2013 年 14 巻 1-2 号 p. 9-13
To manage the American mink, Neovison vison, effectively, its densities were estimated in the Fujita and Yata Rivers, tributaries of the Abukuma River, in Koriyama, Fukushima Prefecture. For the calculation for the Fujita River, minks were trapped until all field signs disappeared in two study areas set along the river, a 1.8-km-long middle area and a 1.5-km-long lower area, from mid-October to mid-November in 2009 and 2010. For the Yata River, the minks were captured in a 6.5-km-long area extending from the middle to the lower basin of the river from August 3 to September 24, 2010, and the density was estimated using the removal method. Except for the lower area of the Fujita River in 2009 failed to catch some minks, the estimated density of mink per km was 2.8 in 2009 and 2010 in the middle area and 4.7 in 2010 in the lower area of the Fujita River. Estimated by the removal method in the Yata River, it was estimated to be 4.8. These estimated densities approximated or exceeded the maximum density estimated for areas in Britain, Easter Europe, Patagonia, and North America. The high density is probably related to the abundance of prey animals such as frogs and crawfish supplied to these rivers via the waterways around rice paddy fields. The environment of many other tributaries of the Abukuma River is similar to that of the study rivers, and the density of mink in the other tributaries is expected to be equally high. In order to manage the mink population in this region effectively, the simultaneous measures for the whole Abukuma River basin are necessary.