Distribution pattern of Limnoperna fortunei in typical hydropower stations of Lancang River and corresponding prevention and control recommendations

Southwest China is rich in hydropower resources, with numerous hydropower stations, some of which are facing bio-fouling issues caused by Limnoperna fortunei. A three-year monitoring program was conducted at a typical hydropower station on the Lancang River, which preliminarily revealed the distribution patterns of adult Limnoperna fortunei and larvae within the station and identified key driving factors affecting their growth and development. Based on these findings, prevention and control measures for Limnoperna fortunei in large hydropower stations and reservoirs were proposed. The monitoring results showed that the larval density of Limnoperna fortunei in the reservoir area ranged from 0 to 920 ind./m³, showing a gradual increase and accumulation from the upstream reservoir area to the downstream area near the dam. In terms of vertical distribution, larval density exhibited an initial increase followed by a decrease with water depth. In the 0~28 m water layer, density increased with depth, with average density rising from 20 ind./m³ to 150 ind./m³. In the 28~50 m water layer, density gradually decreased with depth, reaching an average of only 37 ind./m³ at 50 m depth. Larvae of Limnoperna fortunei were detected from March to November at the station, with significantly higher larval densities during the wet season than during the dry season. The monthly average total larval density during the wet season was 311 ind./m³, compared to only 52 ind./m³ during the dry season. Through an analysis of larval density and water quality parameters at various sampling points using Random Forest analysis, linear regression, and correlation analysis, we found that the key driving factors for larval distribution include habitat quality, dissolved oxygen, chlorophyll-a concentration, and water flow velocity. Specifically, larval density showed a highly significant negative correlation with habitat quality (or specific indicators) (p < 0.01), a significant negative correlation with dissolved oxygen (p < 0.05), and a significant positive correlation with chlorophyll-a concentration and water flow velocity (p < 0.05). Based on the distribution patterns, attachment characteristics, and life habits of Limnoperna fortunei, a comprehensive prevention and control system centered on "monitoring and early warning-source control-process interruption-end treatment-operation and scheduling" was established, along with recommendations for future prevention and control efforts.