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SEAFDEC/TD conducted a preliminary inspection of the fish passage construction at the Hauy Wang Chang Weir in Sangkom District, Udonthani Province, Thailand from 12 to 15 June 2020. The fish passage was constructed under the project of “Implementing the Lower Mekong Fish Passage Initiative in Cambodia, Thailand, and Viet Nam” supported by USAID – DOI. The inspection was intended to evaluate the performance of the fish passage during the rainy season right after it was constructed. The water flow, endurance of crushed stone bottom of the exit channel, and efficiency to allow fish to migrate up-stream were observed. Moreover, the crushed stone bottom was firmly fixed and did not sink or slid away from the original layout. Even though it was only an initial observation, the seven fish species (i.e., Labriobarbus siamensis, Trichohodus pectoralis, Mystus mysticetus, Esomus longimana, Rasbora spilocerca, Channa striata, and Rasbora aurotaenia) which were sampled after two days indicated the efficiency of the fish passage. On the other hand, the water way beside the fish passage that serve as ramp for small fishes should be improved.
Fish passage, also known as a fish ladder fishway, or fish steps, is a structure on or around artificial and natural barriers (such as dams, locks and waterfalls) to facilitate diadromous fishes' natural migration as well as movements of potamodromous species. Most fishways enable fish to pass around the barriers by swimming and leaping up a series of relatively low steps (hence the term ladder) into the waters on the other side. The velocity of water falling over the steps has to be great enough to attract the fish to the ladder, but it cannot be so great that it washes fish back downstream or exhausts them to the point of inability to continue their journey upriver.
