ROUNDUPS

• Research progress on commercial tropical tuna habitat

  ZHOU Cheng, HU Yuanyuan, WAN Rong, XU Liuxiong, ZHU Jiangfeng, LI Yunkai

  2026,50(1):019301-019301, DOI: 10.11964/jfc.20230614052

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  The tuna fishery is one of the largest commercial and recreational fisheries in the world. Tropical tuna as the primary source of global tuna production holds significant commercial value. Its wide distribution, migratory and movement patterns make it subject to the jurisdiction of multilateral and international fisheries management organizations. A better understanding of the geographical distribution of tropical tuna habitats and the marine environmental characteristics influencing habitat selection could help drive the development of optimal sustainable fisheries management strategies. Globally, the biology and ecological roles of tropical tunas have been extensively and well-studied. However, there is currently a lack of comprehensive and systematic review study domestically on the habitat partitioning of three commercial tropical tuna species and their environmental adaptability. This study reviews the research on tropical tuna habitats over different periods, both domestically and internationally. We explore the impact of the physiological mechanisms and behavioral characteristics of tropical tuna on the habitat selection from a physiological and ecological perspective, and provide a classified overview of the two primary methods used in habitat research, direct observation and habitat modeling. We also present a comprehensive analysis of the interspecific variations among three tropical tuna species regarding their global geographical distribution, vertical depth distribution, and preferences and tolerance to different marine environmental factors. Researches indicated that tropical tuna exhibit significant inter-specific differences in their vertical habitat distribution, along with diurnal distribution variations, demonstrating diurnal vertical migration behavior. Tropical tuna typically dive deeper at dawn and ascend at dusk, aligning with the vertical migration pattern of the deep scattering layer. Changes in the marine environment primarily drive the dynamics of tropical tuna population structure and abundance, impacting their habitat distribution. The key environmental characteristics of tropical tuna habitats can be classified into three main categories: physical environmental factors, chemical environmental factors, and biotic factors. Also, the present study comprehensively compiles the environmental characteristics of tropical tuna habitat in thirteen major global marine ecological regions by summarizing the findings from the literature. The ecological regions occupied by tropical tuna can be classified into three main types: the first type consists of regions with high temperatures, low productivity, and relatively shallow mixed layer depth; the second type includes regions with low temperatures, high productivity, and moderate mixed layer depth; and the third type comprises regions with both high temperatures and high productivity. Finally, we offer insights into future research opportunities in the hotspots of tropical tuna habitat by integrating the research frontiers in fisheries and oceanography. In particular, it is essential to focus on the impact processes and driving mechanisms of climate change on population resource dynamics and to distinguish the specific responses of different species to climate change. This knowledge will support relevant organizations in formulating effective measures to address the future impacts of climate change on fisheries.

PAPERS

• Functional differentiation of pcolcea and pcolceb genes in bone development in Danio rerio

  WANG Wenxiu, CHEN Yulong, XIAO Zhengyu, GAO Zexia, NIE Chunhong

  2026,50(1):019102-019102, DOI: 10.11964/jfc.20241214817

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  Procollagen C-proteinase enhancer protein (PCOLCE) is a secreted protein that enhances the activity of procollagen C-proteinase, thereby facilitating the maturation of collagen and influencing the process of bone formation. Down-regulation of pcolce expression compromises the maturation of collagen, ultimately leading to a reduction in bone mass. In teleost fish, the occurrence of genomic duplication events has led to the emergence of two paralogs of pcolce, designated pcolcea and pcolceb, whose functional roles in skeletal development remain incompletely characterized. To delineate the functional divergence of pcolcea and pcolceb in zebrafish (Danio rerio) osteogenesis, this study employed a multi-faceted approach integrating computational analysis of sequence features, spatiotemporal expression profiling, and phenotypic characterization of targeted mutants. The results indicated that pcolcea and pcolceb comprise 8 and 9 exons, respectively, with pcolceb being significantly longer; both genes were predominantly expressed in the vertebrae, head, and pectoral fins. Through targeted gene knockout, we generated pcolcea^-/- and pcolceb^-/- homozygous mutants. The pcolcea^-/- mutant carried a 229-bp deletion in exon 1, while the pcolceb^-/- mutant carried a 7-bp deletion in exon 3. Compared to wild-type D. rerio, pcolcea^-/- and pcolcea^-/-; pcolceb^-/- double mutant D. rerio exhibited a marked reduction in vertebral tissue mineral density, whereas pcolceb^-/- D. rerio showed no significant difference. Subsequently, the expression of genes related to bone development (runx2b, entpd5a, alpl, bglap, sp7), collagen development (col1a1a, col1a1b, col1a2), and downstream effector genes (bmp1a, bmp1b) was quantified by RT-qPCR in the caudal vertebrae of the mutants. RT-qPCR results showed that expression of bmp1b, col1a1a, col1a2, runx2b, alpl, and sp7 was significantly downregulated in pcolcea^-/- mutants. In pcolcea^-/-; pcolceb^-/- double mutants, the expression of bmp1b, col1a1a, col1a1b, col1a2, runx2b, entpd5a, bglap, and sp7 was significantly lower than in wild-type D. rerio. Collectively, these results demonstrated that loss of pcolcea impaired skeletal tissue mineralization in D. rerio, and this phenotype was significantly exacerbated by the concurrent deletion of pcolceb. This study elucidates the distinct roles of pcolcea and pcolceb in D. rerio bone development and provides a foundation for understanding the molecular mechanisms governing skeletal formation in fish.

• Characterizing IL-12 expression and identifying its isoform profiles in largemouth bass (Micropterus salmoides)

  YAN Mengzhi, WANG Dandan, YANG Jing, LI Jie, ZENG Hui, ZHANG Yongan, ZHOU Yang

  2026,50(1):019103-019103, DOI: 10.11964/jfc.20250214885

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  Interleukin-12 (IL-12) is a heterodimeric cytokine composed of p40 and p35 subunits linked by an interchain disulfide bond, and it plays a broad and essential role in the immune system. To characterize the molecular composition and function of IL-12 isoforms in largemouth bass (Micropterus salmoides), we cloned the cDNA sequences of four IL-12 subunits (p35a, p40a, p40b, and p40c) and analyzed their sequences, revealing conserved cysteine residues that are critical for disulfide bond formation. We examined the tissue-specific expression profile of IL-12 subunits in M. salmoides using quantitative real-time PCR (qPCR). Time-series transcriptome analysis was conducted to track expression changes of IL-12 subunit genes in M. salmoides following Nocardia seriolae infection. Two fusion proteins of IL-12 were overexpressed to investigate their functional characteristics. The results indicated that the amino acid sequences of the four IL-12 subunits contain multiple conserved cysteine residues involved in disulfide bonding. Tissue-specific expression profiling via qPCR revealed differential expression patterns of these subunits across six organs (liver, spleen, head kidney, etc.). Time-series transcriptome analysis showed that the p40c gene was persistently suppressed in both the head kidney and spleen, while p40b expression was continuously suppressed in the head kidney and transiently upregulated in the spleen on the second day post-infection before gradually decreasing. Additionally, p35a, p40a, and p40b exhibited divergent expression profiles in the head kidney and spleen. Co-IP assays confirmed interactions between p35a and p40b/p40c. Overexpression of the two fusion proteins p40b-p35a and p40c-p35a in M. salmoides demonstrated that both dimers formed by p40b+p35a and p40c+p35a significantly upregulated IFN-γ expression in the spleen. Our study identifies two functional IL-12 isoforms in M. salmoides, composed of p40b+p35a and p40c+p35a, providing important insights into IL-12-mediated immune responses in teleost fish.

• Expression and functional study of Cyp17a1 in Bellamya purificata

  MIAO Yulin, Lü Huohong, GU Yang, JIN Xin, WANG Ping, WANG Guiling, LI Jiale

  2026,50(1):019104-019104, DOI: 10.11964/jfc.20241114753

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  Bellamya purificata, a unique edible freshwater snail in China, has considerable economic value. To study the role of the steroidogenic enzyme gene Cyp17a1 in the hormone synthesis process of B. purificata, this study cloned the open reading frame (ORF) region of the Cyp17a1 gene. The expression patterns of Cyp17a1 in B.purificata were analyzed using quantitative real-time PCR and in situ hybridization. RNA interference was performed on the Cyp17a1 gene, and B. purificata was immersed in different concentrations of hormones to explore the role of Cyp17a1 in the synthesis of steroid hormones. The results showed that the ORF region of Cyp17a1 in B. purificata is 1 572 bp in length, encoding 523 amino acids. The expression of Cyp17a1 varied across different tissues of B. purificata, with significantly higher expression in males than in females, except in the gills. The gene was primarily expressed in spermatocytes and spermatids in the testes. After 12 hours of RNA interference with Cyp17a1 in the gonads, testosterone levels significantly decreased in both males and females, while estradiol levels significantly increased. Immersion in different concentrations of hormones for 24 days revealed that treatment with 40 ng/L of 17β-estradiol (E2) and 17α-methyltestosterone (MT) resulted in an initial decrease followed by an increase in Cyp17a1 expression. In contrast, treatment with 200 ng/L of E2 and MT led to an initial increase followed by a decrease in Cyp17a1 expression. These findings indicate that Cyp17a1 is involved in the synthesis and transformation of steroid hormones in B. purificata. This study provides valuable insights into the steroid hormone synthesis process in B. purificata and lays a theoretical foundation for research on sex regulation and gonadal development in this species.

• Industrial indoor breeding, early growth and development characteristics of Plectropomus leopardus

  LI Wensheng, GUO Xiaoli, YANG Chuanjun, HE Xinlei, PANG Zunfang, MA Wenhui, ZHANG Yingguang, SUN Fangfang, ZHANG Jiawei, YUAN Songzhu, ZHANG Quanqi, CHEN Songlin

  2026,50(1):019605-019605, DOI: 10.11964/jfc.20250114832

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  This study accomplished the fully industrialized indoor breeding of Plectropomus leopardus and investigated the characteristics and patterns of embryo and early post embryonic development of P. leopardus in the north indoor factory workshops. This study used microscopic imaging and morphological measurement observation methods to track the early developmental processes and characteristics of fertilized eggs of P. leopardus obtained through indoor factory cultivation and natural reproduction. We found the zygotes were transparent floating spherical eggs with an average diameter of (887.08±10.28) μm and a single oil bulb with an average diameter of (166.60±10.81) μm. Embryonic development experience 8 classical developmental stages, including fertilized egg stage, blastodisc stage, cleavage stage, blastula stage, gastrula stage, neurula stage, organo-forming stage, and hatching stage, subsequently divided into 27 stages. The fertilized eggs were hatched at 27 h 13 min after fertilization followed by the larval stage. The total length of the newly hatched larvae was (2.156±0.281) mm. According to the absorption of yolk sac, larval stage was further divided into pre-larval stage [0-3 (days post hatching, dph), not complete absorption of yolk sac] and post-larval stage (4-30 dph, complete absorption of yolk sac). The oil globule disappeared at 4 dph and the swimming bladder appeared at 8 dph. At 28 dph, the total length (15.32±1.98) mm, the length of the second dorsal fin spine (8.04±1.06) mm, and the length of the first pelvic fin (5.97±1.37) mm, extended to the maximum value. Afterwards, the length began to shorten. When the dorsal fin spine contracted to the minimum value (3.26±1.13) mm, all kinds of fins were fully formed, scales began to appear and body color began to deepen, marking the entry into the juvenile stage. At 71 dph, entering the adult fish, the total length (40.21±1.33) mm，the body shape was similar to that of the adult fish and the whole body was covered with scales and baby blue spots. For the first time, this study achieved the natural reproduction spawn and artificial cultivation of P. leopardus in the northern industrial workshop, revealing its early growth and development characteristics and pattern,laying a theoretical and technical basis for the the full factory batch cultivation of leopard coral grouper seedlings.

• Morphological comparison of two Opsariichthys uncirostris populations and analysis of embryo development and growth between their complete diallel crossing progeny

  XUE Lingzhan, FEI Fan, ZENG Gaoxiong, CHEN Jiajia, HU Zhenxi, CHEN Duhuang, FU Jianjun, ZHU Wenbin, LUO Mingkun, WU Meiying, WU Bin, MIAO Linghong, DONG Zaijie

  2026,50(1):019606-019606, DOI: 10.11964/jfc.20241214785

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  Opsariichthys uncirostris is a small, omnivorous freshwater fish with slightly predatory behavior. It has diverged into two subspecies, O. uncirostris amurensis (northern China) and O. uncirostris bidens (southern China), with distinct physiological adaptations to their respective northern and southern geographic climates. O. uncirostris amurensis is characterized by a shorter maturation cycle (precocious maturity), whereas O. uncirostris bidens exhibits faster growth rates. With the growing consumer demand for stream fish, aquaculture production has intensified. However, this has led to increased inbreeding, resulting in declining seed quality and disease resistance, which has impeded sustainable industry development. To address this issue, there is an urgent need to develop new strains with superior traits. This study aimed to conduct a comparative morphological analysis of these two subspecies and perform a diallel cross to evaluate heterosis in embryonic development, larval viability, and growth performance. The ultimate goal was to produce a novel hybrid strain that outperforms both parental lines, providing a genetically improved stock to support the high-quality development of the industry. In this study, we measured morphological trait indices of O. uncirostris bidens (Minjiang River Population) and O. uncirostris amurensis (Songhua River Population). Through path and correlation analyses, the influence of each trait on body weight, and the embryonic development and growth of the offspring of the complete diallel crossing between two populations were evaluated and analyzed. Morphological quantifiable trait analysis showed that the morphological differences between different genders in the two populations of O. uncirostris amurensis and O. uncirostris bidens were mainly concentrated in aspects such as the overall contour of the fish body, head shape, and fish body size. Among them, the TRL/BL standardized index of female O. uncirostris amurensis was the largest (0.47 ± 0.02). The PFL/BL standardized index of male O. uncirostris bidens was the largest (0.18 ± 0.01). Stepwise discriminant analysis identified 10 significant traits, leading to a discriminant equation with an overall accuracy rate of 98.33% to distinguish the two populations (F = 38.881 X₁ - 53.252 X₂ - 59.503 X₃ - 7.545X₄ + 22.466 X₅ + 22.387X₆ - 20.866 X₇ - 0.306 X₈ + 0.228 X₉ + 0.376 X₁₀ - 6.082). Correlation analysis showed that the 17 growth traits of the two groups were positively correlated with body weight. Path analysis showed that the correlation coefficient between body weight and body thickness was the largest (0.93). In O. uncirostris amurensis, the correlation coefficient between total length and body weight was the largest (0.92). Embryonic development times for offspring from shortest to longest were as follows: self-crossed progeny of O. uncirostris bidens (SS, 37 h 28 min), progeny of O. uncirostris bidens male × O. uncirostris amurensis female (SN, 38 h 6 min), progeny of O. uncirostris amurensis male × O. uncirostris bidens female (NS, 40 h 57 min), and self-crossed progeny of O. uncirostris amurensis (SS, 42 h 8 min). Analysis of the growth differences and mid-parent heterosis of the complete diallel crossing progeny showed the progeny of NS group hybrids exhibited heterosis in body weight and total length at 30, 60, and 90 days after hatching, with superior parent heterosis observed at 30 and 60 days after hatching. The SN group hybrid progeny showed mid-parent heterosis for body weight at 90 days after hatching. The study demonstrated the hybridization between the Minjiang River population of O. uncirostris bidens and the Songhua River population of O. uncirostris amurensis has certain heterosis, providing a valuable reference for new breed development.

• Prediction of the migration route of Ommastrephes bartramii in Northwest Pacific Ocean based on Habitat Suitability Model and its relationship with ENSO

  HAN Guanrong, CHEN Xinjun, LIU Bin, XIE Mingyang

  2026,50(1):019307-019307, DOI: 10.11964/jfc.20230413970

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  The environmentally sensitive neon flying squid (Ommastrephes bartramii) undertakes large-scale, long-range and seasonal migrations between spawning and feeding grounds in the Northwest Pacific to seek the optimal habitat conditions for growth and development. To elucidate the general feeding migration routes of the neon flying squid in the Northwest Pacific Ocean, this study developed a Habitat Suitability Index (HSI) model utilizing environmental data, including Sea Surface Temperature (SST), Sea Surface Height (SSH), and Photosynthetically Active Radiation (PAR), along with fisheries catch statistics. The model was applied to analyze the squid's migration distribution during the feeding season (from July to November) from 1998 to 2020 and its relationship with the El Ni?o Southern Oscillation (ENSO). The results indicated that in early July, the squid were widely distributed within 152°-165°E and 38°-42°N. The feeding migration comprised three distinct phases: 1) Initially, the squid aggregated rapidly northwestward, reaching 155.48°E, 41.75°N by early August. 2) Subsequently, they turned northeastward, progressed slowly along the Subarctic Front, and arrived at the northernmost point (156.56°E, 43.46°N) in late September. 3) Finally, they commenced a direct return migration southwestward, arriving at 151.52°E, 41.26°N by late November. Over the past 23 years, significant interannual variability was observed in the migration routes, with longitudinal and latitudinal shifts of approximately 1.7° and 0.5°, respectively. The research reveals that ENSO events influence the spatiotemporal distribution of juvenile squid, leading to a more eastward-biased northward feeding migration. Compared to normal years, during La Ni?a events, the expanded suitable habitat promoted faster growth and a quicker northward migration, resulting in a more northerly terminus (43.76°N). Conversely, during El Ni?o years, the migration tended to stall south of 43°N, with slower north-south progression. Furthermore, constrained by regional environmental conditions, the squid exhibited a higher aggregation tendency from mid-August to early October, which enhanced the commercial fishing efficiency. It is concluded that the neon flying squid in the Northwest Pacific follows a defined feeding migration route, which exists distinct modifications in response to ENSO events. These findings provide scientific support for understanding and managing the fisheries resource of neon flying squid in the Northwest Pacific Ocean, in particular.

• Preliminary exploration on target species selection strategy for marine ranching in northern Zhoushan archipelago waters

  WANG Zhenhua, YU Jintao, ZHANG Shouyu, LIN Jun, WANG Kai

  2026,50(1):019308-019308, DOI: 10.11964/jfc.20240814655

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  Currently, the East China Sea region is implementing the national "Blue Granary" strategic mission. A key component of this mission is the scaling up and high-quality development of marine ranching, aiming to gradually replace highly destructive traditional fishing practices in nearshore and offshore areas. However, a solely conservation-oriented model of marine ranching is insufficient, as it fails to accommodate the labor absorption and industrial restructuring required for the broader transformation of the fisheries sector. Therefore, it is necessary to optimize and adjust the attributes of marine ranching in the East China Sea region and expand and enhance its functions. One of the key steps in this process is the selection and construction of a target species system for marine ranching in the East China Sea region. To optimize the theoretical framework for marine ranching construction in the East China Sea region and enhance the targeted management efforts, this study takes the marine ranching in the northern Zhoushan archipelago waters as an example and employs the Analytic Hierarchy Process (AHP) to comprehensively screen target species for marine ranching in this area. A hierarchical structure model was constructed, encompassing five rule layers: ecosystem status, population regulation function, resource utilization paradigm, economic contribution intensity, and social impact capability, along with 15 specific indices such as energy flow contribution and ecological niche width. Based on this model, the weights of the rule layers and index layers were determined through expert scoring. Representative fishery resource species in the study area were preliminarily screened based on resource abundance and economic value. A total of 39 core target species for marine ranching were identified, including fish such as S. marmoratus and L. maculatus, crabs like P. trituberculatus and C. japonica, cephalopods represented by S. maindroni and O. vulgaris, and shellfish including M. unguiculatus and R. venosa. Based on this, utilization strategies for core target species were refined, establishing a harvesting system centered on sea angling supplemented by gathering and net fishing. This identified sea angling target species like S. marmoratus and C. myriaster, gathering target species like R. venosa and A. japonica, and net fishing target species like P. argenteus and P. trituberculatus. The establishment of a target species selection system for marine ranching in the northern archipelago waters of Zhoushan clarifies the specific objects and priority levels for marine ranch resource production in this area. It identifies breakthrough strategies for developing marine ranches in the archipelago waters of the East China Sea, providing practical guidance for the development of marine ranches and fisheries management in the region.

• Hydroacoustic evaluation of fish resources in the Yangtze River's four major Chinese carps reserve (Chongqing Section) in the early stage of fishing ban

  HE Shiwen, TIAN Huiwu, DENG Huatang, NI Dafu, XIE Wei, DUAN Xinbin, SHAO Jian, ZHOU Junjie, ZHANG Hui, WANG Ke

  2026,50(1):019309-019309, DOI: 10.11964/jfc.20241114774

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  Against the backdrop of global climate change and intensive human activities, fish resources in the Yangtze River Basin have continued to decline. To protect aquatic biodiversity and restore the ecosystem, a comprehensive fishing ban has been gradually implemented since 2018 in 332 aquatic reserves across the Yangtze River Basin, including the National Germplasm Reserve for the "four major Chinese carps" in the Chongqing section. By the end of 2019, Chongqing had taken the lead in completing the withdrawal of fishermen from its aquatic reserves, fully prohibiting productive fishing activities. This study aimed to understand the changes in fish resources within the reserve following the fishing ban. From April to May (fish spawning season) and December (fish overwintering season) of 2023, the research team conducted an 8-day hydroacoustic survey using an EK80 split-beam echosounder across an approximately 125 km river section of the reserve, along with a 52-day catch survey. The hydroacoustic survey revealed that the average fish density during the spawning and overwintering periods was (19.44±29.04) and (5.07±3.93) ind./1 000 m³, respectively, with no significant difference. However, the average target strength differed significantly, measuring (–60.66±6.63) dB and (–57.60±6.44) dB, respectively. During the spawning season, fish tended to aggregate near urban areas, whereas in the overwintering period, they were more dispersed in waters farther from urban zones. In both surveys, the highest fish density was observed at depths of 6-9 m, and the target strength generally increased with water depth. The catch survey identified 47 fish species (5 orders, 12 families) during the spawning season, with Hemiculter leucisculus, Pseudobrama simoni, and Squalidus argentatus being the most abundant. In the overwintering period, 48 species (6 orders, 13 families) were recorded, dominated by Saurogobio dabryi, Megalobrama pellegrini, and Coilia brachygnathus. Compared to pre-ban data (2017—2019), fish aggregation patterns in the reserve have shifted significantly. The density in the southern Changshou river section was notably higher than before the ban, but the average fish size has decreased. This study elucidates the post-ban distribution characteristics and changes in fish populations within the reserve, providing valuable insights for research on the evolution of fishery resources and regional fisheries management following the fishing ban.

• Stabilized preferred flow velocity of Ctenopharyngodon idella under complex dynamic hydraulic conditions

  SHI Xiaotao, BAO Chunpeng, WANG Yan, XU Xu, SU Xinyi, WU Shuai, SONG Nianxiong, CHEN Xiaolong, SUN Junjian, WANG Yuanming, LI Minne

  2026,50(1):019110-019110, DOI: 10.11964/jfc.20250414977

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  This study investigated whether Ctenopharyngodon idella exhibits a consistent range of preferred flow velocities under complex dynamic hydraulic conditions. C. idella, a commercially important species in the Yangtze River Basin (total length: 20.5-25.5 cm), was selected as the research subject. Laboratory experiments were conducted in an open recirculating flume with variable-frequency control, where three characteristic flow scenarios were established. Each scenario consisted of three parallel flow areas of equal width arranged along the streamwise direction. These areas represented all possible combinations of three velocity levels (low, medium and high): Condition I (high-low-medium: 0.65-0.32-0.47?m/s), Condition Ⅱ (low-high-medium: 0.27-0.78-0.48?m/s), and Condition Ⅲ (low-medium-high: 0.23-0.43-0.91?m/s). The upstream swimming behavior of C. idella under three complex hydraulic conditions was comparatively analyzed by coupling fish trajectories with background flow fields, and Boolean operations on probability density functions were applied to quantify the preferred flow-velocity ranges of C. idella. The results showed that: ① fish residence time increased with decreasing flow velocity, indicating a clear tendency to avoid high-velocity areas and prefer low to medium flow regions; ② under all conditions, C. idella predominantly occupied areas adjacent to flume sidewalls where lower velocities prevailed, with preferred ranges identified as 0.40-0.45?m/s and 0.60-0.67?m/s in Condition I, 0.41-0.50?m/s in Condition Ⅱ, and 0.18-0.31?m/s in Condition Ⅲ; and ③ when background flow distributions were similar (Conditions I and Ⅱ), fish exhibited a stable preference for 0.41-0.45?m/s, whereas under distinct flow regimes (e.g., Condition Ⅲ different from Condition I and Condition Ⅱ), preference shifted toward areas with higher probability density and lower velocities. These findings indicate that C. idella consistently prefers low to medium flow regimes, and C. idella has a stable preferred flow velocity under complex dynamic hydraulic conditions. This study provides scientific reference to support the ecological design of fishways and flow restoration strategies tailored to the behavioral responses of native fish species.

• Phenotypic and physicochemical characteristics of sediment deterioration during the culture of the swimming crabs (Portunus trituberculatus) and their correlations with bacterial community

  ZHOU Jiazheng, WU Qingyang, SHI Ce, MU Changkao, WANG Chunlin, YE Yangfang

  2026,50(1):019611-019611, DOI: 10.11964/jfc.20250414942

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  Deteriorating sediment quality adversely affects the health of aquatic organisms and even threatens their survival. Sediment microorganisms, key drivers of carbon, nitrogen, phosphorus, and sulfur (CNPS) cycling, are closely correlated with water quality changes in aquaculture systems. Yet, studies on the microbial community structure and function associated with sediment deterioration remain scarce. To explore the deterioration characteristics of the sediment during the culture of the swimming crab Portunus trituberculatus and their correlations with bacterial community, a 28-day crab farming trial was simulated in indoor canvas tanks using sea sand as the sediment. We monitored temporal changes in sediment appearance and physicochemical parameters. Using 16S rRNA gene amplicon sequencing, we profiled the sediment bacterial community, and applied redundancy analysis to examine its correlation with the physicochemical factors. Finally, we assessed functional changes via FAPROTAX and quantitative polymerase chain reaction techniques. The results showed that the color of sediment changed from initial grayish-brown to dark brownish-black, accompanied by the generation of an irritating odor. The shell color of swimming crabs changed from bluish-gray to yellowish-brown, and blackish-brown spots appeared on the surface of the shell and chelipeds, with the survival rate dropping to 38.1%. The temperature, pH, and dissolved oxygen content of the sediment continuously decreased, while the levels of ammonia nitrogen (NH₄⁺-N), unionized ammonia (NH₃), and nitrite nitrogen (NO₂^?-N) first increased and then decreased, peaking at day14 and day 21, respectively. In contrast, the levels of nitrate nitrogen (NO₃^?-N) and hydrogen sulfide (H₂S) continuously increased over 28 days. Meanwhile, the α-diversity of the sediment bacterial community first increased and then decreased, while the β-diversity exhibited three typical stage-specific characteristics: before deterioration (day 0), during deterioration (days 7-21), and after deterioration (day 28). Additionally, the dominant bacteria in the sediment shifted from Gammaproteobacteria to Alphaproteobacteria. The dynamic changes in the sediment bacterial community were driven by the synergistic effects of physical indicators such as pH and temperature, as well as chemical indicators such as H₂S and NH₄⁺-N. Functional analysis revealed that the nitrogen cycling functions (nitrification and denitrification) of the sediment bacterial community peaked at day 14 and day 21, with Nitrospira and Nitrospina being the main contributors to nitrification potential. In contrast, sulfur cycling functions significantly increased at day 28, with Desulfofaba, Fusibacter, Desulfovibrio, and other bacteria being the primary contributors to sulfur compound respiration. qPCR analysis revealed significant changes in the expression of 14 nitrogen-cycle and 4 sulfur-cycle functional genes during sediment deterioration, with nitrification (amoB and nxrA) and denitrification genes (nirK1-3 and nirS3) peaking at day 14, while sulfate reducing genes (dsrA, dsrB and aprB) peaked at day 28. These findings indicate that physicochemical indicators of the sediment and its bacterial community interact with each other, jointly driving the deterioration of the sediment. This study can provide basic data and theoretical references for the green and healthy aquaculture of P. trituberculatus.

• Parameter acquisition and model development for the Dynamic Energy Budget (DEB) of oyster Saccostrea mordax

  MA Haojie, ZHANG Yuehuan, WANG Xinmeng, MENG Rongzhao, TAN Liushuyi, GAO Tianxiang, ZHANG Jihong

  2026,50(1):019112-019112, DOI: 10.11964/jfc.20250414976

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  Abstract:

  This study constructed a Dynamic Energy Budget (DEB) model to gain a deeper understanding of the growth, reproduction, and energy allocation of oyster Saccostrea mordax in different marine areas, providing theoretical support for the site selection, design, and sustainable management of oyster reefs. Through model construction and validation, the research explores the impact of environmental factors such as water temperature and chlorophyll concentration on oyster growth, offering technical guidance for optimizing oyster farming strategies as well as marine ecosystem protection and restoration. Seven basic parameters required for the DEB model were measured through indoor physiological experiments, while other parameters were obtained from literature and model calibration. The shape coefficient (δ_m) was determined by regression analysis of shell length and soft tissue wet weight. Based on the measured oxygen consumption rates of oysters at different temperature conditions, the arrhenius temperature (T_A) was calculated. After 45 days of starvation experiments, volume-specific costs for structure [E_G], and maximum storage density [E_M], volume-specific maintenance rate [P?_M] were obtained. Maximum feeding rate per unit body surface area {J?_Xm} and maximum surface area-specific assimilation rate {P?_Am}. Remote sensing technology was used to obtain chlorophyll-a concentration and water temperature from June 2022 to April 2024 at Mischief Reef and Daya Bay. These data were used as forcing functions, and an individual growth model of the S. mordax in Daya Bay was constructed using R software and validated against actual growth data from Mischief Reef. Seven basic parameters required for the DEB model were successfully measured in indoor experiments, with δ_m = 0.270, T_A = 4 900.01 K, [E_G] = 5 600 J/cm³, [E_M] = 6 382 J/cm³, [P?_M] = 26 J/(cm³·d) {P?_Am} = 244 J/(cm²·d) and {J?_Xm} = 325 J/(cm²·d). The model simulation results showed a significant linear relationship between the simulated values of soft tissue dry weight and shell height and the measured values, demonstrating the effectiveness of the DEB model in this experiment. Regarding the growth of the S. mordax, the model indicates that food limitation has a higher impact than water temperature. The constructed DEB model can effectively simulate the individual growth of S. mordax. The temperature and food conditions at Mischief Reef are more suitable for the growth of S. mordax than those at Daya Bay.

• Effects of selenomethionine on the growth performance, feed utilization, muscle histology and antioxidant responses of yellow catfish (Pelteobagrus fulvidraco)

  LEI Xijun, KE Jiang, YANG Hong, XU Pengcheng, ZHANG Xu, HAO Zhiwei, LUO Zhi

  2026,50(1):019613-019613, DOI: 10.11964/jfc.20240614574

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  Abstract:

  To investigate the effects of selenomethionine on growth performance and muscle tissue of Pelteobagrus fulvidraco, we formulated six experimental diets with selenomethionine as the Se source. The supplemental levels of selenomethionine in the six experimental diets (S0, S1, S2, S3, S4, S5) were 0, 0.15, 0.30, 0.45, 0.60 and 0.75 mg/kg, respectively. The Se contents in diets were 0.17, 0.22, 0.29, 0.33, 0.41 and 0.45 mg/kg, respectively. The feeding experiment lasted for 10 weeks. The P. fulvidraco fed with S1 group feed showed the best growth performance and feed utilization rate, and had the most intact muscle histology. However, with the increase of selenomethionine levels in S1-S5 groups, the growth performance and feed utilization rate of P. fulvidraco decreased, the structural integrity of muscle tissue decreased, and the density and diameter of muscle fiber decreased and shortened, indicating that muscle tissue had been damaged. In addition, with the increase of dietary selenometine levels, the selenium content and the activities of antioxidant enzymes CAT, T-SOD and T-AOC in muscle tissue were increased. The mRNA expression of antioxidation-related genes (cat, sod1, sod2 and nrf2) and selenproteins (txnrd, sps2, gpx1, gpx2, msrb1, selenok and selenow) was significantly up-regulated, and the protein expression of NRF2 was significantly up-regulated. These results indicated that the antioxidant capacity and the expression level of selenoproteins in muscle of P. fulvidraco increased with the increase of dietary selenomethionine levels. Dietary supplementation of excessive selenomethionine can affect the growth performance of P. fulvidraco, reduce feed utilization, cause muscle tissue damage and reduce antioxidant capacity. This study determined that adding 0.15 mg/kg of selenomethionine to the diets of P. fulvidraco is most beneficial for its growth, and found that appropriate addition of selenomethionine can enhance the antioxidant capacity of P. fulvidraco muscles.

• Effects of dietary resveratrol supplementation on growth performance, antioxidant response, and ammonia detoxification in largemouth bass (Micropterus salmoides)

  YUE Yingqi, WANG Shidong, TANG Yanjie, FENG Dexiang, LI Ming

  2026,50(1):019614-019614, DOI: 10.11964/jfc.20241214819

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  Abstract:

  In order to investigate the effects of adding resveratrol to the feed on the growth performance, health status and ammonia nitrogen tolerance of Micropterus salmoides, the experiment was conducted on largemouth bass with an average body mass of (7.40±0.05) g. The fish were randomly divided into three groups, each with three replicates of 30 fish each, and were fed with experimental feeds containing 0.00%, 0.50% and 1.00% of resveratrol, and saturated feeding was carried out twice a day for 56 d. The results showed that supplementing the diet with resveratrol significantly enhanced the weight gain rate, protein efficiency rate and food intake, and reduced the feed conversion ratio; increased the serum total protein (TP), albumin (ALB) and globulin (GLB) contents, and decreased the triglyceride (TG), cholesterol (TC), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) contents; increased the activities of total antioxidant capacity (T-AOC), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) in liver, decreased the contents of tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1), and interleukin-8 (IL-8); up-regulated the mRNA expression of superoxide dismutase (sod), catalase (cat), glutathione reductase (gr), glutathione peroxidase (gpx), and b-cell lymphoma 2 (bcl-2) genes, and down-regulated the expression of interleukin-1 (il-1), interleukin-8 (il-8), tumor protein 53 (p53), bcl-2 associated X protein (bax), cysteine aspartate protease 3 (caspase3) and cysteine aspartate protease 9 (caspase9) genes. After 96 h of ammonia exposure, the cumulative mortality and blood ammonia content in resveratrol group were significantly lower than those in control group; but the serum lysozyme (LZM) activity, total complement (CH50), total immunoglobulin contents (IG), antibody titer (Ab titer), the activities of argininosuccinate synthetase (ASS), argininosuccinate lyase (ASL), arginase (ARG), and ornithine carbamoyltransferase (OTC) in liver were significantly higher than those in control group. The study showed that the addition of resveratrol to the feed could improve the growth performance, serum health, antioxidant capacity, inflammation and apoptosis of largemouth bass, and that resveratrol could enhance the ammonia-nitrogen tolerance of largemouth bass by activating the urea cycle, and improve the immune response to the occurrence of stress.

• Mechanism of dietary iron overload inducing hepatocyte damage in grass carp (Ctenopharyngodon idella)

  HUANG Xiaoman, LI Ningjing, YANG Yan, SONG Jialing, TIAN Ye, LIN Li, QIN Zhendong

  2026,50(1):019415-019415, DOI: 10.11964/jfc.20241014717

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  Abstract:

  Iron is an essential trace element in vertebrates, involved in critical biological processes like oxygen transport and energy metabolism. This study focused on Ctenopharyngodon idella, investigating the damaging effects of dietary iron overload. Healthy C. idella weighing 50-80 g were fed a diet supplemented with 0, 400, and 800 mg/kg of ferrous fumarate for 60 days. Growth performance results indicated that excessive iron intake significantly reduced the fish's length growth rate. Iron ion content analysis showed that ferrous fumarate supplementation significantly increased iron levels in serum and liver. ELISA results indicated that dietary iron overload led to an increase in hematocrit, along with significantly elevated activities of ALT, AST, and GPX4 in serum and liver. qRT-PCR results revealed that iron metabolism-related genes Tf, DMT1, Hepcidin, FPN, and NCOA4 were significantly upregulated in the ferrous fumarate group, while TfR1 and Ferritin were significantly downregulated. Furthermore, antioxidant-related genes ho-1, gpx4, and nrf2 were significantly upregulated in the ferrous fumarate group. In vitro experiments showed that FAC incubation of L8824 cells resulted in a significant increase in intracellular iron and ROS; qRT-PCR analysis revealed significant increases in inflammatory genes p65, tnf-α, nf-κb, tlr4, and p38-mapk, along with significant rises in oxidative stress-related genes keap1a, nrf2, and ho-1. In conclusion, this study suggests that dietary iron overload leads to an imbalance in iron metabolism and oxidative stress in C. idella, accompanied by inflammatory responses, providing a theoretical basis for understanding iron metabolism-related diseases and their prevention in C. idella.

• Morphological, histopathological, and molecular phylogenetic analysis of Myxobolus acinosus from Cyprinus carpio var. koi

  GUAN Xitao, ZHANG Xiaoyi, DING Peng, ZHOU Fan, MIAO Xiangjun, LIU Yang

  2026,50(1):019416-019416, DOI: 10.11964/jfc.20241214795

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  Abstract:

  Myxozoans are important parasitic pathogens of koi carp. In the present study, a Myxobolus species was found to infect gills of Cyprinus carpio var. koi. In order to identify this Myxobolus species, it was comprehensively described by morphological, histological and molecular methods, and its phylogenetic relationship was inferred as well. We found that the present Myxobolus species infected the gills of koi carp and formed a number of white plasmodia in all gills. Compared with all reported Myxobolus species, the present Myxobolus species was morphologically indistinguishable from M. acinosus. Histological analysis showed that the plasmodia of the present Myxobolus species developed in gill lamella of host, causing significant epithelial cell proliferation and congestion in the gills. Its parasitic characteristics are consistent with those of M. acinosus. BLAST search showed that SSU rDNA sequence of the present Myxobolus species was identical to M. acinosus (Accession numbers: KX810021-KX810022, MW821466-MW821468). Thus, the morphological, histological and molecular analysis demonstrated that the present Myxobolus species was conspecific with M. acinosus. Phylogenetic analysis revealed that the majority of myxozoans infecting the same host and organ formed independent lineages. However, myxozoans infecting different hosts and the same organ formed larger independent branches, indicating that sites of infection provide a stronger driving force for the evolution of myxozoans compared to host group.

• Rapid detection of ovalbumin in surimi based on colloidal goldimmunochromatography assay

  LI Zhonglin, HUANG Jianlian, ZHANG Lingjing, ZHANG Changgong, CHEN Yulei, WENG Ling, CAO Minjie

  2026,50(1):019817-019817, DOI: 10.11964/jfc.20241214815

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  Abstract:

  Egg white is widely used in the food industry due to its unique properties, particularly in the production and processing of surimi products. However, some manufacturers excessively add egg white as a substitute for fish meat without proper labeling, aiming to reduce production costs. Ovalbumin (OVA), a major allergen in egg white, is the primary protein of concern. Currently, established standards for the use of OVA in surimi products are not available. The addition of non-fish proteins, such as egg white protein, not only constitutes food adulteration but also causes significant health risks to individuals with allergies due to the presence of OVA. Since there is no effective clinical treatment for food allergies, patients are advised to avoid allergenic ingredients in their diets. Therefore, developing a rapid, simple, and sensitive detection method for allergens is of practical significance. In this study, a rapid, simple, and on-site method for detecting the food allergen OVA in surimi raw material and its products was developed based on the colloidal gold immunochromatographic assay (CGIA). Egg white was pretreated using a two-phase aqueous extraction method, and OVA was purified by ion-exchange chromatography. The purity of purified OVA was assessed via sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and further confirmed by mass spectrometry. Polyclonal antibodies against OVA were prepared, and colloidal gold solution was synthesized using the trisodium citrate reduction method. The antibodies were then labeled with colloidal gold. A colloidal gold immunochromatographic test strip for OVA detection was developed based on a competitive assay principle and optimized. Western blot analysis demonstrated that the anti-OVA polyclonal antibodies specifically recognized chicken egg OVA and duck egg OVA without cross-reacting with other proteins in surimi, indicating high specificity. The developed OVA-CGIA-Strip could rapidly detect chicken and duck OVAs in surimi. Four parameter logistic curve was used to fit the standard curve y=7.17-2.79 lgx (R² = 0.9834). The linear range was 0.01 to 20.00 μg/mL, with a limit of detection (LOD) of 0.20 μg/mL and IC₅₀ of (3.13±0.18) μg/mL. The OVA-CGIA method is simple to use, highly specific, and accurate. When combined with a colloidal gold strip analyzer, it enables convenient, rapid, and quantitative detection of OVA in surimi. In summary, the OVA-CGIA-Strip established in this study provides a simple, specific, and accurate approach for rapid on-site detection of OVA in surimi. This method not only helps safeguard the health of allergic individuals but also ensures the integrity of surimi products, with significant implications for both public health and the food industry. Its promising research and development prospects make it a valuable tool for future applications.

• Impact of single-strand diameter changes on the hydrodynamic performance of three-strand ropes with equal strand diameters

  ZHANG Jintao, HUANG Liuyi, BI Chunwei, LAN Gonghai, YOU Xinxing, LI Huanran, ZHANG Xuewen, ZHANG Jinhui, ZHANG Rongjun, Lü Haoyuan, FENG Weidong

  2026,50(1):019718-019718, DOI: 10.11964/jfc.20250114831

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  Abstract:

  This study takes a three-strand twisted rope with a nominal diameter of 40 mm (equal strand diameter) as the prototype. Based on the mathematical equations of the cross-sectional geometry of three-strand ropes, a prototype rope (labeled 40-40) and four variant rope models with modified strand diameters were constructed. The four variant ropes were created by replacing the original strands of the prototype with strands from three-strand ropes of nominal diameters 48, 44, 36, and 32 mm, labeled as 40-48, 40-44, 40-36, and 40-32, respectively. Physical rope models were fabricated via 3D printing, and the effects of strand diameter variations on hydrodynamic coefficients and flow field characteristics were investigated through flume experiments and numerical simulations within a Reynolds number range of 7.96×10³ to 5.57×10⁴. The results revealed that: ① The drag coefficients of all ropes exhibit minimal variation with increasing Reynolds number. ② The drag coefficient decreased with reduced strand diameter, while the lateral force coefficient remained relatively stable. ③ Compared to the prototype (40-40), the average drag coefficients of 40-32 and 40-36 decreased by 7.06% and 4.49%, respectively, whereas those of 40-44 and 40-48 increased by 2.22% and 5.51%, respectively. ④ The high-velocity zones around the ropes and the areas of positive/negative pressure on the rope surfaces diminished as strand diameter decreased, accompanied by weakened downstream turbulence, leading to reduced pressure difference resistance and lower drag coefficients. This study demonstrates that reducing strand diameter effectively decreases rope resistance and mitigates downstream turbulence. The findings provide valuable insights for hydrodynamic research on fishing gear and innovative design of rope-based materials in fisheries engineering.