Over the last century, rivers in Australia have become increasingly disconnected, through urbanisation and the construction of barriers such as dams and weirs. A major consequence is the impeded passage for native fish needing to migrate for crucial life history processes, such as spawning. Coastal rivers in Victoria are home to numerous migratory fish species, however the rivers in which they inhabit have different levels of connectivity for movement due to human influence. Some have no barriers at all, some have seemingly impassable barriers, while others have engineered solutions built to aid fish movement. Increased permeability and therefore, fish movement, is largely considered very positive for native fish, however there may be some unintended and unknown consequences of reducing permeability. For example, fish might require a particular level of boldness or exploratory ability to successfully pass through obstacles or fishways, resulting in only bolder individuals being able to move. Therefore, it is possible that structures within rivers may be imposing artificial selection on populations, benefiting only individuals with bold or exploratory phenotypes. We assessed whether river permeability plays a role in structuring the behavioural traits in fish populations in coastal streams in Victoria and tested whether there could be consequences for other important traits such as somatic growth rates.