Distribution and feeding ecology of fin (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) in the Norwegian Sea during the summers of 2013 to 2018
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- Master theses 
This study aims at describing the current (2013 to 2018) summer distribution and feeding ecology of fin whales (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) in the Norwegian Sea. These waters function as a migration corridor and feeding ground for several cetacean species during the summer months. Oceanographic conditions, e.g. temperature, both at surface and in deeper waters, have been reported to be above long-term averages during the last decades. This has been found to impact prey feeding conditions and will potentially also alter traditional cetacean species composition and spatial distribution patters in the area. Cetacean sightings data were collected, in combination with concurrent collection of environmental variables, onboard vessels involved in the International Ecosystem Summer Survey in the Nordic Seas (IESSNS), covering large parts of the Norwegian Sea and associated waters. The data reveal that fin- and humpback whales are some of the most commonly observed species during all summer seasons. Similar numbers of fin-and humpback whale were observed each year, with the exception of 2014 which had an overall much lower number of cetacean sightings than other years. There was some spatial distribution variation in where the whale species where observed between each year, but most observations were made in the most northern part of the survey both species. A two dimensional Kernel-density estimation analyses revealed a pronounced hotspot for fin whales on the shelf-area between Svalbard and Norway, and around Bear Island for humpback whales. Fin whales were found associated with the occurrence of blue whiting (Micromesistius poutassou), capelin (Mallotus villosus) and mackerel (Scomber scombrus), humpback whales were associated with plankton and euphausiids in particular, capelin, herring (Clupea harengus) and mackerel. The results from this study provides and update the knowledge about these large cetacean species distributions and feeding patterns. This study shows a more northern distribution that differs from the previous descriptions that found a more spread and central spatial pattern and a higher association for macro-zooplankton and herring in the Norwegian Sea for both whale species.