Wednesday, October 27, 2010

October 27: The Miracle of Fishes

You know how people say when it's raining, "Nice weather... if you're a duck!"? I was thinking tonight as  I drove over the Ducktrap River in a torrential downpour that it's also nice weather if you're a spawning salmon. Late fall is when Atlantic salmon--the few indigenous fish that remain--return to their natal rivers to spawn. The Ducktrap River is running high now with all this rain, so returning adult fish can more easily make their way upriver over all those shoals and stones to find the optimal gravel beds in which to make their nests or redds.

As I made my way along rain-slick Route One, I thought about this, and began to wonder how the salmon know which river to come back to. I remember reading something once about salmon being guided by their sense of smell. Maybe they simply swim along the shoreline until they smell home. Or is it a sense of taste? Nothing tastes quite like the waters of the home river. If any creature could sense that, it would be a salmon, a creature of both fresh and salt water.

According to Stephen D. McCormick of the Conte Anadromous Fish Research Center, Atlantic salmon may find their way from the feeding grounds in the North Atlantic, where they've been maturing for several years, to the right area of coastline using a magnetic or solar compass. But no one knows for sure--it's one of those mysteries of science.

Another mystery: why do Pacific salmon species die after spawning but not Atlantic salmon? Apparently the word for the type of fish that survive spawning is "iteroparous," although spawning takes such a toll on a fish's body that even Atlantic salmon don't always make it back to the sea afterward.

Rain fills the river,
spillway for spawning salmon
smelling their way home.

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