Description: Understanding the dynamics of cetacean distribution in ecologically vulnerable regions is essential to interpret the impact of environmental changes on species ecology and ecosystem functioning. Species distribution models (SDMs) are helpful tools linking species occurrences to environmental variables in order to predict a species’ potential distribution. Studies on baleen whale distribution are comparably rare in polar regions, mainly due to financial or logistic constraints and habitat suitability models are scarce. Using SDMs, this master thesis aims at identifying areas of suitable habitats for fin whales (Balaenoptera physalus) in the Nordic Seas during summer. A further aim is to identify important environmental variables that potentially drive the species’ distribution. Opportunistic data were collected during ten RV Polarstern cruises from 2007 to 2018 during summer months (May to September) along with complementary opportunistic data from open source databases. Environmental covariates were chosen based on ecological relevance to the species, comprising both static and dynamic variables. MaxEnt software was used to model fin whale distribution, with presence-only data as a function of carefully chosen environmental covariates. This master thesis is one of the first studies to use SDMs to model suitable habitats of fin whales in the Arctic Ocean and revealed a link of the occurrence of fin whales to specific environmental variables. Most contributing variables were distance to shore and distance to sea ice edge, suggesting both static and dynamic variables to have an impact on habitat suitability in the Arctic Ocean. Four other environmental variables, namely bathymetry, slope, variability of sea surface temperature and mean salinity at 100 m depth were shown to also have an impact. Areas of high suitability were pronounced around the southwestern and -eastern side of Svalbard, as well as on the northern tip of Norway and southern East Greenland. These results generally demonstrate the effective use of SDMs to predict species distribution in highly remote areas, constituting a cost-effective method for targeting future surveys and prioritizing the limited conservation resources. Results can be applied in a variety of purposes, such as designing marine protected areas, guiding seismic surveys and support the further use of opportunistic data in research.

Description: Understanding the dynamics of cetacean distribution in ecologically vulnerable regions is essential to interpret the impact of environmental changes on species ecology and ecosystem functioning. Species distribution models (SDMs) are helpful tools that link species occurrences to environmental variables in order to predict a species’ potential distribution. Studies on baleen whale distribution in polar regions are comparably rare, mainly due to financial and logistic constraints. Here we use SDMs to predict habitat suitability for fin whales (Balaenoptera physalus) in Arctic waters. A combination of opportunistic and systematically collected visual observations from 2007 to 2018 was used. Opportunistic data were collected during ten RV Polarstern cruises in the Arctic Ocean (including the Barents-, Norwegian and Greenland Sea). Complementary visual data were obtained from open source databases. Environmental variables were chosen based on ecological relevance to the species, comprising both static and dynamic variables. We used MaxEnt software to model the distribution of fin whales, using presence-only data as a function of carefully chosen environmental covariates. MaxEnt’s predictive performance has been shown to be consistently competitive with the highest performing methods. We were able to reveal important factors affecting the distribution of fin whales in the Arctic Ocean and how they respond to them. Results demonstrate the effective use of SDMs to predict species distributions in highly remote areas, constituting a cost-effective method for targeting future surveys and prioritizing the limited conservation resources. Results can be applied in a variety of purposes, such as designing marine protected areas and support the further use of opportunistic data to understand the ecological drivers of species distribution.

Description: Understanding cetacean distribution is essential for conservation planning and decision-making, particularly in regions subject to rapid environmental changes. Nevertheless, information on their spatiotemporal distribution is commonly limited, especially from remote areas. Species distribution models (SDMs) are powerful tools, relating species occurrences to environmental variables to predict the species' potential distribution. This study aims at using presence-only SDMs (MaxEnt) to identify suitable habitats for fin whales (Balaenoptera physalus) on their Nordic and Barents Seas feeding grounds. We used spatial-block cross-validation to tune MaxEnt parameters and evaluate model performance using spatially independent testing data. We considered spatial sampling bias correction using four methods. Important environmental variables were distance to shore and sea ice edge, variability of sea surface temperature and sea surface salinity, and depth. Suitable fin whale habitats were predicted along the west coast of Svalbard, between Svalbard and the eastern Norwegian Sea, coastal areas off Iceland and southern East Greenland, and along the Knipovich Ridge to Jan Mayen. Results support that presence-only SDMs are effective tools to predict cetacean habitat suitability, particularly in remote areas like the Arctic Ocean. SDMs constitute a cost-effective method for targeting future surveys and identifying top priority sites for conservation measures.