‘Johnny Darter’
Every spring Jenny Kruckenberg gets a permit from the Minnesota DNR for members of the aquarium society to collect darters in a couple of southern minnesota locations. These darters were collected from the Cannon River in Welch, MN, very close to where I now live.
Two of the darter species in the Cannon, E. nigrum and E. flabellare, usually spawn right after collection, probably prompted by the temperature change that results from moving from a chilly snowmelt river into an indoor tank. I’m told that E. flabellare (‘fantail darter’) eggs always fungus, but multiple people have had Johnny darter eggs hatch out.
The parent stayed close to the eggs and guarded them until hatching. As soon as the fry were free-swimming they ate baby brine shrimp and developed quickly. New fry are already benthic and darter-shaped, miniature versions of the parents.
As far as I can tell darters and gobies are essentially unrelated (they’re both ray-finned fish, and that’s it). The convergence is impressive, though — apart from the dorsal fin (or fins, in the case of gobies) they’re the same shape, swim in the same way, and have similar spawning behavior even down to the parental care of eggs. There must only be one good way to live in the rapids.