Surprising but true: fish have ear bones, also called otoliths, which they use for hearing and balance. We humans have similar structures inside our inner ears that help us to sense gravity and motion.

Because otoliths grow incrementally throughout a fish’s lifetime and are influenced by factors such as water temperature and salinity, scientists use them to study the environmental history of fish populations. This information is important for ensuring the sustainable management of commercial fish stocks as well as the survival of threatened fish species.

Naturally-occurring strontium is a key part of otolith analysis because its abundance varies from location to location and it’s easy to detect.

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