Effects of temperature on the induced spawning of channel catfish and the production of channel × blue catfish hybrid fry

Hybrid catfish (channel catfish, Ictalurus punctatus, female × blue catfish, I. furcatus, male) can be obtained by induced spawning and artificial fertilization but with variable results. Temperature of the surrounding environment affects the rates of physiological processes in fish including time to ovulation following hormone injection and time post-ovulation when quality eggs can be obtained. Brood females were held at 24, 26, and 28 °C in 100 L aquaria and injected with LH-RHa at 20 μg/kg followed 12 h later with 100 μg/kg. Fish were monitored hourly recording the time of the first egg deposit. Some females were manually stripped soon after the first eggs were observed, and the remaining females were stripped 4-6 h after the first eggs were observed. Eggs were artificially fertilized with blue catfish sperm and incubated. The percent of females that ovulated were 52.9%, 82.4% and 95.5% at 24, 26, and 28 °C (P = 0.001) respectively. The majority of females that ovulated did so between 58 to 64 h at 24 °C, 48 to 52 h at 26 °C and 24 to 40 h at 28 °C for a degree hour response time of 1405 ± 117, 1141 ± 238 and 951 ± 261 respectively (P < 0.001). Differences in eggs/kg female, eggs/g of eggs, percent viable eggs, percent hatch and survival of sac fry to swimup resulted in an average of 384.4 ± 316.97 fry/kg female at 24 °C, 370 ± 219.2/kg at 26 °C and 1284 ± 1394.1/kg at 28 °C (P = 0.136). Egg quality varied with how soon eggs were stripped after the first egg was observed. For fish held at 26 and 28 °C. the combined effects of egg quality and fry survival resulted in an average 1081 ± 1483.9 fry/kg female for fish stripped within 2 h after the first eggs were released and 500 fry/kg female when stripped after 4 or more hours once the first eggs were released.