Carbon dating for tree rings has been a well developed tool to study the age of a tree, but just recently scientists found that this same technique can be used to figure out where salmon go and what they have been eating when they travel out to sea to feed.
The University of Southampton researchers Dr Kirsteen MacKenzie and Dr Clive Trueman shows that the chemistry of fish scales will unlock the mystery of what the British salmon are eating. All British salmon do not migrate from their home rivers and end up in the same feeding grounds. Different salmon may respond differently to environmental change. Know one knows just yet.
Research shows that fish carry natural records of feeding location hidden in the chemistry of their scales.
The chemistry of animal tissues reflects the composition of food and water in the area where they live and feed, and can act as a natural tag. Using this idea, the Southampton team, working with scientists from the Centre for Environment, Fisheries and Aquaculture Science (Cefas), the Game and Wildlife Conservation Trust (GWCT) and the National Oceanography Centre (NOC), looked at the isotopes of carbon contained in historical records of scales of Atlantic salmon.
The scales grew while the salmon were feeding at sea, so the carbon isotope values of the scales reflect the values of their diet in the feeding grounds. The team compared the scale values through time with satellite records of sea surface temperature across the North Atlantic. The locations of sea where the time series match best are most likely to be the areas where the fish have been feeding.
“As every single salmon contains the natural chemical tag, we can now see where fish from individual rivers go to feed in the Atlantic,” lead author Dr Kirsteen MacKenzie said.
This may be the first step into unlocking the mystery of why the salmon population has been in a steady decline for years. It could help us conserve the species.
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