Aquac. J., Volume 2, Issue 3 (September 2022) – 3 articles

Juvenile African catfish (Clarias gariepinus Burchell, 1822) were reared within two experiments (a research facility and a local catfish farm, E1 and E2, respectively) for 102 d each under commercial recirculating aquaculture conditions. The mixed-layer clay mineral montmorillonite–illite/muscovite (1g557) was applied as a feed additive at concentrations of 0.5% and 2.0%, which were compared with an unsupplemented control (0.0%) over 70 d. For E1, feeding was automatic at night, while E2 was fed manually during the day. The growth and physiological welfare parameters of the fish were monitored, including the mortality, skin lesions, stress responses after confinement (plasma cortisol and glucose), and additional blood parameters. Tendentially, the most efficient growth in both the experiments was observed in the 0.5% groups, which performed slightly better than the controls (E1: 0.8% and E2: 3.2%) despite a lower nutrient content (p > 0.05). In E1, the negative skewness of the leptokurtic distribution also revealed the highest number of larger-sized fish per batch. Mortality was low in all the treatment groups (E1 control/0.5%/2.0%: 3.6%/4.9%/2.9%; E2 control/0.5%: 2.6%/5.5%). After only 29 d in E1, the number of skin lesions per fish decreased significantly (p < 0.05 between each of the 0.5% and 2.0% groups, compared to the control (E1 control/0.5%/2.0%: 1.2/0.8/0.8). In both E1 and E2, the number of lesions per fish decreased even further after 70 d, significantly between the treatment groups and the control (E1 control/0.5%/2.0%: 0.9/0.4/0.5 and E2 control/0.5%: 0.6/0.3). In E1, the cortisol and glucose concentrations increased strongly in all the groups due to the induced stress, whereas this was not evident in E2 based on the different sampling procedure. The additional blood parameters (aspartate aminotransferase, glutamate dehydrogenase, urea, calcium, phosphate, total protein, leucocytes, erythrocytes, hematocrit, cholesterol, triglycerides, sodium, potassium, and chloride) revealed no significant difference between the treatment groups in either experiment, indicating no negative effects of 1g557 on the organs or metabolism of the fish. Supplementation with 0.5% 1g557 in the common commercial feeds for African catfish increases growth performance (p > 0.05), reduces size variance, and supports fish welfare under different commercial aquaculture conditions in the present study. Full article

In this study, three growth trials were conducted to check the efficacy of poultry corn by-product meal, which was a combination of wet poultry processing waste and corn that was co-dried. It was relatively a new product, and its first growth trial was conducted in a laboratory (aquarium study) to evaluate the substitution of whole corn meal with poultry plus corn by-product meal (PCBM) in practical diets for channel catfish. In this trial (84 days culture period), 7 levels of PCBM (0, 5, 10, 15, 20, 25 and 30%) were evaluated in a practical diet containing 32% protein and 6% lipid. The results indicated that fish fed PCBM20 had the highest FW, WG and WG% among all the treatments, and these values were significantly higher (p < 0.05) than at baseline or with PCBM5 treatment. The second trial (fingerlings to sub-market) was conducted in 12 raceways with 4 levels of PCBM (0, 10, 20 and 30%) and 600 fish (mean initial weight 42.3 ± 5.06 g) in each raceway. After 143 days of culture, the results demonstrated that there were no significant differences (p > 0.05) between the FW, WG and WG% and the survival of the fish. To validate our results again, the third trial (sub-market to market) was conducted in 6 raceways with 2 levels of PCBM (0 and 30%). A total of 600 fish (mean initial weight 136.8 ± 6.3 g) were stocked in each raceway. The results revealed that there were no significant differences (p > 0.05) between the FW, WG and WG% and fish survival after the culture period of 133 days. In all three trials, upon termination, the hepatosomatic index (HIS), the intraperitoneal fat (IPF), and the dress-out (headed and gutted) percentages were measured for trials 2 and 3. The results showed that there were no significant differences (p > 0.05) between all these parameters except for HIS in trial 1 and IPF in trial 2 (p < 0.05). In conclusion, PCBM can be used up to 30% in the diets of channel catfish. Full article

Fish farming is a rapidly growing food sector in developing nations. Liberia is an example of a least developed country with a large population facing high poverty levels. This has led to the adoption of aquaculture as one of the most important strategies for solving malnutrition and food security problems. However, since the introduction of fish farming, fish yields have been persistently low. To address the shortcomings in fish yields in Liberia, a study was conducted to provide information on fish farming intensities, types, and quality of feeds used by farmers in the culture of O. niloticus in Bong, Lofa, Nimba, and Grande Gedeh counties. Using stratified purposive sampling, 120 farmers were interviewed, and their fish feeds were sampled for proximate nutrient analyses. The results demonstrated that fish farming of O. niloticus in Liberia is mostly semi-extensive (81.6%), mainly practiced in paddy, barrage, and earthen ponds. On average, farmers produce 165.7 kg ha⁻¹ of O. niloticus annually, translating to USD 414.25. Farmers use mixed feeding regimes, comprising farmer-made, kitchen waste, and blended commercial feeds. Farmers, on average, spend 43% of their operation cost on feeds, which makes it unsustainable to maintain semi-intensive systems. The main feed ingredients used by Liberian fish farmers are rice bran, wheat bran, corn, palm kernel, and fishmeal. Crude protein levels in feed ingredients are as follows: rice bran (3.7 ± 1.3%), wheat bran (16.4 ± 1.5%), corn (6.3 ± 1.1%), palm kernel cake (14.8 ± 1.4%), and fishmeal (63.8 ± 1.3%). Crude proteins were low in formulated feeds, ranging from 8–15% CP. From this study, poor yields and the slow growth of O. niloticus can be attributed to low-protein diets, rendering farming ventures unprofitable and unsustainable for resource-poor farmers in Liberia. Full article