Scientists Discover Origins of Chinook Salmons By Tracking Bone in the Inner Ear

Researchers have developed a technique that makes it possible to trace the birthplace of Chinook salmon and learn about where the fish originated and where they spent their lives in the ocean.

A chemical signature recorded on the ear bones of the salmon. This bone is called  an otolith, and it accumulates layers as a fish grows, similar to trees. These "growth rings" are produced throughout a salmon's life.

Scientists can tell where the fish lived by matching the chemical signatures of the otolith with the chemical signatures of the water in which they swim, according to a study published May 15 in the online, open-access journal Science Advances.

"Using this method, we can trace where the salmon were born and where they moved while they were growing in the rivers and streams," said University of Utah geochemist Diego Fernandez, co-author of a study published this week. "This could be useful for protecting fish and understanding how many salmon we can take from nature."

"Each fish has this little recorder, and we can reveal the whole life history of the fish from the perspective of the otolith" lead researcher of the study, Sean Brennan says. "Each growth ring is a direct reflection of the environment the fish was swimming in at the time it was formed."

"This particular element and its isotopes are very strongly related to geography" coauthor, Matthew Wooller says. "It is a really good marker for where animals have been and whether they move around in their environment."

"Alaska is a mosaic of geologic heterogeneity. As long as you can look at a geologic map and see rocks that are really different, that's a good potential area."