Variation in hatch date distributions, settlement and growth of juvenile plaice (L.) in Icelandic waters

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Hatch date distribution, larval phase and subsequent growth of juvenile plaice (Pleuronectes platessa L.) in different regions around Iceland were determined by otolith microstructure analysis. Length, age and hatch date frequency distributions were obtained from juveniles captured in a 1 m beam trawl on 30 stations at 0.5-1 m depth all around Iceland in July 2006. The main spawning has generally been assumed to take place on the south and southwest coasts. Eggs and larvae are then distributed by currents along the west and north coasts. Contrary to expected dispersal pattern, both size and age of juvenile plaice decreased from south to north. The results indicates that the observed spatial variation in size of the juveniles is not explained by different growth rates but by age. The juveniles at the south coast hatch earlier than juveniles on the north and east coasts, have a shorter larval period, and higher growth rates. The study provides evidence that the juvenile plaice population may in fact originate from multiple spawning sites located not only along the south and southwest coasts, but along the entire coast of Iceland. The findings are discussed in relation to currents and temperature in Icelandic waters.