主視覺

  • 常常聽到人們形容“碧綠”的溪水,一直在想真的有“碧綠”的水嗎?還是這只是個誇大的形容詞,亦或是多年的污染使得這樣的景象不復見?
  • 台中旱溪康橋水環境營造緣由:時光倒回1970年代台大水工試驗所數值模擬-顯示旱溪從東門橋分洪大里溪不會產生河床不穩定及淤積,誕生今日新聞熱點的康橋計畫。
  • 鱉溪組曲 吉哈拉愛之歌
我們家附近有一條溪
叫做鱉溪
因為之前有非常多的鱉
我們常常
在鱉溪玩水打水漂.....
:::

網站地圖

:::國內案例

An evaluation of fishway functions

  A fishway or fish pass is a biological path that allows fish to swim upstream or downstream. When the environment changes, they have opportunities to seek escape routes. It is an important appended facility to the horizontal constructions in rivers. In Taiwan, there are many ways to evaluate a fishway. Among them, trap catching is the most direct one. It is possible for us to understand the species and quantity of fish using the pass. In this essay, 3 methods for the evaluation of fishways are proposed to explain the functions after installing a fishway.

  The 1st case is No. 2 Sand Bank Fishway in Tsukeng creek, Yilan. This fish pass is a Larinier fishway (fish-bone-type fishway). Completed in August 2001, it has been 15 years since then. The 2nd case is No. 3 Sand Bank Fishway, a pool and weir type fishway, in Cukeng River, Yilan. Built in 1993, it has been 22 years since then. It has been maintained in good condition, providing good functions. The 3rd case is No. 5 sand bank in Pinglin. Being a modified boat-passage fishway, it was built in June 2001. It has been installed for 15 years.
 

Fig. 1 Larinier fishway shortly after its completion

(Photo by Hu Tung-che on Aug. 21 2001)
1. No. 2 Sand Bank Fishway in Tsukeng creek, Yilan
The upper stream of the Tsukeng creek is Fushan. With clean and clear water, the watershed is maintained in good condition. In the No. 2 Sand Bank, it is appended with a Larinier fishway. Its newly built conditions are shown in Fig. 1. After 15 years, the fishway is still preserved in very good condition. As shown in Fig.2, the difference of the elevation between the outlet of the fishway (intake) to the entrance (outlet) is 4.9m. The gradient is divided into two sections 1:8 and 1:12, with a length of 72m. After the investigation of fish above and below the sand bank, there is no difference in fish species. Although it functions in primary investigation, it is not possible to evaluate its function with trap catching since its construction. On October 16, 2014, stainless steel framed traps, one on the right side and one on the left side, were installed on the upper stream of the fishway (as shown in Fig. 3) with two purposes, one of them was to understand the function of the fishway, and the other was to understand whether fish preferred to swim by the mountain wall (the left half) or upstream on the right half. As the mountain trails were difficult to walk along, it took the researcher 7 days to enter the mountains for inspection. The trap was examined on October 23, 2014, it was discovered that there were fish entering both traps, one on the right and the other on the left, willingly. There were more fish species in the trap on the left by the mountain wall (38 fish of 5 species) as shown in Fig. 4. Meanwhile, there were fewer fish in the trap on the right half (4 fish of 2 species). It is possible that fish have the natural habit of hiding from their predators. Therefore, they would choose to swim by the mountain wall. As this fishway is symmetric on both sides, it will be money saving if we just build the left half of it. In Fig.5, it explains that the fish species caught in the trap are: Onychostoma barbatulum, Opsariichthys pachycephalus, Formosania lacustre, Hemimyzon formosanum, and Acrossocheilus paradoxus. They are all frequently-seen fish in the Tsukeng creek. Among them, Onychostoma barbatulum is larger in quantity, being the advantageous fish species in Tsukeng creek.

相關圖片

相關圖片
Fig. 5 Quantity and species of fish caught in the trap in the fishway

相關圖片
2. No. 3 Sand Bank Fishway in Tsukeng creek, Yilan
  In the No. 3 Sand Bank Fishway in Tsukeng creek, a pool and weir type fishway was installed. The difference of the elevation between the outlet of the fishway (intake) to the entrance (outlet) is 6.5m. The average gradient is 1:10. The level difference is 17cm-22cm. After the ecological investigation above and below the sand bank, there is no difference in fish species. Although it was evaluated that the fishway functioned properly or not, since it construction, there had been a lack of evaluation with the trap catching method. On October 30, 2014, a trap was installed in the upper-stream of the fishway (Fig. 6). A week later, November 6, 2017, researchers entered the mountain to inspect the trap. 40 fish and 2 Macrobrachium asperulum Von Martens that swam into the trap willingly was caught. As shown in Fig. 7., there were Onychostoma barbatulum and Formosania lacustre. It is obvious that the fishway is used by fish.

3. No. 5 sand bank in Pinglin.

  No. 5 sand bank in Pinglin is an appended fishway built as a modified boat-passage fishway (Fig. 8). It was built by The Taipei Watersh Management Office, WRA on June 2001. The total length of the fishway was 27m, with the width of 2.15m and gradient 6%. A trap was installed on August 1, 2009 (Fig. 9). After observing the trap for 24 hours, 1188 fish that swam willingly into the trap were caught. The quantity and species of the fish are shown in Fig. 10. They include 9 different species Cobitis sinensis, Opsariichthys pachycephalus, Candidia barbata, Onychostoma barbatulum, Zacco platypus, Rhinogobius candidianus, Pseudobagrus adiposalis, Opsariichthys pachycephalus, and Microphysogobio brevirostris. Zacco platypus is the species that use the fishway most frequently, occupying 87% of the total. The fish that use the fishway are small fish with the length of 4-5cm, occupying 75%. The fish trapped are shown in Fig. 11. On the day of installing the fishway (August 1, 2009), the water is in the temperature of the summer, at 31.80C. The fishway provides fish a way to swim upstream and downstream to seek a chance of survival. If the temperature of the water is too high, some fish can hardly survive. The appended fishway of No. 5 sand bank in Pinglin functions very well, providing a successful case for the study of fishway. 


相關圖片

相關圖片

相關圖片
Fig. 11 The species of fish caught in the trap in the fishway on No. 5 sand bank in Pinglin




關鍵字

相關圖片

  • 02

延伸閱讀

選項