Aquac. J., Volume 5, Issue 1 (March 2025) – 7 articles

The rising scarcity and cost of fishmeal due to overfishing and environmental challenges demand alternatives. Black soldier fly (Hermetia illucens) larvae (BSFL) meal, with its nutritional value, shows promise as a sustainable supplement for aquaculture species. This study evaluated the effects of BSFL meal supplementation on growth performance, survival, feed conversion efficiency, and meat quality in juvenile swamp eels (Monopterus albus) initially weighing 4.0 ± 0.5 g. The eels were fed diets with 0% (control), 10%, 30%, and 50% BSFL meal for three months. Growth performance was assessed using the absolute growth rate (AGR) and the specific growth rate (SGR). Feed conversion ratios (FCRs), survival rates, and meat quality metrics, including fillet percentage, crude protein, and moisture content, were analyzed. Statistical differences among groups were evaluated using one-way ANOVA followed by Tukey’s post hoc test for pairwise comparisons. The 30% BSFL group exhibited superior performance, achieving the highest AGR and SGR (p < 0.05) and the lowest FCR (2.33 ± 0.03). Fillet percentage was highest in this group (27.3% ± 0.7%), with no significant differences in crude protein or moisture content. Survival rates were consistent across treatments (75.2–76.0%, p > 0.05). These results confirm that 30% BSFL supplementation optimally enhances productivity and meat quality in swamp eels, highlighting BSFL meal’s potential as a sustainable aquafeed alternative. Full article

The expansion of aquaculture necessitates innovative disease detection methods to ensure sustainable production. Fish diseases caused by bacteria, viruses, fungi, and parasites result in significant economic losses and threaten food security. Traditional detection methods are labor-intensive and time-consuming, emphasizing the need for automated approaches. This study investigates the application of convolutional neural networks (CNNs) for classifying freshwater fish diseases. Such CNNs offer an efficient and automated solution for fish disease detection, reducing the burden on aquatic health experts and enabling timely interventions to mitigate economic losses. A dataset of 2444 images was used across seven classes—bacterial red disease, bacterial Aeromoniasis disease, bacterial gill disease, fungal disease, parasitic diseases, white tail disease, and healthy fish. The CNNs model incorporates convolutional layers for feature extraction, max-pooling for down-sampling, dense layers for classification, and dropout for regularization. Categorical cross-entropy loss and the Adam optimizer were used over 50 epochs, with continuous training and validation performance monitoring. The results indicated that the model achieved an accuracy of 99.71% and a test loss of 0.0119. This study highlights the transformative potential of artificial intelligence in aquaculture for enhancing food security. Full article

The covert mortality nodavirus (CMNV), an emerging pathogen that infects several species severely in aquaculture, including marine shrimps, freshwater prawns, and crabs, has been detected in both wild Artemia and commercial Artemia cysts. Utilization of Artemia from unknown sources can impose considerable biosecurity risks in hatchery operations; therefore, effective hatching methods to eliminate the pathogenic potential from CMNV-positive (CMNV+) Artemia cysts are urgently needed. In this work, we assessed the efficacy of three treatment methods of disinfecting CMNV+ Artemia cysts during hatching: (1) decapsulation of Artemia cysts with Na₂CO₃ (sodium carbonate) and NaClO (sodium hypochlorite) at various durations before hatching; (2) application of different concentrations of formalin in hatching water; (3) combinations of decapsulating Artemia cysts and formalin-treated hatching water. Hatching CMNV+ Artemia with disinfected seawater only served as the control. The virus located on the cyst shells attached/infected Artemia larvae during hatching and remained active for a prolonged time of 7 days. The viral load of empty shells decreased with the decapsulation treatment time. After a 45 min treatment of decapsulation, CMNV on shells, as well as larvae, were eliminated successfully. Furthermore, decapsulation shortened the hatching time of the cysts from 19 h to 12 h. Ten ppm formalin in the hatching water could block the transmission of CMNV from the shells to the newly hatched larvae, although at this level it was insufficient to eliminate the virus from the shells completely. While use of 30 ppm formalin or higher dosage could eliminate CMNV, however, it also reduced the hatching rates of the Artemia cysts. A combination of decapsulation (treated with Na₂CO₃-NaClO for 15 min) and 10 ppm formalin in hatching water effectively eliminated the CMNV. This study developed a practical, effective, and reliable treatment method for hatching Artemia to ensure biosecurity in aquaculture hatcheries. Full article

High evaporation rates due to solar intensity and low precipitation could represent a challenging culture environment in northwestern Mexico, generating osmotic stress in shrimp due to high salinity. Bacterial infections by pathogenic Vibrio strains are highly virulent in shrimp culture. This study evaluated betaine aldehyde dehydrogenase (BADH) activity and glycine betaine (GB) levels in Litopenaeus vannamei under high salinity levels plus experimental infection with virulent Vibrio parahaemolyticus. At 35 ppt (control group) and 40 ppt after infection, GB levels increased two-fold in the gills except at 45 ppt and were significantly higher at 50 ppt. The highest GB levels were in the hepatopancreas of the uninfected group at 45 ppt. In the gills, BADH activity decreased after 2 h of exposure at 40 and 45 ppt; at 50 ppt, there was a significant increase in the uninfected groups. However, upon infection, activity increased at all salinities except 50 ppt. In the hepatopancreas of the uninfected groups, the highest activity was at 40 ppt and this was lowest at 50 ppt after 8 h. In the muscles, BADH was detectable at all salinities; infection caused an increase in its activity at 45 and 50 ppt. Despite sudden exposure to high salinity plus experimental infection, our results show that Litopenaeus vannamei does not inhibit BADH activity, allowing GB synthesis, which may play a role in shrimp survival under these conditions. Full article

Disinfection of fish eggs with iodophor is a common biosecurity procedure. This study evaluated the effects of three concentrations of iodine on walleye (Sander vitreus) egg survival and bacterial loadings. Approximately five hours post fertilization, eggs from ten female walleyes were disinfected in active iodine concentrations of 0, 100, 200, and 400 mg/L for 10 min. There was a significant decrease in survival in the 200 mg/L treatment group compared to the 0 mg/L (control) and 100 mg/L groups. Near-total mortality occurred in the eggs receiving the 400 mg/L disinfection regime. Bacterial Colony Forming Units (CFU) were significantly reduced with any iodine disinfection compared to the control, but there was no significant difference in CFU among any of the iodine treatment concentrations. There was no relationship between egg survival and either pre- or post-disinfection CFU levels. These results indicate that 10 min treatments of active iodine at a concentration of 100 mg/L can be safely used to reduce bacterial loadings on newly spawned walleye eggs, but complete disinfection will not occur. Higher iodine concentrations, which lead to walleye egg mortality, do not further decrease bacterial numbers. Full article

Comparable and reproducible research is needed to improve Pacific white shrimp (PWS) aquaculture. These experiments typically involve before-and-after measurements of the same individual for paired statistical testing. However, marking shrimp with external or internal tags is challenging, especially for juveniles. A possible alternative is to rear shrimp individually in single-shrimp systems. While such systems may also prevent competitive interactions, PWS are considered social animals and individual rearing may negatively affect social behavior. Therefore, the general goal of this study was to evaluate the effects of single-shrimp versus multi-shrimp systems on the survival, growth, and welfare of juvenile PWS using a randomized controlled trial with group sizes of one, three, and five individuals. We found that shrimp kept individually had a higher survival rate, higher final body weights and lengths, and longer antennae than shrimp kept in groups of three or five. The incidence of eye cataracts was not significantly different among groups. Based on these results, we conclude that the individual rearing of juvenile PWS has no negative effects on survival, growth, or welfare. Therefore, a single-shrimp system could be an alternative to individually marked shrimp to allow paired statistical testing in experimental trials, especially when using post-larvae or juvenile specimens. Full article

The tambaqui (Colossoma macropomum) is Brazil’s most farmed native species, playing a crucial role in aquaculture. This study aimed to evaluate growth, hematological, biochemical, and body condition (Kn) parameters of tambaqui under two stocking densities in a recirculating aquaculture system (RAS). A total of 240 tambaqui (12.2 ± 4.1 g; 6.63 ± 0.73 cm) were distributed across six experimental units in two treatments (SD1 = 140 fish m⁻³; SD2 = 180 fish m⁻³) with three replicates. After 45 days, no significant differences were observed in water quality or zootechnical performance (p > 0.05), with final productivities of 8.64 ± 1.85 kg m³ and 9.46 ± 1.95 kg m³ for SD1 and SD2, respectively. Elevated plasma glucose, cholesterol, and triglyceride levels indicated energy reserve mobilization, suggesting some physiological response to higher stocking densities. However, other hematological and body condition parameters, including condition factor (Kn), indicated no significant adverse effects. These findings suggest that tambaqui can tolerate these stocking densities in RAS without compromising body condition, supporting the species’ intensive farming potential in controlled systems. This study highlights the importance of balancing productivity and physiological conditions in aquaculture management. Full article