长江中下游干流江豚岸线栖息地质量评估长江中下游干流江豚岸线栖息地质量评估

RIVER BANK HABITAT ASSESSMENT OF THE YANGTZE FINLESS PORPOISE IN THE MAIN STEM OF MIDDLE-LOWER YANGTZE RIVER

  • 摘要: 栖息地环境质量直接影响长江江豚的种群数量与分布, 但当前长江中下游全尺度的江豚栖息地质量状况尚不清楚。研究于2017年11月10日至12月17日“2017年长江江豚生态科学考察”期间, 使用相机拍照采样的方法, 开展了长江中下游干流宜昌至上海江段江豚岸线栖息地质量现状调查。一共采集了794个有效岸线样点, 观察到江豚318次631头次。卡方拟合优度检验结果显示, 江豚在自然岸线的观测频数占比显著性高于其期望频数占比(χ2=68.99, P<0.001), 而在半自然岸线和固化岸线中结果却相反(χ2=39.26, P<0.001; χ2=12.15, P<0.001), 自然岸线是江豚偏好分布的栖息地类型。同时调查表明长江中下游干流自然岸线受到严重破坏, 半自然岸线和固化岸线占比达45.47%。此外, 岸线栖息地破碎化显著, 自然岸线的区域中间都间杂了半固化的或者完全固化的岸线, 这可能是导致长江干流江豚破碎化分布的主要原因。当前长江中下游干流岸线栖息地质量衰退与破碎化现象十分显著, 是江豚生存的重要威胁, 建议实施硬化岸线的自然恢复和重建破碎化岸线的连通性。

     

    Abstract: Habitat quality can directly affect population abundance and distribution of the Yangtze finless porpoise. This study investigated habitat status of both south and north banks of the main stem of the Yangtze River by taking high-resolution digital photos systematically during the 2017 Yangtze Freshwater Dolphin Expedition from 10th November to 17th December, 2017. The survey area covered the entire middle and lower reaches of the Yangtze River from Yichang to Shanghai (1669 km in length) and a total of 794 photo samples were collected. We recorded 318 sightings with 631 individuals of the Yangtze finless porpoise. The Chi-squared goodness of fit test revealed that proportions of observed frequency are significantly higher than the expected frequency in natural river banks (χ2=69.81, P<0.001). Whereas the result is opposite in the semi-natural and solidified river banks (χ2=39.26, P<0.001; χ2=12.15, P<0.001), indicating that the natural river banks were the preferred habitat of the Yangtze finless porpoise. The length of the semi-natural river and solidified banks accounted for 45.47% of the total length of the river bank, which intermingled with the patches of the natural river banks, demonstrating that the natural habitat was severely degraded and highly fragmented to impact the distribution of the Yangtze finless porpoise. Our study suggested that habitat degradation and fragmentation pose a significant threat to the survival of the Yangtze finless porpoise. Future conservation research and practice should focus on habitat restoration of the solidified river banks to reestablish and enhance habitat connectivity.

     

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