Captive Care Notes: Silvery Minnows (Hybognathus, Family Cyprinidae)
Few fishkeepers seek Hybognathus for their aquaria. Usually they're just bycatch, that unidentified silvery minnow that makes it into the collecting bucket simply because it turns up in nearly every seine haul. Maybe it'll color up in the aquarium after the stress of capture has worn off. Except that Hybognathus never color up. They remain plain, which is not to say that a small school of them, under proper lighting that picks up the shimmering glint in their scales, makes for a plain exhibit. As with other dull, silvery, schooling fishes, Hybognathus are best maintained as a group in a large community tank. They'll hang together, forming a moving, living, aesthetically pleasing contrast to more charismatic solitary fishes. Brassy Minnow (H. hankinsoni) are easily alarmed in captivity, forming pods under vegetation after swimming eratically or a minute or two. Despite some skittishness, captive Hybognathus are hardy and accept just about any aquarium fare that's small enough to be swallowed.
Plains Minnow (H. placitus) and Rio Grande Silvery Minnow (H. amarus) have been spawned in laboratory aquaria by researchers studying their reproductive biology. Specimens were collected from the wild, injected with carp pituitary extract to induce spawning, and maintained in greenhouse aquaria with natural sunlight. (All attempts to spawn the minnows without the horome were unsuccessful.) The temperature was 27C (80.6F). A tubular air-diffuser across the width of the aquaria provided oxygen and current. Males pursued a single female, nudging her abdominal region. When the female was ready, the male wrapped around it. Eggs and milt were expelled at the same time. Some individuals spawned several times, with at least 10-minute intervals between each event. Both males and females ate their own eggs.
Eastern Silvery Minnow (H. regius) are easily cultured in shallow earthen ponds. Raney (1942) describes raising several thousands minnows in a 0.15-acre pond ranging from four inches to four feet in depth. The pond was fertilized three times during the summer with cottonseed meal, and fresh-cut timothy was scattered along the pond's shallow borders several times. The bottom was silt and lacked vegetation except for filamentous algae later in the summer. The fish were not fed. Spawning occurred in late April and early May. A stocked total of 68 males and 14 females produced 6,650 young 4-7 cm (1.5-2.75 in) in length by the end of September.