Thumbing through the West Australian catalogue of fish ear bones is a bit like looking at the abstract shapes in a modern art gallery.
"They're essentially sculptures and works of art," the state's chief fisheries scientist, Dan Gaughan, says.
"Each species of fish [ear bones] is unique in some way from every other fish, some are similar, but each one is slightly different."
More practically, these ear bones — called otoliths — can help detect seafood fraud, manage fish stocks and give an insight into environmental conditions from the years past or even the present.
After more than three decades of collecting fish ear bones for stock assessments, the Department of Primary Industries and Regional Development has over 350,000 otoliths in a library.
Generally, WA fisheries scientists target the species favoured by anglers and commercial boats in their work to manage stocks.
But they have incidentally managed to gather samples from 267 species from Shark Bay to Esperance.
Seeing the fish from the trees
Fisheries management first used scales to help determine the age of fish populations.
The scales grew yearly with new "rings" which could be counted up like the ones in a tree.
But Dr Gaughan said scales were found to be unreliable with many species so scientists turned to otoliths, which also added new bands annually.
"Determining the health state of populations of fish, we need to know that they've got a good spread of ages through the populations," he said.
"So young fish, medium age and old fish."
The ear bones could also be found in the bellies of other fish and birds, since they are the last thing to be digested, helping expand dietary studies into other animals.
Their unique shapes allow scientists to identify a species without seeing the rest of the fish.
Otoliths — which are made from calcium carbonate, making them more like rock than bone — are used for hearing, balance and perceiving acceleration.
"With each fish having its own behaviours ... the otoliths have just evolved over time to be as efficient as they can," Dr Gaughan said.
"And because of this, you see quite a variety of different shapes, some you might ... say they look like a grain of rice or a bit of a blob and others are quite fantastic internal sculptures."
Otoliths abroad
Great leaps in otolith research are being made around the world every year and many of the people behind them come together to share knowledge at semi-regular symposiums held since 1993.
Professor Bronwyn Gillanders, from the University of Adelaide, will be one of the keynote speakers at the next symposium in October and said they were amazing events to attend.
"You get a group of people that are really keen on otoliths," she said.
"Whether it's from a fisheries application point of view or a more ecological application point of view or talking about some of the latest innovations in otoliths."
Professor Gillanders has looked at the composition of otoliths by using the Melbourne synchrotron to study trace elements.
The synchrotron produces powerful beams of light that are used to examine the molecular and atomic details of different materials.
She has also helped with archaeological studies using Aboriginal middens.
"Analysing things like manganese and other trace elements, you can pick up hypoxic water events, you can pick up whether fish are migratory or resident from within the same population," Professor Gillanders said.
"The other one that we've more recently been looking at is samples collected from different markets and then looking at fish provenance ... and seeing whether they're really from where people claim that they're from so you can detect fraud."
