Fish Ear Bones Provide Clues about Climate Impact

Otoliths or fish ear bones consist of three pairs of small carbonate bodies found in the heads of bony fishes. Generally otoliths are used by the fishes for maintaining balance and sound detection. They not only function similar to the inner ear of mammals but also give a good and helpful insight into age, growth rate, life history and taxonomy.

In bony fishes these otoliths have more to offer, an understanding of climate change.

"Otoliths can form the basis of new techniques for modelling fish growth, productivity and distribution in future environments," said Dr John Morrongiello of Commonwealth Scientific and Industrial Research Organisation's Wealth from Oceans Flagship, lead author of the study.

"They are widely used to support fishery stock assessments and are beginning to be used to measure and predict ecological responses to ocean warming and climate change.

"Any change identified in growth and age maturity, especially of commercially-important species, clearly has implications for forecasting future stock states and the sustainable management of fisheries," said Dr Ron Thresher, CSIRO Marine and Atmospheric Research

"Millions of otoliths are archived in research laboratories and museums worldwide, and many fish species live for decades and some, such as orange roughly, live for up to 150 years.

"Their otoliths record variations in growth rates that reflect environmental conditions. Longer-lived fish and older samples take us back as far as the 1800s."

This paper was co-authored by Dr Ron Thresher and Dr David Smith of CSIRO. It builds on earlier research by Dr Thresher that worked on understanding environmental change by using fish 'hard parts' such as otoliths and deep ocean corals.

Their finding presents a summary with the help of which the Australian research institutions can analyze hard parts and assess past and future impacts on a range of species.

The next task will be to study selected species of commercial interest, including tiger flathead, black bream, blue gropers, barramundi and tropical snappers. This will be done by the scientists at CSIRO, the Australian Institute of Marine Science and the University of Adelaide.

"We will use otoliths to investigate the environmental drivers of fish growth for many species around Australia," Dr Morrongiello said.

"This will allow us to generate a continental-scale evaluation of climate change impacts on Australia's fishes and help to guide the conservation and management of our aquatic environments into the future."

According to Dr Thresher, there has already been widespread use of hard part records from corals to reflect on climate variability, such as El Nino events and to reconstruct environmental histories.

"Any change identified in growth and age maturity, especially of commercially-important species, clearly has implications for forecasting future stock states and the sustainable management of fisheries," Dr Thresher said.

"A better ability to predict such change will greatly enhance our ability to forecast, manage and adapt to the impacts of climate change in marine and freshwater systems."

This paper is published online Nov. 28 in Nature Climate Change.