Pipe fishways: Opportunities and challenges for effective fish passage

Instream barriers obstruct fish passage, threatening ecosystem dynamics in rivers and estuaries, and accelerating the global decline in aquatic biodiversity. The ecological repercussions of disrupted migration highlight the urgent need for effective fish passage solutions. Traditional open channel fishways often come with high costs, and their efficiency can vary across diverse fish species and flow conditions, underscoring the need for diverse solutions. We present the first comprehensive review of pipe fishways, categorised as closed-conduit systems with the primary purpose to transport fish across barriers in natural environments. We examine the mechanisms and performance of pipe fishway designs from around the globe, and then assess their strengths and limitations compared to open channel fishways. Pipe fishways are revealed to be an adaptable technology for fish passage due to a capacity for rapid and temporary deployment of trial models, potential cost-effectiveness, and flexible placement. However, as a newer technology, more research is needed to demonstrate both short- and long-term efficacy through transparent, peer-reviewed field studies. A continued interdisciplinary approach, blending hydraulic engineering and fish ecology, will be key for addressing these challenges and developing the promise of pipe fishways as an effective solution for fish passage.