Scientists Save Chinook Salmon From Extinction

Scientists have found a way to track and study Chinook salmon from Alaska’s Bristol Bay region due to a chemical signature recorded on their ear bones.

By using atom tracking isotopes and examining so called “growth rings” within the ear bones, researchers are able to collect answers to questions such as where the endangered Chinook salmon are born and how they spend their first year of life.

This in turn will provide experts with the needed data to recreate the environment and protect the species from going extinct.

The discovery was made by researchers at the University of American state Fairbanks, who looked at specimens captured from Alaska’s Bristol Bay region way back in 2011 and noticed a chemical signature on the Chinook salmon’s ear bones (also knows as “otolith”).

The researchers found that the otolith grows layers all throughout a fish’s life and that these growth rings persist throughout a fish’s life as well. They store valuable information, informing scientists where a specimen has lived by comparing the chemical signatures of its otolith to those of the water in which it swims, or used to swim in.

The chemical signatures itself originates from isotopes of strontium, commonly found in bedrock. When rushing water bursts through the rocks, strontium is dissolved and released into the water. It then gets picked up by the Chinook salmon and its ions are deposited onto the otolith. When a fish is caught, scientists can compared its signature to a river system that has been mapped extensively for its strontium isotope variation.

The signatures do not disappear overtime, or when the fish moves into new waters, but rather pile on top of each other in neat, clean layers.

Sean Brennan, lead author and postdoctoral researcher at the University of Washington’s School of Aquatic and Fishery Sciences, gave an excited statement saying that “Each fish has this little recorder, and we can reveal the whole life history of the fish from the perspective of the otolith. Each growth ring is a direct reflection of the environment the fish was swimming in at the time it was formed”.

The information is so precise that scientists were even able to determine a set of streams where the fish hatched and grew before migrating downstream into the ocean. The Chinook salmon that scientists examined for the study had been born in the Nushagak watershed and stayed there for about a year before migrating downstream into the ocean.

Co-author Matthew Wooller, director of the Alaska Stable Isotope Facility at University of Alaska Fairbanks, explained that this particular element and its isotopes are very strongly related to geography and it serves as a really good marker for where these animals have been and whether they move around in their environment.

The data collected from the otolith is believed to be crucial in understanding the declining in the Chinook salmon’s population (due to climate change, industrial development and overfishing), what kind on environment is favorable to their survival and reproduction, and what kind on environment is harmful to them.

Roughly 200.000 Chinook salmon migrate every summer from the ocean into the Nushagak River’s upper tributaries and streams to spawn. When their eggs hatch in the spring, young Chinook salmons spend the first year of their life in the river, feeding and growing. It’s after that that they migrate to the Bering Sea and the Pacific Ocean.

Christian Zimmerman, an ecologist at the U.S. Geological Survey and the co-author of the study, believes that mapping salmon productivity and determining how freshwater habitats influence the ultimate number of salmon is science responding to a societal issue and need.

Alaska’s Bristol Bay region is one of the last remaining ones in the world where wild salmon can be found running free.

Image Source: fishandgame.org.nz