Ecosystem ecology - Original Paper


, Volume 168, Issue 3, pp 829-838

First online:

Fish mediate high food web connectivity in the lower reaches of a tropical floodplain river

  • Timothy D. JardineAffiliated withAustralian Rivers Institute, Griffith University Email author 
  • , Bradley J. PuseyAffiliated withAustralian Rivers Institute, Griffith University
  • , Stephen K. HamiltonAffiliated withKellogg Biological Station and Department of Zoology, Michigan State University
  • , Neil E. PettitAffiliated withCente of Excellence in Natural Resource Management, University of Western Australia
  • , Peter M. DaviesAffiliated withCente of Excellence in Natural Resource Management, University of Western Australia
  • , Michael M. DouglasAffiliated withCharles Darwin University
  • , Vivian SinnamonAffiliated withKowanyama Aboriginal Land and Natural Resource Management Office
  • , Ian A. HallidayAffiliated withQueensland Department of Employment, Economic Development and Innovation
  • , Stuart E. BunnAffiliated withAustralian Rivers Institute, Griffith University

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High levels of hydrological connectivity during seasonal flooding provide significant opportunities for movements of fish between rivers and their floodplains, estuaries and the sea, possibly mediating food web subsidies among habitats. To determine the degree of utilisation of food sources from different habitats in a tropical river with a short floodplain inundation duration (~2 months), stable isotope ratios in fishes and their available food were measured from three habitats (inundated floodplain, dry season freshwater, coastal marine) in the lower reaches of the Mitchell River, Queensland (Australia). Floodplain food sources constituted the majority of the diet of large-bodied fishes (barramundi Lates calcarifer, catfish Neoarius graeffei) captured on the floodplain in the wet season and for gonadal tissues of a common herbivorous fish (gizzard shad Nematalosa come), the latter suggesting that critical reproductive phases are fuelled by floodplain production. Floodplain food sources also subsidised barramundi from the recreational fishery in adjacent coastal and estuarine areas, and the broader fish community from a freshwater lagoon. These findings highlight the importance of the floodplain in supporting the production of large fishes in spite of the episodic nature and relatively short duration of inundation compared to large river floodplains of humid tropical regions. They also illustrate the high degree of food web connectivity mediated by mobile fish in this system in the absence of human modification, and point to the potential consequences of water resource development that may reduce or eliminate hydrological connectivity between the river and its floodplain.


Stable sulfur isotopes Flood pulse Liver Gonad Income breeding