Markus Brand

• The Arctic is one of the areas that is most affected by global climate change (IPCC 2014). As a result of anthropogenic Arctic warming, the Arctic fish community might change, and species from temperate areas are expected to invade (Cheung et al. 2009). In this context, it is critical that “Arctic marine fishes are indispensable to ecosystem structuring and functioning, but they are still beyond credible assessment due to lack of basic biological data“ (Christiansen et al. 2014). Especially in the shallow-water zones (3 - 12 m) of Arctic fjord systems only qualitative data on fish community composition are available. In other ecosystems, it was shown that the structured shallow-water zone has special ecological functions (Seitz 2014, Pondella et al. 2015). Therefore, the objective of this study is to increase our scientific knowledge on the fish assemblage of this special area by performing a quantitative first-time assessment of its species composition and abundance as well as the size and age structure of selected species. As study site, Kongsfjorden (79°N, 12°E) at the west coast of the Svalbard archipelago was chosen. It is one of the best investigated fjords in the Arctic, and the local AWIPEV research base provides one of few sites where this project could be logistically supported. Despite the local infrastructure, access to the field was restricted due to the challenging climatic regime of Kongsfjorden. A thorough risk assessment resulted in the finding that no fishing from small boats can be performed safely during the polar night. Fish assessments were therefore conducted with two complementary methodologies. The first method was seasonal fyke net fishing in June/July and September of the years 2012 to 2014. The second method was a year-round assessment via a stereo-optic imaging system, which was connected to an underwater observatory.