Did you know Atlantic salmon are big travelers? They are born in the rivers of New England and meet salmon from around the world in Greenland. They can make this trip several times in their life. We know this because scientists at the National Oceanic and Atmospheric Administration (NOAA) studied the trips that these salmon do. They do not ask them directly or take their passport to check the stamps. Ruth Haas-Castro, a scientist at NOAA knows how to ask salmon in a more scientific way.
She and her team go to different places between Maine and Greenland and chase salmon using an electric taser. While they are immobilized, scientists take a small sample from a fleshy part, the adipose fin and scales from their body. It doesn’t hurt or change much the life of the salmon, because it is like taking a tiny piece of the lobe of your ear and a few hairs from your head. From the little piece of fin, DNA is purified to make genetic analysis and Ruth herself looks the scales very closely under the microscope.
It happens that when salmon are going down the river on their way to Greenland, they are going to find the ocean. Going from fresh water to salt water is a shock that changes their entire physiology and maybe even the way they think about things. This event shows on their outside too, making the scales a bit different to the eye. This is not a momentary change or a color change. It is an additional layer on the scales that leaves behind a piece of history on their bodies. Ruth can count the layers on the scales when she looks them under the microscope.
The more trips the Atlantic salmon makes from home to Greenland and back, the more history it collects on its body. Trouble is, Atlantic salmon are not arriving in Greenland anymore in the numbers that they used to. At first, I thought they changed their vacation destination, but Ruth clarified my doubts. The reality is that the salmon population is shrinking and not many of them make it all the way to Greenland. NOAA teams have studied them for years, because salmon lifestyle is sustainable only if humans keep their lifestyle in check.
The life and travel of the Atlantic salmon are tightly linked to the health of the planet and their environment. Global warming has made the rivers of the southern part of New England too warm and salmon is not seen there anymore. The modification of New England rivers by modern infrastructure blocks the salmon’s way to their place of birth, where they need to go back to have babies. We have made the life of the salmon so hard that they are in a list of endangered animals at the moment.
NOAA keeps monitoring the number of salmon and the trips they make by checking on the marks in their scales hoping they survive for 5-8 years and make 3-5 trips in their life as it is naturally expected. The more marks the scales have, the older the salmon are, and the better possibilities we have for the salmon to be rescued from possible extinction and maybe to help our own future.
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