Blacknose dace and Johnny darters are slim, 2-inch fish that live in various-sized waterways in the eastern United States, including southeastern Pennsylvania.

And, although these streamlined, minnow-like species are adaptable to an extent, they thrive best in clear, flowing brooks and smaller streams.

Dace and darters have characteristics in common because of the little running waterways they share. Each habitat on Earth causes its inhabitants to be similar (convergence) to be able to cope with conditions in that habitat, like fish and whales in the ocean being streamlined and having fins.

Dace and darters ingest a variety of invertebrates, the dace from the surface and midstream of the little waterways they live in and the darters on the stony bottoms of those same brooks and streams.

Obviously, competition for food between these species is lessened, to the benefit of both, which allows them to peacefully share waterways.

Being streamlined helps these small fish swim easily into waterway currents. They both thrive best in cold, running water, which is highly oxygenated. Both kinds spawn in June. And both are attractive and camouflaged above the stony bottoms of their waterways, which makes them nearly invisible to predators, including herons, kingfishers, mink, brook trout, and others.

Dace are brown on top and silvery below. A black stripe on each side of every dace from nose to tail disguises its shape, again making it hard for predators to spot these little fish.

Dace live in groups called schools in “holes” of deeper, slower water that is easier to swim in. Sometimes, the shadows of these fish on the pebbly bottoms of streams are more quickly noticed than the critters themselves. Those shadows give away their presence.

During June, male dace have orange-red fins and orange along each flank, indicating their readiness for spawning. Female dace become rounded with eggs.

This species spawns over gravel or mud in quiet, inch-deep water along the waterways’ shores. Each female produces 400 to 1,000 eggs. The tiny young school together in the shallows to avoid larger fish, and they feed on miniscule invertebrates.

Darters live singly between stones on waterways’ bottoms. They are resigned to bottom living and swimming in spurts because they don’t have an air bladder that would suspend them in mid-depth like most fish.

Darters are brown all over, with beautiful, darker markings that blend them into stream bottoms. They are almost impossible to spot when motionless among the stones.

Pairs of darters spawn over bottom gravel that protects the eggs and small young from predators. Each female spawns up to 300 eggs.

I’ve seen dace and darters many times over the years and have always been impressed with their grace and beauty in their lovely habitat. They are perfectly built for where they live, as all species of life are in their habitats.

There are no greater beauties and intrigues on Earth than forms of life well adapted to their various habitats.

 

Clyde McMillan-Gamber is a retired Lancaster County Parks naturalist.

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