Shark scientists looking to better understand the diet and eating habits of some of the ocean’s rarest or best protected species have realised the answers eluding them may have been staring them in the face this whole time – in the jaws kept in museums and private collections.

Teeth from shark and rays are routinely used by researchers to study the diet of a species, providing valuable insight into the foraging habits of a keystone species within the marine ecosystem. One of the biggest challenges in shark science, however, is collecting samples from rare and critically endangered species.

In a groundbreaking development for the science, researchers from Flinders University in South Australia have now found that the jaws of shark and rays kept in museums and private collections can serve as an ‘untapped resource’ for teeth with the potential to provide valuable scientific insight.

The technique here is called ‘stable isotope analysis’; a biochemical approach that examines the isotopes within a shark’s tooth. Published this month in the scientific journal, Marine Environmental Research, findings indicate that chemicals used to preserve shark jaws do not actually affect these isotopes; meaning these preserved jaws can be used to reveal not only what these sharks ate, but where they ate it.

“The chemicals in teeth provide a story of what the shark has eaten and from where, whether that be sea lions in South Australia, or tuna in New South Wales,” said the paper’s lead author, Laura Holmes from the Southern Shark Ecology Group in the College of Science and Engineering at Flinders University.

Working with the Isotope Ratio Mass Spectrometry Laboratory in the University of Tasmania, the researchers examined cownose rays, gummy sharks, and broadnose sevengill sharks; three species with different tooth structures.

Despite the different tooth structures across the three species, none were altered by the ethanol, bleach, or hydrogen peroxide used to clean the jaws and whiten the teeth in the preservation process.

“Most shark jaws in museums and private collections are chemically treated, so understanding if – or how – these treatments affect tooth isotopes is crucial,” said Flinders University research associate, Dr Lauren Meyer.

“Finding that preservation chemicals had no impact on isotope values opens the door for the use of jaws from historic collections across Australia and globally.”

This study contributes valuable insights to the field of stable isotope analysis in shark and ray teeth, offering practical recommendations and expanding the range of available samples for investigation.

“This is especially useful for rare or threatened species, for which standard tissue samples may not be readily available, but for which trophy jaws have been collected, such as white sharks, tiger sharks, and makos” continued Dr Meyer.

“Now we can begin to use museum collections and jaws from the 1970s and 1980s to explore the historic diet of shark species that now face a myriad of anthropogenic pressures.”

Researchers are hopeful that insights from this study may now also open pathways for investigations into the diets of other animals like orca, sperm whales, and fur seals – species for which teeth from historic jaws are available in museum collections.

“This study opens the door to use a tremendous resource of samples to untangle the current and historic diet and foraging habitats of complex predators – making the most exciting finding from this study the capacity for new research that is now possible,” said Dr Meyer.

The research paper – titled  ‘Isotope values from preserved elasmobranch jaws: Implications for ecological studies from existing collections’, written by Laura Holmes, Charlie Huveneers, Vincent Raoult, Thomas Clarke, Christain Dietz and Lauren Meyer – has been published in Marine Environmental Research.

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