Influence of Photoperiodic Levels on Skin Melatonization in Heteroclarias Fingerlings in Relation to Water Physico-Chemical Properties in Minna, Nigeria

Abstract

An 8-week experiment was carried out to investigate the effects of photoperiodic levels on skin color of laboratory reared Heteroclarias fingerlings. Artificial lightning was used to simulate a range of photoperiod namely, continuous light period (24L: 0D), total darkness (24D: 0L), 12 hours of darkness and 12 hours of light (12D: 12L) and normal day and night period (control, i.e. ambient photoperiod). Adequately replicated representative number of Heteroclarias fingerlings were exposed to the various photoperiods and monitored for eight weeks. Results of physical observation of the fishes, following recommended fish skin color grading revealed that fingerlings reared in 24D: 0L had the darkest skin color, while those exposed to 24L: 0D had the lightest skin color. In addition, the fingerlings exposed to normal day and night period (control) had a light skin color while those exposed to 12L: 12D had a dark skin color. The physico-chemical parameters such as water temperature, pH, ammonia, biological oxygen demand and dissolved oxygen concentration were within the recommended range for fish culture and also indicated no significant differences(p>0.05) in all the treatments throughout the experimental period irrespective of photoperiodic condition. It is hoped that the findings of this study will guide commercial fish farmers in raising Heteroclarias fish according to the preferences of market demand with respect to skin color.