Juvenile Chinook salmon. Credit: Rodger Tabor/USFWS |
I was talking with Ray Jones, a biologist from the Idaho
Fisheries Resource Office this morning about our upcoming Spring Chinook Salmon
release and the conversation took a very interesting turn towards the process
of smolting. When an anadromous fish smolts it goes through a series of physiological,
morphological and behavioral changes that readies its body for the transition from
freshwater to saltwater habitats. The most noticeable change we see in smolting
fish is body coloration. Pre-smolts, or parr show distinct pigment spots or
bars. Smolting fish show a distinct silvering of their scales and underlying
skin. This silvering is caused by the synthesis of guaine and hypoxanthine, two
purines that are the result of protein catabolism (the breakdown of complex
molecules into simpler ones). If you
think about the habitat a salmon smolt is transitioning to you can realize the
importance of this adaptation. A slivery colored fish will blend into a pelagic
(open ocean) environment much better than a brownish fish with spots and bars.
Chinook salmon smolt are silver in color and lose their parr marks. Credit: Dr. Billy Conner/USFWS |
There is a lot going on inside the fish too. There are a
host of hormonal and cellular transformations that allow the fish to survive in
salt water. These changes are very complex and are only seen in anadromous
fish. It is amazing to know that these animals make the transformation from
freshwater fish to saltwater fish and then one to four years later do the reverse!
Schooling Chinook and Coho smolts. Credit: USFWS courtesy of Yakama Nation Fisheries |
So next time you see our friend the salmon, whether it be at
the Hatchery, in the grocery store, or on the end of your fishing line,
remember the journey these amazing fish undergo for their survival, and to
benefit of all the animals (and people) that depend on them!
By Angela Feldmann
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