Too late for regulatory management on Pacific oysters in European coastal waters?

• Published in: Journal of Sea Research
• Main Authors: Hansen, Benni Winding, Dolmer, Per, Vismann, Bent
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Biodiversity; Biogenic reefs; Competition; Ecosystem impacts; Eradication; Regulation; Pacific; Pacific oyster
• Online Access: https://curis.ku.dk/portal/da/publications/too-late-for-regulatory-management-on-pacific-oysters-in-european-coastal-waters(bb135322-b7fe-4951-9400-b90aa490c70f).html; https://doi.org/10.1016/j.seares.2022.102331; https://curis.ku.dk/ws/files/334256983/1_s2.0_S1385110122001691_main.pdf

This research presents the invasion history as well as an up-to-date distribution of the Pacific oyster Magallana gigas in European coastal waters, concluding that this invasive species has spread to large parts of all coastal biotopes. Moreover, the measures and management of the Pacific oyster invasions of coastal and marine ecosystems is discussed including restoration and resilience of invaded ecosystems. When Magallana gigas is well established and has reached adjustment phase characterized by firm biogenic reefs, eradication or even decimation is difficult and costly. During the establishment phase and maybe also the expansion phase, where the oyster appear as single individuals spread out on the sediment and yet not forming larger clumps and reefs, it is more realistic to implement mitigation tools. These initiatives cannot be implemented everywhere. They should be reserved especially for protected areas under national or international legislation e.g., Natura2000 areas, where smaller areas can be restored. The present contribution discusses and evaluates known mitigation tools like physical damaging of individual oysters, dredging, small-scale hand picking as well as various fishery concepts. Additionally, this research proposes some novel strategies where triploidity is suggested for implementation to avoid or decimate further spread of the species. As well as some initiatives based on choking and/or starving out the oysters by deploying a thick layer of sand/gravel or food for the competing blue mussels over oyster reefs. The efficiency of the different strategies, as well as the required frequency of follow up initiatives, are evaluated. The major conclusion from this research suggests that decisions to combat the alien oyster are mainly based on political/socioeconomic arguments and less on ecological arguments. This is because reefs of Pacific oysters most likely lead to equal or higher biodiversity as compared to native (e.g., blue mussel) beds and the oysters serve a redundant role in a trophic ...