The importance of floodplains for fish in Kakadu

4 December 2012

Floodplain environments produce a lot of food and nutrients for animals living in rivers.

During the wet season, all fish can move out onto the floodplain, but it is likely that the use and importance of the floodplain to their growth and reproduction differs between species.

There has been very little scientific research on the movements of fish in the Northern Territory. We don’t know whether fish that use the floodplain more grow faster than those in the main channel.

Researchers from the Northern Australia Hub would like to talk to Traditional Owners and fishers about which sites they should sample, and whether they would like to be involved in sampling and radiotracking field trips.

There are two components to the project:

Fish movements between the main channel and the floodplain

This project will use radio tracking to monitor the movements of barramundi, forktailed catfish and mullet between the main channel and floodplain throughout 2013.

Fish will be collected from the South Alligator River using an electric charge from a boat or a backpack which momentarily stuns the fish (electrofishing). Up to 30 of each species collected will have radio transmitters surgically implanted. The fish are then released and ‘tracked’ on a regular basis using boats and helicopter surveys.

Fish body condition

This project will examine fish body condition by measuring the length, weight and fat content of fish in different habitats at key periods throughout the year (during the wet, runoff, early and late dry periods).

The fish will be caught from about five wetland sites and five river sites in the South Alligator River region, possibly near Cooinda, using electrofishing, dip netting, and cast nets.

On every field trip, 30 of each species will be measured for length and weight. Tissue samples will be taken from larger fish for fat content analysis before they are released, while 30 of the smaller fish will be collected and taken back to the laboratory for processing.

Target species include barramundi, forktailed catfish, mullet, eel‐tailed catfish, bony bream, rainbowfish and archerfish.

Read more about the project here.

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