圖書典藏及影音數位平台

中庄堰、隆恩堰、上坪堰及羅東堰魚道水理及生物使用狀況調查及魚道效益評估

In order to understand the effectiveness and bio-utilization of seven fishways in following four weirs: Long-En Weir in Tou-Qian River, Shang-Ping Weir in Shang-ping River, Jhong-Jhuang Weir in Da-Han River, and Luo-Dong Weir in Luo-Dong River, which are under the jurisdiction of the Northern Region Water Resources Office, Water Resources Agency Ministry of Economic Affairs, the ecological survey had been made every month since January 2018. The main structure of the fish pass, the hydraulic characteristics, and the function of ecological corridor were evaluated. A total of 12 months of continuous ecological survey around seven fishways in four different weirs had been made, as the result, the most diverse biological species composition and also the most abundant individual quantity were found in Long-En Weir in Tou-Qian River (fish 34 species, shrimp/carb eight species). Among the total recorded species in Long-En Wier, 11 species of them were diadromous. There were 29 fish species and 13 shrimp/carb species were recorded in Luo-Dong Weir. Although the total number of individuals recorded was fewer, there were 15 diadromous species found in Luo-Dong Weir. There were 32 fish species and two shrimps recorded in Jhong-Jhuang Weir, two of them were diadromous species. There were 12 fish species and one shrimp species recorded in Shangping Weir, only one diadromous fish. Despite many of the recorded species in those four weirs are primary freshwater species; they still have to migrate in the river. Therefore, setting fishway in the river is necessary. Among the seven fishways in this survey, the hydraulic characteristics (velocity and discharge) were most ideal in the Half-Cone-Type Fishways in the both side of secondary dam of Long-En Wier. In the same time, those two fishways had most frequent biological utilizations. However, the Modified Larineir Pass in the main dam of Long-En Weir was not ideal for biological utilization due to insufficient discharge and excessive velocity. Due to the siltation in the intake of Shangping fishway, there was no water flow in the fishway, so the function of the fishway has not been played. Luodong Weir was under maintenance; therefore most of the time there was no water in the fishways. Only when water flow test performed in Luodong weir, the Denil Type Fishway could function normally; the Plain Type Fishway could not provide fish migrating to upstream due to velocity was too fast. There was water flow in the fishway only when Jhong-Jhuang Weir storing water, however, the discharge was too heavy in the fishway. Modification by installing a baffle at the intake of the fishway in order to reduce the discharge was needed for recovering the fishway function. On the whole, the ecological resource surrounding by the four weirs was abundant in this survey. Meanwhile, there were many diadromous and potamodromous species. Therefore, in order to improve the function of each fishway, the following suggestions are proposed: 1. The fishway on both sides of the secondary dam of Long-En Weir is quite good, but it is necessary to pay more attention to the usual management and reduce human interference. 2. The discharge amount should increase in the fishway of the main dam of Long-En Weir, and at the same time modify the structure of the intake to reduce the velocity to achieve greater efficiency. 3. The exit (intake) and entrance (outlet) of the fishway of Shangping Weir need to be properly dredged, otherwise they will not function properly. 4. The exit (intake) of the fishway in Jhong-Jhuang Weir must be equipped with a baffle to reduce the discharge, and the fishway can function normally. At the same time, there is still a high drop in the entrance of the fishway. If the baffle plates can be added, it will be more conducive for up-migration of the fishes. 5. The Plain Type Fishway attached to Luodong Weir must be equipped with a deceleration device in order to perform its intended function.