松花江梧桐河生态修复工程鱼类栖息地模拟及调查

通过对松花江一级支流梧桐河中下游河道栖息地模型模拟和实地鱼类调查,分析了修复工程丁坝的水动力变化对鱼类栖息地的改善作用。基于流量内增加法(IFIM),应用水生生物栖息地模型(River 2D),考虑鱼类栖息地的流速、水深、遮蔽回水面积比3项指标,定义栖息地为差、中、良3个等级,模拟从小到大4个不同流量条件下顺直河道和丁坝河道鱼类栖息地等级的分布及变化,并通过实地鱼类调查数据验证修复工程丁坝对鱼类栖息地质量的改善情况。结果表明,在不同流量条件下,顺直河道和丁坝河道鱼中等级栖息地占84%以上;从生态流量到多年平均流量的过程中,顺直河道和丁坝河道不同综合适宜性指数(Combined Suitable Indexes,CSI)等级的栖息地面积变化较大,其中两者CSI差等级的栖息地面积占比分别减少4.9%和4.8%,顺直河道CSI中等级的栖息地面积占比升高4.9%,丁坝河道CSI中等级的栖息地面积占比下降6.0%,丁坝河道CSI良等级的栖息地面积占比从0%升高到10.8%;当流量大于多年平均流量26.42 m~3/s时,各种等级的栖息地比例变化不大,多年平均流量对鱼类生长而言是最佳下限流量。从2016年和2017年9月两河段的鱼类调查情况来看,丁坝河段鲫(Carassius auratus)和蛇鮈(Saurogobio dabryi)的平均体重和平均体长更大,模拟和实测数据一致,说明丁坝在一定程度上改善了鱼类栖息地的质量。

Wutong River Fish Habitat Survey and Modeling Under Ecological Restoration

Wutong River is the primary tributary of Songhua River, and historical data shows that it was an important fish spawning ground. In recent years, the fishery resources in Wutong River have declined as a result of rapid economic development. In this study, we analyzed the effects of hydrodynamic changes resulting from ecological restoration of Wutong River fish habitat, based on field investigations and habitat modeling. The reaches investigated are in the Xiaoshanliangzi section of the lower Wutong River. The fish survey was conducted in a straight reach (SR) in September, 2016 and the spur dike reach (SDR) in September, 2017. Based on the intra-flow increase method (IFIM), The RIVER-2D model was applied to simulate fish habitat in the SR and SDR sections under four different flow regimes. Habitat suitability under the different flow conditions was evaluated based on flow velocity, water depth and the proportions of pool, backwater and marsh areas. The combined habitat suitability index (CSI) was used to classify habitat as good, moderate or poor. The distribution of different habitat grades in the SR and SDR sections under the four flow regimes were modeled and the results were verified using fish survey data. These results were used to evaluate the improvement of fish habitat due to the ecological restoration project. Overall, moderate level habitat accounted for >84% in both the SR and SDR at the different flow rates. Increasing the flow rate from the ecological (base) flow (7.92 m3/s) to the average annual flow (26.42 m3/s) significantly changed the proportions of habitat area for each grade. The proportion of poor habitat decreased by 4.9% in the SR and 4.8% in the SDR. The proportion of moderate habitat increased by 4.9% in the SR and decreased by 6.0% in the SPR, and the proportion of good habitat in the SDR increased from 0% to 10.8%. When the flow rate was higher than the annual average flow, the changes in habitat grade were small. Therefore, the average annual flow is the lower limit of optimal flow for the fish community. According to the field fish survey data in the two reaches in September 2016 and 2017, the average body weight and length of Carassius auratus and Saurogobio dabryi in the SDR were heavier and longer than those in the SR. The modeling results and field data were generally consistent and indicate that the spur dike improved, to some extent, the quality of fish habitat.