American Eel

Posted by Al Agnew on December 25th, 2014
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When I was a kid, I spent a lot of time fishing for catfish at night on Big River. We all lived around the upper river, where the catfishing wasn’t all that good except for bullheads; we were happy if we caught one or two channel cats or flatheads in a night. When we got just a little older, and some of us could drive, we started fishing a little farther downstream, in the area north of Bonne Terre, where the catfishing was better.

I don’t remember who first hooked an eel, but when whoever it was brought in the writhing, 3 foot critter, we were amazed. None of us had ever seen an eel before, though we immediately knew what it was. We soon found that a couple of the pools in that section of river held eels and we sometimes caught several in one night the next couple of years, until we all got too grown up and stopped catfishing at night for other things. I’ve never caught an eel since, and for a long time I had no idea of the incredible life history or those strange fish.

Eels are native to most of the Ozark streams, or they once were. The biggest reason that they are gone from many of the rivers of the Ozarks is because they are catadromous–which means that they migrate from freshwater to saltwater to spawn, just the opposite of anadromous salmon, who migrate from salt to fresh to spawn. The dams on many Ozark streams blocked the subadults from making it above the lakes, and the adults from getting downstream past them.

Yes, those eels we caught all those years ago on Big River would one day migrate down nearly 100 miles of that river, another 30 miles or so of the Meramec into the Mississippi, and all the way down the Mississippi to the Gulf of Mexico. And they wouldn’t stop there, because ALL eels, or at least all the eels that have ever been studied both in North America and in Europe, spawn in ONE place in the Atlantic Ocean, the Sargasso Sea, a huge gyre or eddy, 700 by 2000 miles in size, located northeast of Cuba and extending to nearly the mid-point of the Atlantic. The Sargasso is named for the abundant seaweed of the genus Sargassum that is found in this great gyre, and is also known for its depth and exceptionally clear blue water. It was first discovered by Columbus, whose sailors were afraid that the ships would be entangled in the beds of seaweed, and it roughly corresponds to the infamous Bermuda Triangle. But the life cycle of the eels that begin life there is almost as amazing as any of the stories of the Bermuda Triangle, and has the added benefit of being true!

Those eels we caught on Big River began life by hatching from eggs less than 1/16th of an inch within the seaweed mats of the Sargasso Sea. The hatchlings were a larval form called a leptocephalus that did not resemble the adult eels, being transparent, leaf-shaped, with a small, pointed head and large teeth. They would drift with the Atlantic currents for 7 to 12 months, by which time they would reach coastal waters. At that point they would be 2 to 2.5 inches long, and would begin to transform into the next stage of their life cycle, called “glass eels”, with body shapes resembling the adult form, but still transparent. They would gradually move on toward estuaries and rivers, gradually growing and attaining color. At some point, they would become “yellow eels”, with yellowish sides and creamy bellies, and it would be at this point that they would differentiate in sex; in other words, up until this point they wouldn’t “know” whether they were males or females. It is believed by researchers that differentiation depends upon the numbers of eels in the area–more eels makes more of them turn into males. By the time they became males or females, they would be about 10 inches long. At this point, they are all still in estuaries or near the mouths of streams running into the ocean, and the males will stay there throughout the rest of their growing up, but the females will begin migrating on up the rivers, some of them all the way to near the sources of the streams. Which means, of course, that all those eels we caught on Big River were females.

The males never grow more than 18 inches, but females can grow in freshwater up to 52 inches. They spend anywhere from 5 to 20 years in freshwater, feeding upon fish, crayfish, and other aquatic critters all that time.

And then, at some point, they stop feeding altogether, and begin heading back to the Sargasso Sea to spawn and die, making that immensely long trip through freshwater and saltwater, back to their nursery. The females lay from a half million to 8 million eggs each, the males fertilize them, and another life cycle begins.

There is one other theory about eels that I find very interesting. Plate tectonics may have played a large part in their amazing life cycle. As mentioned above, both European and American eels spawn in the Sargasso Sea only, and the European eels must travel even further, halfway across the Atlantic. Plate tectonics tells us that Europe and North America were once all the same continent, split apart at the formation of the Atlantic, and have been spreading further apart ever since. The theory is that these eels evolved as a single species at about the time the continents first split, and at that point, they were spawning in the warm, narrow sea between the two continents. As the continents continued to drift further and further from each other, the eels’ migration to their spawning grounds become longer and longer. But they were hard-wired to spawn in the middle of that widening sea, and so they continued to make the ever-longer migration to spawn and die in the calm waters of what eventually became the Sargasso Sea, out in he middle of the vast Atlantic.

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