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China has the world’s largest fisheries industry that has provided a healthy and high-quality food source. Currently, guaranteeing national food security, implementing an all-encompassing approach to food, and establishing a diversified food supply system all pose a great demand for the high-quality development of China’s fisheries industry. This study explores the development status and trend of fisheries in China from the aspects of fishery resources and capture, aquaculture and marine ranching, and aquatic product processing and circulation, and examines major problems through industry research and extensive discussion. Industry development goals and key measures are further proposed. Results found that the pressure on offshore capture is too high, understanding of deep-sea and polar resources is insufficient, the independent capability of technologies and equipment is inadequate, the mechanized, automatic, and intelligent levels of aquaculture are low, high-quality feed and raw materials rely heavily on imports, the basic software and hardware capabilities of the intelligent fisheries are deficient, and the aquatic product processing capacity is lagging behind. Therefore, the following key measures are proposed: conservation and restoration of offshore fishery resources, development and scientific utilization of deep-sea fishery resources, construction and application of a new technology system for green and healthy aquaculture, research and application of deep-sea aquaculture platform technologies, construction and promotion of new aquaculture models, and green processing and high-value utilization of aquatic products.Through the high-quality development of fisheries, China is expected to become advantageous in fisheries science and technology by 2035, with a total output of 8.1×107 t of aquatic products. By 2050, intelligent fisheries is expected to be realized in China, outputting 1×108 t of aquatic products.

Dietary betaine supplementation has been reported to alleviate the adverse effects of high‐carbohydrate diets on Megalobrama amblycephala, while the regulatory mechanism remains largely unknown. In the present study, a 79‐day feeding trial was conducted with 450 juvenile Megalobrama amblycephala (average weight 6.75 ± 0.10 g), which were fed with five high‐carbohydrate diets (43%) supplementing betaine at 0% (CD group), 0.2% (0.2Bet group), 0.4% (0.4Bet group), 0.8% (0.8Bet group), and 1.6% (1.6Bet group), respectively. Results showed M. amblycephala in 0.8Bet group exhibited the best growth performance, indicated by the largest weight gain ratio (142.88%) and least feed conversion ratio (1.63). Moreover, liver health was promoted in 0.8Bet group, with decreased number of non‐nucleated cells and less lipid accumulation, which was accompanied by the lowest hepatosomatic index (1.38%). In order to further illustrate the regulatory mechanism, metabolites assay indicated that dietary betaine supplementation significantly increased plasma contents of methionine, serine, hypotaurine, and taurine, but did not affect plasma contents of cystathionine, cystine, or cysteic acid. Accordingly, the mRNA expressions of cysteine sulfinate decarboxylase in cysteine sulfinic acid pathway and cysteamine dioxygenase (ADO) in sulfinic acid (CS) pathway, which were both involved in taurine synthesis, were also upregulated in the liver. Meanwhile, the microbial communities in M. amblycephala intestine were more stable and uniform with betaine supplementation. Therefore, dietary betaine supplementation may exert its protective roles in improving feed efficiency and liver health of M. amblycephala via promoting de novo taurine synthesis and stabilizing intestinal microbial communities. [ABSTRACT FROM AUTHOR]

Pikeperch (Sander lucioperca) is a species with great potential for aquaculture in Eurasian countries, while feed costs limit the scale of pikeperch farming. Adding carbohydrates to the feed as an energy source is a viable approach to reduce costs and to improve the culture status of pikeperch. In this study, in order to determine the optimal carbohydrate requirement of pikeperch, three tapioca starch (8%, 10%, and 12%) added feeds were produced with isonitrogenous (51%) and isolipidic (11%). For 8 weeks, body weight was 1.20 ± 0.01 g, pikeperch were manually fed the trio of experimental diets until they seemed fully satisfied. The finding revealed that pikeperch can utilize dietary carbohydrate, but excessive dietary carbohydrate will adversely affect the growth performance. The growth and survival rate were decreased in pikeperch in S12 (P < 0.05). The α‐amylase activity of S12 reduced in the intestine and lipid deposition was observed in the liver compared with the S8. In addition, proinflammatory cytokines, interleukin 1 beta (il1-β), interleukin 8 (il8), and tumor necrosis factor beta (tnf-β), in the liver and intestine elevate and anti‐inflammatory cytokines, interleukin 10 (il10) and transforming growth factor beta (tgf-β), decrease with increasing dietary carbohydrate levels. Hepatic and intestinal antioxidant capacity were also adversely affected, with S12 significantly increasing malondialdehyde (MDA) contents and decreasing glutathione (GSH) and total antioxidant capacity (T‐AOC) (P < 0.05). The intestinal barrier function is also damaged, the height and width of intestinal villi decreased, and the expression of occludin-a, occludin-b, and zonula occludens‐2 (zo-2) genes was decreased. Elevated levels of starch intake led to harm to gut microflora, reducing bacterial populations, simultaneously boosting the presence of detrimental bacteria (Proteobacteria, Actinobacteriota, Achromobacter, and Rhodococcus) and diminishing the beneficial bacteria (Firmicutes). In conclusion, moderate addition of starch as an energy source can reduce feed costs; however, over addition can bring about organism damage and is recommended to be added at less than 10%. [ABSTRACT FROM AUTHOR]

Starch is a common source of carbohydrates in aqua feed. High-starch diet can cause hepatic injury and lipid accumulation in fish. Mangiferin (MGF) can regulate lipid metabolism and protect the liver, but there is limited research on its effects in fish. In the present study, we investigated whether MGF could ameliorate high-starch-induced hepatic damage and lipid accumulation in channel catfish. The channel catfish (Ictalurus punctatus) were fed one of four experimental diets for eight weeks: a control diet (NCD), a high-starch diet (HCD), an HCD supplemented with 100 mg/kg MGF (100 MGF), and an HCD supplemented with 500 mg/kg MGF (500 MGF). The results demonstrated that the weight gain rate (WGR) (p = 0.031), specific growth rate (SGR) (p = 0.039), and feed conversion efficiency (FCE) (p = 0.040) of the 500 MGF group were significantly higher than those of the NCD group. MGF supplementation alleviated liver damage and improved antioxidant capacity (T-AOC) compared to those of the HCD group (p = 0.000). In addition, dietary MGF significantly reduced plasma glucose (GLU) (p = 0.000), triglyceride (TG) (p= 0.001), and low-density lipoprotein cholesterol (LDL) (p = 0.000) levels. It is noteworthy that MGF significantly reduced the plasma total cholesterol (TC) levels (p = 0.000) and liver TC levels (p = 0.005) of channel catfish. Dietary MGF improves cholesterol homeostasis by decreasing the expression of genes that are involved in cholesterol synthesis and transport (hmgcr, sqle, srebf2, sp1, and ldlr) and increasing the expression of genes that are involved in cholesterol catabolism (cyp7a1). Among them, the largest fold decrease in squalene epoxidase (sqle) expression levels was observed in the 100 MGF or 500 MGF groups compared with the HCD group, with a significant decrease of 3.64-fold or 2.20-fold (p = 0.008). And the 100 MGF or 500 MGF group had significantly decreased (by 1.67-fold or 1.94-fold) Sqle protein levels compared to those of the HCD group (p = 0.000). In primary channel catfish hepatocytes, MGF significantly down-regulated the expression of sqle (p = 0.030) and reduced cholesterol levels (p = 0.000). In NCTC 1469 cells, MGF significantly down-regulated the expression of sqle (p = 0.000) and reduced cholesterol levels (p = 0.024). In conclusion, MGF effectively inhibits sqle expression and reduces cholesterol accumulation. The current study shows how MGF supplementation regulates the metabolism and accumulation of cholesterol in channel catfish, providing a theoretical basis for the use of MGF as a dietary supplement in aquaculture. [ABSTRACT FROM AUTHOR]

To explore the effects of dietary threonine on growth and ovarian development of red swamp crayfish (Procambarus clarkii), crayfish (5.48 ± 0.19 g) were fed six isoproteic and isoenergetic diets with varying levels of threonine (7.16 g/kg (control), 9.19, 12.74, 16.44, 20.83, and 23.78 g/kg) for 8 weeks. The results showed that weight gain rate, feed conversion ratio, protein efficiency rate, protein deposition rate, and essential amino acid deposition rates obtained the optimal values when the dietary threonine level was 12.74 or 16.44 g/kg. Compared to the control group, the 12.74 g/kg group exhibited enhanced nonspecific immunity and antioxidant properties. The 16.44 g/kg group demonstrated a significant increase in the frequency of B cells and R cells in the hepatopancreas, the length and width of intestinal villi, and the activities of protease and lipase. It also showed elevated ecdysterone hormone, gonadal index (GI), cAMP content, and the relative abundance of beneficial intestinal microflora. Compared to the control group, the mRNA expression of mTOR, S6K1, 4EBP1, EcR, RXR, chitinase, PKA, Vg, cdc2, and cyclin B was significantly upregulated, and the mRNA expression of MIH was significantly downregulated in the 16.44 g/kg group. Overall, optimal dietary threonine could improve intestinal health, regulate immune function, and enhance protein utilization, molting, and growth performance of red swamp crayfish. Additionally, it improved the synthesis of yolk substance and facilitated the development of ovarian cells of female crayfish. The optimal threonine level was 14.87–16.94 g/kg (dry matter), corresponding to 42.51–48.42 g/kg of dietary protein in red swamp crayfish. [ABSTRACT FROM AUTHOR]

An 88-day feeding trial was conducted to evaluate the effects of dietary inosine 5′-monophosphate (5′-IMP) on the growth performance and salinity and oxidative stress resistance in the juvenile gibel carp CAS III (Carassius auratus gibelio; initial body weight: 7.48 g). Four isonitrogenous and isoenergetic diets containing exogenous 5′-IMP were formulated. P1, P2, P3 and P4 were diets containing 5′-IMP at four concentrations (0, 1, 2 and 4 g kg−1). The four diets were randomly allotted to triplicate tanks in a recirculating system. After the feeding trial, six fish per tank were netted randomly and placed into 12‰ saline water to test their response to salinity stress. The results indicated that the feed conversion rate was enhanced by dietary supplementation with 5′-IMP. The appetite, plasma neuropeptide Y level and feeding rate of the P3 group were lower than those in the control treatment group. Dietary supplementation with 5′-IMP improved the osmoregulatory adaptation of gibel carp under acute salinity stress. Six hours after the salinity stress treatment, in the dietary 5′-IMP treatment group, the plasma cortisol and K+ concentrations were lower and the Na+/K+-ATPase activity was greater than that in the control group. Dietary supplementation with 5′-IMP promoted the expression of the glucocorticoid receptors NKA-α1b and NKCC and retarded the expression of Hsp70 in P4-treated gill filaments and kidneys. Dietary supplementation with 5′-IMP resulted in a stable oxidative-stress-resistant phenotype characterized by increased levels of cellular antioxidants, including SOD, catalase, glutathione peroxidase, glutathione reductase and MPO. The above results of the current study demonstrate that supplementation of 5′-IMP can promote feed utilization and have positive influences on the salinity and oxidative stress resistance of gibel carp. [ABSTRACT FROM AUTHOR]

The trial was conducted to investigate the effects of the replacement of dietary fishmeal (FM) by the blend of Tenebrio molitor meal (TMM), Chlorella meal (CM), Clostridium autoethanogenum protein (CAP), cottonseed protein concentrate (CPC) on growth, protein utilization and intestinal health of gibel carp (Carassius gibelio, CAS Ⅴ). The FM-based diet was used as the control, and the blended proteins (TMM: CM: CAP: CPC) at ratios of 1 : 1:8 : 2 (BLEND A), 1 : 1:6 : 4 (BLEND B), and 1 : 1:4 : 6 (BLEND C) were used to replace FM at three levels (33%, 67%, 100%), respectively. The results showed that, compared to the control group, growth performance increased significantly when dietary FM was fully replaced by BLEND B (P < 0.05), while decreased by BLEND A (P < 0.05). The complete substitution of FM with BLEND B significantly upregulated the mRNA expression of intestinal proinflammatory cytokines, anti-inflammatory cytokines, and tight junction-related genes (P < 0.05), improving intestinal tissue morphology and health. And it also significantly increased intestinal trypsin activity (P < 0.05), upregulated the mRNA expression of amino acid sensory receptor-related and amino acid or peptide transport-related genes (P < 0.05), increased protein apparent digestibility coefficient (P < 0.05). The 100% substitution of FM with BLEND A significantly upregulated the mRNA expression of intestinal proinflammatory cytokines and downregulated the mRNA expression of anti-inflammatory cytokine il-10 (P < 0.05), reduced intestinal villus height (P < 0.05), and decreased protein apparent digestibility coefficient (P < 0.05). In conclusion, BLEND B could completely substitute dietary FM and was beneficial to the growth and health of gibel carp. Dietary digestible essential amino acids index (DEEAI) was found as an important indicator and should be higher than 79.5% to meet the maximum growth of fish. [ABSTRACT FROM AUTHOR]

Simple Summary: The development of novel protein sources plays an important role in improving the economic benefit of aquatic products. The Chlorella vulgaris (C. vulgaris) powder is a novel non-grain single-cell protein with a high reproductive rate, short growth cycle, strong environmental tolerance and easy artificial cultivation. In this experiment, grass carps (initial weight: 20.13 ± 0.09 g) were fed diets by replacing 0% (SM), 25% (X25), 50% (X50), 75% (X75) and 100% (X100) of SM with C. vulgaris for 8 weeks. In conclusion, the C. vulgaris powder replacement of 50% soybean meal was recommended as feed for grass carp. However, the positive effects were apparently weakened when the soybean meal was replaced with high levels of C. vulgaris powder. Chlorella vulgaris (C. vulgaris) powder is a novel non-grain single-cell protein with enormous potential to be a protein source. However, it is poorly studied in aquatic animals. The purpose of the present study was to explore the optimum replacement ratio of C. vulgaris powder and the influence of the substitution of soybean meal with C. vulgaris on grass carp (Ctenopharyngodon idella) in terms of growth performance, intestinal integrity and the microbial community. Five isonitrogenous and isolipidic diets were formulated by replacing 0% (SM, containing 30% soybean meal), 25% (X25), 50% (X50), 75% (X75) and 100% (X100) soybean meal with C. vulgaris. The feeding trial period lasted 8 weeks. At the end of the experimental trial, the X50 group showed higher FW, WGR and PER than the SM group (p < 0.05). The feed conversion ratio (FCR) of the X50 group was significantly lower than that of the SM group (p < 0.05). The X50 group showed the highest value of the goblet cell number, intestinal amylase and trypsin activities when compared with the SM group (p < 0.05). Replacing 50% soybean meal with C. vulgaris improved the intestinal barrier integrity, as evidenced by upregulating zo-1, zo-2 and occluding transcript (p < 0.05), and alleviated oxidative stress by an increased SOD enzymatic activity and transcript level, probably mediated through the Nrf2-keap1 signaling pathway (p < 0.05). Meanwhile, the X50 group enhanced intestinal immunity, as manifested by increased ACP and LZM activities (p < 0.05), and downregulated the tlr-4, tlr-7, tlr-8 and il-6 through the tlr pathway (p < 0.05). The functionally predicting pathways related to the nitrate respiration and nitrogen respiration were observably activated in the X50 group (p < 0.05). The X50 group improved the biological barrier, as manifested by increased Firmicutes and Rhodobacter (p < 0.05). In conclusion, dietary C. vulgaris powder could promote the growth performance of grass carp by restoring intestinal morphology, increasing digestive enzyme activities, improving antioxidant properties and immunity and optimizing the microflora structure. A C. vulgaris powder replacement of 50% soybean meal was recommended as feed for grass carp. [ABSTRACT FROM AUTHOR]