Cetacean stranding records along the Danish coastline: records for the period 2008-2017 and a comparative review
For the period 2008-2017, finds of stranded cetaceans along the Danish coastline are listed and reviewed in comparison to the preceding 40-year period (1968-2007). The harbour porpoise (Phocoena phocoena) was by far the most commonly stranded species with a total of 1177 individuals for the period 2008-2017. Of these, 62.4% (n=735) originated from the North Sea and Skagerrak coastlines, i.e. the outer Danish waters (ODW), 37.0% (n=435) from the Kattegat and Belt Sea, i.e. the inner Danish waters (IDW), and 0.6% (n=7) from the waters around Bornholm (WAB), i.e. the Baltic Sea proper. Due to the large number and the amount of information for these records only a summary is given. In addition, 90 strandings of twelve other cetacean species occurred between 2008-2017. These comprise 49 white-beaked dolphins (Lagenorhynchus albirostris), three white-sided dolphins (Leucopleurus acutus), seven common dolphins (Delphinus delphis), a striped dolphin (Stenella coeruleoalba), a Risso’s dolphin (Grampus griseus), four long-finned pilot whales (Globicephala melas), a killer whale (Orcinus orca), a Sowerby’s beaked whale (Mesoplodon bidens), six sperm whales (Physeter macrocephalus), 14 minke whales (Balaenoptera acutorostrata), two fin whales (Balaenoptera physalus) and a humpback whale (Megaptera novaeangliae). During the last 50 years (1968-2017) five additional cetacean species have stranded on the Danish coasts: bottlenose dolphin (Tursiops truncatus) in 1968, 1975 and 1976, beluga (Delphinapterus leucas) in 1976 and 1987, northern bottlenose whale (Hyperoodon ampullatus) in 1969 and 1998, Bryde’s whale (Balaenoptera brydei) in 2000, and sei whale (Balaenoptera borealis) in 1980. The cetacean fauna around Denmark falls into the following categories: 1. native species such as the harbour porpoise, white-beaked dolphin, and minke whale; 2. resilient visitors, i.e. species such as common dolphin, fin whale and humpback whale that during their occurrences adapt well to altered environmental conditions encountered; and 3. erratic stragglers of oceanic, pelagic origin failing to adapt, such as long-finned pilot whale, Sowerby’s beaked whale and sperm whale.