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Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/8/2014 Publication Date: 10/8/2014 Citation: Chatakondi, N.G. 2014. Suspending mammalian LHRHa-injected channel catfish, Ictalurus punctatus in individual nylon-mesh bag reduces stress and improves reproductive performance. Journal of the World Aquaculture Society. 45(5):604-612. Interpretive Summary: Hybrid catfish fry embryos are produced fertilizing stripped eggs of hormone-induced channel catfish females with blue catfish sperm. Communally held mature channel catfish are handled repeatedly and are subject to maternal stress, which affect the quantity and quality of the progeny produced in the hatchery. There are no known ways of predicting ovulation of hormone-induced channel catfish other than periodic handling of expectant ovulating females. This research compared the stress response and reproductive performance of suspending post-hormone injected broodfish in individual soft-mesh bags and communally held in tank during latency. Suspending broodfish in soft-mesh bags facilitates periodical observation of ovulating females without subjecting broodfish to repeated handling at latency. . Suspending post-hormone injected broodfish in individual soft-mesh bags facilitated identification of ovulating females and also reduced stress levels (cortisol concentration) to improve the reproductive output (improved hatch and fry produced per kg BW) compared to the fish held communally in tank. This simple technique of holding post-hormone injected fish in soft-mesh bags appears to improve egg quality of stripped eggs, increase the hatching success of hybrid catfish eggs and an increase of hybrid catfish fry produced per kg of body weight compared to communal holding of broodfish in tank, subject to repeated handling. Three commercial hatcheries adopted this method of holding hormone-injected broodfish during latency. Currently (2013) six of the eight commercial hybrid catfish hatcheries have adopted this method and appears to have increased hybrid catfish fry production by 10 – 15% apart from improved utilization of their labor, hatchery space and resources. Technical Abstract: Hormone induced spawning of channel catfish held communally in tanks is a reliable method to produce channel catfish, Ictalurus punctatus ' x blue catfish, I. furcatus ' F1 hybrid catfish fry. However, mature catfish are crowded, and repeatedly handled during the process of induced ovulation. Repeated handling of gravid females is stressful and may impair ovulation, egg quality, and reproductive performance. Three trials were conducted to evaluate the effects of two methods of confining post-hormone injected female channel catfish on stress response (cortisol concentrations) and reproductive performance: fish were either held individually while suspended in soft, nylon-mesh bags or communally in a concrete tank. Percent of females ovulated to hormone treatment, relative fecundity, percent egg viability, and latency of channel catfish did not differ for fish in the two treatments. However, percent hatch and fry/Kg of females was higher (P < 0.05) for fish held in bags that for fish held communally in tanks. Mean plasma cortisol response immediately prior to the first hormone injection (0 h) did not differ among fish groups in the two treatments. However, mean plasma cortisol concentrations were significantly lower (P < 0.05) for fish in the bag treatment at 16 and 36h compared to fish held communally in tanks. Plasma estradiol levels (measure of oocyte maturation) were assessed at 0, 16, and 36 h post hormone injection and did not differ for fish in the two treatments (P > 0.05). Suspending hormone-injected broodfish individually in soft bags reduced stress response, improved egg hatching rate, and increased hybrid fry produced per kg weight of female broodfish. Using this simple technology, farmers can improve the efficiency of hatcheries producing hybrid catfish fry. |
