Non-Indigenous Species Dynamics in Time and Space within the Coastal Waters of The Netherlands

• Published in: Diversity
• Main Authors: Arjan Gittenberger, Marjolein Rensing, Marco Faasse, Lodewijk van Walraven, Sander Smolders, Helena Keeler Perez, Edmund Gittenberger
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2023
• Subjects: marine invasive species; cryptic species; monitoring effort; origins; stepping stones; temporal trends; Biology (General); QH301-705.5; Pacific; Stepping Stones; Pacific oyster
• Online Access: https://doi.org/10.3390/d15060719; https://doaj.org/article/0bc53d47a1de4f6590506eedfb513c78

Information on temporal and spatial trends with regard to the introduction of non-indigenous species (NIS) is often sparsely available. These trends may potentially help improve the design and focus of monitoring programs, give insights into new pathways and hotspots, and facilitate horizon scanning. We provide an overview of 215 marine and brackish water NIS recorded in The Netherlands. Temporal trends over the most recent three decades for taxonomic groups, species origin, introduction vectors, and water systems were analysed. We attempt to explain the observed patterns and discuss factors that hamper their explanation. A shift in the region of origin from Pacific to W Atlantic can potentially be linked to legislation prohibiting Pacific oyster imports, whereas a subsequent shift backwards cannot. Case studies illustrate that NIS may not be first detected in the water systems where they were originally introduced. Additionally, it is shown that changes in allegedly native species’ distribution or seasonal pattern should be linked to an introduced cryptic NIS instead. We also discuss the shortcomings of monitoring programs that were originally not focused on NIS, the importance of naturalists’ observations, and the added value of a more recent network that is focused on NIS detection in the coastal waters of The Netherlands.