Einar Ringø

The composition of fish gut microbiota has direct implications for aquaculture productivity as alterations in these microbes profoundly affect several physiological functions of the fish. Nowadays, aquaculture feeding strategies increasingly shift from animal‐derived diets toward more sustainable plant‐based diets; understanding how the influence of a specific dietary component on fish gut microbiota has become increasingly important. Furthermore, the advancement of microbial genome sequencing technologies provides more comprehensive information on the effects of various dietary components on the gut microbiota of fish. Changes in these macronutrients and micronutrients can disrupt the eubiosis, gradually leading to dysbiosis by selectively enriching microbial guilds with distinct metabolic capacities, ultimately affecting the host‐microbial interaction, gut homeostasis, and overall fish health. Mostly, animal‐derived proteins and marine oils often favour the growth of bacteria that can metabolize proteins and lipids, whereas plant‐based proteins support the growth of bacteria that can ferment complex carbohydrates to produce beneficial metabolites, including short‐chain fatty acids. Feed additives are important to modulate the gut microbiota of fish via enhancing the abundance of beneficial bacterial species. Therefore, formulating aquafeeds by targeting on promoting the growth of beneficial gut microbiota and assessing the value of feed ingredients via considering the gut homeostasis indices seems useful. This review upgrades our knowledge on how dietary components interact and regulate the gut microbiota, ultimately influencing overall fish performance. Designing next‐generation aquafeeds and developing precision nutrition for the fish and their microbiota using advanced omics and artificial intelligence technologies to develop climate‐resilient fish farming is crucial.

Copepods are a good live feed for aquaculture because they feed a variety of fish and crustacean larvae. Their roles in larviculture are explained by their ecological role in the transfer of energy from primary producers to higher trophic levels. Copepods exhibit higher levels of protein, amino acid profiles, digestive enzymes, and essential fatty acids, such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which are critical for larval growth, neural development, stress resilience, and survival, when compared to conventional live feeds like rotifers and Artemia nauplii. Despite all of these advantages, copepod use is constrained by significant production constraints. Complex life cycles, sensitivity to environmental changes, changes in the nutritional makeup of algal diets, and difficulties achieving reliable high-density production are some of the difficulties that mass culture faces. The persistent obstacles continue to restrict their widespread commercial use. This review summarizes what is currently known about the ecological importance of copepods, assesses their nutritional value and production limitations, and suggests important lines of inquiry to improve their widespread use as sustainable live feed in aquaculture.

This study investigates the impact of dietary supplementation with nanoparticles of Arthrospira platensis (previously known as Spirulina platensis ) on the performance of the mullet Mugil cephalus during a 63‐day feeding trial. Fish (14.75 ± 0.23 g/fish) were randomly distributed into five groups of 30 fish per hapa, with three replicates per group. Five experimental diets were prepared to assess nano‐ A. platensis supplementation at three inclusion levels: 0.5, 5, and 10 g/kg (SN _0.05% , SN _0.5% , and SN _1% ). Two control groups were included for comparison: a negative control without additives (S _0% ) and a positive control with 1% non‐nanoform A. platensis (S _1% ). Among all SN groups, the fish fed the SN _0.05% diet showed significant ( p ≤ 0.05) values for final weight (FW), specific growth rate (SGR), weight gain (WG), feed conversion ratio (FCR), protein efficiency ratio (PER), and feed efficiency ratio (FER). Also, the middle intestine showed marked improvements ( p ≤ 0.05) in villus height and width, muscularis mucosa thickness, and the number of goblet cells when fish were fed the various SN levels or the S _1% diet. Moreover, fish treated with A. platensis nanoparticles showed a noticeable enhancement in hepatic histomorphology, with the SN _0.05% group exhibiting the most intact hepatic structure. However, the S _0% diet had the highest alanine aminotransferase (ALT) and aspartate aminotransferase (AST) compared to other diets supplemented with different A. platensis levels. No significant difference ( p > 0.05) in albumin levels was observed. Non‐nano A. platensis improved immunoglobulin M (IgM) activity compared with the control (S _0% ). The nanoform diets resulted in the highest lysozyme (LYZ) activity, with the SN _0.05% treatment showing the highest values of all groups. Fish fed A. platensis , either as nanoparticles or in its non‐nano form, showed significantly lower triglyceride and cholesterol levels ( p ≤ 0.05) than those that were fed the control diet (S _0% ). Additionally, all diets containing either nano‐ or non‐nanoform A. platensis (SN _0.05% , SN _0.5% , SN _1% , and S _1% ) resulted in increased activities of glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT), alongside decreased malondialdehyde (MDA) levels, in comparison to S ₀ %. In general, our findings showed that A. platensis nanoparticles improve M. cephalus growth performance, intestinal and hepatic histomorphology, immune response, feed utilization, and antioxidant enzyme activity. Therefore, nano‐ A. platensis could be an efficient feed additive for M. cephalus , making mullet farming more environmentally friendly and cost‐effective.

Aquaculture faces escalating bacterial disease burdens and mounting antimicrobial resistance (AMR) driven by intensive production and extensive antibiotic use, threatening animal health, productivity, and One Health security. This review synthesizes current knowledge on natural antibacterial compounds derived from aquatic animals, with a primary focus on antimicrobial peptides (AMPs) and related metabolites from finfish, crustaceans, mollusks, echinoderms, gastropods, cnidarians, and other invertebrates. After outlining the global status of major Gram-negative and Gram-positive fish and shellfish pathogens, their infection routes, and the limitations of conventional control measures, the review critically examines skin mucus, serum and organ factors, hemolymph-derived AMPs, tissue lectins, and non protein bioactives such as chitin, chitosan, and carotenoids. Particular emphasis is placed on cationic, α helical AMPs (≈350 reported from aquatic invertebrates) that exhibit broad-spectrum activity against Vibrio spp., Aeromonas spp., Streptococcus spp., Staphylococcus aureus, Escherichia coli, and Salmonella through membrane disruption, intracellular targeting, and immunomodulation, often with lower resistance propensity than conventional antibiotics. Less conventional sources, including echinoderms, gastropods, and cnidarians, are highlighted for their structurally diverse peptides, saponins, and microbiome-derived metabolites that show promising in vitro and in vivo efficacy and compatibility with saline environments. The review further discusses omics driven discovery, bioinformatics-guided peptide design, and biotechnological production (recombinant systems, synthetic analogs, and valorization of processing by products) as key enablers for scale up and standardization. Finally, major challenges—variability of natural sources, cost, regulatory hurdles, safety, and environmental fate—are evaluated alongside research and policy priorities needed to translate aquatic-animal-derived antibacterials into integrated, commercially viable tools for sustainable, antibiotic sparing aquaculture.

Shrimp aquaculture is a key element of the global seafood sector. However, outbreaks related to bacterial and viral infections pose a serious threat to its productivity and sustainability. While the application of antibiotics has been a long-standing practice of combating these infections, their uncontrolled use has led to antimicrobial resistance, ecological disturbance, and perturbation of the beneficial microbiota. This review critically examines current antibiotic alternatives in shrimp aquaculture, with a particular focus on strategies targeting viral diseases. Emphasis is placed on biological approaches – using probiotics, prebiotics, immunostimulants, phytobiotics (e.g., herbal extracts & essential oils), and dietary interventions – as well as emerging technologies including nanotechnology and phage therapy. By synthesizing recent research, the review highlights eco-friendly, effective methods for enhancing shrimp health and disease resistance. It aims to bridge existing gaps in shrimp immunoprophylaxis and offer a framework for sustainable, antibiotic-free disease management in aquaculture.

The gut microbiome plays a significant role in regulating gastrointestinal (GI) function and modulating the gut–brain axis, which describes the bidirectional communication between the GI tract and the central nervous system (CNS). Its involvement in digestion, immunity, and neurophysiology is well recognized. This study offers novel insights by focusing on psychobiotics, a class of probiotics with targeted neuroactive properties. These microorganisms influence brain function through defined mechanisms, including modulation of neuroinflammation, neurotransmitter production (GABA, serotonin), regulation of the hypothalamic–pituitary–adrenal (HPA) axis, and vagus nerve signaling. Our work critically examines recent advances in applications of psychobiotics for neurological disorders such as Parkinson's disease, Alzheimer's disease, multiple sclerosis, and autism spectrum disorder. By integrating evidence from microbiome research, neuroimmunology, and clinical studies, we identify promising microbial strains and mechanistic pathways with therapeutic potential. This study contributes original perspectives by highlighting underexplored microbe–host interactions and proposing targeted microbial interventions as adjuncts to conventional neurotherapies. Further research is needed to validate strain-specific effects, long-term efficacy, and safety profiles in clinical settings.