Effect of simulated rainfall on gonadal maturation and ripeness in female catfish (Clarias anguillaris, Linnaeus, 1758) in the semi-arid region of Nigeria
Rainfall and flooding which are major factors in the breeding of catfish in the North Central zone of Nigeria (Semi-arid) were mimicked all-year-round so as to determine if the duration of breeding and hence fingerling production could be extended longer than the usual 5 -6 months period per year. Four different environmental situations i.e. - shaded outdoor concrete tanks with showers; unshaded outdoor concrete tanks with showers, unshaded outdoor concrete tanks without showers and shaded outdoor concrete tanks without showers, were simulated as treatments with a view to controlling rainfall/flooding and thus the gonadal development of the catfish Clarias anguillaris. Spent but healthy brooders of C. anguillaris Linnaeus (mean body wt: 445 15g) were selected and stocked in the various treatment tanks at 10 fish per tank and fed formulated catfish feed of 35% c.p. at 3% of their body weights per day. The feed was divided into two equal rations and fed in the morning (09.00-10.00 h) and evening (16.00-17.00 h). Rainfall and flooding were mimicked for 90 minutes twice every week for 12 months by flooding and draw-dawn and the brooders were sampled fortnightly for survival, growth, and gonadal maturation. At the end of the 12 month experimental period, no fish mortality was experienced. All the brooders in Treatments 1-3 got ripe within the period but ripeness was sustained for 9 months in the outdoor tanks with roof and showers (Treatment 1, no rain but only shower) while the outdoor tanks without roof and showers (no rain, control) sustained fish ripeness for only 6 months. The outdoor tanks without roof but with showers (Treatment 11) sustained ripeness for 7 months while the outdoor tanks without shower but with roof had less than 50% ripeness for only 3 months. For a prolonged duration of gonadal maturation and ripeness and hence high fry/fingerling production in catfish, Clarias gariepinus outdoor concrete tanks systems with showering to mimic rainfall and flooding should be adopted.
Key words: Rainfall, gonadal maturation, Clarias anguillaris, catfish, Semi-arid region.