长江干流江豚栖息地选择机制的研究

The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is listed as Critically Endangered on the International Union for the Conservation of Nature Red List of Threatened Species. As an icon of the Yangtze ecosystem and the only freshwater porpoise in the world, this species is currently found only in the main stem of the middle and lower reaches of the Yangtze River and the adjoining Poyang and Dongting Lakes. Unfortunately, many of these porpoises live in areas that are undergoing rapid and increasing habitat destruction and suffering from sharply declining fish stocks and the porpoise distribution has become more restricted and fragmented with more gaps in their distribution. Besides, the decline in the Yangtze finless porpoise population is more rapid than previously estimated, Consequently, If more active conservation not be implemented urgently, these porpoise are at risk of extinction similar to the Yangtze River dolphin (Lipotes vexillifer), which was likely driven to extinction by human activity. The fragmented distribution pattern of the Yangtze finless porpoise indicating a trend of habitat preference and the Information on the habitat use of the Yangtze finless porpoise is critical for its conservation. By using simultaneous visual and acoustical methods, The current research proposal targeting at the time and special distribution pattern of the finless porpoise in two extreme 50 km regions (honghu with the lowest porpoise density and Anqing with the highest porpoise density) of the Yangtze River along with simultaneous observations of environmental parameters, such as fish density, water temperature, water depth, velocity, boat traffic and ambient noise conditions. The correlation between distribution of the finless porpoise and environmental parameters will be investigated by using GIS special model. Boosted regression trees will be further applied to discriminate the main factors which result in the habitat preference of the porpoise. The resulted findings of the habitat preference mechanism of the porpoise can shield some light and be used to improve the conservation of the Yangtze finless porpoise.

长江江豚是我国珍稀的淡水鲸类动物，仅分布于长江中下游干流及两大通江湖泊鄱阳湖和洞庭湖中。过去几十年，由于长江中下游流域环境的持续恶化，其种群数量呈现加速下降，在干流的分布也呈现破碎化。长江江豚破碎化的分布状况，揭示它们对不同的栖息地存在显著的选择偏好。本项目拟采用目视和被动声学相结合的考察方法，在洪湖（江豚分布密度低）和安庆（江豚分布密度高）各选50km长的江段调查长江江豚的时空分布规律，并采集这些水域的环境数据，包括鱼类资源、水质、流速、水温、盐度、深度、背景噪声、航行密度等。首先通过GIS空间模型分析，评估各环境因子与长江江豚分布的关系。然后采用步进回归树(Boosted regression trees)的方法，进一步研究导致长江江豚栖息地选择的主要因子，阐明其栖息地选择机制，为长江江豚自然栖息地的保护和修复提供科学依据。

项目基本按照原计划执行，包括以下五个部分的内容：（1）长江干流长江江豚栖息地选择研究的主要研究地点由洪湖和安庆各选50 km 江段扩展为长江湖口至镇江之间（约600 km），研究内容不变。结果显示河道曲度和岸线利用格局是影响江豚分布的主要原因。（2）利用2015年3月至2016年7月的种群监测数据，对何王庙/集成垸故道的长江江豚的栖息地选择进行了研究。江豚喜好的栖息地特征为坡度平缓（<2°），水深7-12米的区域。（3）根据最新的长江江豚种群动态及遗传多样性结构数据，应用VOTEX模型，进行了洞庭湖、鄱阳湖及干流种群的集合种群分析，探究不同栖息地类型生活的江豚种群迁移对江豚种群长期生存的影响。（4）2017年11月10日至12月17日，利用“2017年长江江豚生态科学考察”机会，采用渔政船作为考察平台，对长江中下游干流（约1700 km）进行了长江江豚和环境采样，探究流域尺度长江江豚的栖息地选择机制及可能对其生存构成威胁的潜在环境风险。（5）利用搁浅长江江豚胃容物分析，对长江江豚的食性进行了初步研究。结果显示江豚时典型的机会型捕食者。结合食性研究，阐释长江江豚栖息地选择受食物资源影响的相关机制。