Risk assessment of six marine invasion pathways into California estuaries

Background/Question/Methods

The spread of aquatic invasive species (AIS) in marine environments is accelerating globally and continuing to cause ecological and economic damage. California is a recognized hotspot of invasion and a focal point for invasions to other locations. While the importance of ballast-mediated transfer of invasive species has been recognized for some time, there are several other under-regulated invasion pathways (vectors) introducing species into California ecosystems. Using extensive field work, examination of shipping permits, surveys, and quantitative analysis of data in literature, we characterized the impact and flux of six invasion pathways into California: recreational vessels, fishing vessels, aquaculture, aquarium/ornamental trade, live bait, and live seafood.

Results/Conclusions

We found striking differences in the volume and types of organisms associated with each vector. Furthermore, the impact types (ecological, economic, and health) associated with each vector also varied considerably. We also identified gaps in monitoring, permitting, and scientific study that hinder our understanding of impacts and the prioritization of intervention strategies among pathways.