The influence of dietary protein concentration on digestive enzyme activities, growth, and body composition in juvenile bullseye snakehead (Channa marulius)

The bullseye snakehead (Channa marulius) is considered as an affordable and robust freshwater fish for farming in Asia. However, there is limited knowledge on the species' full nutritional requirements to date with extensive gaps in our knowledge and particularly in precision aspects of protein requirements. Therefore, a three-month feeding trial was conducted under semi-intensive farming conditions to determine the protein requirement of bullseye snakehead using test diets containing 40 (P40), 45 (P45), 50 (P50), and 55% (P55) crude protein levels. The growth performance results revealed that the 55% dietary protein group (P55) had the highest final mean weight (14.09 g fish-1), and net weight gain (12.82 g fish-1). When compared to other dietary treatments, the final weight (R2 = 0.921), and weight gain (R2 = 0.913), displayed a linear increasing trend as dietary protein is raised. The lowest FCR was observed in 50% (1.94±0.01) and 55% (1.97±0.01) CP diet groups compared to dietary treatments. Further analysis has shown that the body protein content also significantly increased as dietary protein was raised to 55%. Although, a reverse trend was found in body lipid levels with increasing protein in the diet. The incremental dietary protein also elevated proximal intestinal protease activity but decreased amylase and lipase activity. The overall essential and non-essential amino acids levels of snakehead fillet muscle reflected an increase in dietary protein. Overall, this study has shown that the fish fed a diet with 55% crude protein attained the highest growth performance and nutrient profile of the whole fish when compared to other dietary treatments tested. It would appear we did not obtain the maximum potential for growth under the present experimental conditions due to the upper protein constraint of 55% in the diet. Further quantitative studies are suggested.

Microplastics abundance in abiotic and biotic components along aquatic food chain in two freshwater ecosystems of Pakistan

Contaminants of global concern, microplastics (MPs) have been lately reported to be found almost everywhere. Yet there is limited evidence to suggest if these tiny particles can bioaccumulate and biomagnify along the food chain. The current study was conducted to quantify MPs load in two fresh water bodies i.e. River Ravi (Pakistan) and a fish rearing pond fed with ground water to trace MPs along the food chain including biotic and abiotic components. Samples were taken from air, water, sediments, planktons, fish and avian specimen from both water bodies. Higher MPs were found in all samples taken from river Ravi ranging from 3.0 ± 1.58 MPs items in water to 15.20 ± 3.35 MP items in air as compared to 2.8 ± 1.79 MPs in water to 11.20 ± 1.89 air-borne MP items in fish rearing ponds respectively. The mean value of MP items in the GIT of all species was higher (5.05 ± 2.25) as compared to the respiratory tract (1.57 ± 1.3) suggesting ingestion as main mode of exposure. However, this mode of exposure needs to be further investigated along with other exposure routes. Presence of MPs at all trophic levels under investigation indicates some degree of bioaccumulation of these pollutants in the ecosystems.

Administration of vitamin E and C enhances immunological and biochemical responses against toxicity of silver nanoparticles in grass carp (Ctenopharyngodon idella)

The aim of the current study was to evaluate the toxic effect of silver nanoparticles (Ag-NPs) on biochemical biomarkers, immune responses, and the curative potential effects of vitamin C and E on grass carp. Fish (n = 420) with an average initial body weight of 8.045 ± 0.13 g were shifted to glass aquaria (36 x 18 x 18 inches, filled with 160-L tap water) in triplicates. Aquaria were randomly designated as A, B, C, D with alone Ag-NPs (Control (0), 0.25, 0.50, 0.75 mg/L) and E, F, G with Ag-NPs + Vit. C + Vit. E (0.25+0.25+0.25, 0.50+0.50+0.50, 0.75+0.75+0.75 mg/L). NPs particles were administrated viz, oral and intravenous routes for 7 days. The results indicated that both routes had non-significant effect, but levels of Ag-NPs had significant effect. Treatments C, D and G showed significant decrease in levels of RBC, HGB and HCT except for WBC and NEUT levels, which significantly increased. ALT, ALP, AST, urea, and creatinine showed significant increase in activity in the C, D, and G groups. CAT, SOD decreased significantly in all Ag-NPs alone groups, while significantly increased with vitamin E and C. LYZ, TP, ALB, GLB showed significant low activity in the B, C, and D groups while significantly high activity in the E, F, and G groups. Cortisol, glucose and triglycerides showed significant increase in the B, C, and D groups, while E, F, and G groups showed significant low levels of triglycerides, COR, and GLU. Cholesterol level was same across all treatment groups. In conclusion, vitamin E and C as powerful antioxidants protect the fish against Ag-NPs except high dose level of 0.75mg/L, while 0.25mg/L of Ag-NPs was presumably safe for C. idella.

Performance evaluation of the commercial aquafeeds available in the market of Pakistan on Channa marulius (Sole)

The present study aimed to determine the effect of different levels of protein on the growth, body composition, amino acid profile and serology of Channa marulius fingerlings. The experiment was conducted in ten happas installed in earthen ponds, each stocked with 10 fishes for 90 days. Four commercial fish feeds having 25%, 30%, 32% and 40% crude protein (CP) levels were fed to fish at 3% of their wet body weight three times a day. The results of the study revealed that highest weight gain, feed conversion ratio and survival rate were observed in 30% protein feed. Meanwhile, moisture content was higher in fish fed with 30% CP feed while highest crude protein was recorded in 40% CP fed fish. Lowest fat content was observed in 32% CP feed. Amino acid profile of fish revealed better results in 30% CP feed. Total protein, glucose and globulin were also highest in fish feeding 30% CP feed, while albumin was highest in 40% CP feed. It is concluded that 30% CP feed showed better results in terms of growth, amino acid profile and serological parameters without effecting fish body composition.

Impact of dietary leaf extracts of Black pepper Piper nigrum L. on the growth, hematological and immunological parameters of Labeo rohita (Hamilton, 1822) cultured in glass aquaria

A study was conducted to evaluate the effect of Piper nigrum (black pepper) leaf extract on on the growth performance, proximate composition, hematological parameters, and immune response of Labeo rohita fingerlings with an average weight of 22.14 ± 0.98g. Aftrer acclimation for two weeks, fish (n=25) were randomly selected and placed in four glass aquaria (T0, T1, T2 and T3) at constant water temperature (30.0 ± 1.0 °C), pH (7.50 ± 0.5) and total hardness (200 ± 2.0 mgL,-1) for a period of 12 weeks, with three replicates each. Fish were fed with P. nigrum leaf extract supplemented feed @ 0.0%, 1.0%, 2.0% and 3.0% in T0, T1,T2 and T3, respectively. At the end of experiment, five fish were randomly selected from each aquaria for proximate composition, gut and skin microbial load, hematological parameters. Total proteins, albumins, and globulins were also recorded to evaluate immunological memory. The result revealed that fish in T2 showed better growth performance with an average weight gain of 56.11 ± 0.51 g. Thus, it had been concluded that Piper nigrum, a medicinal plant, can also be used to enhance the growth performance and immune response of Labeo rohita as attractive alternatives against antibiotics and vaccines and has shown no negative side effects on fish health as well as on its environment.

Evaluation of Fish Health Status and Histopathology in Gills and Liver Due to Metal Contaminated Sediments Exposure

Health status of freshwater fish, Cirrhina mrigala was studied by qualitative and quantitative histopathological analysis, alterations in frequency/prevalence percentages (%) and histological alteration indices (HAI) in response to metal contaminated sediments of the River Ravi aquatic ecosystem. Histo-structures of gill and liver samples of fish were analyzed and comparison between the degree of damage of the alterations in fish organs was performed after exposure to metal contaminated sediments for 7, 14 and 28 days under semi-static water renewal bioassays. Histopathological studies revealed marked histological alterations in the gills and liver of exposed fish as compared to normal tissue structure observed in control fish. The frequency and prevalence percentages observed in 28-day exposed fish were significantly higher as compared to 7- and 14-day exposed fish. The order of frequency and prevalence percentage for gills and liver of exposed fish was as: 28-day > 14-day > 7-day. The highest prevalence percentages recorded were 83 and 80% as focal area of necrosis in gill and liver, respectively, after 28-day exposure. The lowest prevalence percentage observed in 7-day exposed Cirrhina mrigala was dilation of sinusoids (17%).