Annual year-class strength in North Sea plaice Pleuronectes platessa Linnaeus, 1758
appears to be determined by the connectivity of eggs and larvae between open-sea spawning
grounds and coastal nursery areas. Hydrodynamic modelling studies indicate that coastal nurseries
can be supplied with larvae from multiple offshore spawning locations. To verify this, we
compared relative size-frequency distributions of demersal juvenile plaice just after larval
immigration between coastal nurseries as a proxy for larval origin. During 12 yr, up to 21 stations in
the Dutch coastal zone and international Wadden Sea were visited and sampled at the beginning of
May at the end of larval immigration. The results of the size-frequency analysis showed 2 distinct
clusters of stations. The first cluster included all stations along the Dutch coast and Wadden Sea up
to Wangerooge in the German East Frisian Wadden Sea, most likely dominated by supply from
spawning grounds in the Southern Bight, with contributions from the English Channel and the
Dogger Bank. The second cluster included all stations in the North Frisian Wadden Sea, most
likely supplied from spawning grounds in the German Bight and near the Dogger Bank. The higher
interannual variability in the first cluster might be caused by a larger variability in the relative contributions
from multiple spawning areas (English Channel, Southern Bight, Dogger Bank). The
comparison of the relative size-frequency distributions at the end of larval immigration introduced
in this study may also be a useful tool for the validation of connectivity modelling studies in other
areas and for other species.
