Invasion trajectory of Pacific oysters in the northern Wadden Sea

Feral populations of Pacific oysters (Crassostrea gigas) in the northern Wadden Sea exhibit dynamic invasion trajectories characterized by phases of establishment, exponential expansion, and adjustment, driven by environmental conditions. The study reveals that sea-based oyster farming facilitated the inevitable establishment of feral oysters, while mussel beds provided ideal attachment substrates and growth conditions around low tide levels. Cold summers in the 1990s limited recruitment but ensured persistence due to oyster longevity. Since the 2000s, warmer summers have led to regular recruitment and peak abundances exceeding 1000 individuals per square meter, though these were followed by recruitment failures and ice-related mortalities. The population is expected to stabilize around 1000 m−2 but remains susceptible to density-dependent (e.g., diseases) and density-independent (e.g., weather anomalies) fluctuations. This pattern may repeat in other marine introductions with continued global warming.

Reise, K., Buschbaum, C., Büttger, H., Rick, J., & Wegner, K. M. (2017). Invasion trajectory of Pacific oysters in the northern Wadden Sea. Marine Biology, 164(4). https://doi.org/10.1007/s00227-017-3104-2