Publication (Media): Ears Have it When it Comes to Cold Water

Publication Type:	Media Release
Publication Name:	Ears Have it When it Comes to Cold Water

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Peterson, Kylie (2002) Ears Have it When it Comes to Cold Water - Mar 01 2002, CRCFE, Canberra - Media Release.

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1 March 2002 FOR IMMEDIATE USE

Ears Have it When it Comes to Cold Water

Kylie Peterson, a University of Canberra PhD student, is making some interesting discoveries about the lives of baby fish in the Murrumbidgee River.

To reveal how old the fish larvae are and how quickly they are growing, Kylie uses otoliths, the ear bones of fish.

Kylie explains, “Otoliths are tiny, some are only the size of a grain of sand and hardly visible to the naked eye, yet they can tell you the life history of a fish. They can tell you when a fish was spawned, when it hatched, its age and how fast it’s growing.”

“Under the microscope, otoliths look like a series of concentric rings, much like the growth rings in trees. The width of the rings reflects the growth rate. If the rings are far apart, the fish is growing quickly; if the rings are close together, the fish is growing slowly.”

Kylie is using otoliths to see how coldwater releases from dams are affecting fish in the Murrumbidgee River (below Burrinjuck Dam). Cold water released from the bottom of dams for irrigation or consumption can be 10 oC colder than it would be naturally in that part of the river.

Kylie says, “Coldwater releases stunt the fish’s growth within 1-2 days in some fish species. In these fish, the otolith rings suddenly get closer together, showing that the fish’s growth has dropped sharply. These larvae lose condition quickly and may die as a result.”

These findings have direct relevance for dam operations and management. Ideally, we should be looking at changing dams to avoid coldwater releases, especially at egg laying (spawning) time for some fish species. Avoiding coldwater releases after spawning is equally important to ensure the survival of the newly hatched larvae into juveniles.

Kylie is completing her PhD at the CRC for Freshwater Ecology based at the University of Canberra.

Vision and interviews available

Digital still images of Kylie in the field, Murray cod, and Otoliths are available. For interviews and media assistance, please call Lynne Sealie on 02 6201 5168; email: lsealie@enterprise.canberra.edu.au

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