Tropical rivers in Northern Australian are largely pristine, however they are facing threats from developments that require water extraction or damming.  It is crucial then, to understand the importance of river connectivity to productivity and biodiversity. Macrobrachium spinipes is thought to be amphidromous, plays a critical role in riverine food webs and is culturally significant to Indigenous and non-Indigenous people. There are however, considerable gaps in our knowledge of its life history. This project collected adults and larvae over two years from the Daly River, Northern Territory and conducted a series of laboratory experiments to determine patterns of reproduction, abundance and migratory behaviour.  We found that reproduction occurred across a 400 km length of the river and that females were not moving downstream to the estuary to breed. Larvae were produced in high numbers throughout the river and required saltwater to develop. Larvae have only 5-7 days to reach saltwater, making flow a critical determinant in successful recruitment.  This study confirms the amphidromous life history of M. spinipes and highlights the importance of natural flows for maintaining existing populations.