Journal of The World Aquaculture Society最新文献

Members of Bacillus cereus have been documented as important bacterial pathogens in aquaculture. However, scarce information is available on B. cereus isolates as causal pathogens of big-belly seahorses Hippocampus abdominalis. In the present study, a B. cereus isolate (SH1), recovered from a disease outbreak on a seahorse farm, was identified as a bacterial pathogen of big-belly seahorses, and its pathogenic potential in terms of pathogenicity-related factors, antimicrobial resistance, and virulence were analyzed. The isolate possessed β-hemolytic and proteolytic activities, and harbored 31 pathogenicity-related genes, including 20 virulence genes inhA, alo, cytK, hblA, hblC, hblD, nheA, nheB, asbA, asbB, asbC, asbD, asbE, asbF, dhbA, dhbB, dhbC, dhbE, dhbF, and hal encoding exoenzymes, exotoxins, and nutritional/metabolic factors, as well as 11 resistance genes BcI, BcII, BcIII, EF-Tu, vanR, vanS, mphM, satA, rpoB, fosB, tet(45) conferring resistance to β-lactams, elfamycins, glycopeptides, macrolides, nucleosides, rifamycins, phosphonic acids, and tetracyclines. Furthermore, the isolate correspondingly displayed phenotypic resistance to chephalosporins and penicillins and showed in vivo virulence to big-belly seahorses with the seven-day median lethal dose (LD₅₀) value of 1.51 × 10⁶ CFU/mL. To our knowledge, this is the first study to describe B. cereus as a pathogen of big-belly seahorses. The findings of this study underscore the need for targeted management of B. cereus infection in seahorses.

Ensuring fish welfare during stunning and slaughter is essential, as these procedures represent critical points in the production cycle that can significantly impact animal welfare. Cardiac activity serves as a key physiological indicator to assess stress responses and welfare in fish. Prolonged cardiac activity may reflect delayed death, which is relevant for evaluating welfare during the slaughtering process. In the present study, the effects of different slaughtering combinations on cardiac activity and internal temperature were evaluated in European seabass (Dicentrarchus labrax). To continuously monitor heart rate, biologgers were surgically implanted in adult seabass. Fish were subjected to different pre-slaughter treatments (ice slurry immersion or electrical stunning) followed by various slaughter methods (ice slurry, ikejime, or anesthetic overdose). The selected stunning and slaughter combinations represent the most used techniques in commercial aquaculture (ice treatments) and new alternatives that are currently under evaluation (electric stunning) or used as control treatments (ikejime and anesthetic overdose). Results indicated that slaughter in ice slurry resulted in the longest duration of cardiac activity, whereas ikejime and anesthetic overdose led to the fastest cessation, particularly when preceded by stunning. Electrical stunning significantly reduced the time to cardiac activity cessation compared with ice slurry immersion alone. The welfare concerns related to ice slurry slaughter are based on the prolonged cardiac activity observed, which may indicate physiological stress and delayed time to death. Based on cardiac activity and from an ethical and welfare perspective, electrical stunning followed by ikejime appeared to be the most effective method, ensuring rapid cessation of cardiac activity. However, both electrical stunning and ikejime require further neural validation to confirm that they reliably induce immediate and sustained loss of consciousness. While this combined method shows promise, its economic feasibility and practicality in commercial settings must be improved. At present, electrical stunning followed by ice slurry slaughter represents a more viable alternative, although it also requires neural validation. Future research should refine electrical stunning parameters, incorporate neurophysiological and biochemical indicators, and explore innovations to enhance welfare standards in seabass aquaculture.

The present study compared the effectiveness of dopamine antagonists and commercial hormonal agents containing GnRH analogs combined with dopamine antagonists for inducing ovulation and spermiation in Caspian kutum (Rutilus frisii) spawners. For this purpose, females (n = 15 for each treatment) and males (n = 10 for each treatment) were treated with different agents as follows: (1) Ovulin (sGnRHa combined with domperidone), (2) Ovopel (mGnRHa combined with metoclopramide), (3) domperidone, (4) metoclopramide, and (5) 0.9% saline solution (control group). During the study, ovulation success, latency time, reproductive performance, egg quality, sperm quality parameters, seminal plasma characteristics, relationships between sperm quality parameters and seminal plasma characteristics, and the performance of the freshly hatched larvae were recorded. There were no differences in the latency time of ovulation, which ranged from 340 to 450 degree-hours (DH) in treated groups (p > 0.05). Ovulation and spermiation rates were similar (p > 0.05) after treatment with hormonal agents (Ovulin or Ovopel) and dopamine antagonists (domperidone or metoclopramide). The number of stripped oocytes (116.1–137.3 g female⁻¹), fertilization success (86.9%–92.3%), and larvae survival rates (73.4%–81.1%) were comparable across all treatments (p > 0.05). However, MET-treated fish had the highest hatching rate at 90.8%, which was significantly higher than DOM (81.0%) and Ovopel (75.4%) treatments (p < 0.05). Moreover, lower larval malformation rates (1.1%–1.2%) were observed in domperidone and metoclopramide-treated groups (p < 0.05). The results of sperm volume, spermatozoa concentration, motility, and total sperm produced in dopamine antagonist-treated fish were within favorable ranges with no notable differences compared to the samples from the hormonal-treated groups (p > 0.05). The osmolality of seminal plasma was highest following application of hormonal treatments (252.2–260.7 mOsmol L⁻¹), which did not significantly differ from those stimulated with the dopamine antagonists (238.7–241.3 mOsmol L⁻¹) (p > 0.05). Together, these results demonstrated that both dopamine antagonists, domperidone and metoclopramide, were effective in inducing spawning of Caspian kutum without the addition of GnRHa. Therefore, their application can be suggested as efficient induction agents for controlled reproduction and conservation programs of Caspian kutum in hatchery centers.

Since the turn of the century, oysters have been the most successful US aquaculture product in terms of production growth. Most oysters are sold either at restaurants or in retail stores. However, there is very limited knowledge with respect to the market dynamics at the retail level. This is important as there is significant variation in seasonal availability and high price volatility. Moreover, many producers put an additional emphasis on product attributes like origin, as this can create price premiums. This article investigates sales trends of oysters at the retail level in the United States, utilizing weekly retail-level scanner data from 2016 to 2021. The total sales value of oysters has been rising annually, peaking at $146.9 million in 2021. There is strong seasonality in oyster sales, with a peak in November and December, and live oysters are the most popular category. The sales exhibited strong regional variation across distinct geographical market locations and oyster origin (e.g., Pacific oyster, Chesapeake Bay, etc.), but overall, there was limited differentiation, as 46.9% of the sales were labeled as generic oysters without any additional information.

Olive flounder (Paralichthys olivaceus) is known for its growth performance in aquaculture. Fish are typically raised at high densities in recirculating aquaculture systems (RAS), which may impact animal health. Flounder (55.2 ± 16.3 g) were stocked at three densities: a low density (LD) of 3 kg/m², medium density (MD) of 6 kg/m², and high density (HD) of 9 kg/m² in 1.2 m² tanks. Each treatment contained three replicate tanks, all of which shared a common sump and filtration system. Stress indicators, including serum cortisol, glucose, growth hormone (GH), and insulin-like growth factor-1 (IGF-1) levels, were analyzed. At the end of the 93-day experiment, individual weight was significantly higher in LD, followed by MD and HD, and survival was over 95% in all treatments. There was significantly greater biomass in HD, followed by MD and LD. No significant differences were found in GH and IGF-1 levels. However, glucose concentration was significantly higher in HD fish on day 30 and LD on day 93; cortisol levels were significantly lower in MD on day 30 and HD on day 61. Results suggest that olive flounder can be grown at a density of 55 kg/m² with little impact on health. However, a tradeoff exists between density and individual performance. This species seems well suited for RAS, although further research under commercial conditions is necessary.

This study examined the effects of fishmeal substitution with mealworm meal (MWM) in the diets of rainbow trout fingerlings (Oncorhynchus mykiss) on growth performance, flesh quality, amino acid digestibility, and digestive system histology. Five diets, which were iso-nitrogenous (average of 46.50% crude protein), iso-lipidic (average of 19.76% crude lipid), and iso-energetic (average of 15.74 kJ/g), were formulated and fed to triplicate groups of rainbow trout fingerlings (17.02 ± 1.33 g) for 90 days. Dietary treatments included one control (100% fishmeal) and four experimental diets. The experimental diets included MWM30 (150 g/kg MWM, no addition of methionine or arginine), MWM50 (250 g/kg MWM, 1 g/kg methionine, 1 g/kg arginine), MWM70 (350 g/kg MWM, 2 g/kg methionine, 2 g/kg arginine), and MWM100 (500 g/kg MWM, 4 g/kg methionine, 3 g/kg arginine). The growth performance was optimal up to the MWM70 group, while there was a significant decrease in the MWM100 group for weight gain (70.33 ± 1.13 g) and increased feed conversion ratio (1.04 ± 0.04). There was no significant difference in the proximate composition of MWM on crude protein and lipid levels in whole-body and fillet samples. Apparent digestibility coefficients were at acceptable levels, although there was a decrease in crude protein, crude lipid, and amino acid digestibility in parallel with increasing MWM levels. Histological analyses showed little adverse effects, with a significant reduction in liver vacuolization in MWM70 and MWM100 groups, and the experimental treatment did not result in severe negative effects on the formation of interstitial tissue, tubules, or glomeruli in the kidney.

Dissolved oxygen management of ponds plays a critical role in ictalurid catfish aquaculture production. If the minimum dissolved oxygen concentration falls below 3.0 mg O₂ L⁻¹, appetite is reduced, and production ultimately decreases. Although the effect of dissolved oxygen management on catfish production has been well characterized, how dissolved oxygen and aeration impact other water quality parameters is less understood. Six 0.10-ha earthen catfish ponds were stocked with 7500 (74,300 fish ha⁻¹) hybrid catfish (male Ictalurus furcatus × female I. punctatus) fingerlings averaging 39.5 g and were managed for either high (3.3 mg O₂ L⁻¹; high dissolved oxygen [HDO]) or low (1.2 mg O₂ L⁻¹; low dissolved oxygen [LDO]) minimum dissolved oxygen concentrations. Catfish in the HDO treatment grew 35% larger than their LDO counterparts, reached 456 ± 10 g after 189 days and had average net production of almost 30,000 kg ha⁻¹. Although HDO ponds ate 38% more feed on average, total (TAN) and un-ionized (NH₃) ammonia concentrations were not different between treatments. However, nitrite (NO₂⁻) and nitrate (NO₃⁻) concentrations were both significantly higher in the HDO ponds, indicating a greater proportion of ammonia was oxidized through nitrification while maintaining similar concentrations of nitrogen assimilated by phytoplankton. Higher rates of nitrification in HDO ponds are supported through higher dissolved oxygen concentrations, increased water circulation from aeration and increased suspended solids that lead to ammonia oxidation in the water column.

Soybean meal-induced enteritis (SBMIE) remains a major barrier to reducing fishmeal use in salmonid aquaculture. This study evaluated physiological and molecular responses associated with SBMIE resistance in rainbow trout (Oncorhynchus mykiss) by comparing a commercial strain (Com) and a selectively bred strain (Sel) with over two decades of selection for plant-based diet tolerance. Both strains were fed either a traditional fishmeal-based (FM) or high-soybean meal plant-based (PM) diet for 7 months. Growth performance was monitored monthly, and intestinal histology and proteomics were assessed at early (2-month) and late (7-month) timepoints. The Sel strain consistently outperformed the Com strain in final weight, weight gain and feed conversion ratio (p < 0.05), with no differences in feed intake or mortality (p > 0.05). Average weight gain was greatest in the Sel strain across diets (497.3 g on PM; 610.2 g on FM), while Com trout gained less, particularly when fed the PM diet (387.9 g on PM; 482.6 g on FM). Significant strain by diet interactions in distal intestinal histology (p < 0.05) indicated that only the Com strain developed SBMIE on the PM diet, characterized by shortened, widened villi, mucosal fold clubbing, and inflammatory infiltration. Ordinal histopathology scoring confirmed interactions for goblet cells, submucosa, lamina propria, and inflammatory cell counts (p < 0.05), confirming the SBMIE susceptibility in the Com strain. Label-free proteomics identified only 18 significantly altered proteins (FDR ≤0.05, |log₂FC| ≥1), exclusively in plasma, despite pronounced intestinal pathology in Com PM. Key plasma DEPs included upregulation of the inflammasome sensor Nlrp1 in Com PM relative to Com FM, providing molecular evidence for systemic inflammation linked to SBMIE. Exploratory gene set enrichment analysis revealed distinct functional profiles, notably heightened stress, DNA damage, and innate immune signaling (e.g., TLR pathways) in Com PM intestine, while inflammatory signatures were absent in Sel PM. These findings highlight coordinated histological and molecular adaptations underpinning SBMIE resistance in the Sel strain, demonstrate the utility of plasma proteomics for detecting systemic biomarkers like Nlrp1, and emphasizes the combined roles of diet and genetics in improving feed flexibility and sustainability in aquaculture.

Geosmin (GSM) and 2-methylisoborneol (MIB) cause objectionable off-flavors in fish produced in recirculating aquaculture systems (RAS). Remediation solutions have not been developed; therefore, a study was conducted to determine if microbial maturity limits off-flavor production. Triplicate RAS with newly established nitrification (“immature”) were compared to “mature” RAS operated continuously for 2.5 years, while growing market-size Atlantic salmon, Salmo salar. Mean waterborne GSM and MIB levels peaked at 35–40 ng/L in the immature RAS but were maintained at <13 ng/L in the mature RAS. Similar trends were reflected in salmon flesh. After 2 months, fillet GSM levels in the immature and mature RAS were 696 ± 31 and 247 ± 30 ng/kg (p = 0.001) respectively, and MIB was consistently higher in salmon from the immature RAS. The abundance of off-flavor-producing organisms was not associated with off-flavor trends, suggesting production was related to the RAS environment. Total ammonia nitrogen, nitrite-nitrogen, total suspended solids, heterotrophic bacteria count, and true color were significantly higher in the immature RAS, and nitrifier abundance was generally lower and less stable. Of these, machine learning identified true color as the most important feature affecting GSM. Ultimately, the microbially mature RAS minimized off-flavor in water and salmon flesh.

Microalgae are a valuable source of nutrients that are widely used in aquaculture to support the growth of aquatic species. This study aimed to assess the effect of replacing fishmeal with Spirulina powder (Arthrospira platensis) on the growth, survival, body coloration, and meat quality of Macrobrachium caementarius. We investigated the effects of diets containing different levels of fishmeal replaced by Spirulina powder: 0% (control), 25% (S25), 50% (S50), and 75% (S75), using 48 prawns during a 90-day experiment. Our findings indicated that the experimental diets containing Spirulina did not significantly contribute to the growth of the prawns, although the survival rate remained high. The highest (p < 0.05) dry hepatosomatic indices were observed in the prawns fed the S25 (2.85%) and S75 (2.56%) diets. We noted distinct color differences based on the diet: prawns fed the S25 exhibited a yellow-orange color, while those on the S50 and S75 diets developed a red-orange hue. Prawns of the S75 diet had significantly higher (p < 0.05) numbers (239.00/mm²), indices (4.76), and coefficients of chromatophores (95.20). Prawns fed the S50 and S75 diets showed higher protein content but lower lipid levels compared to the control diet. Our findings highlight the potential of Spirulina powder to replace fishmeal in diet formulations without compromising prawn M. caementarius performance. Diets containing 50% and 75% Spirulina powders are recommended as a fishmeal substitute. These results could contribute positively to the developing aquaculture sector for this valued species.