Fish passes and ladders restore connectivity to rivers fragmented by dams and weirs. Their design and effectiveness directly determine welfare outcomes for migrating fish populations.
Fish ladder welfare encompasses both the welfare of individual fish attempting to migrate and the population-level welfare consequences of migration failure. Individual salmon and trout struggling repeatedly at impassable barriers experience physical exhaustion and injury, and the reproductive drive that brings them to rivers is ultimately frustrated. For the individual fish, a barrier that prevents spawning migration is a welfare failure at one of the most important moments of their life. At the population level, barriers that prevent sufficient upstream migration cause population collapse and genetic erosion. The welfare-positive intervention hierarchy is clear: remove unnecessary barriers where possible, and install the most effective, species-appropriate fish passes where barriers must remain. Public funding for fish pass installation on private land removes the economic barrier to connectivity restoration.