AbstractTropical rivers in northern Australia are largely unregulated with intact hydrological connectivity, however, the region is likely to face future developments that will threaten this connectivity. It is important then, to understand the role of river connectivity to productivity and biodiversity to help decision makers maintain the ecological values of these rivers. This study investigated the role of hydrological connectivity in the life history of the newly described species, Macrobrachium spinipes. This research used a combination of multi-year field sampling and laboratory experiments to determine patterns of reproduction, abundance, early life history characteristics (including larval distribution, salinity requirements, transport to the estuary, and juvenile upstream migration) and habitat use of M. spinipes in the Daly River in northern Australia.
This research found that reproduction occurred and larvae were produced in high numbers across a 400 km length of the river. To develop, the larvae require salt water within 5-7 days of hatching. This is achieved by drifting to the estuary, making flow a critical determinant in successful recruitment. Once larvae develop to post-larval juveniles, they migrate upstream throughout the wet season but primarily once the hydrograph is receding to base flow. This migration consisted of approximately 18 million individual shrimp and transported approximately 100 kg of carbon and 28 kg of nitrogen upstream. There was no evidence of marine carbon in migrating individuals. As juveniles, their habitat use was strongly associated with well-structured bank environments early in the dry season. By the mid dry season, they switched to using sand habitats recently colonised with macrophytes and filamentous algae.
This thesis confirms the amphidromous life history of M. spinipes, identifies a novel life history strategy that enables larvae to survive long drift times and advances our understanding of amphidromy in large tropical rivers. These findings will provide crucial information for the development of environmental flow requirements in northern Australia.
|Date of Award||Jun 2015|
|Supervisor||Michael Douglas (Supervisor), Erica Garcia (Supervisor) & Bradley Pusey (Supervisor)|