The river darter relies on frictional contact with the substratum to maintain its position while minimizing its energy usage. The river darter's enlarged pectoral fins help create negative lift and increase the friction between its body and the ground to counteract turbidity. As current speed increases, the river darter, like many lotic fishes, increases its frictional contact with the river bottom by releasing gasses from its swim bladder, which increases its density and keeps it near the river bottom.
