Abstract
The location of Iceland at the junction of submarine ridges in the North-East Atlantic where warm and cold water masses meet south of the Arctic Circle contributes to high productivity of the waters around the island. During the last two decades, substantial increases in sea temperature and salinity have been reported. Concurrently, pronounced changes have occurred in the distribution of several fish species and euphausiids. The distribution and abundance of cetaceans in the Central and Eastern North Atlantic have been monitored regularly since 1987. Significant changes in the distribution and abundance of several cetacean species have occurred in this time period. The abundance of Central North Atlantic humpback and fin whales has increased from 1,800 to 11,600 and 15,200 to 20,600, respectively, in the period 1987-2007. In contrast, the abundance of minke whales on the Icelandic continental shelf decreased from around 44,000 in 2001 to 20,000 in 2007 and 10,000 in 2009. The increase in fin whale abundance was accompanied by expansion of distribution into the deep waters of the Irminger Sea. The distribution of the endangered blue whale has shifted northwards in this period. The habitat selection of fin whales was analyzed with respect to physical variables (temperature, depth, salinity) using a generalized additive model, and the results suggest that abundance was influenced by an interaction between the physical variables depth and distance to the 2000m isobaths, but also by sea surface temperature and sea surface height, However, environmental data generally act as proxies of other variables, to which the whales respond directly. Overall, these changes in cetacean distribution and abundance may be a functional feeding response of the cetacean species to physical and biological changes in the marine environment, including decreased abundance of euphausiids, a northward shift in summer distribution of capelin and a crash in the abundance of sand eel.
Highlights
Cetaceans are important top predators in Icelandic waters with a total of 23 species recorded (Hersteinsson, 2004) of which 12–14 species are considered regular inhabitants
The habitat selection of fin whales was analyzed with respect to physical variables using a generalized additive model, and the results suggest that abundance was influenced by an interaction between the physical variables depth and distance to the 2000 m isobaths, and by sea surface temperature (SST) and sea surface height (SSH), environmental data generally act as proxies of other variables, to which the whales respond directly
Similar changes were observed in temperature further north on the Latrabjarg section in the northward flow of the branch of the Irminger Current which feeds the inflow of Atlantic water to the area north of Iceland, i.e., the North Icelandic Irminger Current (Figure 2B)
Summary
Cetaceans are important top predators in Icelandic waters with a total of 23 species recorded (Hersteinsson, 2004) of which 12–14 species are considered regular inhabitants. In terms of biomass and consumption, cetaceans play an important role in the Icelandic ecosystem. Sigurjónsson and Víkingsson (1997) estimated the total annual consumption by 12 cetacean species as 6 million tons corresponding to around four times the total Icelandic fishery landings. The diet composition of these cetaceans is poorly known except for common minke whales (Balaenoptera acutorostrata), fin whales (Balaenoptera physalus) and harbor porpoises (Phocoena phocoena). Fin whales feed almost exclusively on euphausiids, mostly Meganyctiphanes norvegica, on the traditional whaling grounds in the Irminger Sea (Víkingsson, 1997). Common minke whales have a much more varied diet ranging from euphausiids to large gadoid fish. Sand eel (Ammodytes sp.), herring (Clupea harengus) and www.frontiersin.org
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