Biology and Life Sciences

Abstract: The freeze-thaw process in sperm cryopreservation generates reactive oxygen species (ROS) that impair motility, viability, and fertilizing capacity in fish, including the Javan barb (Systomus rubripinnis), an endemic Indonesian cyprinid of conservation concern. This study evaluated five natural antioxidants: basil leaf extract (BLE), noni fruit extract (NFE), moringa leaf extract (MLE), sambiloto leaf extract (SLE), and honey-egg yolk (HEY). Radical-scavenging capacity was measured by DPPH assay (IC₅₀: BLE 134.06, MLE 297.04, NFE 422.86, SLE 3010.46 ppm), and post-thaw motility, duration of motility, viability, abnormality, fertilization rate, and ATP bioluminescence were assessed. Optimum doses were 1% for BLE, NFE, and MLE, 1.25% for HEY, and 7% for SLE. BLE at 1% gave the best overall profile (motility 85.15 ± 0.88%; duration 7.14 ± 0.38 min; viability 82.21 ± 1.86%; abnormality 18.29 ± 0.16%), significantly exceeding the control (65.00 ± 2.31%; 4.56 ± 0.33 min; 68.00 ± 2.42%; 23.54 ± 0.28%; p < 0.05), whereas SLE sustained the longest motility. All extracts supported fertilization rates above 82% versus 70.08 ± 3.82% in the control, and 1% BLE preserved post-thaw luminescence equivalent to fresh sperm (165,217 vs. 164,087 RLU), interpreted comparatively. These plant-derived antioxidants are promising supplements for Javan barb germplasm conservation.

Abstract: Our current understanding of the early developmental characteristics and growth traits of the potato grouper (Epinephelus tukula) is limited but necessary for the development of large-scale aquaculture farming of this species. To investigate this, this study used artificially propagated E. tukula and systematically observed embryonic and morphological development processes of both larvae and juvenile fish and analyzed the growth characteristics during the young developmental stage. Under water temperature and salinity conditions of 23.9 ± 0.4°C and 28-30 ppt, respectively, the fertilized eggs completed embryonic development in 25 h 34 min, sequentially passing through seven typical stages: fertilization, cleavage, blastula, gastrula, neurula, organogenesis, and hatching. The newly hatched larvae had an average total length of 1.60 ± 0.17 mm. The yolk sac and oil globule were visible at 1 dph (days post-hatching); at 3 dph they began exogenous feeding; the prototype of the “trident” appeared at 9 dph; by 30 dph, the fins were almost fully developed and the fish entered the juvenile stage; by 35 dph, the second dorsal fin spine and pelvic fin spine began to shrink; by 55 dph, spots and scales covered the entire body, and the fish entered the young developmental stage. After 105 dph, average body weight increased from 34.134 ± 5.85 g to 135.28 ± 20.11 g, and average total length increased from 13.41 ± 0.81 cm to 21.29 ± 1.15 cm. The best-fit model between average total length (TL) and age was the quadratic function TL = -0.001t² + 0.283t - 11.018 (R² = 0.982). The results of this study showed that the E. tukula has a relatively fast embryonic development rate, typical morphological changes in larval and juvenile stages, and rapid early growth in the young developmental stage, while the specific growth rate decreased with prolonged culture time. This study provides relevant biological information for the artificial propagation, fry rearing, and selective breeding of this species.

Abstract: Dissolved iron and low pH are widespread stressors in streams draining iron-rich soils, wetlands and former lignite-mining areas. The biological effects of ferrous iron are difficult to assess from iron concentration alone, because toxicity depends on pH, exposure duration, chemical form and species sensitivity. This study examined the combined effects of dissolved ferrous iron (Fe²⁺) and pH on the survival of brown trout (Salmo trutta), common dace (Leuciscus leuciscus) and European eel (Anguilla anguilla) exposed in flow-through cages in Danish lowland streams.Groups of five fish were exposed under field conditions, and survival was recorded after approximately one week and one month. Mean Fe²⁺ concentration and mean pH during each exposure period were related to survival using observed Fe²⁺–pH distributions and binomial generalised linear models. The final dataset comprised 128 one-week and 102 one-month observations for brown trout, and 21 observations for each exposure period for common dace and European eel.Brown trout showed the clearest response. Survival decreased consistently with increasing Fe²⁺ concentration and decreasing pH after both one week and one month. Common dace showed a more variable response, with weaker statistical support, especially after one month. European eel was the most tolerant species, with high survival across much of the observed Fe²⁺–pH range, although mortality occurred under some low-pH and high-iron conditions.The results show that no single Fe²⁺ concentration can be used as a universal survival threshold. Assessment of iron-rich streams should consider Fe²⁺ concentration together with pH, exposure duration, species and life stage.

Abstract: This study integrates cohort number and biological production, food consumption, feeding ecology, growth and mortality of brown trout (Salmo trutta) in Danish lowland streams monitored over long-term periods. Increasing trout density reduced instantaneous growth rate and final body size of Age-0 brown trout while increasing within-cohort variability, demonstrating strong density-dependent growth regulation. Total cohort production and food consumption increased with recruit abundance, whereas production and consumption per recruit declined strongly with increasing density, indicating reduced individual performance under crowded conditions. Despite marked interannual variation in yearly production, total yearly consumption remained comparatively stable, suggesting an upper energetic constraint imposed by prey production and stream carrying capacity. Energetic P/C ratios differed markedly between streams, averaging approximately 0.068 in BRB and 0.142 in TJB, and declined strongly with increasing body mass. Natural mortality increased with population density but decreased strongly with body mass and consumption per individual, indicating that survival was closely linked to energetic status and cumulative growth history. Feeding analyses showed that trout in both streams fed mainly on aquatic invertebrates, and prey composition overlapped substantially between streams. Overall, the results demonstrate that production, consumption, growth and mortality are tightly interconnected through density-dependent and bioenergetic mechanisms operating simultaneously at cohort and individual levels.

Abstract: To systematically evaluate the growth heterosis and genetic characteristics of the hybrid offspring E. moara ♀ × E. tukula ♂, this study assessed the phenotypic growth pattern through a comparative breeding experiment and cytogenic and molecular genetic characteristics through integrated chromosomal karyotype and mitogenomic analyses. The results showed that at 9 months of age, the body weight of the hybrid offspring reached 137.08 ± 26.41 g, which was 1.50 times that of the maternal E. moara (91.60 ± 18.63 g), but significantly lower than that of the paternal E. tukula (178.19 ± 32.74 g), exhibiting a mid-parent growth heterosis (1.62%). The chromosome number of the hybrid offspring was 2n=48, with a karyotype formula of 2sm+1st+45t, NF=51, and an intermediate chromosomal composition between the parents. The mitochondrial genome was 16,405 bp, and its gene composition, arrangement order, base composition and codon usage preference were highly consistent with those of E. moara. A phylogenetic analysis further supported that its mitochondrial genome strictly followed maternal inheritance. This study provides a theoretical foundation for evaluating the breeding potential and germplasm characteristics of E. moara ♀ × E. tukula ♂ hybrids.

Abstract: Adult crayfish P. leniusculus originating from wild stocks of northwestern Greece, Epirus County, were randomly allocated in indoor RAS aquaria, following two dietary protocols: a semi-purified diet by total substitution of fish oil and entire substitution of fishmeal with plant-derived materials, and a control diet consisting of fresh Pangasianodon spp. and mixed vegetables. The semi-purified diet had a P: E ratio of 22.74 mg Prot. kj-1, a Protein level of 38.68% and a Crude Lipid level of 9.51% (on a DM basis), while the control diet had a P: E ratio of 22.13 mg Prot. kj-1, a Protein level of 37% and a Crude Lipid level of 4.5% (on a DM basis). Despite the total substitution of corn oil by soy oil, the exclusion of fish oil and the entire substitution of fishmeal by other plant-derived materials, the semi-purified diet did not hinder growth throughout the experiment with acceptable survival rates. It has also been demonstrated that the signal crayfish P. leniusculus has limited dietary requirements for the PUFAs EPA & DHA and that dietary linoleic and linolenic acids are indispensable for the species. Finally, the ability of signal crayfish for bioconversion of EPA to DHA remains questionable.

Abstract: Tenacibaculosis, caused by Tenacibaculum maritimum, remains a major bacterial disases affecting marine aquaculture, particularly European seabass farming. This study evaluated the immune response and efficacy of a formalin-inactivated T. maritimum vaccine administered by immersion or intraperitoneal (i.p.) injection in European seabass (Dicentrarchus labrax). Fish were challenged 36 days post-vaccination. Vaccine performance was assessed by relative percent survival (RPS), expression of immune markers (IL-1β, IL-10, IgT), and specific IgM production. Intraperitoneal vaccination provided significant protection, with 87% survival and an RPS of 67.5, accompanied by elevated serum IgM levels and strong systemic immune activation. Immersion vaccination resulted in complete survival under the experimental conditions; however, low mortality in the control group prevented reliable assessment of vaccine efficacy. Gene expression analysis revealed distinct immune profiles: immersion vaccination induced rapid but transient mucosal and systemic responses, whereas i.p. vaccination elicited stronger and more sustained systemic responses, particularly in innate and humoral pathways. Principal component analysis confirmed clear separation of immune responses according to vaccination route. Overall, i.p. vaccination induced stronger protective immunity, while optimization of immersion vaccination protocols is needed to improve protection against tenacibaculosis in European seabass.

Abstract: The taxonomic composition and zoogeographic characteristics of the malacofauna of the upper Konda River basin, a major left tributary of the Irtysh River within the taiga zone of Western Siberia, were identified. A total of 27 species of freshwater mollusks were recorded, including 19 bivalves and 8 gastropods. In terms of taxonomic structure and species composition, the malacofauna of the upper Konda differs significantly not only from most local freshwater mollusk faunas of Western Siberia but also from the middle reaches of the same river system. This indicates the impossibility of directly applying the River Continuum Concept in this case. The greatest genetic relationship between the populations of the studied species in the study area and populations from European Russia and Europe is demonstrated. Not all populations had similar haplotypes; in some cases, intrapopulation haplotypes differed significantly. The results of testing the a priori classification of water bodies based on the composition of malacocenoses indicate a lack of reliable support. A typology of freshwater mollusk habitats in the upper reaches of the Konda River basin is proposed, based on patterns of their distribution across environmental gradients.

Abstract: Invasive species are managed to mitigate ecosystem effects; however, unintended consequences from suppression may result. Investigating effects of management actions on lower trophic levels and nutrient dynamics can help avoid unintended consequences. Fish carcasses were deposited in the littoral zone in Yellowstone Lake, Wyoming, U.S.A. during autumn to suppress embryos of invasive trout at spawning sites. We studied the degree to which adding carcasses to the littoral spawning sites indirectly benefited invasive trout by altering food resources. We used carcasses as a natural isotopic tracer to estimate the degree to which carcasses were integrated into the food web. We compared basal resource and amphipod δ15N and δ13C signatures at reference and treatment sites. We also estimated the contribution of carcasses to amphipod diet, and the contribution of amphipods to invasive and native trout diets using stable isotope mixing models. Isotopic signatures of basal resources did not differ between treatment and reference sites. Amphipod isotopic signatures changed after treatment, but &lt; 3% of amphipod diet was carcass. Amphipods contributed &lt; 24% of estimated diet for invasive trout, but &gt; 55% of estimated diet for native trout. δ13C values of amphipods and phytoplankton increased at reference and treatment sites after autumn turnover suggesting carcass material was distributed throughout the lake. Unused carcasses from gillnetting discarded in the profundal zone since 1995 appeared to influence nutrient dynamics more than those added to the littoral zone. We demonstrate that investigating food web dynamics simultaneously with suppression to prevent unintended consequences can aid in developing effective management plans that minimally alter ecosystems.

Abstract: Laos is one of the 32 landlocked developing countries (LLDCs) of the world, where the isolation from the sea and the lack of a large-scale fishing industry have a direct effect on fish supply and fish consumption. Per capita fish consumption in LLDCs amounted to 4.6 kg/year in 2017, which is much lower than the world average (20.3 kg) as well as the Developing Regions average (19.4 kg). However, per capita fish consumption in Laos has reached 25.57 kg/year in 2021 representing the highest among the 32 LLDCs. Relying on the results and experiences of several decades of work in aquaculture development in Laos and taking into account the observations of local and international publications, documents and statistics included, the authors have investigated the reasons for the elevated fish consumption in Laos from different perspectives including that of aquaculture, and Lao language, culture, and religion. In this review, the authors analyzed the availability of aquatic resources, the role of fishing and aquaculture in the Lao economy and social life, market realities, as well as the importance of fish in the Lao culture.

Abstract: Functional feed ingredients with antimicrobial activities are being explored as a tool to mitigate diseases in Atlantic salmon (Salmo salar L.). Skeletonema marinoi is a marine diatom known to have antimicrobial activity. Here, two separate experiments, including a growth study (Exp.1) and a bacterial challenge (Exp.2), were conducted to evaluate the effects of dietary S. marinoi as a functional feed ingredient on the growth, feed utilization, stress biomarkers, antioxidant defense, and immunogenic responses of Atlantic salmon. In Exp 1, a 16-week growth trial was conducted in a recirculating aquaculture system (RAS) stocked with ten fish (59.6 ± 1.6 g, initial weight) in each of five replicate tanks per treatment. Fish were fed twice daily with either the reference diet or the reference diet supplemented with 0.5% S. marinoi. In Exp. 2, a 27-day bacterial challenge with Vibrio anguillarum Serotype O3 (SO3) was conducted in RAS using 36 fish (100–150 g) per 150 L tank in triplicate. Fish were acclimatized to the RAS for 14 days and fed twice daily with the reference or 0.5% S. marinoi diet prior to the bacterial challenge. Blood plasma, liver, and intestine samples were collected after the growth trial, before (initial, 0 day) and post-challenge (5, 10, 27 days). The results indicated that in Exp. 1, there were no significant differences in survival, final weight, weight gain, feed intake, feed efficiency, condition factor, and hepatosomatic index between fish fed with the reference diet and 0.5% S. marinoi diet. In Exp. 2, before challenge, Atlantic salmon fed the diet with 0.5% S. marinoi showed significantly higher superoxide dismutase (SOD) activity in comparison to fish fed the reference diet. On day 5 post-challenge, significantly higher liver peroxidation or malondialdehyde (MDA) level was measured in the 0.5% S. marinoi group compared to the reference group. Plasma immunoglobulin M (IgM) level and intestinal IgM gene expression increased after challenge in fish fed 0.5% S. marinoi, in contrast to those fed the reference diet at 27 days post-challenge (P < 0.05). Overall, these findings suggest that S. marinoi is more likely to be associated with immune modulation rather than adverse stress response; however, further work is required to confirm pathogen-specific immunity.

Abstract: Extensive networks of irrigation canals and drainage collectors have been established across much of the Syr Darya River basin, substantially modifying natural freshwater habitats. We examined the diversity of macroinvertebrates and fish in two types of ditches and adjacent river sections in relation to eight abiotic environmental variables and dominant algal groups, with particular emphasis on blackflies (Diptera: Simuliidae) and fish as ecologically and socioeconomically important taxa in the region. Drainage ditches were characterized by low summer water temperatures and reduced turbidity compared with adjacent river habitats. These conditions likely contributed to the formation of a distinct faunal assemblage. Of the 46 animal species recorded, 11 were restricted to ditches, indicating the development of a specific ditches-associated community. Both kind of the ditches provided favourable conditions for Simuliidae larvae and played an important role in supporting local blackfly populations. Fish assemblages in drainage ditches and collectors were dominated by non-native species, indicating strong anthropogenic influence. In the Syr Darya and Arys rivers, blackfly larvae serve as a food resource for at least ten fish species; however, despite their abundance in ditches, they were not a primary prey item for fish inhabiting these habitats. Overall, collectors and drainage ditches represent important secondary aquatic habitats that significantly contribute to regional biodiversity patterns and influence the distribution and ecological interactions of key aquatic taxa in the Syr Darya River basin.

Abstract: Background: Aquaculture supplies over half of global fish consumption but faces challenges including disease outbreaks, oxidative stress, antimicrobial resistance, and reliance on finite fishmeal and fish oil resources. Methods: This review synthesizes research on freshwater and marine microalgae, focusing on their bioactive compounds and functional roles in aquaculture nutrition and health. Results: Microalgae provide proteins, carotenoids, vitamins, polyunsaturated fatty acids, and immunostimulants that act via immunomodulation, antioxidant defense, gut microbiota regulation, anti-inflammatory activity, growth promotion, and pigmentation enhancement. Applications include live feed in larval rearing, dried biomass in compound feeds, and microalgal oils as fish oil substitutes. Conclusions: Incorporating microalgal nutraceuticals into aquafeeds offers a sustainable strategy to improve aquaculture productivity, animal health, and product quality, supporting the transition toward resilient and ecologically sustainable systems within the One Health framework.

Abstract: To optimize spat stocking rates for Pacific calico scallop (PCS, Argopecten ventricosus) during nursery culture, two consecutive 8-week trials were conducted to evaluate growth in land-based downweller and upweller systems. Four stocking rates (60%, 70%, 80%, and 90% of silo bottom coverage) were tested in the downweller system, whereas three stocking rates (50%, 70%, and 90% of silo bottom coverage) were evaluated in the upweller system. In the downweller system, spat stocked at 60% generally exhibited the best growth performance, with significantly higher relative growth rate (RGR, mm/day) in shell height compared with higher stocking rates. In the upweller system, spat stocked at 50% and 70% showed similar growth performance and both outperformed the 90% stocking rate treatment in shell height, dry weight, RGR, specific growth rate (SGR, %/day), and condition index (CI). These results suggest that moderate stocking rates, approximately 60% in downweller systems and 50–70% in upweller systems, provide favorable conditions for PCS spat growth under the present culture conditions. The present study demonstrates the feasibility of PCS spat nursery culture in land-based systems and provides practical information for hatchery production and nursery management of this emerging aquaculture species.

Abstract:

Integrated proteomics and untargeted metabolomics were employed to systematically characterize molecular differences between high-quality (HQ) and low-quality (PQ) eggs of Acipenser schrenckii. Among 1,636 proteins and 1,102 metabolites, 220 differentially expressed proteins (DEPs) and 365 differential metabolites (DMs) were identified. Functional enrichment demonstrated that HQ eggs were predominantly enriched in pathways associated with amino acid biosynthesis, glycolysis/tricarboxylic acid cycle, nucleotide metabolism, and mRNA surveillance, which collectively supported material accumulation, energy supply, and embryonic developmental competence. In contrast, PQ eggs were mainly enriched in oxidative phosphorylation, mitochondrial stress response, arachidonic acid metabolism, and immune and inflammatory signaling pathways, indicating severe lipid metabolic disorders and excessive oxidative stress. Spearman correlation analysis identified L-pyroglutamic acid and ascorbic acid as core metabolic hubs responsible for maintaining high egg quality, whereas natamycin and tetrahydrocorticosterone served as characteristic metabolic biomarkers of deteriorated eggs. Key protein hubs closely associated with egg quality included GAPDH, glutathione S-transferase, and CYP450 2E1. Collectively, this study elucidates distinct molecular regulatory patterns and establishes a reliable multi-omics biomarker for evaluating sturgeon egg quality formation and deterioration.

Abstract: This study evaluated the use of finishing diets to reduce fish oil (FO) inclusion in European sea bass feeds while preserving fillet quality and n-3 fatty acid content. Fish (197 g) were fed for 25 weeks with a control FO diet, based on 9% FO and 6% plant oil, or diets where 6% FO was replaced by rapeseed oil (RO) or microalgae (AO; Nannochloropsis sp. and Schizochytrium sp.). After 13 weeks, 2 groups of fish fed the RO diet were switched to the FO or AO finishing diets for the final 12 weeks. Growth, feed efficiency, body composition, and health were unaffected by dietary treatments. However, long-term RO feeding reduced EPA and DHA and increased monounsaturated and n-6 fatty acids compared to fish fed AO or FO. Finishing diets effectively restored morphometric traits, fatty acid profiles, liver histology, and overall fish quality, with FO outperforming AO in recovering the original fatty acid composition of FO-fed fish. Longer finishing periods may further enhance fillet quality when using microalgae-based oils.

Abstract: This study presents the development and application of an integrated Geographic Information System (GIS)-based Marine Spatial Planning (MSP) framework for identifying suitable offshore aquaculture development zones in Cyprus. The methodology, developed within the OS AQUA project, combines environmental exclusion analysis, weather and proximity assessment, stakeholder and policy evaluation, and carrying-capacity estimation within a unified spatial decision-support framework. A sequential three-phase analytical workflow was applied to progressively refine candidate offshore areas under environmental, operational, infrastructural, regulatory, and governance considerations. The analysis identified four candidate offshore aquaculture zones in Cyprus — Xylofagou West, Larnaka (Faros area), Governor’s Beach, and Aphrodite Hills/Avdimou — demonstrating comparatively favourable conditions for offshore aquaculture development. The results highlight the importance of integrating environmental compatibility, operational feasibility, accessibility, stakeholder acceptance, and sustainability considerations within offshore aquaculture planning processes. Carrying-capacity assessment further indicated substantial offshore production potential under precautionary operational assumptions. Beyond the Cyprus case study, the proposed GIS-MSP framework offers a transferable methodological roadmap for offshore aquaculture zoning, Allocated Zones for Aquaculture (AZA) establishment, and sustainable marine spatial planning in the Mediterranean region.

Abstract: Using marine resources’ colouring agents as nutrients, medicaments and in luxury products colouring is rooted in human history. The handy obtainable marine biological pigments (MBPs), consider as inexpensive materials since colourants. They were a part e of blue technology for colouring purposes, as nutrient additives, cosmetic gradients, beauty products, staining addresses and fashion colour in luxury. Today, they still broaden many new applications. They can be concentrated on the bodies of marine creatures providing unique colour, properties and complement activities. They can stand alone to process unique activities. In addition, some are essential for host survival. Out of their primary hosts, they stay either unmodified or can be changed or associated with other micro and/or macromolecules in their secondary hosts (consumers). Few were extracted, purified, identified and formulated as drugs. Many share properties like being antioxidants, having the ability to protect from sunlight (as UV waves) and improving eye vision. They are involved in health protection or illness treatment, as anticancer, anti-inflammatory, anti-neuro-degradation, antiaging, anti-wrinkle, and as antimicrobial. Even they hold many undiscovered properties that make them an uncountable source for de nevo applications with innumerable chances that mastery the colourful fields. This review summarizes the importance of marine pigments and addresses important applicable properties that made them interesting in nutraceutical, medicinal, pharmaceutical, cosmeceutical and industrial applications. In addition, it is concerned with discussing some facts that have attracted the attention of humans in the past today and some expectations for the MBPs future.

Abstract: Linking community variation to environmental gradients is central to reservoir ecology and monitoring, yet the strength of detected associations can depend on how community change is represented. Using phytoplankton surveys from a tropical reservoir (Corumbá River, Brazil) sampled across wet and dry seasons, we compared taxonomic beta diversity with two functional representations: Reynolds functional groups and a set of widely used morphological traits combined into functional beta-diversity indices. We partitioned beta diversity into turnover and richness-difference components and quantified environment–community associations with constrained ordination. Overall, the representation chosen altered both the magnitude and the seasonal consistency of environmental associations: trait-based indices (particularly dendrogram-based metrics weighted by biovolume) tended to show stronger associations with environmental gradients related to mixing, light availability and nutrients, whereas functional groups and species-level data emphasized complementary aspects of community change. Turnover and richness-difference components did not respond uniformly across representations, highlighting that component choice can shift ecological interpretation. Rather than providing a universal ‘best’ approach, our results suggest practical trade-offs among representations when the goal is to detect and interpret environmental structuring along reservoir gradients, especially during highly dynamic conditions typical of early post-impoundment phases.

Abstract: Reliable age information is needed for fisheries assessment, but conventional otolith reading requires trained readers and considerable time. This study evaluated whether convolutional neural networks could classify reader assigned age classes of Japanese jack mackerel Trachurus japonicus directly from sagittal otolith images. Otolith images from fish aged 0 to 4 years were used to compare three image only backbones: Inception v3, Xception, and EfficientNet B4. The models were trained under the same data split, preprocessing, augmentation, and evaluation framework. In Stage 1, Inception v3 showed the highest validation macro F1 score (0.933) and was selected as the image only baseline. After additional optimization, the selected model reached a validation macro F1 score of 0.944, validation exact accuracy of 0.935, and validation agreement within one age class of 1.000. On the independent test set, the optimized image only model achieved exact accuracy of 0.866, macro F1 score of 0.873, and agreement within one year of 1.000. These results indicate that otolith images contain useful age related visual information. Convolutional neural networks may support age class screening in T. japonicus, although they should complement rather than replace expert otolith reading.