Abstract
Since its introduction in the 1960’s for aquaculture, the Pacific oyster Magallana gigas (Thunberg, 1793) has successfully spread along almost all European coasts with far-reaching consequences for marine ecosystems. Up to now, it has not been recorded from the Baltic Sea proper. This was considered a consequence of the low salinity conditions, which are not suitable for larval development. Here we report our first records of Pacific oysters in the German Baltic Sea, specifically in the Kiel Bight. We confirmed their species identification by genetic barcoding. We suggest that Pacific oysters were able to settle in the Baltic Sea proper due to unusually high salinities that prevailed since the summer of 2018. Should these conditions occur more frequently in the future, or M. gigas be able to adapt to lower salinities, oysters may become established in the Baltic Sea proper.
Highlights
The Pacific oyster Magallana gigas (Thunberg, 1793), formerly Crassostrea gigas, is an established nonindigenous species along all European coasts with the exception of the Baltic Sea proper (Diederich et al 2005; Cardoso et al 2007; Wrange et al 2010)
The discovery of feral oysters in the Baltic Sea proper represents a noteworthy expansion of its range; it appears to mark an expansion into brackish water that exceeds the physiological limits of M. gigas larvae
The salinity and temperature were unusually high during the late summer of 2018, suitable for the development of M. gigas larvae (Fig. 3)
Summary
The Pacific oyster Magallana gigas (Thunberg, 1793), formerly Crassostrea gigas, is an established nonindigenous species along all European coasts with the exception of the Baltic Sea proper (Diederich et al 2005; Cardoso et al 2007; Wrange et al 2010). Introduction The Pacific oyster Magallana gigas (Thunberg, 1793), formerly Crassostrea gigas, is an established nonindigenous species along all European coasts with the exception of the Baltic Sea proper (Diederich et al 2005; Cardoso et al 2007; Wrange et al 2010). Here we report the first natural settlement of the Pacific oyster Magallana gigas in the Baltic Sea proper, in the German Kiel Bight.
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