Design and effect evaluation of tube fishway in Low Head Dams

There is a huge demand for fish passing through low head dams in China, and there is an urgent need to build low-cost portable fishways without construction. In view of this, this study independently designed a tube fishway to assist fish migration, analyzed the fish passing effect of Hypophthalmichthys molitrix through portable tube fishways at three tube angles and two charge conditions, obtained evaluation indicators for the fish passing effect of new tube fishways, and constructed a risk proportional regression model based on attempt rate, passage rate, and maximum ascent distance to identified the key factors affecting the fish passing effect of tube fishways. Research has shown that: ① The optimal attempt rate model found that charge is a key factor affecting the attempt of hypophthalmichthys molitrix to enter the fishway; There is a significant negative correlation between charge and ascent migration attempt rate of hypophthalmichthys molitrix in tube fishways. ② The highest passage rate of the tube fishways can reach 90.5%. Through the optimal passage rate model, it was found that the angle of the tube, water temperature, and number of attempts are key factors affecting the passage of hypophthalmichthys molitrix through the fishway; The lowest passage rate occurs when the tube angle is 90 °; There is a significant negative correlation between the number of attempts and the ascent passage rate of hypophthalmichthys molitrix; There is no significant difference in the ascent passage rate under the conditions of tube angle of 30 ° and 45 °, but both are significantly higher than 90 °. ③ The optimal maximum ascent distance model found that water temperature and tube angle are key factors affecting the probability of hypophthalmichthys molitrix passing through the maximum ascent distance; there is a significant positive correlation between water temperature and the probability of the maximum ascent distance that hypophthalmichthys molitrix can pass through; the probability of the maximum ascent distance that hypophthalmichthys molitrix can pass through is not significantly different under tube angles of 30 ° and 45 °, but both are significantly higher than 90 °.