In the frame of our long-term study of cetacean abundance and distribution in polar marine ecosystems begun in 1979, a drastic increase in the bowbead Balaena mysticetus North Atlantic ＂stock＂ was observed from 2005...In the frame of our long-term study of cetacean abundance and distribution in polar marine ecosystems begun in 1979, a drastic increase in the bowbead Balaena mysticetus North Atlantic ＂stock＂ was observed from 2005 on, by a factor 30 and more： from 0.0002 per count between 1979 and 2003 （one individual, n=5430 cotmts） to 0.06 per count from 2005 to 2014 （34 individuals, n=6000 counts）; the most significant part of the increase occurred from 2007 on. Other large whale species （Mysticeti） showed a similar pattern, mainly blue Balaenoptera musculus, humpback Megaptera novaeangliae and fin whales Balaenoptera physalus. This large and abrupt increase cannot logically be due to population growth, nor to survival of a hidden ＂relic＂ population, nor to a changing geographical distribution within the European Arctic, taking into account the importance of the coverage during this study. Our interpretation is that individuals passed through the Northwest and/or Northeast Passages from the larger Pacific stock into the almost depleted North Atlantic populations coinciding with a period of very low ice coverage -- at the time the lowest ever recorded. In contrast, no clear evolution was detected neither for sperm whale Physeter macrocephalus nor for Minke whale Balaenoptera acusrostrata.展开更多
The orbit of the the whale is quite modiffied, shows much more variation in comparison to that of the better studied mammals, and is composed of the maxillary bone, lacrimal bone,frontal bone, temporal bone, zygomatic...The orbit of the the whale is quite modiffied, shows much more variation in comparison to that of the better studied mammals, and is composed of the maxillary bone, lacrimal bone,frontal bone, temporal bone, zygomatic bone, parietal bone and sphenoid bone. The whale’s eyeball usually protrudes beyond the bony otbital rim, based on the oborvation of this study. Our observation in this study that the whale has an enclosed orbit differs from that of Prince (1956), who mentioned that the whale has an open othit.展开更多
文摘In the frame of our long-term study of cetacean abundance and distribution in polar marine ecosystems begun in 1979, a drastic increase in the bowbead Balaena mysticetus North Atlantic ＂stock＂ was observed from 2005 on, by a factor 30 and more： from 0.0002 per count between 1979 and 2003 （one individual, n=5430 cotmts） to 0.06 per count from 2005 to 2014 （34 individuals, n=6000 counts）; the most significant part of the increase occurred from 2007 on. Other large whale species （Mysticeti） showed a similar pattern, mainly blue Balaenoptera musculus, humpback Megaptera novaeangliae and fin whales Balaenoptera physalus. This large and abrupt increase cannot logically be due to population growth, nor to survival of a hidden ＂relic＂ population, nor to a changing geographical distribution within the European Arctic, taking into account the importance of the coverage during this study. Our interpretation is that individuals passed through the Northwest and/or Northeast Passages from the larger Pacific stock into the almost depleted North Atlantic populations coinciding with a period of very low ice coverage -- at the time the lowest ever recorded. In contrast, no clear evolution was detected neither for sperm whale Physeter macrocephalus nor for Minke whale Balaenoptera acusrostrata.
文摘The orbit of the the whale is quite modiffied, shows much more variation in comparison to that of the better studied mammals, and is composed of the maxillary bone, lacrimal bone,frontal bone, temporal bone, zygomatic bone, parietal bone and sphenoid bone. The whale’s eyeball usually protrudes beyond the bony otbital rim, based on the oborvation of this study. Our observation in this study that the whale has an enclosed orbit differs from that of Prince (1956), who mentioned that the whale has an open othit.
