A new study published in the journal Science Advances says that isotope tracking could be a new way that helps saving salmon, which is threatened by climate change, overfishing and industrial development. According to scientists salmons have “ear bones”, a strontium chemical signature which could reveal essential habitats for the fish.
The strontium chemical signature in the salmons’ ear bones allows scientists to identify particular streams where the fish hatched and lived before being caught at sea. The new tool developed by researchers may help with the discovery of critical habitats for salmon. Co-author of the study geochemist Diego Fernandez of the University of Utah said:
“Using this method, we can trace where the salmon were born and where they moved while they were growing in the rivers and streams. This could be useful for protecting fish and understanding how many salmon we can take from nature.”
Over a long period of time researchers have tried to find out the exact place where Alaska’s Chinook salmon has hatched. Although the process is known and the migratory patterns are mapped so far scientists were not able to determine the story of its origins. Using “otolith”, the chemical marker which accumulates in the salmon’s inner ear bone, scientists now have hope that they can determine the waters from which any Chinook salmon came before emerging in Alaska’s Bristol Bay.
Researcher from Alaska Fairbanks, the U.S. Geological Survey, Universities of Utah and University of Washington examined strontium isotope ratios in otoliths in the case of 255 Chinook salmon. The analysis helped identifying where the fish hatched and lived in seven sets of two to five streams of Nushagak River (third largest river of Alaska).
Sean Brennan, the lead-author of the study, explained that each fish has a small recorder and the researchers can determine the life history of the salmon by analyzing the otolith. Every growth ring represents a direct proof of the environment the fish was living in at the time when it was formed.
Besides finding the fish’s spawning grounds this process also helped scientists discover which fish are the most fit and which population within the species is most prosperous.
Co-author of the study Christian Zimmerman of the U.S. Geological Survey said that this approach will help mapping salmon productivity and establish how the number of salmon is influenced by freshwater habitats. Since Chinook salmon has declined in Western Alaska such information could guide conservation.
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