Comparison of Manual Stripping and Pen Spawning for Production of Channel Catfish × Blue Catfish Hybrids and Aquarium Spawning of Channel Catfish

Abstract

We compare manual stripping to pen spawning for production of hybrids of female channel catfish Ictalurus punctatus × male blue catfish I. furcatus, as well as to aquarium spawning of channel catfish. The ovulation rate for manually stripped females (91%) was not significantly different from that of females spawned in aquaria with channel catfish males (67%; P > 0.05); however, ovulation rate of manually stripped females during week 10 (80%) was superior to that of females spawned in pens (15%; P < 0.05) with blue catfish males. Female channel catfish spawned in aquaria with male channel catfish produced more (P < 0.05) eggs per kilogram body weight (6,607) than manually stripped females (4,587). Pen spawning of female channel catfish and male blue catfish also produced significantly more (P < 0.05) eggs per kilogram (7,950) than hand-stripping females (3,448) during week 10. Hatching rate (21%) and fry per kilogram (1,065) of female body weight were higher (P < 0.05) for channel catfish spawned with channel catfish in aquaria than for channel catfish manually stripped and fertilized with blue catfish sperm (8% and 325 fry/kg). This difference in means was a result of spawning technique because we have previously demonstrated that blue catfish and channel catfish sperm fertilize channel catfish eggs at equivalent rates. Hatching rate (66%) was also higher (P < 0.05) for pen-spawned hybrid embryos than for hybrid embryos produced by manual stripping and artificial fertilization (21%). However, fry per kilogram of female body weight was not different (P > 0.05) for manual stripping and pen spawning (851 and 821, respectively). The results from both experiments indicate that the quantity and quality of eggs and embryos obtained by manual stripping and artificial fertilization are inferior to eggs and embryos produced naturally but with hormone injections. Artificial fertilization procedures need to be improved. Hybrid fry produced per kilogram of female body weight for manual stripping and pen spawning were almost identical because of the low hatch rate for manually stripped eggs and the low spawning rate for pen spawning. Therefore, neither technique is better for commercial production of channel catfish × blue catfish embryos; improved hatching rates for manual stripping or higher ovulation rates for pen spawning would enhance production.