Tracking Lamprey to find their spawning grounds

Lamprey are an eel-like fish that spend most of their adult life at sea, moving into rivers and migrating upstream when it’s time to spawn.

Lamprey numbers in the Murray-Darling Basin have declined due to barriers to migration and reduced river flows. When there is no flow through the Murray barrages during winter and early spring, they can’t swim in from the ocean and up the river.

Fishways installed at the barrages and the locks and weirs along the River Murray have provided lamprey, and other migratory fish, with a continuous path from the sea to Hume Dam or from the sea to Menindee Lakes.

But we don’t know where lamprey go to spawn. When we do, we can work out how to manage river flows to support lamprey breeding.

The South Australian Research and Development Institute, supported by the MDBA and Basin governments, is using the PIT (Passive Integrated Transponder) receiver system installed on each fishway to track lamprey movements.

This work is showing that lamprey move hundreds of kilometres upstream. The PIT system, however, can only tell us which fishways lamprey have passed through, it cannot tell us if lamprey have swum up a tributary or into an anabranch.

Acoustic transmitters and listening stations are now being used to provide a better picture of where these mysterious creatures go.

During July and August, pouched lamprey (Geotria australis) have been trapped at the barrages, acoustic tags have been attached and the lampreys released.

A network of receivers will record the signal of each tag and scientists will analyse the data to determine where lamprey may be heading to.

The network of receivers is also helping scientists understand fish movement in other regions of the river. A number of tagged fish from other studies have been detected in the Murray and Darling rivers, having moved hundreds of kilometres away from where they were being studied.

Flows to support lamprey are included in the 2017 environmental watering priorities prepared by the MDBA. For further information on basin-wide environmental watering priorities, visit:

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