三峡水库调控下漂流仔鱼时空分布模式及其栖息地选择研究

Hydraulic and hydro-power engineering changed river connectivity and its natural hydrological regime enormously and irreversibly, and could lead a long-term effect on the decline and extinction of local fish population. Recently, besides for the building of fish passage and artificial releasing, the implementation of protection and rehabilitation of fish habitat is being paid more and more attention, and to get knowledge of how fish select and utilize their habitat is an important research aspect for guiding this measure. However, with respect to fishes in the early life history stage, a knowledge gap existed obviously between the mechanism research for habitat selection and utilization of larval fishes and effective action aiming to protect fishes and their habitat in this stage. In this study, a research domain in the Jingjiang reach, that under hydrological control of the Three Gorges Reservoir was chosen, using a combined method of larvae-sampling in multi-sections and multi-sites, habitat investigation in multi-scales, along with hydrodynamic model building and boosted regression trees statistical analyzing, to study the following contents: Spatio-temporal distribution of drifting larvae in different species and development stages; Comparison of larvae distribution pattern among in different habitat types, and key environmental factors affecting their distribution pattern; Coupling analysis of larval drifting density and key habitat factors to identify the response correlations between the two; Exploring their environmental preference and habitat choice mechanism for biological-specific larval fishes. The result would provide a scientific basis on the habitat identification, evaluation and rehabilitation that utilized by fishes in early life history stage.

水利水电工程对河流的连通性和水文节律带来不可逆转的改变，其长期效应可导致鱼类种群的衰退甚至灭绝。除了过鱼设施和人工增殖放流措施之外，开展关键栖息地的保护与修复工作逐渐受到重视，而弄清鱼类对栖息地的选择和利用机制是其中的关键所在。目前国内有关早期发育阶段鱼类对栖息地的选择和利用研究相对缺乏，无法行之有效地实施栖息地的保护与修复。本项目在受三峡水库调控的长江中游荆江河段作为研究区域，采用多断面-多位点仔鱼采样、多尺度栖息地环境因子调查技术，联合水动力模型构建、推进回归树等统计分析方法，研究不同种类、不同发育阶段漂流仔鱼的时空分布特征，比较不同类型栖息地仔鱼分布模式的差异；遴选影响仔鱼分布的关键生境因子，将仔鱼漂流密度与关键因子耦合分析，识别不同仔鱼与栖息地要素的响应关系，最终探讨不同生物学特征仔鱼的生境偏好及其栖息地选择机制。研究结果将为开展鱼类早期发育阶段栖息地辨识、评价和修复提供理论依据。

鱼类早期资源是渔业资源的重要补充群体。目前，国内河流仔稚鱼与栖息地关系的基础性研究相对缺乏，使得针对鱼类早期资源保护的河流栖息地保护与修复工作基本空白。本项目在长江中游沙市江段设置多个采样点，通过调查仔鱼组成、丰度、体长生物学特征，同步观测栖息地水环境及水动力因子，初步探索了长江中游仔鱼生物学特征与栖息地要素的响应关系，获知了部分种类仔鱼的生境偏好。主要研究结果如下：（1）野外调查时间为6月底至8月初，采样时沙市断面流量分布范围为15800~33000 m3/s，水位分布范围为35.87~40.66 m。水环境因子变动范围如下，透明度10~55 cm、流速0.2~1.44 m/s、水深2~20 m、水温22.6~25.5 ℃、溶氧4.26~11.13 mg/L、电导率288~391.3、pH 7.88~11.21。浮游植物多样性指数（Shannon's diversity index）变动范围为1.115~2.347、浮游甲壳动物丰度范围为未检出~18.133个/L。（2）构建了沙市江段二维水动力模型，对采样点江段水流运动情况进行模拟，计算了各采样点的流速、水深、弗劳德数等水力学参数。（3）调查期间共采集到仔鱼21种，仔鱼的发育阶段从眼全黑到臀鳍形成期，主要分布在眼全黑和鳔雏形2个时期。各采样点仔鱼漂流密度变动范围为0~90.497个/m3、均值为2.978个/m3，丰度较高的种类包括飘鱼、䱗、银鮈、蛇鮈、鰕虎鱼和四大家鱼。（4）不同采样断面的仔鱼密度平均值存在一定差异，单因素方差分析显示其在统计学上不存在显著性差异。仔鱼密度的分布范围较为狭窄，仔鱼密度与离岸距离呈现明显的幂函数关系。（5）仔鱼逐日密度的空间分布主要受PBD （浮游植物多样性）、WT（水温）、PH值、WL（水位）、FD （流量）以及DFB（离岸距离）的影响；当浮游植物密度大于2.069×10 6cells/L(100.487-1)时，鲌类仔鱼的逐日密度最大；当浮游植物密度大于0.570×10 6cells/L(100.196-1)且离岸距离小于8.300 m时，鮈类仔鱼的逐日密度最大。总体上，沙市江段不同种类仔鱼丰度主要受浮游植物密度、离岸距离的影响，而与其它生境要素的关系不大。后续需进一步扩展研究范围，包括漫滩、湾汊、汇源区、半淹水区、入湖口廊道等，进行更为全面、深入的调查研究。