长江安庆段长江江豚分布特征及其影响因子探究

DISTRIBUTION CHARACTERISTICS AND ITS INFLUENCING FACTORS OF THE YANGTZE FINLESS PORPOISE IN ANQING SECTION OF THE YANGTZE RIVER

研究于2021年秋季至2023年夏季在长江安庆段(安庆市程营村-凤凰码头)开展了2个周年共8次目视考察,从种群数量、集群规模、迁移规律、栖息地偏好四个方面探讨了该水域长江江豚(Neophocaena asiaeorientalis asiaeorientalis)的分布特征及影响因子。研究期间共观测到长江江豚555群次、1000头次,最大单次评估结果为192头;其中2023年观测到长江江豚336群次、603头次,较2022年分别上升53.4%和51.9%。研究期间长江江豚最大集群规模为8头,平均集群规模为1.8头/群。考察发现长江安庆段长江江豚总体呈连续分布,但存在明显的热点区域,其中张家州北汊、上三号洲、下三号洲洲尾及清洁洲洲头水域为长江江豚的重要栖息地,四个栖息地内观测头次分别占总头次的19.3%、4.9%、12.6%和10.8%。禁捕后长江江豚在河口汇流区活跃的月份增加并有从八里江安徽段向下游扩散分布的趋势,但码头、崩岸区对其栖息地范围的拓展仍存在一定影响,华阳河口以下江段仍只有清洁洲洲头水域为长江江豚的重要栖息地。因此研究认为在十年禁渔及鄱阳湖极端枯水频发的背景下,长江安庆段的长江江豚数量有明显上升趋势,同时长江江豚对各重要栖息地斑块之间迁移通道的利用情况逐渐好转,分布更具连续性。研究建议,应在长江江豚可能的聚集觅食区及迁移通道保持自然岸线占比,加大岸线整治力度,加强人类活动管控;根据极枯水位下鄱阳湖长江江豚迁移入江的时序特征,制定湖口-华阳河口水域的应急管理预案。

In this study,we conducted a total of 8 visual surveys in the Anqing section of the Yangtze River(Chengying Village-Fenghuang Wharf)spanning from fall 2021 to summer 2023,covering two consecutive years.Our aim was to investigate the distribution characteristics of Yangtze finless porpoises(Neophocaena asiaeorientalis asiaeorientalis)in this watershed and the factors influencing them across four dimensions:population number,cluster size,migration pattern,and habitat preference.During the study period,a total of 555 groups and 1000 individuals were observed,with the largest single assessment recording 192 individuals.Notably,in 2023,we observed 336 groups of porpoises comprising 603 individuals,marking an increase of 53.4%and 51.9%respectively compared to 2022.The maximum observed cluster size of porpoises during the study was 8 individuals,with an average cluster size of 1.8 individuals per group.Our observations revealed that porpoises in the Anqing section of the Yangtze River exhibit a continuous distribution,with distinct hotspots identified.Particularly noteworthy were the North Branch of Zhangjiazhou,the Upper No.3 Sandbar,the tail of the Lower No.3 Sandbar,and the head of the Clean Sandbar,which emerged as important habitats,collectively accounting for 19.3%,4.9%,12.6%,and 10.8%of total observations respectively.Following the fishing ban,porpoises have displayed increased activity in the estuarine confluence area for more extended periods,with a tendency to spread downstream from the Anhui section of the Bali River.However,the expansion of there habitat is still constrained by factors such as wharf infrastructure and collapsed bank areas.Notably,only the Clean Sandbar area below the Huayang estuary remains as an important habitat for porpoises in the lower river section.Conclusively,our study indicates a significant upward trend in the Yangtze finless porpoise population in Anqing section of the Yangtze River,attributed to a decade-long fishing ban and the frequent occurrence of extreme droughts in Poyang Lake.Additionally,porpoises are displaying improved utilization of migration corridors between important habitat patches,resulting in a more continuous distribution pattern.Based on our findings,we recommend maintaining a proportion of natural shoreline in potential gathering,foraging areas,and migration corridors of porpoise,increasing shoreline improvements,and strengthening control over human activities.Furthermore,considering the temporal and sequential characteristics of Yangtze finless porpoise migration into the river during periods of extremely low water levels in Poyang Lake,we advocate for the formulation of a contingency management plan for the waters from the Hukou estuary to the Huayang estuary.