The Rivanna Rambler

October 23, 2008

 

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  This show originally aired on October 30, 2008 on “The Rivanna Rambler,” a weekly public affairs show airing every Thursday at 11:55 a.m. on WTJU 91.1 FM or wtju.net.

I do not have a lot of experience counting fish that are schooling, but as our canoe floated by the long olive green shapes in the clear water of the lower Rivanna, I couldn’t help but cry out, “There must be fifty of them!”

Well, as soon as I said it, I began to wonder if I was even close.  True, it was only Becky and me in our canoe paddling down the shallow sunlit water towards the Rivenna Mills sampling site in Fluvanna.  But the claim could not go unverified, so budding naturalists that we are, we turned around and cautiously paddled back upstream, hugging the bank as far away as possible from where we’d seen the fish  that were also swimming upstream.  Turning once again, we floated back down in the foot deep water, slow enough to count them as we drifted by.  Close enough to admire the broad flat tail fin, ridged and undulating, gently propelling the fish upstream.  Close enough to see the unmistakable body shaped like a cylinder, olive green and spotted with black from tail to head.  And close enough for the give –away that makes it possible for even a non-fishermen like me know for sure that the slender tapering snout must be the long nosed gar.  There’s nothing else like it in these waters save, perhaps, the American eel, and I know just enough about fish to know that these were no eels.

Sometimes called pike, sometimes gar-pike, these long-nosed gar, were proceeding by in a lazy upstream stroll, in groups of three and five.  The long-nosed gar is the only species of gar native to Virginia, and today they ranged from foot long adolescents to close to three feet long.  The gar is often called a living fossil, because its family has survived with little change since the time of the dinosaurs.  The Latin name, osseus, confirms its structure:  Genus name, Lepisosteus,  comes from Lepis, Greek for scale, and osteus meaning boney in Latin.  The species name, osseus, repeats the boney description for added measure, just like the fish, whose touch, over-lapping plate-like scales wrap it in a virtual coat of armor, leaving it few predators in the wild.

Locals nod knowingly when we tell them we have seen gar along this stretch of the Rivanna. Though they can make for a good fight on the end of the fishing line, they are commonly thought of as noxious predators, eating all the game fish around.  But they actually play a special role in the ecology of the river – true predators, they help balance the populations of other fish.  Armed with rows of razor-sharp teeth, they lie still and ready to ambush the unwary fish that swims close by with a quick thrash of the snout, and they prefer smaller fish and minnows.

The long-nosed gar has evolved to handle varying levels of oxygen in the water.  Typically, like other fish,  it breathes through gaseous exchange at its gills – but the gar also has a swim bladder connected to its esophagus that serves as an auxiliary breathing apparatus when oxygen levels in the water are low or not even present.  They are sometimes seen at the surface of the water, gulping the air.  Thus, they do well in slow moving streams and behind impoundments.  Though I have no way of measuring it, today I suspect that the low flowing Rivanna, absent the flush of any recent high waters, is also deficient in the life giving oxygen.

As it turned out, there were actually fifty-one long-nosed gar schooling in this stretch of the Rivanna.  Now, if one can describe crows as “a murder of,” or geese as “a gaggle of,” how do we talk about a convocation of fish?  I’ve heard of a shoal of bass and a hover of trout, and, given the ancestral ties and the strong prehistoric countenance, I guess I call what we saw an “exhibit of gar.”  Behind the glassy surface of the water, living in the world that they have inhabited for over 250 million years, who would have thought we’d have such a survivor in our watershed?