Lack of oxygen proves lethal for Top End’s fish

WITH the build-up season approaching, the chances of early significant rainfall across the Territory is a possibility

Most of the Top End's fish kills are natural low-oxygen events.

WITH the build-up season approaching, the chances of early significant rainfall across the Territory is a possibility.

Unfortunately, during this time of the year fish kills or mass fish deaths may occur, particularly in wetlands, waterholes and billabongs in the lowland river channels of the Top End.

Fish Kills can be caused by a few factors. The most common are environmental factors such as low dissolved oxygen levels, large algal blooms, salinity changes, increased temperature and acidity levels.

Other factors may include toxicants/pollutants and aquatic diseases.

Most of the fish kills in the Top End are natural low-oxygen events that result in fish gasping on the surface struggling to breathe and eventually dying.

Early storms in the build-up wash large amounts of organic matter and other soil materials into water bodies. As it rots most of the available dissolved oxygen is used with no oxygen left for the fish, and they unfortunately die.

The most common species reported and observed in fish kills are mullet, scats, archerfish, catfish, bony bream, barramundi, freshwater crustaceans and molluscs.

While most fish kills are natural occurrences, please report any as soon as they are witnessed so they can be investigated to determine the cause.

Take pictures if possible, record when and where you saw it, note GPS coordinates if possible and collect dying fish by placing into in a plastic bag and ice slurry.

You can report a fish kill to the Fishwatch Hotline on 1800 891 136, the NT Fishing Mate app or by contacting us at [e-mail]