Managing invasive alien species is particularly challenging in the ocean mainly because marine ecosystems are highly connected across broad spatial scales. Eradication of marine invasive species has only been achieved when species were detected early, and management responded rapidly. Generalized approaches, transferable across marine regions, for prioritizing actions to control invasive populations are currently lacking. Here, expert knowledge was elicited to prioritize 11 management actions for controlling 12 model species, distinguished by differences in dispersion capacity, distribution in the area to be managed, and taxonomic identity. Each action was assessed using five criteria (effectiveness, feasibility, acceptability, impacts on native communities, and cost), which were combined in an 'applicability' metric. Raising public awareness and encouraging the commercial use of invasive species were highly prioritized, whereas biological control actions were considered the least applicable. Our findings can guide rapid decision-making on prioritizing management options for the control of invasive species especially at early stages of invasion, when reducing managers' response time is critical.

In the near future, the oceans will be subjected to a massive development of marine infrastructures, including offshore wind, tidal and wave energy farms and constructions for marine aquaculture. The development of these facilities will unavoidably exert environmental pressures on marine ecosystems. It is therefore crucial that the economic costs, the use of marine space and the environmental impacts of these activities remain within acceptable limits. Moreover, the installation of arrays of wave energy devices is still far from being economically feasible due to many combined aspects, such as immature technologies for energy conversion, local energy storage and moorings. Therefore, multi-purpose solutions combining renewable energy from the sea (wind, wave, tide), aquaculture and transportation facilities can be considered as a challenging, yet advantageous, way to boost blue growth. This would be due to the sharing of the costs of installation and using the produced energy locally to feed the different functionalities and optimizing marine spatial planning. This paper focuses on the synergies that may be produced by a multi-purpose offshore installation in a relatively calm sea, i.e., the Northern Adriatic Sea, Italy, and specifically offshore Venice. It analyzes the combination of aquaculture, energy production from wind and waves, and energy storage or transfer. Alternative solutions are evaluated based on specific criteria, including the maturity of the technology, the environmental impact, the induced risks and the costs. Based on expert judgment, the alternatives are ranked and a preliminary layout of the selected multi-purpose installation for the case study is proposed, to further allow the exploitation of the synergies among different functionalities.