Exploratory GIS Data Analysis and Regional and Transferred Maxent Modelling of the Round Goby Neogobius Melanostomus and Chinese Mitten Crab Eriocheir Sinensis in Stockholm and Blekinge County Baltic Sea Coastal Areas

Abstract: This study is a multidisciplinary approach to Species Distribution Modelling (SDM) where predictive models have been developed regarding the current distribution and potential spread of two invasive species found in Baltic Sea waters. Invasive species in the Baltic have long been an ecological and economic problem and the two species studied are well known for their adaptability in colonization and detrimental effects on local ecology all over the world. First, the Round Goby (Neogobius Melanostomus) has been steadily colonizing the Swedish Baltic coastline since 2008, the impact of which on local ecosystems is not fully understood. Also, the Chinese Mitten Crab (Eriocheir Sinensis), found in Swedish waters since the 1930’s, has been known to be a robust invader of ecosystems but presence in the Baltic is still not well explained. Four high spatial resolution models have been developed, three respective Round Goby and one for Mitten Crab. Two models are specific to the Blekinge/Hanöbukten region of the Swedish Baltic Sea coast, showing predicted current distribution of Round Goby. Two are predictions of Round Goby and Mitten Crab transferred or projected to other regions, with different approaches in setting model parameters and choosing variables, showing current and potential distribution. This study features: exploratory data analysis and filtering using GIS tools, highly discriminant environmental variable selection and rejection, and several different approaches to modelling in Maxent using custom and default settings. Predictive maps have been developed showing current distribution and potential spread as well as explanatory tabular data outlining direct and indirect drivers of species presence. Maxent has proven to be a powerful predictive tool on a regional basis, and proximity to introduction locations play a major role. Maxent, used in combination with spatial data modelling, exploration and filtering techniques has yielded a valid explanatory model as well. Transferring predictions to other regions is quite sensitive, however, and can depend heavily on species, sampling strategy and similarity of habitat type. Round Goby predictions were successfully created regionally and transferred to Stockholm, but Mitten Crab predictions were not successfully transferred to Blekinge.