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Golden perch ear bones have a story to tell

about 2 years ago

Golden perch, Drawing by Marjorie Crosby-Fairall.Golden perch travel thousands of kilometres across the Murray-Darling Basin (MDB) during a lifetime and their ear bones can tell us where they were born and where they’ve been.

Understanding their movements can help us manage flows to better support healthy populations of golden perch, one of the most popular recreational species in the Basin.

Otoliths are a bony structure within the ear of fish. Because they are made up of daily deposits, like tree growth rings, they can help us understand how old a fish is.

Water flowing in different rivers has a specific chemical signature and these chemicals are absorbed into the otolith’s structure. As a fish moves, the chemical signature of the otolith also changes.

Otoliths of golden perch are telling us a very interesting story thanks to the work of the South Australian Research Development Institute (SARDI), funded by different government agencies including by MDBA.

Changing chemical signatures in golden perch otoliths show that:

  • eggs and larval golden perch drift hundreds of kilometres downstream, hopefully washing into nursery habitats

  • when flows are right, young fish swim upstream or downstream for hundreds or thousands of kilometres over months to years

  • once young fish become adults, they may migrate upstream to lay eggs and start the cycle again.

Just prior to the end of the Millennium drought high flows in the Darling River led to a major golden perch recruitment event in the lower Darling region. Subsequent flooding across the whole basin the following year triggered young golden perch to disperse in many directions.

Fish with lower Darling origins have been found in the mid-Murray River, the Goulburn River, the Edward-Wakool, and the lower Murray, including the Lower Lakes

A similar, large-scale breeding event has occurred in the Darling River in 2016-17 (keep an eye out for an upcoming story about this).

The 2017-18 environmental watering priorities look to capitalise on these large-scale events by providing dispersal flows in the major rivers and tributaries of the southern MDB.

For further reading on the golden perch otolith research, visit:

http://www.finterest.com.au/natives-and-introduced/fish-detectives-investigating-the-secret-life-of-golden-perch/

For further information on basin-wide environmental watering priorities, visit:

https://www.mdba.gov.au/managing-water/environmental-water/priorities/native-fish


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