ROUNDUPS

• Research progress of carotenoid utilization and function in crustacean aquaculture

  WANG Weilong, MA Zhuojun, LI Weiquan, WANG Xi, XUE Yucai, YI Ganfeng, HUANG Xuxiong

  2025,49(4):049601-049601, DOI: 10.11964/jfc.20231214279

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  Carotenoid plays a significant role in the nutrition and physiology of crustaceans. Crustaceans cannot synthesize carotenoids de novo but can metabolize and converse external carotenoid to meet the specific physiological and ecological adaptation needs during different stages. To date, research on the carotenoid’s nutritional requirements of crustaceans has primarily focused on the impact of adding astaxanthin to their diets on parameters such as growth performance, colouration regulation, antioxidant capacity, reproductive performance, immune function, and stress resistance. However, there is still limited understanding of the metabolic pathways and regulatory mechanisms of carotenoids within crustaceans. This necessitates further research to uncover these aspects. Building on the comprehensive analysis and summarization of studies regarding the composition and distribution of carotenoids within crustaceans, the types and sources of external carotenoids, the effective utilization of external carotenoids by crustaceans, and the nutritional requirements of crustaceans for external carotenoids, this article proposes a deeper exploration of the metabolic pathways of carotenoids within crustaceans. It suggests identifying the key enzyme genes involved in carotenoid metabolism and elucidating their biological functions. This approach aims to advance our understanding of the metabolism and regulation of carotenoids, which are essential conditional nutrients for crustaceans, and provide a scientific basis for efficiently utilising of external carotenoids in crustacean aquaculture.

• Feed and feeding management in aquaculture: concept, technological scheme and practices

  WANG Yan

  2025,49(4):049602-049602, DOI: 10.11964/jfc.20231114226

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  Feed has become a key determinant of the benefits of aquaculture practices, as the proportion of fed aquaculture now exceeds 70% of global aquaculture production. Enhancing fish growth and feed utilization efficiency, particularly dietary protein retention efficiency (NRE), is a common objective in breeding, nutrition, feed, and aquaculture management research. Feed and feeding management (FFM) is defined as a method to improve the growth and health of farmed animals while reducing production costs and negative impacts of farming practies on natural resources and the environment by providing high-quality, cost-effective diets at appropriate feeding regimes. As an integraton of feed management and feeding management, FFM is recognized as one of the most important components in optimizing the aquaculture mode (AM). Nutrient requirements, diet formulation, and feeding of aquatic animals belong to different displines, such as nutrition, feed science, and feeding ecology, respectively. Although numerous attempts focused on investigating nutrient requirements, feed and feeding of fishes, however, few studies concern the integration of feed and feeding to establish FFM under specific farming conditions for the fish species commercially important to fed aquaculture. In this review, the author defined the concept of FFM based on the studies of feed management or feeding management of fishe and elucidated its role in optimizing the aquaculture model. First, the author indicated the technology diagram for optimizing FFM includes: ① determining the nutrient requirements of the farmed animals, ② designing high-quality, cost-effective diet formulas using feed ingredients that are rich in nutrients, low in anti-nutritional factors, and consistently available to meet the nutrient requirements of farmed animals, ③ determining the optimal feeding regimes for farmed animals fed with diets formulated according to the high-quality, cost-effective diet formula, ④ integrating the high-quality feed and optimal feeding regimes to determine the FFM scheme and assessing its benefits on production, production cost, natural resource depletion, and environmental pollution. Second, the author briefly reviewed researche on establishing FFM for the large yellow croaker (Larimichthys crocea), largemoth bass (Micropterus salmoides), golden pompano (Trachinotus ovatus), and cuneate drum (Argyrosomus amoyensis) and presents prelimnary results on FFM schmes for these fish species, including optimal dietary protein and lipid levels, minimum fish meal content in diet formulas, and optimal feeding frequency and ration levels. Specifically: ① For L. crocea reared in net pens, the optimal dietary protein level, lipid level, and protein-to-energy ratio were 490-520 g/kg, 100 g/kg and 27.6 MJ/kg, respectively, with a minimum dietary fish meal content of 160 g/kg. The optimal feeding frequency and ration level were 2 meals/d and 2.1% BW/d. ② For M. salmoides reared in earth ponds, the optimal dietary protein and lipid levels were 480-510 and 120 g/kg, respectively, with a minimum dietary fish meal content of 80 g/kg. The optimal feeding frequency and ration level were 3 meals/d and 2.2% BW/d. ③ For T. ovatus reared in net pens, the optimal dietary protein and lipid levels were 450-490 and 110 g/kg, respectively, with a minimum dietary fish meal content of 140 g/kg. The optimal feeding frequency and ration level were 3 meals/d and 5.7% BW/d. ④ For N. miichthioides reared in net pens, the optimal dietary protein, lipid and energy levels were 450 g/kg, 150 g/kg and 19.0 MJ/kg, respectively, with a minimum dietary fish meal content of 75 g/kg. The optimal feeding frequency and ration level were 1 meal/d and 2.1% BW/d. Finally, the author provided suggestions for establishing and optimizing FFM schemes for fish farming, which included: ① considering the effects of fish species and genetic characteristics as well as environmental conditions on FFM scheme, ② ensuring the reliability and accurancy of the data (nutrient requirements of the farmed fish and quality assessment of feed ingredients) used in diet formula, ③ recognizing the interactive effects between diet formulation and feeding regimes on fish growth and feed utization efficiency, ④ evaluating the benefits of the FFM scheme based on long-term field experiments and the their impact on ecosystem service values.

PAPERS

• Tissue expression and target gene verification of microRNA-novel_176 in Trachinotus blochii

  SONG Feibiao, SHI Liping, ZHENG Da, LIANG Huan, JI Xinxin, TONG Jinfeng, BU Shaoyang, SUN Junlong, LUO Jian

  2025,49(4):049603-049603, DOI: 10.11964/jfc.20230514026

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  MicroRNAs, as non-coding RNAs, play important roles in many key physiological processes in organisms and can significantly impact gonadal development in fish through the regulation of target gene transcription. Therefore, this study investigated the previously identified key miRNA-novel_176 involved in gonadal development. Various experimental techniques including fluorescence quantitative PCR, fluorescence in situ hybridization, dual-luciferase reporter gene assay, RNA interference, and overexpression were employed to systematically validate its regulatory relationship with target genes and explore its potential biological functions. The results showed that miRnovel_176 was expressed in various tissues of Trachinotus blochii, with higher expression levels observed in the ovary than in the testis, although the difference was insignificant. miRnovel_176 was primarily localized in the cytoplasm of ovarian cells, with positive signals mainly detected in oocytes and granulosa cells. Weak hybridization signals were also observed in the supporting cells and spermatogonia of the testis. miRnovel_176 was found to target the 3'-UTRs of the esr2 and foxo3 genes, significantly inhibiting luciferase activity. Following transfection with novel_l76-antagomir and novel_l76-agomir, the expression levels of miRnovel_176 were significantly downregulated and upregulated, respectively, leading to significant opposite expression changes in the target genes foxo3 and esr2. This study indicates that the target genes of miRnovel_176 are esr2 and foxo3, and miRnovel_176 can regulate their expression levels by targeting their 3'UTR regions. This study provides new evidence for further revealing the function of miRNAs in the gonadal development of fish and also provides new candidate miRNAs for the study of gonadal development of T. blochii.

• Identification and expression pattern analysis of seven members of the non-receptor tyrosine kinase family in Apostichopus japonicus

  WANG Jiping, WAN Junjie, PENG Yuhui, ZHAO Xuelin

  2025,49(4):049404-049404, DOI: 10.11964/jfc.20230914154

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  The SFK gene family is a family of non-receptor tyrosine kinases that function in apoptosis, phagocytosis, inflammation, and other immune processes in innate immunity. This study first analyzed the gene structure and evolutionary relationship of SFK gene family members of Apostichopus japonicus by bioinformatics methods to elucidate the function of the non-receptor tyrosine kinases (SFKs) gene family in response to pathogen stress. qRT-PCR analyzed the temporal and spatial expression patterns of SFK gene family members under pathogen stress. In the present study, seven members of the SFK gene family were identified in A. japonicus, which were divided into two subfamilies SrcA and SrcB, distributed unevenly on three chromosomes. The domain and motif analysis showed that six members had conserved SH3 domain, SH2 domain and tyrosine kinase core domain except SrcB-3. Among them, five motifs that make up the core domain of tyrosine kinase existed widely in all members, and different members of the SH3 domain and SH2 domain had the same motif composition, indicating that the AjSFK family was relatively conservative in evolution. The analysis of SFKs gene expression patterns in different tissues showed that SFKs were widely expressed in various tissues of A. japonicus, and had apparent tissue specificity with high expression in the intestines and tentacles. In addition, the expression levels of SrcB-1-3 significantly increased after 6 h of infection with Vibrio splendidus, and the expression levels of SrcA-1 and SrcB-2 significantly increased after 24 h of LPS stress in vitro. The study showed that SFKs of A. japonicus had a high immune response and played an important role in responding to pathogen stimulation. This study was the first systematic identification and functional analysis of the SFK gene family in A. japonicus, and provided an important theoretical basis for disease resistance.

• Analysis of heat tolerance in different populations of Micropterus salmoides and the effects of high temperature on gill tissue and antioxidant enzyme activity

  XIE Yujing, LI Shengjie, DU Jinxing, ZHU Tao, SONG Hongmei, LEI Caixia, WEN Qiqiao

  2025,49(4):049405-049405, DOI: 10.11964/jfc.20230514007

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  A total of three Micropterus salmoides populations ["YouLu No.3" (YL), Taiwan population (TW) and introduced population (M. salmoides salmoide)(BF)] with an average body mass of (15.61±1.25) g were used in this study to study the acute high-temperature tolerance of different populations and the effect of high-temperature on gill tissue and antioxidant enzyme activity. The water temperature was raised from 27 to 35, 36, 37, 38, 39 °C with a rate of 2 °C/h and maintained for 12 h. Each temperature group included three replicates and ten fish per repeat. Half-lethal temperature (LT₅₀) was predicted according to the mortality rate. The results showed that fish death in three populations beginning to occur at 36 °C, the LT₅₀ of YL was 37.47 °C, which was significantly higher than that of TW (37.15 °C) and BF (37.01 °C). By subjecting M. salmoides to high-temperature stress, and the gill tissue damage of M. salmoides at different temperatures (27, 35, 37 and 39 °C) was compared and analysed, with the increase of temperature, the separation of the epithelium of gill lamellae from the basement membrane increased, and the gill lamellae gradually became shorter and thicker, and the gill tissue damage was the most serious at 39 °C. The activities of antioxidant enzymes of M. salmoides at different temperatures (27, 35, 37and 39 °C) and different stress times (0, 3, 6 and 12 h) at 37.5 °C showed that the activities of superoxide dismutase (SOD) and catalase (CAT) increased and then decreased with increasing temperature, and the highest activities were observed at 37 °C. The activities of SOD and CAT increased and then decreased with increasing stress time. SOD and CAT activities showed trends of increasing and then decreasing with increasing stress time, and the highest activity was observed at 3 h. In summary, the heat tolerance of YL was significantly higher than that of the TW and BF. The high temperature stress caused stress damage to M. salmoides. Our study provides basic data and theoretical references for breeding high temperature tolerance M. salmoides.

• Comparison of otolith geometric morphometrics for Coilia nasus from the northern Poyang Lake

  XIAO Baiyi, JIANG Tao, LIU Hongbo, CHEN Xiubao, YANG Jian

  2025,49(4):049306-049306, DOI: 10.11964/jfc.20230113876

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  Coilia nasus belongs to Clupeiformes, Engraulidae, Coilia, which is a commercially valuable fish in China. Otoliths (sagittae, asteriscus, or lapillus) are complex tissue structures with calcium carbonate (CaCO₃) as the main component, and their shapes vary markedly depending on the species and population. Because sagittae (saccular otoliths) are the largest and present the most significant interspecific variation among the three pairs of otoliths, thus they are the most used in research. To compare with traditional morphological surveying methods, geometric morphometric methods transform qualitative analysis into quantitative analysis. Especially, landmark-based geometric morphometric analysis is attracting more and more attention in recent years and has been applied to a variety of fields of fish otolith investigation. In order to understand the variation in the otolith shape of C. nasus (including the long supermaxilla and short supermaxilla C. nasus ecomorphotypes, the latter was once named C. brachygnathus) populations from different sites (i.e., Xieshan site of Hukou County, Liaozuitou site and Huoyanshan site of Lushan City, Piaotou site of Yongxiu County) in northern area of the Poyang Lake and reveal their population connectivity, landmark-based geometric morphometric analysis was used in the present study. The otolith morphometric characteristics were documented with relative warp principal components analysis, discriminate analysis, cluster analysis, and further visualizing grid deformation by thin plate spline. The results showed that landmarks in the sulcus had the main contribution (77.9%) in explaining the primary source of otolith morphometric variation. Discriminate analysis of relative warps obtained 100% classification success for the variation between long supermaxilla and short supermaxilla C. nasus for the first time, demonstrating the tremendous difference in geometric morphometrics between the two ecomorphotypes. Viewing from long supermaxilla C. nasus, discriminate analysis showed that the highest identifying accuracy (95%) was found for the fish population from the Liaozuitou site, followed by those populations from the Huoyanshan site (90%), Piaotou site (55%), and Xieshan site (50%). Cluster analysis indicated that the relative closer distance could be found among the populations from Huoyanshan, Xieshan and Piaotou sites than that population from Liaozuitou site. The present study first discovered the distribution of long supermaxilla C. nasus in waters of the Liaozuitou, Piaotou and Xieshan site. It was believed that the long supermaxilla C. nasus from the Liaozuitou site might be a relatively independent population, while certain connectivity could be available among the remaining populations of this ecomorphotype from other sites in the northern area of the Poyang Lake. By analysing variation in the otolith shape of C. nasus from different sites, the present study interprets population connectivity in corresponding areas in the Poyang Lake. It possibly provides scientific basis and theoretical support for fishery management and conservation of C. nasus.

• Trophic niche characteristics of Siganus canaliculatus and Halichoeres nigrescens in Wanshan Islands

  SHI Juan, LI Chunhou, WANG Teng, WANG Chunling, ZHAO Jinfa, SONG Xiaoyu, WU Peng, XIAO Yayuan, LIN Lin, LIU Yong

  2025,49(4):049307-049307, DOI: 10.11964/jfc.20230213896

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  Siganus canaliculatus and Halichoeres nigrescens are the dominant fish in Wanshan Islands. The trophic niche and the competition relationship between the populations were revealed by the carbon and nitrogen stable isotope technology analysis to explore the reasons of the two fish species became the dominant species in Wanshan Islands. The samples in this sea area were collected by three-layer gillnet in the spring (March) and autumn (September) of 2021. Then they were measured by Elementar isoprime visION stable isotope mass spectrometer, and the trophic niche and structure were analyzed. The results showed that the δ¹⁵N values ranged from 9.15‰ to 14.09‰ of S. canaliculatus and 10.34‰ to 14.60‰ of H. nigrescens. The δ¹³C values ranged from -19.87‰ to -14.54‰ of S. canaliculatus and -18.16‰ to -15.60‰ of H. nigrescens. The trophic level of S. canaliculatus and H. nigrescens was 2.97 and 3.23, respectively. The analysis of δ¹³C-δ¹⁵N trophic niche structure showed that there was a resource competition between the two populations. The trophic niche breadth and trophic diversity of S. canaliculatus were higher than those of H. nigrescens, indicating that S. canaliculatus had more food sources and stronger ability to compete and use resources. Pearson correlation analysis showed that there was no significant correlation between body length and δ¹³C of the two populations, but there was a significant correlation between body length and δ¹⁵N. There was a significant positive correlation of S. canaliculatus and a very significant negative correlation of H. nigrescens. The results indicated that the feeding patterns of the two communities changed with ontogeny, and the S. canaliculatus tended to be high-trophic diet organisms, while the H. nigrescens tended to be low-trophic diet organisms. There was a sharp increase in the trophic niche width of S. canaliculatus and H. nigrescens in the range of 90-100 mm and 100-110 mm, respectively, which was just near the length of their first sexual maturity or sexual reversal, suggesting that the feeding habits of the two species changed during the period of gonadal development and maturity. This study revealed the trophic niche characteristics of the two dominant species in Wanshan Islands, which can provide important data reference for the study of the trophic structure and material recycling process of the whole food web in Wanshan Islands and support the conservation and rational utilization of the population, and the assessment of ecological capacity.

• Analysis of trends of skipjack tuna (Katsuwonus pelamis) resources in different spatial locations in the Central and Western Pacific

  WANG Shuang, XU Zhenqi, WANG Jintao, LEI Lin, Lü Zehua, CHEN Xinjun, HE Haiping, JIA Haibin, CHEN Jiongjie

  2025,49(4):049308-049308, DOI: 10.11964/jfc.20220713600

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  This research took 5°×5° spatial resolution as a research grid to analyze the trends in abundance of skipjack tuna (Katsuwonus pelamis) resources in the Central and Western Pacific Ocean based on spatial location and to construct a prediction model. Meanwhile, the total catch sum of 144 grids within 130°E-140°W and 20°N-20°S sea areas from 1990 to 2019 were calculated, the top ten grids sea areas for analysis (accounting for 70% of the total catch in the study sea area) were selected, and the dynamic factor analysis method to reduce the 10 grids were used. We used dynamic factor analysis to downscale the time series trends of the 10 grids into two time series trends, determined the two time series trends corresponding to each of the 10 grids according to the factor loadings, explored the contribution of three key environmental factors, namely sea surface spacing, sea surface temperature and mixed layer depth, to the two trends of K. pelamis abundance using relative importance analysis, and constructed SARIMA models for each of the two time series trends to predict the abundance of K. pelamis in the Central and Western. The SARIMA model was constructed to predict the resource abundance of K. pelamis in the Central and Western Pacific Ocean in the next three years. The range of the highly productive sea area of bonito in the Central and Western Pacific Ocean was 5°S-5°N,145°-180°E; the first time series trend spatially corresponded to the sea area of 5°S-5°N,145°-160°E and the second time series trend spatially corresponded to the sea area of 0°-5°S,160°-180E°. The distribution of the two common trends in space was with 160°E as the dividing line. The seasonal variation of the two time series trends was obvious, with higher resources in the first half of the year than in the second half of the year. In recent years, the first time series trend (spatially distributed corresponding to the western equatorial Pacific Ocean) had been decreasing and the second time series trend (spatially distributed corresponding to the eastern equatorial Pacific Ocean) had been increasing. Sea surface temperature anomalies had contributed the most to bonito resources. For two common trends, SARIMA(9,1,0)(1,0,1) [12] and SARIMA(2,1,1)(1,0,1) had the smallest AIC and RMSE with good model prediction fit and high prediction accuracy, which were 607.45 and 0.86, 595.27 and 0.64, respectively. From 2020 to 2023, the growth of K. pelamis resources in the eastern equatorial Pacific Ocean was on an upward trend, while K. pelamis resources in the western equatorial Pacific Ocean would be downward. The study results provides a decision basis for corporate decisions, such as annual production arrangements, fishing entry decisions and sustainable development of bonito resources.

• The growth performance of the larvae of GIFT Oreochromis niloticus cultivated by biofloc technology (BFT) and its relationship with intestinal microorganisms

  XU Zhibing, LIU Wenchang, TAN Hongxin, LUO Guozhi, SUN Dachuan

  2025,49(4):049609-049609, DOI: 10.11964/jfc.20221213852

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  This research used BFT to feed larvae with an initial weight of (15.35±10.62) mg for 37 days at a feeding density of 5 000 tail/m³ to investigate the effect of biofloc technology (BFT) on the growth of GIFT Oreochromis niloticus larvae and its relationship with gut microbiota. A survival rate of (65.08±13.55)% and a final density of (3 254±678) tail/m³ were obtained at the end of the experiment. The body weight of fry in class B (0.1-0.2 g) was the most, which was significantly higher than that of the other four classes (0<A≤0.1 g，0.2 g<C≤0.3 g，0.3 g<D≤0.4 g，0.4 g<E). Proteobacteria, Chloroflexi, Bacteroidetes, Actinobacteria, and Firmicutes were the dominant phyla in the five grades of larvae. Among the dominant genera of intestinal flora, probiotics such as Bacillus (3.17%-5.32%), Rhodibacter (1.91%-3.26%), Reyranella (1.90%-2.62%) were detected. There were also some potential pathogens at the same time, such as Flavobacterium (4.98%-9.20%), Enterovibrio (0.21%-6.47%), Mycobacterium (2.16%-4.37%), Aeromonas (0.29%-1.10%). The relative abundance of Aeromonas and Enterovibrio was higher in the lower weight class. The health status and growth rate of larval tilapia were affected by intestinal probiotics and potential pathogenic bacteria. However, excessive pathogenic bacteria might break the balance of bacterial flora and further affect the growth rate of GIFT O. niloticus. The results of this study illustrated the possible relationship between the growth rate of GIFT O. niloticus larvae and the gut microbiota, and provided a reference for the cultivation of GIFT O. niloticus larvae by BFT.

• Optimization research on artificial reproduction technology of Mystus macropterus

  LI Xiaoli, WU Xingbing, LI Xuemei, SHI Zechao, ZHANG Yuansong, LIU Tao, ZHU Yongjiu, CHENG Baolin

  2025,49(4):049610-049610, DOI: 10.11964/jfc.20230514021

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  Mystus macropterus, which belongs to the Bagrdae family of the Siluriformes order of Osteichthyes, was a fast-growing and large economic fish species found naturally in the mainstream and tributaries of the Yangtze and Pearl Rivers. It had high levels of protein, fat, essential amino acids, and umami amino acids, making it highly valued for consumption. However, the lack of breakthroughs in large-scale breeding of this species hindered its industrial development. This study aimed to improve the breeding efficiency of M. macropterus by optimizing its artificial insemination process. The study investigated the effect of different sperm preservation solutions (A-F), sperm-to-egg ratios (5.0 × 10⁴, 1.0 × 10⁵, 1.5 × 10⁵ and 2.0 × 10⁵), activation solution (mL) to egg (g) ratio (2∶1, 1∶1 and 1∶2), duration of gamete contact (2, 3 and 4 min), and egg quality (normal or overripe) on fertilization rate of M. macropterus. The experimental results showed that different preservation solutions significantly affected sperm vitality, fertilization rate and hatching rate. Among them, the C solution had the best effect with a fertilization rate of 60.22% and a hatching rate of 41.55%. Meanwhile, the fertilization rate significantly increased with the increase of sperm-to-egg ratio from 5.0×10⁴ to 1.0×10⁵. There was no significant difference in fertilization rate and hatching rate when the sperm-to-egg ratio was between 1.0×10⁵ and 2.0×10⁵, and a regression equation was established to determine the relationship between sperm density and fertilization rate. In addition, the highest fertilization rate and hatching rate was achieved when the ratio of activating solution to egg weight was 2∶1, which was significantly higher than that of 1∶1 group and 1∶2 group. There was no significant difference between the latter two. The fertilization rate ranged from 54.21% to 59.29%, and the hatching rate ranged from 37.40% to 40.91% in the three designed sperm-egg contact durations, and there was no significant difference among them. The maturation status of eggs had a significant impact on the fertilization rate of M. macropterus, with the fertilization rate of over-matured eggs (24.00%) significantly lower than that of regular eggs (34.38%). The study screened appropriate sperm preservation solutions, sperm-to-egg ratios, activating solution amounts, and duration of gamete contact for M. macropterus, providing references for large-scale and efficient breeding of this species.

• Investigation and research on the cultivation environment and health index of triploid Crassostrea gigas in the North Yellow Sea during summer

  GE Ping’an, GAO Lei, WANG Ling, ZHOU Keli, LI Lei, WANG Lingling, SONG Linsheng

  2025,49(4):049611-049611, DOI: 10.11964/jfc.20240514545

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  This study conducted three surveys in the floating raft cultivation area of triploid oysters in Wangjiadao Town (123.07oE, 39.45oN), Zhuanghe City, Liaoning Province, from July to August 2023, to elucidate the cultivation environment and health characteristics of the triploid Pacific oysters Crassostrea gigas in the North Yellow Sea during summer. The results revealed that the surface water temperature in the surveyed area ranged from 20.6 to 24.2 °C, posing high-temperature stress on C. gigas. The pH of surface seawater remained relatively stable, ranging from 7.70 to 7.83 across the three surveys. The average concentration of Chl.a in the water was 1.810 to 4.395 μg/L, which was lower than that reported in the same area for diploid oysters during the same period in 2021. The abundance levels of total bacteria in the water and in the gill tissues of triploid oysters ranged from 3.93×10⁷ to 2.89×10⁹ cells/L and 1.10×10⁷ to 1.64×10⁸ cells/L, respectively. The abundance levels of Vibrio species in the water and gill tissues of triploid oysters ranged from 8.40×10⁵ to 8.20×10⁶ cells/L and from 732.43 to 2.26×10⁴ cells/L, respectively, both of which were lower than those in the same period in 2021. During the three surveys, the glycogen content of the adductor muscle of triploid oysters increased gradually, with values of 6.41, 8.09, and 8.10 mg/g, respectively. The glucose content in the adductor muscle of triploid oysters was 4.72, 3.11, and 2.86 μmol/g, respectively, with no significant differences among samples (P > 0.05). The MDA content in the gills decreased significantly, with values of 17.40, 11.76, and 8.09 nmol/mg prot, respectively (P < 0.05). There was no sustained differential expression of cytokine mRNA in haemocytes. In summary, the water in the cultivation area of triploid oysters in the North Yellow Sea experienced high-temperature stress during the summer of 2023, with Chl.a concentration and Vibrio abundance in water and gill tissue lower than those in the same period in 2021. The glycogen storage level in the adductor muscle did not show a significant decrease, and there were no apparent abnormalities in the oxidative stress levels in the gill tissues and the expression of cytokines in haemocytes. These findings contribute to a comprehensive understanding of triploid oysters' health and environmental changes in summer cultivation, providing a theoretical basis for preventing and controlling large-scale mortality in summer and promoting the green and high-quality development of the shellfish industry.

• Effects of water renewal rate on water quality of the hatchery system and larval survival, growth, and development of the sea cucumber (Holothuria leucospilota)

  CEN Yikun, WU Hong, HONG Zesen, WANG Dong, HUANG Zhaolei, YU Zonghe

  2025,49(4):049612-049612, DOI: 10.11964/jfc.20230313954

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  In this study, four water exchange (0, 1/4, 1/2 and 3/4 per day, respectively) were used in sea cucumber Holothuria leucospilota hatchery. The water quality of the hatchery system and the larval survival, growth, and development of the H. leucospilota was tested to evaluate the optimum water renewal strategy. The results showed that the high water renewal rate could pose adverse impacts on larval survival and growth in the early stage. In contrast, the low water renewal rate correlated with high level of ammonia nitrogen (NH₃-N) and nitrite (NO₂^--N) in the hatchery system in the later stage, which could also pose adverse impacts on larval survival and growth. The biological toxicity experiments were carried out to test the effects of (NH₃-N) on mid- and late-auricularia larvae at water temperature of 27.99 °C and pH of 8.05. The results showed that both of the survival and development potential larvae were negatively correlated with the high NH₃-N concentration level. The 48 h-LC₅₀ of NH₃-N on mid- and late-auricularia were 2.66 and 6.22 mg/L, respectively. While the 48 h-LC₅₀ of un-ionized ammonia (NH₃) on mid- and late-auricularia were 0.19 and 0.45 mg/L, respectively. In summary, water quality was important for H. leucospilota hatchery and effective measure must be taken to control the concentration of NH₃-N in the culturing water. It is recommended that no water change should be carried out at the early-auricularia stage, moderate water renewal at the mid-auricularia stage and high water renewal at the late-auricularia stage.

• Effects of N-carbamylglutamate on growth, liver function, intestinal structure and intestinal flora of Micropterus salmoides

  YU Minghai, FU Xiaozhe, LUO Xia, LIU Lihui, LIANG Hongru, NIU Yinjie, MA Baofu, LI Ningqiu, LIN Qiang

  2025,49(4):049613-049613, DOI: 10.11964/jfc.20221213840

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  The gradient concentration of 0, 360, 720 and 1 800 mg/kg NCG were added to the essential diet respectively, to study the effects of N-carbamylglutamate (NCG) on the growth, intestinal structure and flora of Micropterus salmoides. Meanwhile, the initial weight of (170.0±5.0) g M. salmoides was fed for 10 weeks, which were labeled as T0 control group, T360 group, T720 group and T1800 group, respectively. The results showed that the feed coefficient (FCR) of 360 and 720 mg/kg group was significantly lower than that of 0 mg/kg control group (P<0.05), and the weight gain rate (WGR) of 360 and 720 mg/kg group was significantly higher than that of other groups (P<0.05) . There was no significant difference in specific growth rate (SGR), condition factor (CF), hepatosomatic index (HSI), and viscera weight index (VSI) (P>0.05). The results of the liver tissue sections and related enzyme activity indicators showed that the liver cells of M. salmoides in the NCG supplemented group were closely arranged, and the tissue necrosis or inflammatory cells were reduced. The activities of glutamic oxaloacetic transaminase (ALT), glutamic pyruvic transaminase (AST) and malondialdehyde (MDA) content in the NCG supplemented group were significantly lower than those in the control group (P<0.05). In contrast, the lysozyme (LZM) activity was significantly higher than that in the T0 control group (P<0.05). The results of intestinal tissue sections showed that the villus height (VH), villus width (VW) and intestinal muscle thickness (IMT) of the NCG group were significantly higher than those of the T0 control group (P<0.05). The results of gut microbiome analysis showed that the number of gut microbiota species significantly increased in the NCG addition group, with the T720 group having the most species. The abundance of Plesiomonas decreased significantly, while the abundance of Cetobacterium decreased significantly first and then increased with the addition of NCG. Using the feed coefficient and weight gain rate as indicators, the optimal amount of NCG added to the diet of M. salmoides was determined through line analysis as 345.87 and 916.67 mg/kg, respectively. In conclusion, NCG can improve the liver function and intestinal health of M. salmoides, optimize the intestinal flora structure, promote the growth of M. salmoides, and reduce the FCR. The research results have important reference significance for the green and healthy cultivation of M. salmoides.

• Effects of arginine supplementation in plant-protein-based low-fishmeal feed on growth, feeding, antioxidant, immune and intestinal structure of Macrobrachium nipponense

  WANG Junbao, ZHENG Jinxian, ZHOU Dongsheng, LI Shanshan, KONG Youqin, QI Changle, LIU Yan, XU Qiyou, DING Zhili

  2025,49(4):049614-049614, DOI: 10.11964/jfc.20230714099

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  Abstract:

  Arginine (Arg) plays a vital role in regulating of body growth, antioxidant defense, and protein synthesis. The study aimed to evaluate the effects of plant-protein-based low-fishmeal feed supplemented with arginine on feeding, antioxidant capacity, immunity and intestinal morphology in Macrobrachium nipponense. Five isonitrogenous and isoenergetic dietary groups were formulated to contain varying levels of dietary arginine (0%, 0.60%, 1.20%, 1.80% and 2.40%, respectively) under low fish meal content and high plant protein inclusion. The measured arginine concentrations in diets were 0.80% (0.80% Arg), 1.33% (1.33% Arg), 1.85% (1.85% Arg), 2.24% (2.24% Arg) and 2.65% (2.65% Arg), respectively. The feeding trial lasted for 8 weeks. The results showed that the weight gain initially increased with higher dietary arginine levels before declining. The peak values were observed in the group receiving 1.85% Arg, which significantly surpassed those recorded for the groups receiving diets with 0.80%, 1.33%, or 2.65% Arg (P<0.05). Conversely, the feed conversion ratio (FCR) exhibited an inverse trend, reaching its lowest point in the group fed with a diet containing 1.85% Arg, this value was significantly lower than that of the groups receiving diets with either 0.80% or 2.65% Arg (P<0.05). No significant differences were found regarding survival rate (SR) or feeding rate (FR) among all experimental groups (P<0.05). With the increase in arginine levels, the activity of glutathione peroxidase (GSH-Px) and the content of glutathione (GSH) in the 1.85% Arg group were higher than those observed in the 0.80% Arg group (P<0.05). Additionally, the activity of superoxide dismutase (SOD) in the 1.85% Arg group was also more significant than that found in the 0.80%, 1.33%, and 2.65% Arg groups (P<0.05). The malondialdehyde (MDA) content in the 1.85% Arg group was notably lower than that of all other groups, reaching statistical significance (P<0.05). Furthermore, aspartate aminotransferase (AST) activity was lowest in the 1.85% Arg group and significantly lower compared to both of the 0.80% and 1.33% Arg groups (P<0.05). The alanine aminotransferase (ALT) activity recorded for both of the 1.33% and 1.85% Arg groups was also at its lowest level, significantly less than that in the 0.80%, 2.24% and 2.65% groups (P<0.05). The target of rapamycin (tor) and neuropeptide Y (npy) mRNA expression level in hepatopancreas was upregulated in 1.33% Arg group and higher than that in the other four groups (P<0.05). The ribosomal protein 6kinase (s6k) mRNA expression level in the 1.85% Arg group was the highest and significantly higher than that in 2.24% Arg and 2.65% Arg groups (P<0.05). The leptin mRNA expression level decreased first and then increased, and its expression level was the highest in the 0.80% Arg group. The intestinal microvilli in the 1.85% and 2.24% Arg groups appeared intact, closely arranged, numerous, and slender. It was shown that Arg at a level of 1.85% in plant-protein-based low-fishmeal feed can enhance intestinal morphology, growth performance, antioxidant capacity, and the mRNA levels of genes related to tor signalling pathway and appetite regulation in M. nipponense. Based on second-order regression analysis of weight gain vs. dietary Arg level, the ideal dietary Arg level for M. nipponense was 1.83%.

• Effects of feed protein levels on the circadian clock rhythm, growth, and muscle composition of Exopalaemon carinicauda

  WANG Yongshuai, SHEN Xiquan, SUN Kai, XU Yongjian

  2025,49(4):049615-049615, DOI: 10.11964/jfc.20230513997

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  Dysregulation of the biological clock system is recognized as one of the causes of physiological and metabolic disorders and other undesirable disease development in organisms, and the composition of dietary nutrients influences the rhythmic expression of the biological clock system. Ridgetail white prawn (Exopalaemon carinicauda) is an important aquaculture species in the coastal areas of China. However, there is no specialized aquaculture feed for this shrimp, and the effects and mechanisms of environmental regulation of its biological clock system are also not apparent. This study analyzed the changes in the relative expression and expression rhythms of four key biological clock genes under different protein levels by fluorescence quantitative PCR to explore the effects of different protein levels in feeds on the biological clock system of E. carinicauda, and to find a suitable feed protein level for it. The effects of protein level on the synchronization of the biological clock system were also evaluated. Meanwhile, the growth performance and muscle composition were validated and analyzed to ensure the accuracy of this study. The results showed that the expression rhythms of biological clock genes were changed significantly with the increasing feed protein levels in the liver, but not in the eye-stalk, with substantial dysregulation and synchronization deviation between the two biological clock systems. The highest synchronization between the rhythms of expression of the clock genes in the eye-stalk and liver was observed when the feed protein level was 39%, which corresponded to the highest growth performance and optimal muscle protein content (145.83%±4.34%, 18.88%±0.62%). When the protein levels were below or above 39%, the synchronization of the biological clock system was diminished, and the growth performance and muscle registration were also poorly performed. The present study showed that either too high or too low protein levels were detrimental to the maintenance of synchronization of the biological clock system in E. carinicauda and that dietary protein levels around 39% were most suitable for growth and nutrient retention. This study is an innovative approach to "forcefully" alter the rhythm of the peripheral biological clock by altering the protein level in the feed of the shrimp and aligning it with the central biological clock system to maximize growth and metabolic gains, reduce the incidence of metabolic disorders and other diseases, which is important for promoting the practical production and filling the gaps in biological clock research of the E. carinicauda.

• Effects of mulberry leaf extract on growth performance, carcass composition and serum biochemical indices of Pelophylax nigromaculatus

  CHEN Xiang, LIU Donghua, GENG Linye, SHEN Shijie, WANG Qianru, SHEN Yihong, HUANG Xianzhi, DUAN Biao

  2025,49(4):049616-049616, DOI: 10.11964/jfc.20230714078

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  This study designed gradient concentration of 0 (control), 3, 6, and 9 g/kg mulberry leaf extract (MLE) added to the essential diet and the initial weight of (2.7 ± 0.2) g healthy Pelophylax nigromaculatus was fed for 56 days to investigate the effects of MLE at different levels on growth performance, carcass composition, and serum biochemical indices. The gradient concentration experiment were labelled as C control group, M03 group, M06 group and M09 group, respectively. Survival rate, final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR) initially increased and then decreased with rising MLE levels. The M03 group showed significantly higher FBW, WGR, and SGR by 4.18%, 6.98%, and 2.86%, respectively, compared to the control group(P<0.05). Feed intake rate (FR) and feed conversion ratio (FCR) initially decreased and then increased, with the M03 group exhibiting a significant reduction of 7.73% and 12.32% in FR and FCR (P<0.05). Meanwhile, the M09 group showed no significant difference from the control group (P>0.05). Compared to the control, carcass crude protein and crude lipid in the M03 and M06 groups remained unchanged (P>0.05). The hepatic lipid content significantly decreased by 10.17% and 10.60% (P<0.05). However, carcass protein in the M09 group declined significantly by 4.11% (P<0.05). Serum total cholesterol (TC) and low-density lipoprotein (LDL) in the M03 group decreased significantly by 35.23% and 53.12% (P<0.05). Hepatic superoxide dismutase (SOD) activity in the M03 and M06 groups increased significantly by 18.59% and 9.67% (P<0.05), whereas no significant difference was observed in the M09 group (P>0.05). Hepatic total antioxidant capacity (T-AOC) and malondialdehyde (MDA) levels were higher than the control group but not statistically significant (P>0.05). Dietary MLE supplementation improves feed utilization efficiency, antioxidant capacity and growth performance in P. nigromaculatus. Based on a comprehensive evaluation, the optimal MLE inclusion level in the basal diet was recommended to be 0.34%-0.42%. This study provides a theoretical foundation for the green and healthy aquaculture of P. nigromaculatus.