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Effects of multiple handstrippings of channel catfish (Ictalurus punctatus) females induced to ovulate with carp pituitary extract on production of channel catfish female x blue catfish (I. furcatus) male hybrid fry

ABSTRACT Channel catfish (Ictalurus punctatus) females were injected with carp pituitary extract (CPE) and were multiple handstripped three times to harvest eggs. Eggs were fertilized with sperm from blue catfish (I. furcatus) to produce channel-blue hybrid (CB hybrid) embryos and fry. A higher number of females yielded eggs (P < .05) during the first stripping attempt (90.3 ± 1.1% [mean ± SE]) than during the second (67.6 ± 2.1%) and third attempts (7.6 ± 0.5%). Significant differences also were observed for the number of eggs/kg stripped between the first (5,471 ± 225) and second (2,598 ± 97) and the first and third (1,302 ± 46) strippings. Percent fertilization (71.5 ± 2.7 %) was higher (P < .05) for the first stripping than the second and third strippings, but the second stripping (58.2 ± 1.8%) was not different from the third (51.7 ± 1.6%). The hatching percent of embryos did not vary among the three times strippings. The fry/kg female body weight produced was higher (P < .05) for the first (1,399 ± 112) than the second (471 ± 26) and third strippings (28 ± 2). It is productive to strip the females a second time, as fry production can be increased by 33.7% by waiting 5 h and harvesting the additional eggs ready at that time. The time and effort for a third stripping is not worthwhile because of the low percentage of females releasing eggs at that time and the low fry output.