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Tessellated Darters in the Connecticut River

hand holding a tessellated darter fish

You may have never heard of this little cutie, but the Tessellated Darter (Etheostoma olmstedi) is a pretty neat fish. It’s found in many river systems that drain to the Atlantic Ocean, from the St. Lawrence all the way to Florida. This includes our beloved upper Connecticut River watershed, where it is a native fish that spends its whole life in the river and tributaries.


Tessellated Darters are in the same family as perch, but only get about three inches long at their largest. Snack-sized for larger fish like bass and eel, birds, and even turtles.


tessellated darter fish on a ruler for scale
Photo courtesy of Matt Carpenter, NH Fish and Game

 

Like their name implies, Tessellated Darters have a repeating pattern of spots which if you squint just right some say look like the letters W or M. Another distinguishing physical feature is a vertical black line running through the eye to the corner of the mouth, paired with another bar running from the eye forward to the tip of the nose. This coloration pattern likely helps them to be better camouflaged on the substrate, as they are benthic (bottom-dwelling) fish that prefer slower moving areas of water with muddy to sandy substrates with some small cobble.


They eat benthic invertebrates and dietary studies have reported a preference for midge larvae, with caddisfly larvae becoming a more important food component in the fall. They move in rapid short spurts (ahem… darting!) when they are not sitting on the substrate.

 

Some of these characteristics change temporarily during the spring breeding season. The male darter darkens in color and they seek out rockier areas. Eggs are laid on the underside of smooth rocks or submerged wood that has been cleaned by a male fish. The females may lay eggs in many nests and the males hang around to guard the nest full of fertilized eggs, one fish per nest, defending the eggs and keeping them clean until they hatch.


Interestingly, Tessellated Darters have been reported to exhibit alloparental behavior, where the males tend to nests that are full of eggs fertilized by another male.

 

illustration of tessellated darter fish
Illustration by Ellen Edmonson, 1927 via Wikimedia Commons

And if I haven’t convinced you yet that these fish are pretty cool, remember back to when I wrote about mussels? And how interesting their life cycle is? Well… the Tessellated Darter is one of the host species for the endangered Dwarf Wedge Mussel, transporting the glochidia around in their gills. Which is why even though larger game fish and the (rightfully) celebrated migratory species get a lot of the spotlight, CRC also pays attention to what’s happening with these smaller species that have an equally important role to play in supporting a healthy ecosystem. They get considered when we are planning restoration projects, advocating for water quality improvements and habitat protection, or commenting on the effects of hydro operations or wetlands permits.


So next time you see what looks like a “boring” minnow on the bottom of the river, just think… it might be a Tessellated Darter, guarding a nest or dispersing a mussel glochidia, and show it some appreciation.

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