A large dominant male gilt darter in breeding colors
Late spring is breeding season for the majority of Virginia freshwater fishes; depending upon water temperatures, most darter species breed somewhere between early April to late May. Prior to (potential) spawning, male darters develop more intense coloration and exaggerated patterning than their normal appearance to outdo their male rivals in the hopes of attracting a female.
Male redline darter on display
Mature males will often spar with one another over territory or a single female, nipping at each others's fins and tails (see video below) often violently. Theoretically the dominant male wins out, but often the female pays either off them little notice and casually swims away as the males are still fighting.
Once a couple has paired off, they typically engage is some sort of courtship behavior that signals the beginning of actual mating. Many darter species show similar courtship and mating behaviors; for example the males of Genus Percina and many Etheostoma species as well swim alongside the female often weaving along her body from side to side, then when she settles into a good spot (presumably for laying eggs) he hovers over her and quivers his entire body so fast its a blur. Both videos below show this behavior from two species of each respective Genus.
Two gilt darters mate while a stoneroller watches and then rudely interupts
Two greenside darters mate and then also get rudely interrupted by a stoneroller
As seen in both video, these behaviors - at least in our stream exhibit - also trigger a feeding response in the other fishes looking for an easy meal of freshly lain eggs...or they are just excited by the activity. In either our exhibit or in the wild, successfully fertilized eggs face very long odds to reach maturity, but that's the reason these spawning events are so critical. They must find the right mate with good genes, create enough fertilized eggs to account for all the natural mortality, and spawn at a time when their young will have maximum food available as they grow. Because after their little spawning dance, mom and dad have done all they are ever going to do for their offspring.