The life-history characteristics and behaviour of a species can be affected by their environment; and understanding these relationships is necessary to effectively inform management. Squalus acanthias is a common and abundant shark species in the temperate shelf waters of the world. It is locally abundant in Macquarie Harbour, a large embayment in western Tasmania. During the past decade, declines in dissolved oxygen and benthic conditions have occurred in Macquarie Harbour, associated in part to impacts of large-scale marine farming, raising serious concerns about the environmental health of the system. In this study we examined several aspects of the spatial ecology, reproduction, diet, growth and demographics of this S. acanthias population. Several traits were distinct from what is typical of the species elsewhere. Namely that the population appears demographically isolated and range restricted to the harbour, their diet is heavily reliant on spillover feed from aquaculture, and their reproductive output appears to be severely compromised. These findings are significant, as they highlight the important and complex ecological role of the species in the ecosystem, but also suggest that under current conditions they are unlikely to thrive and will have a severely limited ability to cope with further external pressures.