Globally, fishways are increasingly gaining a reputation for failing to meet conservation goals in certain circumstances. This can be explained by the continuing dominance of diadromous species from the Northern Hemisphere (e.g.Salmonidae) in the science and management of fish passage internationally. Most species have very different life histories, swimming abilities and spatial ecologies to the iconic species of the North, meaning that most fishways do not work well for most fish. This is an especially severe problem in the Global South, where fishways designed for salmonids may exacerbate already serious issues with invasions. Most fish do not undertake long migrations between critical habitats clearly separated in space, yet individual movement and gene flow is critical to the long-term viability of their populations. We review recent, important advances in spatial ecology for dendritic river networks. In doing so, we aim to better define what it means to achieve effective fish passage. By combining critical habitat assessment with metapopulation modelling, undertaking analysis of climate change-driven habitat shifts, estimating adequate gene flow, we recommend a new framework for fishway target-setting and monitoring which is suitable for a wide range of species, including salmonids. We encourage the scientific and management community to take up and develop this framework.