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科 Balaenopteridae - rorquals, finback whales
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纲 |
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Mammalia |
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No. of Genera in Ref. |
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No. of Species in Ref. |
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淡水 : No |
半咸淡水 : No |
海洋 : Yes |
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Diagnostic of this family is the presence of a series of ventral grooves, that enable them to gulp in enormous amounts of water. A well-defined dorsal fin is usually present behind the midpoint of the back. The shape and height of the "blow"(i.e. spout of water vapor) and the surface and dive profiles are important for species identification in the field. As a rule, rorquals are migratory animals with poleward, feeding-area bound migrations in spring, and equatoward, breeding-area bound migrations in autumn. The species can probably be encountered all year round, with northern and southern hemisphere stocks occurring at different times of the year. Bryde's whale (Balaenoptera edeni) with less pronounced migrations is an exception to this rule; it may stay all year found in subtropical or tropical waters. Dwarf forms of minke whales (B. acutorostrata) and blue whales (B. musculus) have been described from the southern hemisphere, and dwarf forms of Bryde's whale are known from Southeast Asia, their taxonomical status still being unsettled. Hybrids are known between blue whales and fin whales (Ref. 68590). |
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