Preliminary studies of artificial spawning of channel catfish as male-female pairs or all-female groups in recirculating systems

Channel catfish Ictalurus punctatus are commonly spawned for research purposes by pairing of a hormonally treated female with a male in flow-through aquaria. A technique that allows hormonal induction of ovulation in females without pairing would accelerate genetic improvement and production of hybrid catfish. Over a 3-yr period (1994, 1995, and 1996) we conducted a series of trials to demonstrate the potential for artificial spawning in recirculating systems, and in 1996 we included trials with grouped females in addition to male-female pairs. Females were induced to spawn with injection of synthetic leuteinizing hormone-releasing hormone, and those that ovulated were stripped and the eggs were artificially fertilized. During 1994 and 1995, all fish were spawned by pairing, and in 1996, half of the females were spawned by pairing and half were grouped in tanks without males. Spawning success (percent of females that produced eggs), latency (time between injection and ovulation), and percent fertilization were observed for the paired and grouped trials. Spawning success was 36% in 1394 (N = 36), 22% in 1995 (N = 54), 41% in 1996 (N = 27), and 58% for grouped females (N = 26). The latency period was 113 +/- 69 h in 1994, 109 +/- 57 h in 1995, 44 +/- 8 h in 1996, and 50 +/- 9 h for grouped females. Percent fertilization was 16 +/- 26% for eggs stripped in 1994, 72 +/- 25% in 1995, 43 +/- 20% in 1996, and 16 +/- 37% for grouped females. In 1995, water quality problems were associated with high mortality of females (24 of 44 females; 4 of 44 males). The metabolic demands of final oocyte maturation in combination with methemoglobinemia caused by high nitrite levels could account for the increased vulnerability of females. These trials indicate that with adequate biofiltration, artificial spawning is possible in recirculating systems and with females grouped rather than paired. Further research on hormone dosage and timing of egg stripping will increase the utility of grouped spawning of channel catfish.