The New Taipei Water Resources Department recently installed new rope ladders to assist crab migration at Bitan Weir. These ladders aim to support the upstream journey of horsehair crabs, which hatch near river mouths and travel upstream to mature in freshwater areas. The department replaced the old ladders because they had worn out.
To better understand the crabs’ movements, the department also set up trapping cages along the river. These cages help track the crabs’ routes and habitats, providing valuable data on their migration patterns. New Taipei Mayor Hou Yu-ih visited the site and praised the efforts. He said the return of horsehair crabs shows progress in restoring the Xindian River’s ecosystem. Moreover, he highlighted the fish ladder’s role in reconnecting upstream and downstream habitats divided by the weir.
However, the fish ladder has sparked controversy. Videos revealed that bighead carp, an invasive fish species, use the ladder to swim upstream. This development worries many environmental groups. A coalition of organizations warned that the ladder might help invasive species spread. They argue that this risk could outweigh the benefits and believe removing man-made barriers is the only true way to restore the river’s health.
In addition, a university professor voiced concerns about invasive species moving upstream. He urged officials to control invasive populations first before fully connecting habitats. On the other hand, the Water Resources Department explained that the ladder was designed for most native aquatic species to access. They stressed that blocking invasive species without harming native ones is very challenging.
Furthermore, a former university professor noted that pre-construction surveys identified native species in the area. He admitted that manually removing invasive species is possible. However, he warned such efforts would demand too much money and manpower to sustain over time. Overall, the crab migration at Bitan Weir continues to improve thanks to the new rope ladders. Yet, balancing ecological restoration and invasive species management remains a complex challenge.
