长江中游四大家鱼产卵场定位及特征研究

The four major Chinese carps as important economic fishes in China primary inhabit and breed in Yangtze River now. Unfortunately, their spawning ground has been seriously affected by the Three Gorges Dam. The previous research found that the underwater topography and hydrodynamic condition between Yichang and Chenglingji sections had continuously changed since the construction of the Three Gorges Dam, leading to the shrink of the fish spawning activity and even the threat of the germ plasm resource. However, due to the limitation of traditional detection tools, the research on the spawning ground characteristics has been rarely carried out and the corresponding spawning-trigger mechanism is still unknown. For this point, this project utilizes advanced detection techniques and conducts the research in the following fields. First, investigate the fish migration habits in the breeding season and the corresponding temporal and spatial distribution along with the ultrasonic telemetry technology. Second, consider the fish egg collection, parent fish capture and hydro acoustic observation collectively, and then develop a new method to locate the precise fish-spawn ground. Third, observe the water flow field in real-time in typical spawning ground and record the explicit underwater topography with acoustic doppler current profilers (ADCP). Finally, analyze the previous works with three dimensional numerical simulation, mathematical statistics and date mining method, and then illustrate the efficient underwater topography and hydrodynamic characteristics of the four major Chinese carps spawning ground. Moreover, the proposed solutions and results will provide theoretical and technological support for the spawning ground evaluation and recovery as well as fish resource protection.

四大家鱼是我国的重要经济鱼类，长江是四大家鱼的主要繁殖栖息地。三峡工程建成后，清水下泄和水库调节导致中游宜昌至城陵矶江段的家鱼产卵场地形和水动力条件发生改变，家鱼产卵规模持续萎缩，种质资源面临严重威胁。目前，受限于家鱼产卵场定位范围较广、精度较差等问题，家鱼产卵场特征及产卵触发机理等方面研究尚未深入开展。针对这一客观需求，本项目应用超声波遥测技术，研究家鱼繁殖期的洄游行为和时空分布，并结合鱼卵采样、水声学观测、家鱼亲本捕捞等方法，准确定位家鱼产卵点位和产卵场细致范围。在此基础之上，应用多普勒流速剖面仪（ADCP），对家鱼典型产卵场进行细尺度的地形和流场同步观测，通过三维数值模拟、数理统计、数据挖掘等方法，揭示家鱼产卵场的关键地形和水动力特征，以期为家鱼产卵的水流触发机理研究、家鱼产卵场评价及修复和鱼类资源保护等工作提供理论基础和技术支持。

产卵场定位是研究地形和水动力特征基础，地形特征是水动力特征研究前提，而产卵场水动力特征是探索家鱼产卵水流触发机理有效途径，三方面环环相扣，是本项目三个主要科学问题。基于此，应用超声波遥测、eDNA、早期资源与地形流场同步观测、数值模拟、数据挖掘等多种技术，对上述科学问题进行探索。研究表明：①长江中游干流家鱼产卵场主要分布在宜昌、枝江、洪湖、团风和鄂州5个江段（规模＞0.5亿），其中宜昌是唯一大型产卵场，2014-2019年宜昌产卵规模13.98亿粒，占干流总规模77.7%。基于原位观测结果，利用超声波遥测技术解析了繁殖亲本时空分布，定位了核心产卵区，精度提高至公里级；应用eDNA技术，设计特异引物，精确了产卵时间和核心区域，eDNA浓度与繁殖时间和核心区域显著相关；②应用ADCP开展地形和流场同步观测，构建了产卵场地形指标体系，筛选出断面复杂系数等5项产卵场地形指标。对比了产卵场与非产卵场、产卵场现状与三峡运行前（2002年）指标差异，表明宜昌产卵场水流紊乱具有更多深潭浅滩分布，产卵场河床地形复杂系数高于非产卵场，产卵场地形粗糙度、起伏度和高程变异系数较三峡运行前明显增大；③构建了长江中游典型产卵场三维水动力模型，解析了家鱼繁殖期时空分布格局和水动力条件偏好选择，量化得出了家鱼产卵场水深（12.77-19.93m）、流速（0.78-1.38m/s）、傅汝德数（0.069-0.109）、涡量（0.39/s-0.48/s）等水动力特征；构建了长江中游产卵场栖息地评价模型，揭示了产卵场生态流量、产卵量及适宜性面积之间响应关系，统计表明82.56%产卵活动发生于适宜性面积大于5km2（面积范围0-6.6km2），产卵量占总规模88.57%，提出了三峡大坝下泄15000-21300m3/s生态流量范围。成果可为家鱼产卵场评价、生态修复、生态调度和资源保护等提供支撑。