This paper argues that it was environmental knowledge, which Aboriginal people held and traded, that formed the basis of the slender chances they had for survival in the changed circumstances of British settlement in Sydney. The case study is centred on the life and work of William Rowley, about whom the little evidence which exists revolves around his use of and trade in his knowledge of the resources of Botany Bay, notably oysters and mangroves. Reference is also made to Biddy Giles, who used her knowledge to act as guide and cultural interpreter but also traded in native flowers. Rowley's life is less well known but focused on the capture of and trade in food resources. This included his employment by Thomas Holt in the series of attempts to establish oyster culture on the shore of land purchased originally as for pastoral enterprise.