• Korean Journal of Ichthyology
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• v.34 no.2
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• pp.127-132
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• 2022

Most of the downstream of the river is blocked by beams, so fishways are required for the movement of conciliatory fish species and connection with the upstream. Therefore, it is very important as an ecological pier that can help free movement of fish. The three previously installed eel ladders use only brushes on the bottom. For find out the effect of the bottom material except to brush, experimented used model glass eel ladders to the ascent of glass eel. The eel ladder model was 1.2 m length, 0.3 m wide, and 0.1 m high, and three gravels of different particles were attached to the bottom of the fish ladder setting on the Geumgang Estuary Bank. The first model ladder was made of gravel with particles of 5 mm, and the second model ladder was made of gravel with particles of 2 mm. The third model ladder was made by solidifying with particles of 1 mm or less cement. All experiments were repeated 5 times for 1 hour. As a result of the experiment, the lower the angle, and the smaller the gravel particles, the more glass eels are ascended to the ladder, but the made of cement was nearly not ascent. The gravel-bottom model ladder has a lower discharge and flow rate than the brush ladder so more glass eels can ascent ladder, and if the glass eel ladder is improved through experiments applying various floor materials and variables in the future, more glass eels are going to ascent glass eel ladder.

• Korean Journal of Ecology and Environment
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• v.55 no.2
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• pp.167-174
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• 2022

The Ministry of Oceans and Fisheries promoted the installation of eel-ladder for the purpose of creating inland water resources. Currently, eel-ladder have been installed and operated at the Geumgang Estuary Bank (2018), Yeongam Embankment (2019), and Asanman Embankment (2020). In this study, the number of glass eels in eel-ladder in 2021 was monitored and factors affecting the rise that from ocean to river of eels were investigated. Glass eels in eel-ladder were found when the salinity was relatively low, and they started when the freshwater and seawater temperatures were above 20℃. Comparing the number of occurrences by year, the largest number of glass eels was observed in 2021, but it is judged that this is not according to the distribution of glass eels in sea, but rather as a result of the investigator's eel-ladder repair and guidance on illegal fishing.

• Korean Journal of Ichthyology
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• v.21 no.4
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• pp.262-272
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• 2009

Upstream behavior of glass eels was examined in an experimental eel-ladder at a laboratory of the National Fisheries Research and Development Institute from March to May in 2008. The study was made under various environmental factors and conditions affecting the upstream migration of glass eels in order to design a functional ladder that would allow the passage of glass eels. The experimental eel-ladder consisted of an upper freshwater chamber and a lower sea water chamber; glass eels in sea water can move up to the upper freshwater chamber through the slope (eel-ladder) between them. The optimal condition of the eel-ladder was estimated by comparing the number of glass eels that moved upstream depending on various conditions. Since the glass eels actively moved up the slope to river water rather than to reservoir water or tap water, the experiment was realized using river water. A significantly higher number of glass eels moved up during the spring tide than during the neap tide, and during night than during the day. Upstream movement was significantly higher during high tide than during low tide. Glass eels effectively moved up through a slope of less than $30^{\circ}$ and water-flow velocity lower than 0.4 m/sec. The fish preferred a coarser ladder bed covered with small gravels, brush or carpet.