In springs of 1995 to 2000, plot sampling was carried out to collect information on eight habitat factors including geographic environment and human activities, etc. According to a map of navigation in middle and low ...In springs of 1995 to 2000, plot sampling was carried out to collect information on eight habitat factors including geographic environment and human activities, etc. According to a map of navigation in middle and low Yangtze River(printed in 1995), regular sampling plots, with a circular area of 500 m in diameter and with equal water and terrestrial, were set every five kilometres along the main stream, which included areas used by Yangtze finless porpoise. A total of 1 225 kilometres of survey was conducted. 247 regular sampling plots were set, of which 66 were utilized by the finless porpoises. The habitat selection of the Yangtze finless porpoises was quantitatively analyzed by Vanderploeg and Scavia selection indices. It was found that the Yangtze finless porpoises prefer cushion waters around large, gooseneck-like, bifurcated water courses, however the selection tended to be random with the decrease of flexuousity and the width to length ratio of the riverway. The feeding grounds of the Yangtze finless porpoises are usually close to sandy areas with reedy swamps where boats traveling upstream, sand excavating, and fishing activities, etc. constitute the potential threats to the finless porpoises. We suggest that the core area of the nature reserve should focus on large bifurcated riverways with cushion waters, and large areas of reedy swamps, where the sand excavating and fishing activities should be prohibited, and the speed of boats traveling upstream must be limitede.展开更多
文摘In springs of 1995 to 2000, plot sampling was carried out to collect information on eight habitat factors including geographic environment and human activities, etc. According to a map of navigation in middle and low Yangtze River(printed in 1995), regular sampling plots, with a circular area of 500 m in diameter and with equal water and terrestrial, were set every five kilometres along the main stream, which included areas used by Yangtze finless porpoise. A total of 1 225 kilometres of survey was conducted. 247 regular sampling plots were set, of which 66 were utilized by the finless porpoises. The habitat selection of the Yangtze finless porpoises was quantitatively analyzed by Vanderploeg and Scavia selection indices. It was found that the Yangtze finless porpoises prefer cushion waters around large, gooseneck-like, bifurcated water courses, however the selection tended to be random with the decrease of flexuousity and the width to length ratio of the riverway. The feeding grounds of the Yangtze finless porpoises are usually close to sandy areas with reedy swamps where boats traveling upstream, sand excavating, and fishing activities, etc. constitute the potential threats to the finless porpoises. We suggest that the core area of the nature reserve should focus on large bifurcated riverways with cushion waters, and large areas of reedy swamps, where the sand excavating and fishing activities should be prohibited, and the speed of boats traveling upstream must be limitede.
