| Abstract: | Abstract: The Cuijiaying navigation-power junction project is located at the Hanjiang River. Its functions include, but are not limited to, navigation, power generation, and irrigation. In order to compensate for the adverse effect of the project on the fishery resource, a fish passage was built. To realize the effect of the fish passage, an investigation was conducted September 19-26, 2012 and the methods of net catch and hydroacoustic monitoring were adopted. Trammel nets were used for fish catching in the fishway. The net was comprised of three layers and the dimensions of the net were 15m×1.2m. The mesh of the middle layer was 4mm and the mesh of the outer two layers was 8mm. Nets were laid at the orifices of the baffle plate and six nets were put out every day, three in the daytime and the other three in the nighttime. The first net was put in the exit of the Cuijiaying fishway and the distance between the net and the exit was 8 meters. The distance of the other two nets to the exit was 18 meters and 28 meters. Hdroacoustic equipment of SIMRAD EY60 was adopted at the front of the exit to see the quantity of fish which can swim across the entire fish passage. The frequency of the equipment was 200 kHz and the angle of the beam was 7°. The equipment was fixed at the exit of the fishway and the distance between the equipment and the exit was 7 meters. Hydroacoustic detection was conducted during day and night time. The results showed that a total of 11 fish species can swim through the passage, which are Pelteobagrus vachelli (Richardson), Rhinogobio typus Bleeker, Megalobrama amblycephala, Saurogobio dabryi Bleeker, Opsariicjthys bidens, Distoechodon tumirostris, Lepturichthys fimbriata (Gunther), Coreius heterodon (Bleeker), Siniperca chuatsi (Basilewsky), Hypophthalmichthys molitrix (Cuvier et Valenciennes) and Hemiculter leucisclus (Basilewsky), among which Pelteobagrus vachelli (Richardson), Hemiculter leucisclus (Basilewsky) and Distoechodon tumirostris are the main species. The quantity and weight of the fish caught was 37 individuals with a total weight of 2813.4g, among which the quantity and weight of Pelteobagrus vachelli (Richardson) accounted for forty-six percent and forty-one percent, respectively. The average length of the caught fish was 166.9mm and the 95% confidence interval was between 152.5mm and 181.3mm. The average weight of the caught fish was 80.0g and the 95% confidence interval was between 58.3g and 101.6g. Hydroacoustic equipment was used for 1267 minutes and 658 signals were detected. During the daytime, 571 signals were detected and the average target strength was -55.68dB. The equation of TS=23.902lgSL-87.3 was adopted to calculate the fish length and the average fish length in the daytime was 33.32cm. The 87 signals in the nighttime were also calculated; the average target strength and fish length were -54.48dB and 34.62 cm, respectively. The fish quantity detected in the nighttime was lower than in the daytime, but the target strength and the average fish length in the nighttime was a little higher. The average length of the detected fish was 33.50cm and the 95% confidence interval was between 30.43cm and 36.55cm. According to our investigation, Cuijiaying fishway offers an exchange channel for fish below and up the dam site in the detected period and protects the fishery resource in the river basin. |
