Tuesday, November 30, 2010


In honor of the thanksgiving holiday I was thinking of writing about wild turkeys. I looked into it and frankly couldn't find a single surprising or interesting thing about them. They're fantastic and beautiful birds, don't get me wrong. I love seeing them around, and you can in most parts of New England. But they're big birds that eat mostly plants. And they are dumb. So ecologically and behaviorally they're just not so fascinating. The one area I did not check is phylogeny. So I guess I challenge my readers, if you're still out there, to prove me wrong. What's interesting about turkeys?

So I thought of another food animal that's just plain weird: the Atlantic Salmon. Salmon are weird partly because they are anadromous, that is they spend some of their lives in fresh water and some in the ocean. But the really weird thing about the Atlantic salmon is that it goes through up to seven life stages. They all start out as alevin, little larval fish living in the gravel in streams or rivers where they were born. The yolk sac of the egg still attached, they live in relative safety. Not needing to feed they are able to hide from predators all the time.

As the energy store of their yolk sac deminishes they must seek outside sources of nutrients and they change into fry, a common word for larval or young fishes. Fry develop quickly into parr and develop the camouflaging vertical stripes necessary for survival in the gravely rivers where they will spend the next few years of their lives. After several years of dwelling in fresh water they undergo yet another change: their bodies become silver and internal chemistry changes to deal with life in salt water. This process is my new favorite vocabulary word: smoltification, as this next life stage is known as the smolt.

They will then spend two to three years in the ocean as smolts. Those who survive will metamorphose yet again into adults, the males growing a distinctive hook on their lower jaw known as a kype. This hook is involved in mate choice just as many bird species have crests or brightly colored feathers. The full grown adults will return to the riverbeds and spawn. Most of their lives end here, but once in a while an adult salmon returns to the ocean again where it is called a black salmon or a kelt. Usually they will live another two to three years, spawn again and then end their lives in the riverbeds where they were born.

And you thought transforming once from a caterpillar to a butterfly was impressive. Well it is. But check out these crazy fish!


Massachusetts Division of Fisheries and Wildlife: http://www.mass.gov/dfwele/dfw/fisheries/anadromous/salmon_life_cycle.htm

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