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The paper aims to study the best immersion period and concentration of the plant extracts under study (water-leaf and Aloe vera gel) that can efficiently remove egg adhesiveness of Clarias gariepinus. Data generated were subjected to Multivariate Analysis of Variance Test, Tukey multiple range tests was used as a follow up procedure. Third order Polynomial regression analysis was then used to determine the best concentration and immersion period that neutralizes adhesiveness in eggs of C. gariepinus. The experiment was carried out at The Teaching and Research Fish Farm, Federal University of Technology, Akure, between October 2018 to December 2018. One male and one female C. gariepinus brood stock weighing 1.0 kg and 1.3 kg, respectively were used for the experiment. Three different concentrations (1, 3, and 5)% of the plant extracts were used. 2 g of urea diluted in 4 g NaCl/L of water was used as reference de-adhesion agent, while water without urea solution nor plant extracts was used as control. The fish eggs were rinsed with the solutions at different durations of 1, 3 and 5 minutes. Each concentration and rinsing time was recorded in duplicates. Results of the study showed that there were no significant differences (p=0.05) in the non-adhesive egg hatching of eggs immersed in Aloe vera gel and Urea solution. Number of non-adhesive egg and hatching increased in waterleaf extract which was significantly different (P=0.05) from eggs immersed in Aloe vera gel and water but not significantly different from urea solution. Therefore this study shows that waterleaf extract at 1% concentration and 1 minute immersion period can efficiently remove egg adhesiveness and increase hatching in C. gariepinus.

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The best immersion period and concentration of bitter leaf plant extract that can efficiently remove egg adhesiveness of Clarias gariepinus was assessed. One male and a female C. gariepinus broodstock weighing 1.3kg and 1.4kg respectively were used for the breeding. Three different concentrations comprising (0.5, 1 and 1.5) % of bitter leaf extract were tested. Tannic acid of 0.75g diluted into one liter of water was used as reference de-adhesion agent while water without solution or extract was used as control. The fish eggs were rinsed with the solutions at different durations of 30, 60, and 90 seconds. Each concentration and rinsing time were recorded in triplicates. Data generated were subjected to Analysis of Variance test, Tukey multiple range tests was used as a follow up procedure. Third order polynomial regression analysis was used to determine the best concentration and immersion period that neutralizes adhesiveness in eggs of C. gariepinus. The result of the study showed that there were no significant differences (p = 0.05) in the non-adhesive egg, percentage hatchability of eggs immersed in bitter leaf plant extract and tannic acid solution. The use of bitter leaf extract at the lowest concentration of 0.5% and 30 seconds immersion period showed great de-adhension efficiency which gave highest percentage fertility, non- adhesive eggs and percentage hatchability of 97.40%, 95.07% and 90.09% respectively.

This study assessed the effects of microalga Phaeodactylum tricornutum supplement on the gustation, stomach histology, growth performance and nutrient utilization of Clarias gariepinus juveniles. One hundred and fifty (150) C. gariepinus juveniles of mean weight 20.05±0.05g were distributed into 15 plastic tanks (40×30×35) cm3. Five graded levels (0.00 (control), 0.50, 1.00, 1.50, and 2.00g/100g of P. tricornutum supplements were included in the diets of C. gariepinus denoted as Control, PT1, PT2, PT4 and PT5, respectively. Fish were fed for 56 days at 5% body weight. Results at the end of the experiments showed that the highest body weight was recorded in fish fed 1.5g/100g P. tricornutum diets. The best feed conversion ratio, specific growth rate, protein efficiency ratio and percentage survival was found in PT3. There was significant difference (p<0.05) in the feed intake of fish with PT4 having the highest feed intake. The stomach histology revealed increase in the gustation cells in the stomach of experimental fish with increasing levels of P. tricornutum supplementation. This study showed that the inclusion of P. tricornutum supplement at 1.5g/100g level in the diet of C. gariepinus juveniles improved the gustation, growth performance and nutrient utilization of C. gariepinus. Keywords: Microalgae, Aqua feed, Nutrition, Gustation, African catfish