Ecological Impacts of the African Catfish Clarias Gariepinus at Environmental Protection Area in Southeastern Brazil

The African catfish (Clarias gariepinus) is considered one of the most important species of catfish for aquaculture. It has a great capacity to withstand several stress factors, such as harsh abiotic conditions, in addition to wide feeding flexibility. However, the species was detected in the Guapimirim Environmental Protection Area in southeastern Brazil, threatening native fish diversity and ecosystem functioning of this ecosystem. In 2018, during the dry and wet seasons, samples of the fish community were collected at thirty-two sites of the Guapi-Macacu River, in addition to abiotic variables (salinity, pH, temperature, turbidity, dissolved oxygen, and transparency) to diagnose which factors influence the distribution of the alien species along the river. Multivariate analyses indicated that African catfish dominate the region in the buffer zone to the Environmental protection area, benefiting from higher levels of dissolved oxygen and temperature. However, C. gariepinus does not dominate yet the most protected area of Guapimirim, where the highest percentage of native fish species inhabit. Climate change associated with changes in abiotic factors might significantly contribute to the dominance of the invasive alien species in this protected area, which might colonize the entire river.

Growth Performance and Carcass Analysis of African Catfish (Clarias Gariepinus) Juveniles Fed Varying Inclusion Levels Of Butterfly Pea (Clitoria Ternatea) Seed Meal

High cost of qualitative fish feed is one of problems hampering the development and profitability of fish farming and consequently leads to food insecurity in terms of food availability and accessibility. The study was conducted to determine growth parameters and carcass composition of Clarias gariepinus juveniles of mean weight 21.74g+0.54g fed with varying levels of dietary inclusion of Clitoria ternatea seed meal substituted for soybean meal over a period of eight weeks. Four iso-nitrogenous experimental diets were formulated at 0% (control), 25%, 50% and 100% inclusion levels of C. ternatea seed meal. The 8-week feeding experiment was conducted in rectangular plastic tanks, each treatment having three replicates with two feeding regime at 5% body weight and weighed every week. At the end of the intensive feeding period, samples from each treatment were oven dried for nutritive analysis of the fish carcass. The values of mean weight gain for diets I and III were 27.7+1.11 and 27.23+0.94 respectively. Comparatively, the growth parameters values; FI(g), SGR(%), FCR(g), PER(%) and NPU(%) for control diet and diet III were the best with no significant difference (p>0.05). The Carcass evaluation revealed that Diet I had the highest crude protein which was not significantly different (p>0.05) from diet III. It was established that fish fed 50% inclusion level of C. ternatea seed meal had effective comparable biological values with the control diet in terms of growth performance and feed utilization. The total fish production (kg) showed no significant difference (p>0.05) between diets I and III.

Histological Alterations in Some Organs of African Catfish (Clarias gariepinus) Exposed to Sub-lethal Concentrations of Glyphosate [N-(phosphonomethyl) glycine]

This study used a static bioassay to investigate the histological effects of glyphosate on the gill, liver and muscle of African catfish (Clarias gariepinus) fingerlings. This was done with a view of further characterising the effect of glyphosate on C. gariepinus fingerlings and other aquatic life forms. Six-week old C. gariepinus fingerlings with an average weight of 10.02 ± 0.2 g were stocked into three exposure sets (control, 2.75 ppm (25% of the 96 h LC50 value) and 5.50 ppm (50% of the 96 h LC50 value)) in triplicate at 30 fish per tank for 70 days. The 96 h LC50 value was 11.00 mg/L. Histological examination of the C. gariepinus exposed to various sublethal concentrations of glyphosate showed that major histological changes in their organs were concentration dependent such as gill arch vacuolation, excessive mucosal secretions, lifting of epithelial, and epithelium thickening, hyperplasia and telangiectasis in the gills, discolouration, change in form and consistent alterations involving hyperplasia, narrowing of the central nerve, necrosis, pkynosis, blood congestion and vacuolation of the liver, mild hyperplasia and inflammatory responses in the muscle of the fish. The severity of histological alteration was more pronounced in fish organs exposed to 5.50 ppm of glyphosate concentration. This study concluded that the toxicant (glyphosate) is highly toxic to C. gariepinus particularly at a concentration of 5.50 ppm, therefore its use near farm lands or adjacent water bodies should be discouraged.

Spearmint (Mentha spicata) Cultivation in Decoupled Aquaponics with Three Hydro-Components (Grow Pipes, Raft, Gravel) and African Catfish (Clarias gariepinus) Production in Northern Germany

Mint (Mentha spicata) was cultivated in different hydroponic components: grow pipes, a raft and an ebb-and-flood gravel substrate system irrigated with aquaculture effluents from intensive African catfish (Clarias gariepinus) production under decoupled aquaponic conditions in northern Germany. The spearmint grew well and plant heights above ground were not significantly different between the gravel (57.7 ± 13.1 cm), raft (58.0 ± 17.7 cm) and grow pipe components (63.6 ± 9.9 cm). Root lengths and root fresh weights were two-fold and four-fold higher in raft (64.3 ± 20.5 cm; 42.8 ± 29.9 g) and grow pipes (59.4 ± 15.2 cm; 41.3 ± 25.7 g) compared with gravel substrate (29.7 ± 7.8 cm; 9.4 ± 9.4 g; raft = grow pipes > gravel). Spearmint leaf number was significantly higher in the grow pipes (770.0 ± 224.4) than in the gravel substrate (499.8 ± 228.4) with intermediate values in the raft. Significantly highest mean fresh biomass was found in the raft (1275.6 ± 33.4 g), followed by grow pipes (1042.0 ± 35.8 g) and gravel substrate (686.3 ± 98.2 g; raft > grow pipes > gravel). M. spicata, under aquaponics, grows best in grow pipe and raft components. An increase in pipe diameter for the grow pipes and a reduction in the channel height for the raft components could optimize aquaponic culture conditions for both industrial production and the hobby sector in the future.

The effect of feed residues on the quality of aquatic environment in circulating aquaculture systems of african catfish (Clarias gariepinus (Burchell, 1822))

Purpose. To study the peculiarities of relationships between the aquatic environment and the extruded feed residues in the circulating aquaculture systems intended for growing Clarias gariepinus, and changes in the concentrations of inorganic nitrogen compounds and phosphorus phosphates. Methodology. The object of study is the quality of the aquatic environment when modeling the food load in accordance with feeding standards of different age groups of Cl. gariepinus. Water quality in experimental tanks was determined by analytical methods. Findings. It was found that the intake of extruded feed residues into the aquatic environment leads to a deterioration in its quality due to an increase in the concentration of compounds of inorganic nitrogen and phosphorus of phosphates, which negatively affects the vital activity of Cl. gariepinus. Nitrification processes are activated under conditions of sufficient dissolved oxygen content in the environment. The overload of the aquatic environment with organic matter promotes the bacterial transformation processes of nitrogen and phosphorus compounds, which are characterized by the predominance of the ammonification process and the suppression of oxidative processes. Upon completion of the mineralization of the excess organic matter, the appearance of a sufficient amount of dissolved oxygen activates ammonium oxidation and intensifies nitrification process. The leading factors in the ammonification and nitrification processes in an environment saturated with organic matter include the dissolved oxygen content, which regulates the activity ratio of anaerobic amonifying and aerobic nitrifying microflora. Optimum aeration in Cl. gariepinus cultivation systems is determined not only by the direct physiological needs of fish, but also by the need to maintain a sufficient content of dissolved oxygen to ensure nitrification processes. Originality. The study investigated the effect of the food load on the quality of aquatic environment in the circulating aquaculture systems for Cl. gariepinus rearing. Practical value. The study results can be used to optimize Cl. gariepinus growing methods in circulating aquaculture systems with adjustable parameters at high stocking densities. Key words: African catfish, quality of the aquatic environment, food load, inorganic nitrogen compounds, phosphorus phosphate content, circulating adjustable systems.

Identification of Antimicrobial Peptides Isolated From the Skin Mucus of African Catfish, Clarias gariepinus (Burchell, 1822)

Antimicrobial peptides (AMPs) constitute a broad range of bioactive compounds in diverse organisms, including fish. They are effector molecules for the innate immune response, against pathogens, tissue damage and infections. Still, AMPs from African Catfish, Clarias gariepinus, skin mucus are largely unexplored despite their possible therapeutic role in combating antimicrobial resistance. In this study, African Catfish Antimicrobial peptides (ACAPs) were identified from the skin mucus of African Catfish, C. gariepinus. Native peptides were extracted from fish mucus scrapings in 10% acetic acid (v/v) and ultra-filtered using 5 kDa molecular weight cut-off membrane. The extract was purified using C18 Solid-Phase Extraction. The antibacterial activity was determined using the Agar Well Diffusion method and broth-dilution method utilizing Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922). Thereafter, Sephadex G-25 gel filtration was further utilized in bio-guided isolation of the most active fractions prior to peptide identification using Orbitrap Fusion Lumos Tribrid Mass Spectrometry. The skin mucus extracted from African Catfish from all the three major lakes of Uganda exhibited antimicrobial activity on E. coli and S. aureus. Lake Albert’s C. gariepinus demonstrated the best activity with the lowest MIC of 2.84 and 0.71 μg/ml on S. aureus and E. coli, respectively. Sephadex G-25 peak I mass spectrometry analysis (Data are available via ProteomeXchange with identifier PXD029193) alongside in silico analysis revealed seven short peptides (11–16 amino acid residues) of high antimicrobial scores (0.561–0.905 units). In addition, these peptides had a low molecular weight (1005.57–1622.05 Da) and had percentage hydrophobicity above 54%. Up to four of these AMPs demonstrated α-helix structure conformation, rendering them amphipathic. The findings of this study indicate that novel AMPs can be sourced from the skin mucus of C. gariepinus. Such AMPs are potential alternatives to the traditional antibiotics and can be of great application to food and pharmaceutical industries; however, further studies are still needed to establish their drug-likeness and safety profiles.

Effect of Partial Soybean Replacement by Shrimp By-Products on the Productive and Economic Performances in African Catfish (Clarias lazera) Diets

The present study was carried out to evaluate the effects of partial replacement of soybean with shrimp by-products (SBp) in African catfish (Clarias lazera) diets on productive (growth, digestibility, body composition, dressing yield, blood parameters, immunity) and economic performances. Therefore, 750 fingerlings (~20.0 g) were distributed into five groups of 150 fingerlings/group with three replicates (n = 50) per group. Group 1 was fed a basal diet, while G2 and G3 were fed diets containing 25% SBp (autoclaved and acid-treated, respectively) as soybean replacer for 12 weeks, while, in G4 and G5, SBp level was 50%. All growth and nutrient utilization parameters (body weight, Wg, ADG, PER, FCR, and digestibility), plasma proteins, and immunity significantly increased in G4 and G5. Anemia screening markers recorded insignificant differences between the tested groups and control one, whereas lipid markers of plasma and fish body decreased by autoclaved SBp and increased by acid-treated SBp. The African catfish body dry matter and crude protein percentages were enriched by the addition of SBp. Replacing the soybean meal decreases diet costs and diet costs/1 kg of weight gain. In conclusion, replacing soybean with SBp (especially 50% acid-treated) positively influenced productive and economic performances with friendly effects to avoid the environmental pollution by these wastes.

Haematological and Histopathological Examinations of African Catfish (Clarias gariepinus) Exposed to Sub-Lethal Concentrations of Paraquat

The study was designed to investigate the sub-lethal effects of paraquat on haematological parameters and histopathology of the gills, skin and liver of Clarias gariepinus juveniles of mean weight (38.26±1.20g) and length (17.50±1.55cm). The fish were exposed to 10, 20, 30, 40 and 50% of the 96hrsLC50 value of 107mg/l estimated from the 96 hours acute toxicity test. Blood samples were collected into heparinized tubes for the analyses of some haematological parameters, while the gills, skin and liver were also removed for histological examinations following standard procedures. The result revealed a significant reduction (P < 0.05) in the values of red blood cells (RBCs), haemoglobin (Hgb), packed cell volume (PCV) and erythrocytes indices from the control. The white blood cells (WBCs) and platelets (Plt) were however increasing significantly (P < 0.05) from those of the control as the test concentrations increased. The histology of the gills revealed some alterations such as epithelial proliferation, vacuolation of the mucus, hyperplasia of epithelial tissue of the gill filament, lifting and necrosis of the secondary lamellae. The exposed skin showed mucous cell proliferation, erosion of the epithelial lining, hypertrophy, necrosis of epithelial cells and widening of the epidermal and dermal layers. The liver exhibited cellular proliferation, sinusoid enlargement, congestion of the central vein, paranchymatous degeneration, vacuolar degeneration, pyknotic nucleic degeneration, legions and necrosis with severity as concentration of paraquat increases. The gills and skin were observed to be the most affected tissues in this study. The study also revealed that paraquat was toxic to C. gariepinus and causes some haematological and histopathological alterations in the fish blood and tissues at concentrations higher than 30mg/l. Therefore, the use of paraquat by farmers should be regulated particularly in area close to the aquatic environment.