长江四大家鱼仔鱼的“扩散-滞留”过程与对沿岸栖息地的利用研究

Drift process during early life history stages is a fundamental process in larval survival and resource recruitment of producing drifting-egg fish. In this proposal, larval drift is assumed as dynamic process of dispersal-retention that larval fish apperceive, select and utilize those inshore habitats where environmental conditions match rearing requirements of larvae; and environmental requirements and capability for apperceiving, selection and utilization of inshore habitats of larval fish are charge coordinated with growth and development of early life history stages..Based on the hypothesis, we select major Chinese carps as model species to clarify the key question that dynamic process of “dispersal-retention” and mechanism of utilization on inshore habitat and nursery of the carps. The carps were selected because the fishes have typical drift process during early history stages, are very important in freshwater fisheries, and are model species in many researches. environmental requirements and retention capability of larval fish under different developmental stages for inshore habitats will be tested using simulation experiments in lab and will be confirmed by recaptured experiments using larval fishes with a chemical marker in their otoliths in the middle of Yangtze. Environmental requirements and utilization of larval fish under different developmental stages for inshore habitats will tested by comparing abundance, dynamics, feeding, growth and recruitment of the fishes among different inshore habitats in a typical section of the middle of Yangtze. And then nursery function of different inshore habitats will be evaluated. Isolation of the affiliated lakes from the Yangtze River blocks the migration routes of the offspring entering the critical nurseries in the lakes, which is an important factor for dramatic decline of the carps in the middle and lower Yangtze River. Utilization on inshore habitat of larval fish is critical to recruitment process and resource dynamic of the carps after lost nurseries in the affiliated lakes. This proposal provides a new ideal and theoretical support for protection of fishery resource and microhabitat, which have important theoretical value and practical guiding significance in the Yangtze River.

早期生活史阶段的漂流过程是决定产漂浮性卵鱼类早期资源存活率和种群动态的关键。本项目基于仔鱼的漂流和对沿岸栖息地主动滞留与利用理论，以典型的产漂浮性卵鱼类长江四大家鱼为对象，解析“四大家鱼仔鱼的‘扩散-滞留’动态过程和对沿岸栖息地的利用与育幼机制”这一科学问题。项目通过水槽实验和河流原位标志重捕实验，研究和验证仔鱼不同发育阶段对沿岸栖息地的选择能力和条件需求；选择长江中游典型河段，研究仔鱼不同发育阶段对沿岸不同栖息地的利用状况和育幼效果。江湖阻隔导致仔稚鱼丧失通江湖泊的育幼栖息地，是长江四大家鱼等种群衰退的重要原因；因此，长江沿岸栖息地的育幼功能对四大家鱼等种群补充尤为重要。项目的开展将为长江鱼类资源和生境保护提供了新的思路和科学支持，具有重要的理论价值和实践指导意义。

掌握鱼类早期生活史阶段种群补充的关键过程和影响因素，是制定鱼类资源保护、恢复和可持续渔业管理有效措施的基础。对于长江四大家鱼等产漂浮性卵鱼类而言，漂流仔鱼能否进入沿岸适宜栖息地，是决定早期个体摄食、生长与存活的关键。基于此，本项目提出：1）仔鱼的漂流是“扩散-滞留”的连续动态过程，随着仔鱼的生长和发育，其感知、选择和利用沿岸栖息地的能力和条件需求发生变化；2）水流条件是影响仔鱼漂流和沿岸栖息地利用过程的关键环境因子；3）仔鱼能否进入适宜的沿岸栖息地并滞留其间，对漂流个体的存活和种群的资源补充过程具有重要的影响。.对干流-沿岸的生境选择与条件需求研究揭示出，仔鱼在河道主槽和沿岸浅水区的分布格局明显，近岸水域的仔鱼种类和密度都明显高于河道主。不同流速水平研究显示，低流速（< 0.3m/s）水域是早期个体丰度分布的主要水域；流速对仔稚鱼群聚的种类数影响不明显，与不同种类分布的关系差异较大，流速对仔鱼分布的影响可能存在重要的种类、发育阶段差异。不同类型生境研究暗示，随岸滩固化程度，仔鱼种类组成有降低趋势，仔鱼群聚相似性降低、离散程度越高；流速、水深和岸滩植被是影响不同岸滩仔鱼群聚结构的主要因子。拥有良好植被条件的自然河漫滩拥有更高的仔鱼多样性和丰度，和更为稳定的仔鱼群落，能够为发育阶段后期的仔鱼提供更加优良的育幼生境，更是四大家鱼等重要经济种类发育阶段后期个体关键栖息地。.仔鱼漂流动态和栖息地利用过程研究表明，中游仔鱼丰度高峰具有明显的梯度变化，随着离坝距离的增加形成3个分布梯度；洞庭湖水系、汉江水系的汇入导致两次仔鱼丰度的脉冲式剧增，表现出支流汇入或者江湖连通对仔鱼丰度格局的重要影响。本项目研究表明，长江干流不同种类和发育阶段个体对沿岸栖息地的感知、选择和利用过程与环境需求具有显著的差异，为长江大保护的关键育幼栖息地识别和鱼类资源保护提供了重要的科学支持。