Aquaculture International最新文献

Fermenting rice bran with baker’s yeast waste introduces a cost-effective, eco-friendly method of valorizing these waste streams into high-value fish feed. This practice not only reduces environmental pollution but also addresses the challenge of sustainable aquaculture inputs. A study was designed to evaluate the impact of baker’s yeast waste (BYW)-fermented rice bran (FRB) on the growth performance, feed efficiency, impact on digestive and antioxidant enzymes, whole-body proximate composition, and hematological indices of silver carp (Hypophthalmichthys molitrix) fingerlings. Rice bran was fermented with BYW for 20 days and then used in the fish feed at incremental inclusions. Five diets were formulated, including the control diet (0%), 5%, 10%, 15%, and 20% FRB. The acclimatized fingerlings (N = 300; average initial weight, 5.65 ± 0.01 g) were distributed into five treatment groups (20 fish/triplicate) and fed at 3% body weight two times a day for 90 days. At the time of harvesting, the growth performance, feed efficiency, crude protein, crude ash, red blood cells, and hemoglobin of H. molitrix were significantly greater in the FRB20 group (20% FRB) than in the UFRB group (0% FRB), i.e., the control group, while no significant differences (p > 0.05) were detected in white blood cells, hematocrit, or mean corpuscular hemoglobin among all treatments. Serum biochemical analysis revealed that the globulin and total protein levels were significantly elevated in the FRB20 group. The levels of digestive enzymes (protease and amylase) and antioxidant enzymes (superoxide dismutase, glutathione peroxidase, and catalase) were increased significantly in the FRB20 group (p < 0.05), and the lowest level of malondialdehyde was detected in the FRB10 group, while the level of lipase (p > 0.05) did not significantly differ among the treatments. These findings indicate that the inclusion of 20% fermented rice bran enhanced the growth performance and overall performance of fish. Therefore, the addition of 20% fermented rice bran (FRB) to the diet can effectively improve the health of H. molitrix fingerlings. However, further research should be conducted to investigate the long-term effects of FRB on fish growth, health, and evaluate its economic feasibility as its utilization in long term might have negative effects.

This study investigated the effects of different forms of dietary vitamin C on growth performance, immune responses, antioxidant defense, and physiological health of grey mullet (Liza ramada, mean initial weight 40.32 ± 0.15 g, n = 3) over a 60-day feeding trial. Five experimental diets were formulated: a control diet devoid of vitamin C (D1) and diets supplemented with 200 mg/kg of crystalline vitamin C (L-ascorbyl-2-monophosphate, L-AMP; D2), liposomal vitamin C (D3), nano-liposomal vitamin C (D4), or a 1:1 mixture of liposomal and nano-liposomal vitamin C (D5). Fish fed D4 exhibited the highest growth performance, with significantly (P < 0.05) greater final body weight, specific growth rate, and better feed conversion ratio compared to other groups. Digestive enzyme activities were markedly enhanced in all vitamin C-treated groups, with D4 showing the highest amylase, lipase, and protease activities. The abundance of pathogenic bacteria decreased while acid-fermentative bacteria increased in the intestinal microbiota of vitamin C-supplemented groups, particularly in D4. Blood biochemical analysis revealed elevated total protein and globulin levels, reduced glucose and cortisol concentrations, and improved lipid metabolism in D3, D4, and D5. Immune parameters, including lysozyme activity and respiratory burst (NBT), were significantly higher in D4 and D5 (P < 0.05). Hepatic antioxidant enzyme activities increased, while malondialdehyde levels decreased in D4 and D5. These findings demonstrate that nano-liposomal vitamin C and its mixture with liposomal vitamin C confer significant benefits to growth, immune function, antioxidant defenses, and overall physiological health, highlighting their potential as effective dietary supplements in aquaculture.

Benzo(a)pyrene (BaP), a widespread polycyclic aromatic hydrocarbon, poses severe risks to terrestrial and aquatic organisms through oxidative damage and necroptosis in vital organs. This study explored the hepatotoxic effects of BaP in Nile tilapia (Oreochromis niloticus) and evaluated the protective potential of N-acetylcysteine-loaded starch nanoparticles encapsulated in porous alginate beads (NAC-SNPs/pALG). NAC-SNPs/pALG were characterized, and drug entrapment efficiency was measured. Six experimental groups (n = 24 each) were established: control, solvent control, vehicle (blank SNPs/pALG), BaP-exposed (50 μg/L), NAC-treated, and NAC-SNPs/pALG-treated groups, with NAC administered at 200 mg/kg fish diet for 4 weeks. BaP exposure significantly impaired growth performance; increased liver transaminases, oxidative stress biomarkers, cortisol, and proinflammatory cytokines; and elevated mRNA expression of CYP1A, caspase3, and BAX. Histopathological analysis revealed severe damage in hepatic, branchial, and intestinal tissues. NAC-SNPs/pALG co-treatment effectively mitigated these effects by improving growth indices, enhancing antioxidant enzyme activities, suppressing cortisol and inflammatory markers, and upregulating the Nrf2/HO-1 pathway. These findings underscore the enhanced bioavailability and therapeutic potential of NAC-SNPs/pALG as a protective strategy against BaP-induced oxidative stress and hepatotoxicity in aquatic organisms.

Rapid growth in aquaculture necessitates sustainable live feed production, particularly addressing the nutritional needs of fish larvae. Among live feed sources, the freshwater cladoceran Daphnia magna is indispensable due to its superior nutritional quality. However, traditional static culture systems suffer from deteriorating water quality, waste accumulation, and low reproductive efficiency. This study optimized a recirculating aquaculture system (RAS) tailored for D. magna cultivation, considering its sensitivity to environmental fluctuations. The designed RAS incorporates efficient water circulation, biofiltration, and controlled environmental parameters to enhance culture stability and productivity. The effectiveness of RAS was assessed relative to a static system with 50% water exchange (SSWE), based on fecundity, ephippia production, mortality, and stress responses. D. magna cultured in RAS exhibited higher fecundity rates (25 ± 2 embryo per female) and lower mortality (5%) compared to SSWEs (18 ± 1 embryo per female; 15% mortality). RAS maintained superior water quality throughout the study, with stable pH, low ammonia levels, and optimal oxygenation. Furthermore, gene expression analysis of stress-related genes (hsp70 and hsp90) indicated no significant physiological stress under RAS conditions, confirming its environmental stability. Additionally, M-ADaM proved to be the most effective rearing medium for D. magna, minimizing mortality. These findings provide a scalable approach to enhance live feed production for aquaculture while promoting sustainability and environmental responsibility.

The effect of replacing fish oil (FO) with linseed oil (LnO) in rohu, Labeo rohita (initial weight 19.1 ± 0.1 g), diets was evaluated in a 90-day feeding trial. Five isonitrogenous (30% crude protein) and isolipidic (11% crude lipid) diets were prepared by substitution of FO (7% FO in the control) with LnO (0, 25, 50, 75, and 100%). Responses of the fish were tested in triplicate for each diet. Partial replacements up to 75% did not cause any significant change in growth performance and feed efficiency. However, total replacement of FO significantly reduced growth performance and feed utilization (P < 0.05). Survival, hepatosomatic index (HSI), and viscerosomatic index (VSI) as well as whole-body proximate composition were not significantly influenced by the dietary treatments. The ratio of alpha linolenic acid (ALA; 18:3n-3) increased in the muscle and liver with the increasing level of dietary LnO, while the percentage levels of eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) decreased. However, EPA and DHA were in considerable level (3.3 and 18.6%, respectively) in muscle even when fed diet with 100% LnO. Hematological parameters such as red blood cell (RBC), hemoglobin (Hb), and hematocrit (Hct) were not influenced by dietary treatments, averaging 2.2 × 10⁶ U/L, 7.6 g/L, and 27.8%, respectively. On the other hand, alanine transaminase (ALT) and aspartate transaminase (AST) activity in serum were significantly elevated with the LnO inclusion levels (P < 0.05), reaching the highest levels (33.0 and 310.7 U/L, respectively) when LnO totally replaced FO. Cholesterol (CHOL), triacylglycerol (TG), high-density lipid (HDL), and low-density lipid (LDL) levels were significantly enhanced (P < 0.05) compared to the control. Cortisol (CORT) and glucose (GLU) were not significantly changed, averaging 1.5 nmol/mL and 20.8 g/dL, respectively. In the liver and serum, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities were significantly reduced, while malondialdehyde (MDA) level was significantly increased (P < 0.05) with the dietary LnO inclusion. Our results indicate that FO can be substituted with LnO up to 75% in practical diet formulations for rohu without any considerable negative effect, which will substantially decrease the dependency on dietary FO.

This study describes mucous cell (MC) parameters in barrier epithelial tissue of Atlantic salmon (Salmo salar) juveniles reared in freshwater flow-through (FT) and recirculating aquaculture systems (RAS). Using Veribarr™ technology, we found no significant differences in the mean MC size and abundance in the gill lamella and skin between FT and RAS systems (p > 0.05, lme). Notably, 100% of gill lamella MC parameters in RAS facilities fell within the most common range (mean ± 0.5 standard deviation, 38% confidence interval) for farmed salmon gill mucosa, whereas MC parameters in only 20% of FT facilities fell in this most typical range. The differences between individual FT facilities resulted in a greater variability in MC parameters compared to RAS facilities, especially in the gills, likely due to a more controlled environment in RAS. MC sizes and abundances in gills at some FT facilities were comparable to those reported in wild Atlantic salmon juveniles. This finding suggests that the water conditions at these facilities may not evoke a response from the gill mucosa, possibly indicating an environment better suited to the natural physiology of Atlantic salmon. Facility-specific conditions, rather than system-specific conditions, play an important role in the health of salmon barrier tissues. The study underscores the potential of using MC parameters as a monitoring tool, paving the way for innovative baseline health promotion as a preventative disease control strategy in aquaculture systems.

Eustrongylides are a nematode parasite of fish and fish-eating birds and have a potential health hazard in humans. The present study was designed to determine seasonal dynamics and molecular characterization of Eustrongylides spp. in Channa punctata collected from Trishal, Mymensingh. A total of 385 fish samples were collected and processed, and isolated parasites were examined under a microscope. After morphological examination, twenty (20) parasites were considered for sequencing using the internal transcribed spacer 2 (ITS-2) gene. The isolated parasites were identified as fourth-stage larvae (L₄) of Eustrongylides according to their morphological features. Of 385 fish samples, 79 were infected with Eustrongylides spp., and overall prevalence, mean intensity, and abundance were 20.5%, 1.86 ± 0.18, and 0.38, respectively. The highest prevalence was found in the rainy season (27.8%), followed by autumn (24.3), and the lowest in winter (15.6) and summer (14.6%). Medium-sized fish (24.5%) were more prone to parasitic infestation than smaller (16.6%) and larger (14.5%) ones. Parasites were more abundant in body cavity (79.5%) than muscle (20.5%). Among 20 sequences, one genotype was identified and showed 100% similarities with reference sequences of Eustrongylides spp. The unique clustering pattern confirmed morphological identification as Eustrongylides spp. Detailed molecular study is essential to explore the genetic diversity pattern of Eustrongylides in C. punctata.

Improving smolt production in Masu salmon is pertinent for controlling its sexual maturation. Both photoperiod and temperature considerably influence salmonid sexual maturation. The first experiment began on June 8 in 2021, with four groups: (1) Advanced Photoperiod (AP; natural photoperiod shifted to 18L, then reduced to 8L after 30 days), (2) temperature manipulation (Advanced Temperature (AT): ambient temperature (10 ˚C) raised to 18 ˚C at 0.5 ˚C/day, then reduced to ambient (12 ˚C) at 1 ˚C/week after 21 days), (3) combined AP + AT, and (4) a control group under natural photoperiod and ambient temperature (no environmental manipulation). In the AP group, plasma steroid hormone levels increased earlier than those in the control group, with ovulation (Sep. 3–22) and exuded milt (Aug. 26–Sep. 3) occurring sooner. AT alone did not affect ovulation timing (Sep. 7–Oct. 18) or exuded milt (Aug. 26–Sep. 27). However, AP + AT manipulation resulted in a smooth transition from elevated estradiol-17β in females and 11-ketotestosterone in males to ovulation (Aug. 20–Sep. 17) and exuded milt (Aug. 6–20). Ovulation and exuded milt were latest in the control group. The second experiment, which began on June 13 in 2022, confirmed the reproducibility of early ovulation and exuded milt in the AP + AT group. These findings demonstrate, for the first time, that sexual maturity in anadromous Masu salmon can be controlled by manipulating photoperiod and water temperature. This approach is expected to be a viable means of extending the growth period for 0 + spring smolts.

Aquaculture is a rapidly growing sector that plays a crucial role in meeting global food demands and providing livelihoods. However, industry faces significant challenges from pathogens like Aeromonas hydrophila, which can lead to severe economic losses. Traditional treatments, such as antibiotics, have become less effective due to the rise of antibiotic resistance, necessitating the exploration of alternative strategies. This review explores the potential of photodynamic therapy (PDT) as an innovative approach to controlling A. hydrophila in aquaculture and evaluates its implications for sustainable practices. We conducted a comprehensive review of the literature on PDT, focusing on its mechanisms, the role of photosensitizers, nanotechnology, pathogen control, photocatalysis, and the generation of reactive oxygen species (ROS). We also examined the logistical challenges of implementing PDT in aquaculture and the need for optimized treatment protocols. Our findings indicate that PDT presents a promising alternative for pathogen control in aquaculture. It also highlights the potential applications of natural and synthetic photosensitizers, emphasizing their role in sustainable aquaculture practices. We also discussed the current challenges in implementation of PDT in aquaculture, logistical issues, light sources, and treatment timing. Integrating methodologies such as PSs and nanotechnology could enhance the efficacy of PDT in combating A. hydrophila and other pathogens. By addressing current challenges and optimizing protocols, PDT has the potential to contribute significantly to sustainable aquaculture, improving food security, and reducing reliance on antibiotics.