Darters

     Rocky-bottomed brooks and streams in Lancaster County, Pennsylvania, as in much of North America, are inhabited by various kinds of minnows and other types of fresh-water fish.  These fish have air bladders that help them hold positions with ease in the water above the stream bed.  There they feed on invertebrates that float in the water in mid-stream and on the surface. 
     But there is a species of small fish living year around on the stony bottoms of Lancaster County waterways that don't have air bladders and can rise from the bottom only with effort, with quick spurts, hence their common name.  These two-inch fish are called Johnny darters that specialize in getting invertebrate food among the pebbles on stream bottoms, the only kind of fish that does so exclusively.  There they are neighbors to crayfish, freshwater snails and clams, and several kinds of aquatic insect larvae.  In fact, these fish ingest some of the eggs and tiny young of those creatures. 
     Darters are streamlined to cope with strong currents, but generally lodge between pebbles to hide and not be swept away in the current.  Since the darters feed in a niche different from the one minnows get food in, competition for food and space is reduced between these different types of fish.  Therefore, they can all live in the same waterways with plenty of food for all.
     Attractive in their own plain way, darters are brown all over with dark markings, which camouflages them among the stones on the bottoms of the waterways.  Of course, they are almost impossible to see, until they move.  But with a bit of patience and time, one or more of these small, interesting fish can be spotted darting among stones on the bottom of a waterway.  And when one is spotted, more are sure to be seen zipping here and there among the rocks in search of food, or mates.
     Darters spawn their eggs on the gravelly bottoms of waterways.  The youngsters hatch and stay among the stones to search for tiny invertebrates or their eggs to eat.
     Though darters live between rocks on stream bottoms, they still fall prey to various predatory creatures when they are noticed dashing about in search of food.  Some of the predators that eat darters include larger fish, water snakes, belted kingfishers, a small variety of herons, mink and other critters.   
     Darters found a niche for themselves on the gravelly bottoms of running waterways.  There they hide, blending in with the colors of the stones.  But with patience and watching, one can see through their camouflage and spot some of them among the stones on the bottom of those streams.