Abstract
Past studies have indicated that there are two different stocks (J and O stocks) in the North Pacific common minke whale Balaenoptera acutorostrata population. These two stocks differ from each other in certain characteristics, such as body size, conception dates, and genetics. However, till date, few studies have investigated differences in the external body appearance between the two stocks. Therefore, in the present study, we focused on the unique white patch on the flipper of this whale species to elucidate inter-stock differences. We used the animals collected from JARPNII research during 2012 and 2013; stock information was determined by microsatellite DNA analysis (n = 220). We focused on the morphological differences in the size and pattern of the white patch on the flipper of each whale. The length of the white patch along the anterior (ventral) margin of the flipper tends to be proportionally larger in O stock. The pattern of the boundary area of the white patch named as the “Grayish Accessary Layer (GAL)” was remarkably different between stocks. Within animals with “no GAL” type, 94% were J stock. Conversely, of animals with GAL expanding over the half the flipper width, 96% were O stock. We concluded from our study that there were clear morphological differences in the flipper color pattern between J and O stocks, which enable to apply widely to other individuals.
Highlights
The common minke whale Balaenoptera acutorostrata is the smallest species of the Balaenoptera whales
There are two distinguishable subspecies, one each in the North Pacific (B. a. scammoni) and North Atlantic (B. a. acutorostrata). There is another population, generally called as “dwarf” minke whales. They may provisionally be regarded as a racesubspecies of common minke whale, but their taxonomical status is not fixed yet due to the scanty data [1]
The values are quite similar between the two stocks, and no statistical differences were observed in this characteristic (Mann-Whitney U-test, p > 0.05) (Figure 4(b))
Summary
The common minke whale Balaenoptera acutorostrata is the smallest species of the Balaenoptera whales. There are two distinguishable subspecies, one each in the North Pacific There is another population, generally called as “dwarf” minke whales. They may provisionally be regarded as a racesubspecies of common minke whale, but their taxonomical status is not fixed yet due to the scanty data [1]. The notable feature of the common minke is the white patch in their flipper which is the unique character of this species. The white patch on the flipper may serve as a useful distinguishing characteristic for taxonomy classification purposes [2] [3]
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