February 24 – A Fish Story

Today’s Factismal: The American shad will swim nearly 12,000 miles in the ocean before returning to its river to spawn.

The American shad is an interesting fish, from its name ( Alosa sapidissima or “most delicious shad”) to its colors (bright silver and brown) to its life (born in a river, lives in the sea). But one of the more interesting things about this member of the herring family is that it shouldn’t be in a lot of places but is anyway, thanks to man.

The American Shad (Painting by Sherman F. Denton)

The American Shad (Painting by Sherman F. Denton)

The American shad begins its life as a fertilized egg, stuck to a rock in a river. After the egg hatches, the larva floats downstream and into an estuary where ocean water and river water mix. The baby fish spends about a year there, nibbling on insects and slowly growing large enough to dare the ocean. The inch-long juvenile fish then swims about in the ocean for about five years, growing up to nearly two feet long and weighing nearly five pounds. Then, one fine finny day, the fish’s thoughts turn to love and it swims all the way back to the river where it was born. The lady fish and the gentlemen fish do what comes naturally and then head back out to the ocean until spawning season comes around again and spurs them once more up the river of love. Interestingly, the American shad that live up North near New York are more likely to be repeat customers than those that live down near South Carolina. Those up North also spawn later in the year.

Because the American shad is such a hardy fish and because it is so tasty, it was only a matter of time before someone got the bright idea to introduce it onto the Pacific coast. And in 1871, that’s exactly what happened. American shad were released into the San Francisco bay, where they immediately moved in, grabbed the remote, and made themselves at home. They have now spread up and down the Pacific coast and can be found from Puget Sound down to San Diego. Ironically, there are now more American shad on the Pacific coast (8 million) than on the Atlantic coast (2 million).

Though this invasive species appears to be relatively benign, scientists are keeping tabs on it in an attempt to decide what (if anything) we should do about it. If you’d like to help, then please consider joining a program that watches for shad and other invasive species:

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