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 ovulat ion in females without pairing would accelerate genetic improvement an d production of hybrid catfish. Over a 3-yr period (1994, 1995, and 19 96) we conducted a series of trials to demonstrate the potential for a rtificial spawning in recirculating systems, and in 1996 we included t rials with grouped females in addition to male-female pairs. Females w ere 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 spaw ned by pairing, and in 1996, half of the females were spawned by pairi ng and half were grouped in tanks without males. Spawning success (per cent of females that produced eggs), latency (time between injection a nd 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 fert ilization was 16 +/- 26% for eggs stripped in 1994, 72 +/- 25% in 1995 , 43 +/- 20% in 1996, and 16 +/- 37% for grouped females. In 1995, wat er 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 nitrit e levels could account for the increased vulnerability of females. The se trials indicate that with adequate biofiltration, artificial spawni ng is possible in recirculating systems and with females grouped rathe r than paired. Further research on hormone dosage and timing of egg st ripping will increase the utility of grouped spawning of channel catfi sh.