae in the plankton. The number per m2 of settling specimens, the decrease of this number and the growth of the bivalves during the first months after spatfall were calculated. The growth rate in the Øresund seems to be smaller than in most other temperate areas. The possible reasons for this discrepancy are discussed and it is suggested that some of the results previously recorded in the literature on growth of newly settled bivalves are inaccurate on account of inadequate sampling-sieving techniques. By comparing the number of settling specimens of the same species in the two localities it was confirmed that bivalve larvae are able to make a choice of settling place in nature. Causes of the heavy decrease in number of spat during the first months after spatfall are discussed.