Tracking ‘Larry the Lamprey’ shows positive signs for river recovery

Lamprey are an ancient native fish that migrate between the Southern Ocean and the River Murray to complete their lifecycle.

A cross-government initiative ‘Where in the MDB is Larry the Lamprey?’ was undertaken recently to help understand more about lamprey migration.

And the results are showing the importance of river flow for these unique species.

Coorong, Lower Lakes and Murray Mouth Program Leader Adrienne Rumbelow said

record numbers of lamprey were tracked migrating from the Southern Ocean to the River Murray in 2020 in search of fresh waters to breed.

“The high numbers of lamprey captured in 2020 highlights the importance of water for the environment in supporting their migration,” she said.

“You need winter flows that are allowed to travel from source to sea, you need fishways at locks and weirs and you need connectivity. If you don’t get these things right you won’t get migration and spawning.

“The fact that we are seeing increasing numbers via our monitoring shows that we have been getting the flow conditions in the river right for these species.

Adrienne explained that two species of lamprey were captured – the pouched lamprey and the short-headed lamprey – and were tagged with PIT (passive integrated transponder) tags which are then scanned as they move through fishways on upstream weirs on the River Murray.

“This helps us learn more about their movement and solve the mystery of where they spawn, as well as help inform how the river is managed to better support these fish,” she said.

Adrienne said water for the environment has been a crucial factor in improving this connectivity, and is largely responsible for driving this increase in lamprey numbers in the Murray-Darling Basin.

“These fantastic migration results would not have been possible without the provision of water for the environment secured under the Basin Plan,” she said.

“The ocean and the Murray must stay connected for lamprey to enter the freshwater system and complete their lifecycle.

“During the Millennium drought, there were no freshwater flows to the ocean from the River Murray at the Lower Murray barrages for almost three years and no connectivity between salt and fresh environments.

“As a result, scientists were alarmed by a lack of winter lamprey migration, and there were grave concerns for the future of the species in the Murray-Darling Basin.

“The Larry project has been a great example of cross-government agencies working together to get conditions right for native fish, with teams involved from the South Australian Research and Development Institute, the CSIRO, the Commonwealth Environmental Water Office and the Living Murray Program, coordinated by the Murray Darling Basin Authority.”

Key results from the research project include:

• 91 pouched lamprey and four short-headed lamprey were trapped and had PIT tags implanted at the Lower Murray barrages near Goolwa.
• 21% of tagged pouched lamprey and 25% of tagged short-headed lamprey reached at least Lock 1 at Blanchetown.
• The longest recorded distance travelled by a pouched lamprey was to Lock 11 (more than 878 km), and for a short-headed lamprey to Lock 2 (more than 362 km).
• September 2020 was the busiest month for lamprey migration with the most fishway detections.
• The fastest lamprey was clocked travelling between Locks 3 and 4 with an average speed of approximately 55 kilometres per day (and as they only travel at night time, this equates to approximately four and a half kilometres an hour).
• The slowest lamprey was clocked at only seven kilometres per day, between the barrages and Lock 1.