Aquaculture International最新文献

Nile tilapia, a widely cultivated freshwater fish, faces significant stressors, such as hypoxia and cold temperatures, which can negatively impact its quality and growth. The current study explored the impact of Chlorella vulgaris (CV) powder and its nanoparticles (CVNPs) on the growth performance, antioxidant capacity, liver protection, and meat quality of Nile tilapia to alleviate hypoxia and cold stress. A total of 450 healthy 28-day-old Nile tilapia fingerlings (average weight 5.32 ± 1.1 g, length 3.1 ± 0.5 cm) were divided into five groups: T1 (2.5 g/kg CV), T2 (5 g/kg CV), T3 (2.5 g/kg CVNP), T4 (5 g/kg CVNP), and the control group received a basal diet without additives, each with three subgroups in tri-replicate (10 fish/replicate). After six weeks of feeding, growth metrics and meat quality parameters were assessed, and each group was subjected to hypoxia, cold stress, or optimal conditions. The results revealed that T4 exhibited the highest weight gain (WG) and lowest feed conversion ratio (FCR), whereas T1 showed the highest specific growth rate (SGR) and length gain. Hypoxia and cold stress significantly (p < 0.05) increased cortisol, oxidative markers (MDA, NO, and GSSG), and liver enzymes (ALT and AST) while reducing (p < 0.05) antioxidant markers (SOD and GSH) and total cholesterol (TC). ATP levels significantly (p < 0.05) decreased in hypoxic fish, indicating muscle energy depletion. T1 significantly (p < 0.05) lowered cortisol levels, whereas T2 and T3 significantly (p < 0.05) increased superoxide dismutase (SOD) levels. T2 also significantly (p < 0.05) increased the TC level. ALT levels significantly (p < 0.05) decreased at T1, T2, and T4, with AST levels reduced at T4 only. CV and CVNP supplementation significantly (p < 0.05) reduced the muscle MDA levels under optimal and stressful conditions, notably at T1 and T4. Additionally, meat lightness, yellowness, and chroma significantly (p < 0.05) increased in stressed tilapia, whereas meat redness was improved under optimal conditions. Fatty acid profiles varied with CV and CVNP levels across different conditions. In conclusion, CV, particularly in the nanoparticle form, enhanced the growth, antioxidant activity, and meat quality of tilapia under physical stress.

As indicated by research conducted in the state of Rio Grande do Norte, located in northeastern Brazil, the region ranks as the second-largest shrimp producer in the country. However, the environmental impacts associated with shrimp production by micro and small-scale enterprises remain insufficiently explored. The aim of this study was to assess the physical, chemical, microbiological, and phytoplanktonic parameters of water quality in both the intake and effluent water from shrimp farms situated around the Guaraíras Lagoon. Results demonstrated that all analyzed physical and chemical parameters adhered to Brazilian environmental regulations (CONAMA 357/2005 and 430/2011). Nevertheless, statistically significant differences (p < 0.05) were observed between sample types for parameters such as pH (8.36 ± 0.22 vs. 8.41 ± 0.24), suspended solids (0.010 mg/L ± 0.015 vs. 1.16 mg/L ± 1.30), and settleable solids. With respect to phytoplankton composition, the predominant classes identified were Bacillariophyceae (44%), followed by Mediophyceae (25%) and Cyanophyceae (17%). A statistically significant difference in phytoplankton composition was observed in intake water during the dry season, where the average concentration exceeded that of the rainy season by more than fourfold, and by over tenfold when compared to effluent samples (p < 0.001). Additionally, species known to potentially produce cyanotoxins were found at concentrations five times higher in effluent samples compared to intake water (p < 0.001). From the standpoint of Brazilian environmental legislation, the results indicate that small-scale shrimp farming exerts a low environmental impact. However, these findings emphasize the importance of further studies focused on cyanotoxin monitoring, with the goal of enhancing our understanding of the potential environmental and public health implications of shrimp farming in the region.

Saprolegniasis is a widespread fungal-like disease, causing serious damage to cultured and wild fish populations and their eggs, with subsequent economic losses. Many existing therapeutics for this disease prophylaxis are toxic with negative impacts on the environment. This study compared the efficacy of three medicinal plant extracts and a chemical compound readily available in Ghana to assess their potential effects on controlling saprolegniasis. The fungistatic and fungicidal properties of three plant leaf extracts, namely neem leaf, bitter leaf, Indian almond leaf and the chemical, potassium permanganate, were investigated under in vitro conditions. Different concentrations ranging from 5 to 20 mg/ml were tested. The average radial growth of the fungi in the presence of the treatments and controls was assessed. The efficacy of bitter leaf extract was further evaluated under in vivo conditions by exposing 200 juvenile Nile tilapia to S. ferax spores and treatment administered at different concentrations. Fish mortality and water quality parameters were monitored. Results from the in-vitro test showed that KMnO₄ and Indian almond leaf extract completely suppressed mycelial growth at the lowest tested concentration. The in-vivo treatment with bitter leaf extract at a concentration of 15 mg/ml demonstrated high efficacy in controlling S. ferax infection in Nile tilapia with a survival rate of 95%. It was concluded that the Indian almond extract was the most effective at the lowest tested concentration under the in vitro conditions. At the same time, bitter leaf was recommended for its safety for fish and widespread availability to fish farmers in Ghana.

The study examined the effects of different probiotics on growth, survival, and immune gene expression in Macrobrachium rosenbergii post-larvae (PL). The PL were fed with MY-1, Enterotrophotic (ENT), and MY-1 + Enterotrophotic (MY-1 + ENT) enriched artemia for a duration of 20 days, with three feedings per day. Throughout the experiment, water quality parameters were closely monitored. Results showed that the postlarvae fed with MY-1 + ENT exhibited better growth in terms of size and weight compared to the other groups. On the 21st day, both the control and treated PL were exposed to pathogenic Vibrio alginolyticus. The groups administered with MY-1 + ENT had higher survival rates compared to the other treatment and control groups. Moreover, the expression levels of immune-related genes such as cytochrome oxidase (COX), prophenoloxidase (proPO), peroxinectin (PE), antilipopolysaccharide (ALF), and lipopolysaccharide glucan binding protein (LGBP) were examined through qPCR. The results indicated a variable expression pattern suggesting that the application of probiotics enhances the expression and regulation of immune genes in the event of infection by V. alginolyticus. The differences in gene expression highlight the opportunity to develop Immune Gene Expression Finger Printing, which may act as an effective tool for evaluating probiotics and immunostimulants by assessing their ability to modulate immune responses in M. rosenbergii. The study warrants field-level validation of the findings to facilitate the adoption in the hatchery technology for scampi seed production too.

This study aimed to assess the water culture supplementation of fermented prebiotic (mannanoligosaccharide, MOS) and probiotic (Bacillus subtilis WB60) on water quality parameters, growth performance, feed utilization, immunity response, intestinal microbes, and histological investigations of Pacific whiteleg shrimp (Litopenaeus vannamei) challenged with Vibrio parahaemolyticus. Shrimp juveniles (4.98 ± 0.11 g) were distributed into four experimental groups (twelve 1 m³ hapa, 25 shrimps/m3/each hapa, 3 triplicates/group). The first group (G0) used only fermented B. subtilis at a rate of 0.2 g/acre. The 2nd, 3rd, and 4th groups contained the same constant level of B. subtilis (0.2 g/acre) with three different levels of fermented MOS at 25, 50, and 75 g/acre (G1, G2, and G3, respectively). The results showed that TAN and NH₃ values were significantly lower in all fermented groups compared to G0. Increasing the levels of fermented MOS led to significant improvements in growth performance, feed utilization, shrimp biomass, survival rate, crude protein, and ash content (p < 0.05). Compared to G0, the values of SOD, CAT, and IgM were significantly improved, while MDA levels were significantly decreased in all fermented MOS levels (p < 0.05). The G3 group exhibited the highest values of immune responses, including total hemocyte count, phagocytic activity, phagocytic index, respiratory burst activity, and lysozyme activity, as well as phenol oxide activity and total aerobic bacteria compared to the other groups (p < 0.05). Moreover, the G2 and G3 groups showed significantly lower mortality (30%) of shrimp challenged with V. parahaemolyticus infection compared to G0. In conclusion, the commercial scale recommends using fermented MOS and B. subtilis (50–75 g/acre) as water culture additives for shrimp L. vannamei due to the improvements in growth performance, feed utilization, immunological, and antioxidant indicators.

Silver arowana Osteoglossum bicirrhosum is a native species of the Amazon basin and presents opportunistic omnivorous habits with ichthyophagous preference. It is subjected to great fishing pressure for consumption and ornamental purposes. Fish farming for this fish is being developed, and one of the main difficulties is food availability for the different stages. This study assessed the effect of feeding with frozen trash fish and commercial feed on the growth and hematological parameters of juvenile silver arowana O. bicirrhosum. A total of 72 juveniles (74.2 ± 0.1 g) were randomly distributed into 12 net cages (6 fish per cage) and fed diets with different protein (P) and lipid (L) levels: frozen trash fish (52P:10L), and commercial tilapia (28P:4L), trout (40P:8L), and arapaima feed (50P:10L) with three replicates twice daily at a daily feeding rate of 6% of biomass for 90 days. At the end of the experiment, growth, hematological parameters, and cost per kilogram of weight gain were evaluated. The results revealed improved growth (P < 0.05) among fish fed with frozen trash fish (172.6 ± 26.9 g) and commercial arapaima feed (174.6 ± 48.8 g), in comparison with those fed commercial trout (120.5 ± 28.9 g) and tilapia feed (106.0 ± 37.1 g). Fish fed with frozen trash fish had lower daily feed intake (0.9 ± 0.1 g) and feed conversion ratio (0.8 ± 0.0), and greater hematocrit (36.2 ± 1.3%), erythrocyte sizes (348.7 ± 37.5 fL), total leukocyte (14.7 ± 0.3 × 10³ µL⁻¹), and lymphocyte levels (10.8 ± 1.1 × 10³ µL⁻¹) than juveniles that consumed the three commercial diets (P < 0.05). Feeding with frozen trash fish reduced (P < 0.05) the cost per kg of weight (USD 2.5) compared to feeding commercial diets for trout (USD 4.3) and tilapia (USD 4.8). The results show that feeding fresh frozen fish allows for healthy and less costly growth of juvenile silver arowana O. bicirrhosum.

Essential oils have been increasingly used as feed additives or preservatives due to their safety and antibacterial activity. However, few studies have examined the effects of combined essential oils on growth performance of aquatic species and the underlying mechanisms. In this study, we found that the combined essential oils, cinnamaldehyde, thymol, carvacrol, and monolaurin, in a certain ratio, promoted the body length and weight significantly in grass carp (Ctenopharyngodon idella), Chinese soft-shelled turtles (Trionyx sinensis), and zebrafish. Mechanistically, the combined essential oils significantly promoted the up-regulation of growth hormone (GH) and insulin-like growth factor (IGF), enhancing the expression of genes involved in insulin-like growth factor I binding, hormone biosynthesis, histidine metabolic process, nutrient reservoir activity, lipid transporter activity, and carbon metabolism. These changes, generally, promoted the expression of the subsequent signaling such as JAK/STAT, PI3K/AKT, and MAPK/ERK significantly in the brain, liver, and muscle, which might jointly contribute to the increased growth performance in grass carp, Chinese soft-shelled turtles, and zebrafish. This study for the first time demonstrates that the four essential oil components, cinnamaldehyde, thymol, carvacrol, and monolaurin, combined in a certain ratio, promote GH-IGF axis and the subsequent JAK/STAT, PI3K/AKT, and MAPK/ERK signaling, thereby enhancing the growth in grass carp, Chinese soft-shelled turtles, and zebrafish generally. This study reveals the potential of combined essential oil in promoting the growth of aquatic species.

Graphical Abstract

Exploring the influence of dietary L-carnitine (LC) supplementation in fish diets with varying lipid levels is essential for comprehending its effects. The present study assessed the effect of dietary LC supplementation on growth performance, feed utilization, body composition, and antioxidant capacity of large yellow croaker (Larimichthys crocea) at two dietary lipid levels. Two diets were formulated with 100 g kg⁻¹ and 140 g kg⁻¹ lipid levels as control diets, which were each supplemented with four LC levels at 0, 0.2, 0.3, and 0.4 g kg⁻¹ to make the experimental diets. These diets were fed to fish weighing 10.80 ± 0.40 g for eight weeks. The results showed that dietary lipid and LC levels, and their interaction affected final body weight and weight gain of fish. The fish fed at 140 g kg⁻¹ dietary lipid level supplemented with 0.2 (HC2) and 0.3 (HC3) g kg⁻¹ LC increased weight gain by 5% and 23%, respectively, compared to those fed on the control diet (HC0). Moreover, the fish fed at 100 g kg⁻¹ dietary lipid level supplemented with 0.2 (LC2), 0.3 (LC3), and 0.4 (LC4) g kg⁻¹ LC increased weight gain by 12.6%, 5.8%, and 8.3% compared to those fed the control diet (LC0). Independently, dietary lipid and LC levels affected serum superoxide dismutase and liver catalase activities. Dietary lipid level affected body lipid and energy contents, serum malondialdehyde content, and liver glutathione peroxidase activity. The optimum dietary LC required for maximum weight gain was 0.31 g kg⁻¹ for fish fed the diet containing 140 g kg⁻¹ lipid level. The present study reveals that the effect of dietary LC varies at different lipid levels. We recommend adding 0.31 g kg⁻¹ LC during the formulation of diets containing 140 g kg⁻¹ lipid to improve growth performance of large yellow croaker during commercial farming.

The objective of this study was to assess the impact of short-term fasting and subsequent re-feeding cycles on compensatory growth performance, blood glucose levels, and digestive enzyme activity in mono-sex juvenile Nile tilapia (Oreochromis niloticus) over a 60-day period. A total of 150 juvenile Nile tilapia (Avg. wt. 9.34 ± 0.97 g) were allocated into five treatment groups: a control group (continuously fed) and four fasting groups—T1 (1-day fasting), T2 (3-day fasting), T3 (5-day fasting), and T4 (7-day fasting). Re-feeding occurred for 7 days in each group immediately following the fasting period in a recurring cycle. The average weight gain, specific growth rate, and feed efficiency ratio significantly (p < 0.05) declined starting from the T3 group. Blood glucose levels during fasting significantly decreased starting from the T2 group, but after re-feeding, they returned to levels comparable to the control group. The liver glycogen levels significantly (p ≤ 0.05) decreased during fasting and completely recovered upon re-feeding, while muscle glycogen levels did not show any significant (p ≤ 0.05) changes throughout the experimental duration. The activities of the digestive enzymes amylase and lipase significantly (p ≤ 0.05) decreased during fasting starting from T1 and T2 groups, respectively, but after re-feeding, they returned to the levels seen in the control group. In contrast, the protease enzyme levels during the fasting period initially increased up to the T2 group and subsequently returned to control levels in the T4 group. The findings of this study indicate that only the groups that experienced very short fasting periods, specifically up to the T2 group, attained body weights like the control group upon re-feeding due to compensatory growth. Therefore, this study concluded that implementing up to 3 days of fasting followed by 7 days of re-feeding in multiple cycles can serve as a strategy for minimizing input costs in tilapia farming.