Ecology and management of the invasive snow crab: Predicting expansion, impacts and sustainability in the Arctic under climate change

The snow crab is a large crustacean that has been invading the Barents Sea since 1996. The origin of this invasion is still unknown. The snow crab is both an invasive species that is rapidly expanding eastwards and northwards in the Barents Sea, but also a species of interest for commercial fisheries. There is thus an urgent need for new data, knowledge and robust predictions on the potential effects of the snow crab in Arctic marine communities as the population expands in the Barents Sea. This new knowledge will provide essential information for the development of robust management measures of a commercial fishery of an invasive species, to ensure the environmental sustainability of the Barents Sea. EISA includes national and international partners that will work together using novel methods and instruments to address main questions: 1) what are the changes caused by the snow crab on the seafloor communities, including other commercial species; 2) what are the dynamics of the snow crab population in the Barents Sea, and what is the origin of the invasion; 3) what are the predictions on the snow crab dispersal and impact, in particular considering changing environmental conditions under the current climate change scenario? At the end of the project, all results and knowledge will be synthesised in a socio-economic and governance framework that can inform environmental management decisions.We combined field sampling, molecular analysis, food-web modelling, and value-chain analysis to achieve a multi-disciplinary view of the past, present, and potential future role of the snow crab in the Barents Sea. Our 12-day cruise to the Barents Sea was highly successful, and we collected information on the epifaunal and infaunal community along a gradient of snow crab density. We also collected samples for molecular analysis of stomach contents and for population genetic studies. Faunal community analysis covered protozoans (foraminifera), infauna, and epifauna, and results were assessed in reference to snow crab densities. We also used historical data from a broader geographical scale to gain insight into potential future impacts of the snow crab. Results suggest moderate impacts to the seafloor community related to snow crab impacts. Regional differences in functional roles of benthic fauna suggest species providing some of the most important functions are most dominant in the central and southern areas. We conducted genetic analysis on snow crab samples from across the Arctic and preliminary results indicate that there is less variability in the Barents Sea population than in crabs from other areas. This suggests a limited number of introductions of the crab, and from a limited number of areas. When results are completed we will have a good idea of the most likely source(s) of Barents Sea snow crab and likely routes of their introduction. Food-web analysis again indicated the importance of functional characteristics of fauna in how food webs respond to crab invasion, and that climate change may act together with crab invasion to alter seafloor communities in the future. Modelling results indicated little impact of the crab on benthic communities over the entire Barents Sea. At greater spatial resolution, however, reductions in most seafloor fauna groups were indicated in areas where crabs have invaded. Global crab-market analysis indicated the different roles different countries play in the markets, from crab production to import. The economic links among different countries are also quite different, with a more complex value chain in the US than in Canada or Norway. These value chains are sensitive to perturbations (COVID, war) that may be difficult to predict, however. Combining economic and ecological models indicated a strong likelihood of enhanced crab production for Norway in the future, something important to consider when managing fisheries and planning industry activities. Research projects of several MS students, a PhD and a postdoc have come from the EISA project. Project findings are being published fort the scientific audience. In addition, the project has also had strong outreach for stakeholders, school children, and the general public through media, school visits, national 'research days,' and other outreach events.

Global invertebrate fisheries have expanded rapidly over the last few decades, however they receive much less attention than finfish fisheries in socio-economic research. Snow crabs (i.e., crab species of the genus Chionoecetes) are some of the most valuable and sought-after crab species on the global stage. They have only arrived in the Barents Sea in the several last decades and have expanded considerably, and indications from other areas in their geographic range suggest they potentially have strong impacts on seafloor, and even pelagic, communities through their predation and competition with commercial fish. There is therefore a strong need to monitor and model the potential food-web effects of snow crab, now and in the future. The results indicate that where snow crab is abundant they appear to have substantial effects across the seafloor community. Potential for regional expansion and increased biomass suggest this will increase over the next 20-30 years. Modelling studies indicate that considering spatial perspectives is critical to more accurately assess impact. Food web structure, including the nature and number of links, and the degree of linkage among different food-web elements is important in assessing change as species expand and/or climate change impacts other aspects of system ecology. Functional traits are shown to be useful, both in comparing different regions within the ecosystem, identifying food-web vulnerabilities. Interactions among multiple environmental and biological stressors were found to be important for projecting how ecosystem function may change as key species invade and spread. From the economic and policy perspectives, value chain and teleconnection analysis were shown to have important implications for future fishery and value growth for Norway. These are important for economic planning and development of sea-going and land-based infrastructure, but important data gaps are frequent and hinder more complete analysis both nationally and internationally. Results of this study also indicated how vulnerable, and to come extent how adaptable, complex socio-ecological systems are to regional and global events.

Twenty-two years after the first record of the snow crab in the eastern Barents Sea, this invasive species has rapidly spread north-westerly. Because of its dual nature as an invasive species and potential exploitable resource, the snow crab’s expansion in the Barents Sea has important ecological, economic and political implications, both nationally and internationally. Although available evidence suggests that large decapods play a role in structuring benthic communities, studies considering long-term changes on the structure and function of the ecosystems impacted by large invasive crustaceans are scarce. There is thus an urgent need for empirical data and modelled predictions on the impact of the snow crab in Arctic systems, to ensure that robust management decisions can be implemented to support sustainable value creation and Blue Growth. EISA addresses this challenge in 4 scientific work packages that will use state-of-the-art methods (sampling, ecosystem modelling, genetics and metagenomics and machine learning) to generate cutting-edge knowledge on 1) the changes the crab causes on the structure and function of the benthic communities, including other commercial species (WP1); 2) the dynamics of the snow crab population in the Barents Sea, including the origin of the invasion (WP2); 3) predictions on the snow crab dispersal and impact, in the framework of climate change (WP3); and 4) synthesise all results in a socio-economic and governance framework that can inform management guidelines (WP4). EISA progress and results will be shared with academic fellows, management authorities, industry and society through a dissemination and communication plan to ensure that the latest knowledge on the snow crab is available for the development of robust ecosystem-based management measures and increased sustainable value creation in the Arctic region. The EISA consortium includes 8 leading research teams and benefits from a dedicated postdoc.