Abstract
The Yangtze finless porpoise is found exclusively in the middle and lower reaches of the Yangtze River and two large river-connected lakes-Poyang and Dongting Lakes. With a considerable stretch of the natural riverbank along the Yangtze main stem replaced by artificial structures and the depletion of fish stocks, prey availability, habitat loss, and fragmentation have become the most important factors affecting the survival of the finless porpoise. To explore the structural characteristics of plant communities and juvenile fish along different shorelines and their potential relationship with the distribution of finless porpoises, we selected 15 typical sections in the Anqing section of the Yangtze River to investigate plant and juvenile fish communities. Simultaneously, three visual surveys were conducted to record the abundance and distribution patterns of the finless porpoise, along with the types ofshorelines. The results showed that: (1) A total of 126, 106, and 89species of vascular plants were collected from the natural, rock, and prefabricated masonry shorelines, respectively, with herbaceous plants being the main life form and Asteraceae, Poaceae, and Cyperaceae as the dominant families. The Ward’s minimum variance method was used to classify plant communities of the three shorelines into four, four, and five community types, respectively. The most frequent plant associations were Ass. Leonurus japonicus + Cynodon dactylon+ Phragmites australis on natural shorelines, Ass. Xanthium strumarium+ Hemarthria sibirica + Panicum bisulcatum on rock shorelines, and Ass. Ipomoea triloba+ Xanthium strumarium+ Erigeron canadensis on prefabricated masonry shorelines, respectively. (2) A total of 130005 juvenile were collected and identified, belonging to 14 genera, 7 families, and 6 orders. Among them, 15, 12, and 13species were collected from natural, rock, and prefabricated shoreline waters, respectively. The six common dominant species across the three shoreline types were Hemiculter leucisculus, Carassius auratus, Cyprinus carpio, Neosalanx tangkahkeii, Protosalanx hyalocranius, and Hyporhamphus intermedius. The endemic dominant species in the rock and the prefabricated shoreline waters was Rhinogobius giurinus. ANOVA indicated that the total number of individual and upper fish species were significantly higher in natural shoreline waters than that in the other shoreline waters. (3) A total of 135 porpoises were sighted during the three surveys, with an average of (45.00±8.66) individuals per survey. Our observations revealed that porpoises in the Anqing section of the Yangtze River exhibit a continuous distribution, with distinct areas of concentrated distribution. However, finless porpoises displayed a noticeable preference for natural shoreline waters. (4) Correlation analyses of plant communities, juvenile fish communities, and finless porpoise distribution showed significant positive correlation (P<0.05) between vegetation cover and juvenile fish species richness, as well as between juvenile fish species richness, the number of small fish, and the distribution of the finless porpoise. (P<0.05). Therefore, we concluded that high vegetation cover, plant species diversity, and the abundance of upper fish in confluence areas are key factors supporting the habitat of the finless porpoise.
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