Aquaculture Journal

Preliminary evidence has showed an emergent serotype O3 (SO3) strain of Vibrio anguillarum to cause mortality in pre-smolt Atlantic salmon (Salmo salar) by injection with >10⁵ colony forming units (cfus). Here, we sought to identify the susceptibility of Atlantic salmon post-smolts to this emergent strain by both injection and cohabitation to better understand transmission risk within cultured salmon and possibly between salmon and Atlantic menhaden (Brevoortia tyrannus), where this strain was identified. We identified that although mortality could be induced with a high-dose (>10⁶ cfus) intraperitoneal injection of the emergent SO3 strain (cumulative mortality of 40%), post-smolt Atlantic salmon were highly refractory to a low dose (<10⁶ cfus; cumulative mortality of 3%) or cohabitation exposure (no mortality). A qPCR assay targeting this strain was developed and analytically validated, revealing the limited presence of bacterial DNA in the spleen of low-dose-injected fish (2/36) and no detections in sampled cohabitants (0/70) across three timepoints during the 27-day challenge. These results suggest that although Atlantic salmon can succumb to high-dose artificial infections with V. anguillarum SO3, the risk of natural transmissibility and susceptibility of Atlantic salmon to this emergent strain is anticipated to be low. Full article

European sea bass (Dicentrarchus labrax) is one of the most significant species farmed in the Mediterranean, yet a very perishable product. Its quality deteriorates rapidly as a result of three mechanisms: microbial activity, chemical oxidation, and enzymatic degradation. Microbial spoilage is the mechanism that contributes most to the quality deterioration of fresh and non-processed fish. To this end, our study aims to identify for the first time the combined effect of aquatic environment and harvest method on the composition and trajectory at storage at 0 °C of the European sea bass skin microbiome. Sampling was performed in two commercial fish farms in Western (WG) and Central Greece (CG) where fish were harvested using different methods: direct immersion in ice water or a mixture of slurry ice; application of electro-stunning prior to immersion in ice water. Samples were collected on harvest day and one week post-harvest. To profile the bacterial communities in the fish skin, 16S ribosomal RNA gene sequencing was used. The results and the following analyses indicated that the aquatic environment shaped the original composition of the skin microbiome, with 815 ASVs identified in the WG farm as opposed to 362 ASVs in the CG farm. Moreover, Pseudomonas and Pseudoalteromonas dominated the skin microbiome in the WG farm, unlike the CG farm where Shewanella and Psychrobacter were the dominant genera. All these genera contain species such as Shewanella putrefaciens, Pseudomonas aeruginosa, Pseudoalteromonas spp., and Psychrobacter sp., all of which have been implicated in the deterioration and spoilage of the final product. The different harvest methods drove variations in the microbiome already shaped by the aquatic environment, with electro-stunning favoring more diversity in the skin microbiome. The aquatic environment in combination with the harvest method appeared to determine the skin microbiome trajectory at storage at 0 °C. Although Shewanella had dominated the skin microbiome in all samples one week post-harvest, the diversity and the relative abundance of genera were strongly influenced by the aquatic environment and the harvest method. This study sheds light on the hierarchy of the factors shaping the fish skin microbiome and their importance for controlling post-harvest quality of fresh fish. Full article

A 60-day feeding experiment was conducted to examine whether (i) soybean meal (SBM) protein in the diet of Nile tilapia (Oreochromis niloticus) can be replaced with protein from spent brewer’s yeast (SBY); (ii) co-rearing with biofloc alters fish growth, feed conversion and protein efficiency compared with rearing in clear water; and (iii) accumulated protein quantity and quality in biofloc acts as a possible feed source for the fish in periods of low feed intake. The fish were reared in either a bio-recirculating aquaculture system (Bio-RAS) or a clear-water RAS (Cw-RAS). In Bio-RAS, the mechanical and biological filters used in Cw-RAS were replaced with an open bioreactor that delivered heterotrophic-based biofloc to the rearing tanks and also acted as a sedimentation trap for effluent water before recirculating it back into the rearing unit. The fish were fed four iso-nitrogenous and iso-energetic diets (~28% crude protein, ~19 MJ kg⁻¹ gross energy) in which SBM protein was replaced with increasing levels of SBY, with triplicate tanks per inclusion level. The results revealed that average fish growth was greater in a biofloc environment compared with clear water and also greater at higher inclusion levels of SBY. However, in both rearing environments, fish growth displayed a second-degree polynomial distribution with increasing SBY inclusion level, with a peak between 30% and 60% inclusion. Fish in the biofloc environment showed better feed conversion ratio and protein retention, likely through ingesting both given feed and biofloc. Biofloc contained a significant amount of accumulated protein with a high biological profile, thereby constituting a possible feed reserve for the fish. A conclusion underlined by the apparent improved feed conversion of Bio-RAS reared fish, where that ingestion of biofloc will reduce the need for external feed per unit growth. Full article

Coastal aquaculture and local fisheries interact in shared marine environments, influencing each other synergistically and/or antagonistically. Salmon farming, notably with open-net sea cages along the Norwegian coast, attracts wild fish due to increased food availability from uneaten feed, but it also exposes wild fish to farm emissions like waste and toxic chemicals (de-lice treatments, antifouling and medical agents). The attraction behaviour of wild fish can impact fatty acid composition in fish tissues, influenced by the high terrestrial fat content in salmon aquafeed. We study how the Atlantic cod, aggregating around salmon farms in a subarctic fjord in Northern Norway, can be affected, potentially altering their natural diet and fatty acid profiles. Our study compares the muscle-tissue fatty acid compositions of cod caught near aquaculture facilities (impact) versus fish caught in neighbouring fjords (control), and we hypothesise decreased omega-3 fatty acids near farms. The analysis revealed no significant differences in the fatty acid concentrations or categories between the impacted and control fish, challenging our initial expectations. However, differences were found for C18:1(n9)t (elaidic acid), with a higher value in the impacted fish. These findings suggest that salmon farming’s influence on cod’s fatty acid profiles in the flesh (i.e., relevant for the nutritional quality of the fillets that consumers eat) may be limited or minimal despite their aggregative behaviours around farms. The threshold levels of salmon feed consumed by wild cod before it affects the quality and survival of, e.g., sperm or other life stages, are not known and require new investigations. This study underscores the complexity of interactions between aquaculture and wild fisheries, impacting both ecological dynamics and consumer perspectives on seafood quality and health benefits. Full article

This study evaluates the effects of Christmas melon (Laganaria breviflorus)-based diets on the growth and hematology of African catfish (Clarias gariepinus) after a 6 (six)-month feeding trial. A total of 240 C. gariepinus juveniles with an average weight of 10.68 g were procured from the Fisheries and Aquaculture Department Hatchery Unit for the feeding trial. After acclimating for a week (7 days) using 2.00 mm Coppens feed (45% CP) twice per day, the fish samples were randomly distributed into 12 tarpaulin tanks of 4 ft × 4 ft × 4 ft with a 200 L water holding capacity (four (4) different treatments presented in triplicate). Twenty (20) fish per tank were fed twice daily with the compounded feed with varying dietary inclusion levels of Christmas melon (0% (control), 5%, 10% and 15%). The weights and lengths of the sampled fish were measured biweekly to determine the growth performance, while hematological parameters, such as the packed cell volume, erythrocytes, hemoglobin, and leucocytes were determined midway through and at end of the feeding trial. The data collected were analyzed using ANOVA, and the results revealed the optimum growth and nutrient utilization and hematological and serum biochemical parameters of C. gariepinus in T3. The length–weight relationship results revealed that the fish exhibited an isometric growth pattern with B-values above 3 across the treatments. In conclusion, the results obtained in this study revealed that Christmas melon (L. breviflorus) could replace wheat offal by up to 10% in the diet of C. gariepinus without negative effects on the obtained optimal growth performance, hematological parameters, or serum biochemistry. Full article

The incorporation of aquaponics into saline integrated multitrophic aquaculture (IMTA) systems, employing biofloc technology (BFT), relies on the cultivation of halophytes capable of withstanding the physical–chemical conditions created by the unique microbial communities in BFT systems. This study aimed to evaluate the integration of the halophyte Salicornia neei with tilapia (Oreochromis niloticus) and marine shrimp (Litopenaeus vannamei) reared in BFT systems dominated by chemoautotrophic (CHE) and heterotrophic (HET) microorganisms over a period of 84 days in southern Brazil. Each BFT treatment had three replicates, composed of IMTA units. The stocking densities were 400 ind. m⁻³ (17 m³ circular tanks), 44 ind. m⁻³ (4 m³ circular tanks), and 30 ind. m⁻² (4.8 m² hydroponic benches) for shrimp, fish, and halophyte, respectively. The highest S. neei individual shoot production (up to 31 g per 30 days) was observed in the CHE treatment, along with favorable agronomic characteristics, possibly due to overall elevated nitrate (98.41 mg N−NO₃ L⁻¹) and phosphate concentrations (4.62 P−PO₄ L⁻¹). Shrimp in the CHE treatment displayed higher average final weight, specific growth rate, productivity, and survival (11.24 g, 2.88% day⁻¹, 3.86 kg m⁻³, and 90%, respectively) compared to the HET treatment. Results indicated no significant difference in tilapia zootechnical performance between treatments. Full article

This paper analyzes the factors influencing households’ resilience capacities to shocks within Kenya’s fisheries and aquaculture sectors and draws from primary data collected from 419 fish-dependent households across Kisumu, Busia, Mombasa, and Kilifi counties. The sample represents a total of 48,000 fishing households. The study adopted a quasi-longitudinal design and computed the household resilience capacity index (RCI) using the resilience index measurement and analysis (RIMA-II) model. The results indicate that male-headed households’ mean household RCI scores (mean = 45.07 ± 10.43) were statistically significant to that of female-headed households (mean = 38.15 ± 9.25), suggesting that female-headed households are associated with lower resilience capacities than male-headed households. Moreover, the study identifies differences in resilience levels across various occupations within the sector. For instance, RCI scores among fish traders (mean = 40.71 ± 9.97), a function performed mainly by women, statistically differed (p < 0.005) from male-dominated cage farming (mean = 48.60 ± 10.47), whereas RCI scores at the production level for fisher folks (mean = 44.89 ± 10.09) and pond farmers (mean = 44.04 ± 12.07) showed no statistical difference (0 > 0.05. Additionally, households with more income sources tend to have higher resilience capacities. Seasonality in fishing cycles limited households’ ability to recover from climate-induced shocks; the more months without fishing activity, the less the odds of recovery from shocks (OR = 0.532, 95% CI [0.163, 0.908], p = 0.022). Furthermore, households that lacked guaranteed market access and inputs during COVID-19 were less likely to recover during and after the shocks (OR = 0.401, 95% CI [0.161, 0.999], p = 0.05). Households organized in cooperatives with better access to credit showed a higher chance of recovery. The study recommends (a) adopting gender-sensitive approaches in fisheries and aquaculture interventions to empower women in trade, (b) strengthening policies to enhance access and adoption of climate-smart technologies such as cage fish farming, (c) promoting livelihood diversification to sustain households’ income during fishing off-seasons, and (d) enhancing market linkages in the fish value chain through coordinated producer organizations. Further research should explore the possibilities of introducing index-based weather insurance and other tested suitable safety nets for the fisheries and aquaculture sector. Full article

This study evaluated the anaesthetic potential of clove basil (Ocimum gratissimum) essential oil (EO-OG) in the post-larvae (PLs) of M. rosenbergii. The PLs were individually transferred to aquariums (500 mL) containing 50, 100, 150, 200, or 300 μL L⁻¹ EO-OG. A sixth group of PLs was exposed to freshwater only, and a seventh group was exposed to the highest concentration of ethanol used to dilute EO-OG. Upon reaching the anaesthesia stage, the PLs were transferred to aquariums (500 mL) with freshwater only to evaluate the recovery time. The shortest sedation times were observed at 200 (15.98 s) and 300 μL L⁻¹ (25.85 s). The shortest anaesthesia time was observed at 200 μL L⁻¹ (22.52 s). The longest recovery time was observed at 100 μL L⁻¹ (1367.10 s); the shortest recovery time was observed at 150 μL L⁻¹ (630.10 s). No mortality or adverse effects were observed in any experimental group. The concentration of 150 μL L⁻¹ resulted in sedation (49.24 s), anaesthesia (80.10 s), and recovery (630.10 s) times within those suggested as adequate for freshwater prawn farming. This research demonstrated the sedative and anaesthetic properties of EO-OG and its potential application in prawn farming. This study recommends using 150 μL L⁻¹ of EO-OG in M. rosenbergii PLs. Full article

This study compared the effects of three supplementary diets—egg yolk, Artemia, and commercial pellets with 48% crude protein—on the growth performance and survival rate of redbreast tilapia (Coptodon rendalli) under intensive culture conditions at the Kamutjonga Inland Fisheries Institute in the Kavango East region of Namibia. The study was conducted from December 2023 to January 2024 using a complete randomized design replicated thrice. Results showed that fish fed with commercial pellets exhibited the highest specific growth rate (1.39 ± 0.80%) compared to egg yolk (0.94 ± 0.54%) and Artemia (0.33 ± 0.19%). Commercial pellets also had the best survival rate (76.19 ± 43.099), compared to egg yolk and Artemia (70.47 ± 40.69; 33 ± 19.05), respectively. However, egg yolk had the best feed conversion ratio (0.20 ± 0.05) compared to the commercial pellets (0.22 ± 0.04) and Artemia (0.26 ± 0.07). Critical water quality parameters were maintained within acceptable survival ranges for C. rendalli across all treatments. These findings highlight the importance of dietary protein content in optimizing the growth and survival of C. rendalli under intensive culture conditions and provide insights for effective feeding strategies. However, commercial pellets are expensive and inaccessible to small-scale fish farmers. As an alternative, egg yolk emerged as a viable and affordable feed option, promoting fish growth and supporting the establishment of small-scale farming practices in the region. Full article

Motile aeromonad septicemia (MAS), caused by the Aeromonas species, has been a serious problem in fish health management, particularly in Nile tilapia (Oreochromis niloticus). This study characterized an Aeromonas species isolated from farmed tilapia fingerlings in Binangonan, Rizal, Philippines, and tested for its pathogenicity in tank trials. The isolate, designated as Aeromonas veronii DFR01 (Diseased Fish Rizal), was identified based on 16S rRNA phylogenetic analysis, 16S rRNA homology, and MALDI-TOF mass spectrometry. Its biochemical profile was generated from API and Biolog Gen III systems. A median lethal dose of A. veronii DFR01 was determined to be 10⁷ CFU/mL in tank trials and was utilized as a whole-cell inactivated antigen for oral vaccine development. The immunized tilapia fingerlings produced elevated levels of immunoglobulin M (IgM) in the blood as determined by an enzyme-linked immunosorbent assay (ELISA). There was a significant increase in IgM levels 14 days post-vaccination. A quantitative polymerase chain reaction (qPCR) showed increasing levels of IgM gene expression after vaccination until 38 days of culture. Vaccinated fish showed 25–35% cumulative mortality after the challenge, while non-vaccinated-challenged fish showed 75% mortality. The findings of this research suggest that the fish oral vaccine may prove beneficial for farmed tilapia populations. The vaccine elicited improved immune responses in the fish and resulted in higher survival rates. Full article

Despite the huge potential of aquaculture in the Amazon, several producers have abandoned the activity due to a lack of assistance, technology, and innovation. Thus, the objective of this study was to identify factors that have contributed to the withdrawal of aquaculturists from the municipality of ‘Vigia de Nazaré’, state of Pará (Northern Region of Brazil). This case study took place in 2022 through a quanti-qualitative survey, applying structured questionnaires to former aquaculturists. A total of 30 fish farms were investigated, with 11 of them being abandoned. They are distributed across 10 rural communities that have developed fish farming, with ‘Vila de Itapuá’ (18.2%) being the most representative. When active, fish farming was practiced by men (100%) aged between 51 to 60 years (54.5%) with an incomplete primary education (100%), who carried out the activity for an average of 5 years (81.8%), quitting fish farming between the years 2019 and 2020 (72.7%). All former aquaculturists owned small properties, with excavated ponds in an extensive system and used family labor. The absence of technical assistance and the high cost of feed were pointed out as the main problems in the production chain. It is worth noting that the monoculture of Tambaqui (Colossoma macropomum) accounted for 63.6% of the species produced in rural communities. In conclusion, former aquaculturists express the desire to return to fish farming due to its socio-economic importance. For this, government actions supporting technical assistance and advanced studies in fish nutrition by educational, research, and extension institutions are necessary. Full article

This study aimed to determine the protein requirements of the fattening phase for Nile tilapia (Oreochromis niloticus) fed fish meal-free diets. A total of 75 Nile tilapia were maintained in a water recirculation system, and five isoenergetic diets were formulated with increasing protein levels encompassing three repetitions each. The findings revealed that protein levels significantly affected (p < 0.05) certain Nile tilapia performance, yield, and composition parameters. The determined parameter values clearly indicated that Nile tilapia can be fed fish meal-free soybean meal and corn-based diets. Furthermore, the metabolic plasticity of this species concerning dietary protein concentrations was also demonstrated, with adequate performance results achieved in treatments containing from 267 to 294 g/kg digestible protein (DP), or 298 to 327 g/kg crude protein (CP), where the balance between essential and non-essential amino acids and energy resulted in adequate performance correlated to satisfactory feed conversion values and filet yields and composition. A DP concentration of 267 g/kg (298 g/kg CP) is recommended when offering corn and soybean meal-based diets during the Nile tilapia fattening phase to fish weighing between 400 and 700 g. Full article

Aquaculture development is a challenge for the economic growth of coastal territories and to promote the food security of their populations. Many efforts have been made by international, national, and local public institutions to develop this sector. Despite this political objective, the coastal zones of Europe and the Mediterranean in general are faced with problems that strongly limit this development. This is linked to several factors, including social opposition, which raises the question of the social acceptability of aquaculture development. Beyond understanding the factors that explain the social rejection of this sector or its products, the key question concerns the capacity of private and public institutions to deal with this social opposition in a practical way. Based on fieldwork and a participatory approach, this paper analyzes the constraints of aquaculture development in Monastir Bay, Tunisia, and in particular, those relying on social dimensions. Under this participatory approach, the authors propose a research–action framework allowing the building of bases for engaging stakeholders in a co-construction process of a shared vision of aquaculture development in Monastir, in accordance with the constraints and ambitions expressed by the local communities regarding territorial needs. This paper shows the value of building the transition from an individual or group vision to a collective vision through a participatory approach that is likely to form a consensus, as opposed to an aggregation of individual visions that can lead to social unacceptance. It also argues that involving citizens in the exploration of aquaculture development scenarios adapted to the territory is an essential prerequisite to exploring the conditions that question the social acceptability and its improvement. Full article

Sulfated polysaccharides (SPs), especially those with immunostimulant effects on shrimp and fish, are bioactive compounds with potential use in aquaculture. In this study, Pacific white shrimp (Penaeus vannamei) were fed diets containing 0%, 0.5%, 1.0%, 1.5%, or 2.0% crude extracts from the microalga Porphyridium cruentum for 30 days. After dietary supplementation, the shrimp were exposed to Vibrio alginolyticus, allowing the assessment of phenoloxidase activity (PO) and total hemocyte count (THC) pre- and post-challenge, as well as shrimp survival rates. Shrimp that received the 1.0% treatment had greater survival (90%) at 48 h post-challenge, while the 0% and 2.0% treatments had survival rates close to 63% in the same period. Furthermore, at 48 h post-challenge, THC was significantly greater (p < 0.05) in the shrimp that received crude extract supplementation compared to that in shrimp of the control group (0%). PO showed a proportional increase according to crude extract inclusion levels. Such dose-dependency in response to PO increases became significantly greater (p < 0.05) in the 2.0% treatment group compared to that in the 0% treatment group in the pre-challenge period and that in the 0% and 0.5% treatment groups in the post-challenge period. These results showed that crude extracts from P. cruentum could be considered immunostimulants by increasing the resistance of P. vannamei exposed to V. alginolyticus, potentially representing a major breakthrough for marine shrimp farming. Full article

This study investigated the adaptability of Dunaliella salina to different salinity levels, with an emphasis on growth, pigment concentration, and desalination potential. It was found that among the 21 salinity levels, Salinity 75 produced consistently favorable results in cell count (13.08 × 10³ ± 1.41 × 10³ cells/mL), dry biomass (2.46 ± 0.06 g/L), pigment content (chlorophyll a = 97,500,000 ± 100,000 pg/L, chlorophyll b = 123,600,000 ± 300,000 pg/L), and desalination (9.32 ± 0.47 reduction). Therefore, Salinity 75 was selected for the final trial (scale-up), which revealed unanticipatedly high cell counts (58.96 × 10³ ± 535.22 cells/mL), with the dry biomass weight being statistically different (higher) than expected (4.21 ± 0.02 g/L) (p < 0.0001), most likely due to the high cell count and energy reserve storage for high-salinity adaption in the form of bio-compounds. Pigment growth continued (chlorophyll a = 95,400,000 ± 2,200,000 pg/L, chlorophyll b = 128,100,000 ± 5,100,000 pg/L), indicating pigment production under salt stress. Notably, desalination did not occur in this stage, possibly due to the necessity for a bigger initial inoculate, prolonged exposure or bioaccumulation becoming the prevailing mechanism over desalination. Nevertheless, the trial highlights D. salina’s strong adaptation to various salinity levels. This suggests a promising future in halophyte research, particularly in understanding the mechanisms that prevent salt accumulation in cells and how to overcome this barrier. Additionally, these results suggest that microalgae could be a viable resource in saline-rich environments unsuitable for conventional agriculture, promoting industrial adaptation to adverse conditions. Full article

Tenacibaculum discolor develops biofilm in marine aquaculture production tanks and is identified as one of the causative agents of tenacibaculosis, a bacterial disease that causes significant losses in marine aquaculture production. In this study, the biofilm characteristics of T. discolor strain FMCC B487 were evaluated. Cell growth and biofilm formation and development were studied in miniaturized assays to assess the effect of different levels of environmental factors temperature and salinity, as well as the presence of monosaccharides potentially found in aquaculture hatcheries. The ability of the strain to grow and develop strong biofilms in ambient to high temperatures and at salinities above 20 g/L was shown. Mannose was the monosaccharide with the most prominent impact on the T. discolor strain FMCC B487 biofilm. The composition of planktonic cell extract, biofilm extracts, and extracellular polymeric substances (EPS) produced by T. discolor strain FMCC B487 were investigated by means of colorimetric and fluorometric assays as well as analyses by electrophoresis, gas chromatography, and high-performance size-exclusion chromatography coupled with a multiangle light scattering detector, revealing the dominance of proteins and lipids and the absence of high-molecular-weight polysaccharides. This information may serve as a basis for considering anti-biofilm strategies against the pathogen T. discolor. Full article

The Italian shellfish industry mainly comprises clams, mussels, and oysters. While clam production thrives and Italy leads Europe, mussel farming faces economic challenges. Oyster production is relatively new and holds potential. Sustainable development is crucial for meeting growing seafood demand while ensuring resource conservation and food safety. This paper, part of the VALUE-SHELL project funded by the Italian Ministry of Agriculture, Food Sovereignty and Forests (MASAF) as part of support activities for the National Strategic Plan of Aquaculture, combines desk research on industry structure and public interventions using a collaborative approach involving stakeholder interviews and focus groups with producers and local entities to assess the sector’s most compelling needs. The collaborative process highlighted key challenges across the following four sustainability pillars: environmental (global warming, predator control, and pollution mitigation are critical concerns for ecosystem balance); economic (increased production costs and limited diversification opportunities affect profitability); social (fear of generational decline due to limited training and education opportunities poses a threat to the industry’s future); and institutional (lack of a dedicated aquaculture law and fragmented governance hinder long-term planning). The project identifies policy bottlenecks hindering the sector’s potential, caused by not fully addressing producer needs. Sustainable development strategies are essential for addressing these challenges and ensuring the Italian shellfish industry’s future. Full article

Chelon labrosus represents a promising species for current aquaculture to lean towards a more sustainable model. The control of reproduction in captivity is essential to develop the industrial production of new species. This work adds to the knowledge of the reproductive aspects of males and females of this species. We aim to (1) develop a methodology for sex identification of reproductive and prereproductive specimens of the studied species based on the plasma levels of steroid hormones—estradiol (E2) and 11-ketotestosterone (11-KT); (2) determine the maturity evolution of the females throughout the spawning season by gonadal biopsy; and (3) describe sperm quality throughout the breeding season (volume, motility, density). The results show that an 11-KT/E2 ratio > 0.4 is 100% effective in distinguishing males from females, provided that individuals present a size greater than that of first sexual maturity. A double trend was observed in the development of oocytes, with an increase in the initial diameter until the middle of the spawning season, followed by a divergence of the group, with some females continuing the maturation process and others going into regression. Sperm data show stable quality at the beginning and in the middle of the spawning season and a significant loss of quality at the end of the reproductive period. The present study also shows that, between the beginning and the middle of the reproductive season, males of this species can recover sperm volume removed by stripping. Full article

The study aims to characterize the immune cell landscape in convalescent Asian seabass (Lates calcarifer) blood samples after exposure to scale-drop disease virus (SDDV). Traditional immunophenotyping approaches used in human and mouse studies are impractical for non-model organisms like the Asian seabass due to the lack of specific antibody-based reagents. To overcome this challenge, 10x Genomics single-cell RNA sequencing was employed. The analysis of blood samples revealed 24 distinct leukocyte clusters, with elevated proportions of B cells, granulocytes, and T cells in the convalescent group compared to the uninfected group. While distinguishing granulocyte and macrophage subsets was challenging, the analysis of differential gene expression in the macrophage population indicated that the upregulated genes were linked to inflammatory processes. Specific T cell clusters showed notable expressions of cd4-1, cd8a, perforin-1 and il-2rβ, suggesting the presence of CD4+ T helper (Th), CD8+ cytotoxic T (Tc) cells, immature T cells, and naive T cells. Attempts to categorize CD4+ T cells into Th subtypes lacked clear distinctions, while CD8+ T cells exhibited three clusters, predominantly Tc1 cells. Furthermore, comparisons between convalescent and uninfected groups revealed increased percentages of activated and antibody-secreting B cells in the convalescent group. This single-cell analysis provides vital insights into the immune cell dynamics in convalescent and uninfected Asian seabass, providing valuable information on potential immune responses to SDDV infection. Full article