Mitochondrial DNA reveals secondary contact in Japanese harbour seals, the southernmost population in the western Pacific.

In this study, we used relatively large number of samples (n = 178) and control region of mtDNA (454bp) to clearify the divergence history of Japanese harbour seals (Phoca vitulina stejnegeri) and phylogenetic relationship between the seals in Japan and other countries. Our results suggested that Japanese harbour seals possibly consisted of more than two lineages and secondary contact of populations after a long isolation. Furthermore, one of the lineage was made only by Japanese harbour seals (Group P1). The proportion of Group P1 was the highest at the South West and gradually decreased towards the North East of Hokkaido, Japan. On the other hand, the haplotypes do not belonged to Group P1 showed close relationship to the seals in the North Pacific. Based on the fossil record of harbour seal in Japan and the range of sea ice during the Last Glacial Maximum (LGM), Group P1 might have entered Japan before the LGM and became isolated due to the geographical boundary, and gradually extended its range from the South West towards the North East of Hokkaido after the disappearance of the sea ice, while the seals which are not in Group P1 immigrated into Japan from the North Pacific.

Host characteristics and infection level of an intestinal parasite Corynosoma strumosum (Acanthocephala) in the Kuril harbor seal of Erimo Cape, Hokkaido, Japan.

The Kuril harbor seal around Hokkaido is presently recovering from a resource crisis while conflicts with local fisheries have become a concern. However, its feeding habits, which are fundamental information for taking proper preventive measures, are still poorly understood. We thus examined the infection status of a trophically-transmitted parasite, Corynosoma strumosum in the seals of Erimo Cape, to assess the host's feeding habits with a practical view of the parasite as a biological indicator. A total of 2802 worms were found from 20 male and 20 female by-caught animals in salmon set nets within local fisheries during August to November 2014. The parasite abundance was explained mainly by the host's developmental stage and intestinal length while weakly affected by gender and body size, through an estimation of generalized linear models combined with hierarchical partitioning. Considering the past records that demersal fishes are the probable main sources of infection, the infection level may owe to individual host differences regarding these sources and/or feeding grounds with relating the host characteristics. This supports that the resource management of Kuril harbor seals requires careful consideration of the individual differences in feeding behavior.