Spawning Fathead Minnows

Plastic irrigation tubing (gut pipe or poly pipe) is often used as a spawning substrate by fathead minnow producers because used pipe is available for free. However, recent research (Masson et al. 2006) has confirmed that fathead minnow eggs do not stick well to smooth surfaces. While rough or textured surfaces retained 72 to 77 % of eggs, only 41% of eggs stuck to poly pipe. Eggs that do not stick in the nest are not likely to survive. Benoit and Carlson (1977) first found that fathead minnow eggs do not adhere well to smooth surfaces when they tested a variety of substrates including cement-asbestos tile, glass, stainless steel screen, and sand-coated, shot-peened and unaltered stainless steel. This is an important consideration for fathead minnow farmers who practice fry transfer and seek to maximize the number of young minnows produced in brood ponds. For those farmers that raise minnows in spawning-rearing ponds, it's likely that there will be sufficient reproduction even when smooth substrates are used.

Rough wood and unfinished fiberglass are two substrates that appear to provide decent egg adhesion. Recent studies at UAPB have been conducted using landscape fabric as a spawning substrate. Landscape fabrics are sold as barriers to prevent the growth of terrestrial weeds and are readily available. Such fabrics typically are woven or perforated, providing a roughened surface, and are UV stabilized. Based on preliminary testing, thin fabrics are unlikely to last in ponds and are easily torn. However, the heavier fabrics have held up well.

Fathead minnows are amazingly fecund and produce lots of eggs over time. Gale and Buynak (1982) found that over the spawning season, female fathead minnows spawned an average of every 3.9 days and produced a volume of eggs that was 3.8 to 6.8 times the volume of their own body! Clemment and Stone (2004) determined that one pound of fathead minnows (4 females: 1 male) would produce an average of 2,700 eggs per day. Production ranged from 8 - 28 eggs/female/day. A review of controls for various toxicity studies found that fathead minnow egg production in aquaria typically averaged between 10 and 66 eggs/female/day (typically 20 - 30 eggs/female/day). Unfortunately, current production systems, using spawning-rearing ponds and fry transfer, do not allow us to take full advantage of all these eggs.

Is there potential for a hatchery system for fathead minnows, similar to what currently exists for golden shiners and goldfish? There are several obstacles, the first of which is that fathead minnow nests are spread out over substrates, so that collecting eggs requires significant labor. An efficient egg collection system is essential. We know that eggs can be removed from substrates using a 1.5% sodium sulfite solution. Eggs can be left in the sulfite solution for up to 30 minutes without apparent harm, although the solution contains no oxygen. Unfortunately loose fathead minnow eggs, even when rolled in hatchery jars, appear exceedingly susceptible to fungus. A hatching system incorporating a fungus control protocol is required. The ultimate obstacle, however, may be the cost of such a system. Currently, production of farmraised fathead minnows has been constrained by the availability of cheap, wild-caught minnows. Furthermore, concerns over wild baitfish as potential carriers of exotic diseases or aquatic nuisance species will lead to new restrictions on harvesting minnows from the wild and could provide increased opportunities for producers of farm-raised fathead minnows.