ROUNDUPS

• Behavioral responses of decapod crustaceans to fishing pots

  ZHANG Jian, TENG Yuxiu, SONG Houcheng, SHI Jiangao

  2025,49(7):079701-079701, DOI: 10.11964/jfc.20240114352

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  With the resurgence of pot fisheries, issues such as discards and mortality of bycatch species and sublegal-sized targets in decapod crustacean pot/trap fisheries have emerged as a central concern in the study of the ecological impacts of fishing. A comprehensive understanding of the mechanisms underlying the response behaviors of target species to pots and their components is critical for optimizing fishing performance, mitigating ecological impacts of the fisheries, and advancing sustainable fisheries management within an ecosystem-based framework. This review initiates with an extensive retrieval of existing literature, systematically categorizing the sequential behavioral responses, from initial bait attraction through capture or escape, of individual or grouped decapod crustaceans to pots into six distinct phases: arousal, location and approach, entrance search, entry, inside the pot, and escape. A standardized quantitative index system is proposed to evaluate the density and intensity of behaviors at each phase. Then, utilizing these behavioral metrics, this review synthesizes the response mechanisms and behavioral patterns exhibited by the main decapod crustacean species in major global commercial pot fisheries. Comparative analyses are conducted to elucidate interspecific variations in behavioral responses to different pot designs, while identifying the principal factors influencing behavioral patterns for each behavioral phase. Furthermore, this review explores the potential applications of these findings in the optimization of pot/trap design, including bait, entrance design, structural features, and escape devices. Such insights have significant potential for reducing bycatch, mitigating ghost fishing effects, and guiding the development of ecologically sustainable, eco-friendly pot designs. This review also addresses methodological challenges inherent in current research on decapod crustacean behavioral responses to pot/trap, particularly those arising from discrepancies in experimental observation techniques, phase delineation, and behavioral quantification methodologies. These challenges hinder a unified understanding of individual and collective behavioral patterns. By providing a critical evaluation of these limitations, this review additionally offers a conceptual framework and methodological insights for future research on marine organism behavioral responses to pot/trap, as well as for the development of pot/trap that aligns with the objectives of contemporary fisheries management and conservation strategies.

• Research advances in the photoreception systems of Echinoderms

  CHEN Muyan, YANG Hongliang, WANG Yanlin, TIAN Xiang, SUN Lidong

  2025,49(7):079102-079102, DOI: 10.11964/jfc.20241014721

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  The photoreception system is essential for regulating animal spatial navigation and foraging strategies. Echinoderms lack specialized photoreceptive organs and instead utilize diffusely distributed photoreceptors to detect and respond to ambient light stimuli. As key deuterostome invertebrates, they occupy a pivotal phylogenetic position linking protostomes and deuterostome vertebrates. Investigating their photoreception provides critical insights into the evolutionary trajectory of bilaterally symmetrical animals and the molecular regulation of photoresponsive behaviors. This article reviews the morphology and structural organization of echinoderm photoreception organs, light-sensory behaviors, the identification and characterization of photoreceptors in echinoderms, as well as the mechanisms by which photoreceptors mediate echinoderm light-sensory behaviors. This review also outlines future research priorities and translational applications of echinoderm photoreception studies, aiming to advance both sustainable aquaculture practices (including aquaculture enhancement) for high-value species (e.g., sea urchins, sea cucumbers) and photobehavior-based biocontrol strategies for ecologically disruptive species (e.g., starfish).

• A study of aquatic animal behavior in the AI era

  ZHANG Dong, DUAN Ming

  2025,49(7):079103-079103, DOI: 10.11964/jfc.20250514996

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  As the importance of ethology in the management of aquatic animals (including natural resources and aquaculture) becomes increasingly prominent, traditional manual observation and data analysis methods can no longer meet the industry's demand for ethological data of aquatic animals. In recent years, with the rapid development of artificial intelligence (AI) technologies, related technologies have played an increasingly important role in the study on aquatic animal behavior, providing strong technical support for accelerating research on aquatic animal behavior and its application in the fisheries industry, such as aquaculture. This paper briefly reviews the latest applications of AI technology in the study of aquatic animal behavior, and the significant advancement in behavioral research from "manual observation" to "intelligent perception", including automatic image and video analysis, behavior pattern recognition, behavior prediction, and applications in aquaculture. Finally, the review discusses the key research directions of aquatic animal behavior in the AI era, providing a reference for researchers in the related fields. In the future, we should particularly focus on the following fields: ① animal personality which is the core of behavioral ecology; ② behavior-ecology-physiology-gene data chain; ③ AI model generalization; ④ data standardization.

PAPERS

• Functional characteristics of zebrafish (Danio rerio) chemical alarm signals and their effects on behavior

  CHEN Qingyu, LIN Tingting, LIU Xin, LI Siping

  2025,49(7):079104-079104, DOI: 10.11964/jfc.20250214903

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  Chemical alarm signals (CAS), released from fish skin upon predator-induced physical damage to provoke fright behavior, play a critical role in enhancing individual survival in natural environments and is a potential tool for behavioral domestication of hatchery-reared fish prior to restocking. However, the behavioral impacts of prolonged and high-concentration CAS exposure remain poorly understood. Using Danio rerio as a model, this study investigated the functional characteristics of CAS and its long-term effects of different concentrations and treatment duration on fish anxiety and exploration behaviors through a series of behavioral assays (fright reaction, novel tank diving, light-dark, and novel object tests). PAS staining results revealed that D. rerio alarm substance cells are localized in the epidermal middle layer with colorless cytoplasm and blue-purple nuclei. In the fright reaction behavior test, skin extract (5.5 mg/mL of stock concentration) significantly increased the duration of initial freezing (244 and 0 s, respectively), total freezing time (244 and 0 s, respectively), and bottom-dwelling (300 and 144 s, respectively) compared to the distilled water control (P<0.05). Dilution experiments demonstrated that 10-fold, 30-fold, and 50-fold dilutions (0.11-0.55 mg/mL) retained CAS efficacy, whereas 100-fold dilution as 0.055 mg/mL concentration markedly reduced freezing and bottom-dwelling behaviors (P<0.05), as no significance compared to distilled water control (P>0.05). CAS stored at 25 °C remained effective for less than 4 h (P>0.05), with significant behavioral attenuation after 6-8 h (P<0.05). The experimental results of long-term continuous stimulation (10 and 20 d) with different dilution (10-fold, 50-fold dilutions, and stock) factors in D. rerio demonstrated that prolonged stimulation duration significantly enhanced anxiety-like behaviors as the latency for entering the top area gradually increased (P<0.05). Moreover, higher concentrations of skin extract (e.g. 5.5 mg/mL stimulation for 20 d) induced greater reductions in exploratory behavior and more pronounced anxiety-like responses in D. rerio (P<0.05). This results reveal that while utilizing the behavioral response characteristics of CAS for stock enhancement behavior conditioning, the long-term effects of high concentrations on fish anxiety and exploratory behaviors must also be considered to avoid counterproductive outcomes. Overall, this study not only advances understanding of concentration-dependent CAS effects on fish behavior but also provides a behavioral framework for conditioning hatchery fish prior to wild release.

• Behavioral and physiological responses of juvenile black rockfish (Sebastes schlegelii) to background colors

  WEI Tao, HAN Yanke, WANG Xinyao, JIA Biao, TIAN Tao, YU Xiaoming

  2025,49(7):079605-079605, DOI: 10.11964/jfc.20241214829

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  To investigate the effects of background colors on the behavior and physiology of juvenile Sebastes schlegelii and identify suitable background colors for their growth, this study examined how five different background colors (red, blue, black, green, and white) influenced growth performance, individual behavior, and serum physiological indicators. Correlation analyses among behavioral metrics were also conducted. The results showed that the black background group’s weight gain rate (44.64%±21.09%) and specific growth rate (1.28%±0.53%) were significantly lower than those in the green (65.41%±25.64%, 1.76%±0.59%) and white (64.53±19.97, 1.75±0.44) groups (P<0.05). Fish in the black group (52.28%±11.11%) took significantly longer to explore novel objects compared to the green group (22.82%±6.87%), while the white group (46.20±26.86) exhibited significantly higher aggression frequencies than the blue (8.00±2.19) and black (8.10±3.44) groups. Additionally, the white group (12.94%±6.07%) spent a significantly higher percentage of time in bright areas than the red (0.87%±0.36%) and black (0.17%±0.10%) groups. Behavioral correlations revealed that boldness was positively associated with exploratory behavior (P<0.05) and aggression (P<0.01) but negatively correlated with anxiety levels (P<0.05). Aggression was positively linked to activity levels (P<0.05) but negatively related to anxiety (P<0.05). Physiological analyses indicated that the hematocrit (Hct) levels in the red (37.87%±1.39%) and green groups (38.35%±1.28%) were significantly higher than those in the blue group (30.15%±3.46%, P<0.05). The red group [(5.24±1.91) U/g prot] showed significantly higher alkaline phosphatase (AKP) activity than the white group [(1.74±0.16) U/g prot, P<0.05], while the white group [(144.87±19.38) U/mL] had significantly lower catalase (CAT) activity than the red [(289.41±13.19) U/mL], blue [(258.47±22.17) U/mL], and black groups [(218.72±25.79) U/mL, P<0.05]. The black group [(14.64±0.92) U/mL] exhibited significantly higher superoxide dismutase (SOD) activity than the red group [(10.45±1.47) U/mL, P<0.05]. In conclusion, background color significantly affects the growth performance, personality traits, oxygen-carrying capacity, antioxidant activity, and non-specific immunity of juvenile S. schlegelii, with correlations observed among individual behavioral indicators. The red background induced higher stress levels, whereas the green background improved welfare. This study identifies optimal background colors for juvenile S. schlegelii, enriching theoretical knowledge on how environmental enrichment influences fish behavior and physiology. The findings provide valuable insights for enhancing aquaculture welfare and optimizing breeding techniques.

• Effects of phenanthrene stress on locomotor activity, anxiety-like and social behaviors in Misgurnus anguillicaudatus

  ZHANG Zikun, XU Huan, GAO Yongyong, GAO Xiaoge, TANG Xu, LEI Xin

  2025,49(7):079106-079106, DOI: 10.11964/jfc.20250214894

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  Polycyclic aromatic hydrocarbons (PAHs) are a class of organic pollutants widely present in aquatic environments. Phenanthrene (Phe), a notable PAH, has attracted significant attention due to its environmental toxicity and bioaccumulation potential. Misgurnus anguillicaudatus, an important freshwater aquaculture species in China, was used as the model organism to study the effects of Phe stress on locomotor activity, anxiety-like behavior, and social behavior. The experiment established four Phe concentration treatment groups (0.2, 1.0, 5.0, and 25.0 μg/L) for toxicity exposure. Behavioral changes were assessed at 15, 30, and 45 days of exposure, as well as after a 30-day recovery period. An animal behavior tracking system recorded velocity, turn angle, angular velocity, cumulative duration time ratio in black and white areas, and cumulative duration time ratio in social and non-social areas. A generalized linear mixed model (GLMM) analyzed the effects of Phe stress duration and concentration on behavioral indicators. Phe stress significantly affected the locomotor activity, anxiety-like behavior, and social behavior of M. anguillicaudatus: Locomotor behavior. At 15 days of exposure, the velocity of M. anguillicaudatus significantly increased in the 0.2, 1.0, and 5.0 μg/L Phe groups. By 45 days, velocity significantly decreased in the 1.0 μg/L group but increased in the 25.0 μg/L group. The turn angle significantly decreased in the 0.2 μg/L group at 15 days, while angular velocity significantly increased in the 1.0 μg/L group. In the 5.0 and 25.0 μg/L groups at 30 days, both turn angle and angular velocity significantly increased. GLMM analysis revealed that exposure time had a highly significant effect on velocity, while concentration significantly influenced turn angle and angular velocity. After 30 days of recovery, velocity in the 1.0, 5.0, and 25.0 μg/L groups remained significantly higher than in controls, and turn angle and angular velocity in the 5.0 μg/L group stayed elevated, indicating lasting impacts on directional changes. Anxiety-like behavior. At 15 days, the cumulative duration time ratio in the black area significantly decreased in the 0.2 μg/L group but increased in the 1.0 μg/L group. By 30 days, the ratio significantly increased in the 25.0 μg/L group, and at 45 days, it increased in the 1.0 and 5.0 μg/L groups. GLMM confirmed that exposure time had a highly significant impact on anxiety-like behavior. After recovery, all treatment groups showed a significantly higher cumulative duration time ratio in the black area compared to controls, suggesting persistent anxiety-like effects. Social behavior. At 15 days, the cumulative duration time ratio in the social area significantly decreased in the 0.2 and 25.0 μg/L groups. By 30 days, the ratio in the non-social area significantly increased in the 1.0 μg/L group, and at 45 days, it decreased in the 5.0 μg/L group. GLMM indicated that Phe concentration had a highly significant effect on social behavior. After recovery, the 5.0 and 25.0 μg/L groups still exhibited a significantly higher ratio in the non-social area, demonstrating persistent and irreversible social inhibition. Phe stress exhibited time- and concentration-dependent effects on M. anguillicaudatus. Short-term exposure to low-concentration Phe inhibited turning ability, while long-term exposure to higher concentrations increased turning ability and velocity. Phe stress significantly induced anxiety-like behavior and suppressed social behavior, with these changes showing persistence and irreversibility. This study provides insights for assessing the ecological risks of Phe, establishing water quality standards based on fish behavior, and improving monitoring techniques for PAHs in aquaculture environments.

• Effects of water velocity on swimming behavior, antioxidant capacity and energy metabolic enzymes in Anguilla japonica

  AI Tongxi, LIU Jialun, LIU Jianyi, YANG Jun, SHANG Meijuan, ZHAO Feng, JIANG Keji, GAO Lei, XU Jiayuan

  2025,49(7):079107-079107, DOI: 10.11964/jfc.20241014742

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  The Anguilla japonica is a migratory fish species of significant economic importance. In intensive aquaculture systems, unfavorable rearing conditions can lead to immunosuppression, rendering the species more susceptible to pathogenic infections. Moreover, following stock enhancement releases, the transition from artificial aquaculture environments to natural ecosystems exposes A. japonica to challenges such as food scarcity and predation, which may compromise its survival and adaptability. Proper flow training during artificial rearing and prior to stock enhancement has been demonstrated to improve health status and enhance survival capacity in the wild to some extent. To date, no studies have examined the effects of flow training on the antioxidative capacity and immune system of A. japonica. Additionally, research on the behavioral biology of adult A. japonica remains limited. This study investigates the relationship between critical swimming speed and body length, as well as the effects of different flow velocities on oxygen consumption rate, energy consumption per unit distance, antioxidative capacity, nonspecific immunity, and energy metabolism. Using swimming performance testing equipment and circular flow systems, physiological parameters were measured under four flow velocity conditions: static water (0.0 m/s), 0.1 m/s, 0.2 m/s, and 0.3 m/s. The results revealed a linear positive correlation between critical swimming speed (U_crit) and body length, with the relationship modeled as: U_crit=1.44L+12.57. The relative critical swimming speed (U_crit') was described by the equation: U_crit'=–0.004 1L+1.896 0. Additionally, the relationship between water velocity and oxygen consumption rate (Mo₂) was expressed as: Mo₂=0.005 8V²+3.808 3V+34.709 0, while the cost of transport (COT) was modeled as: COT=1.145 0×10^–5V² – 0.001 6V + 0.185 8. Regarding antioxidant indices, increases in water velocity significantly enhanced total antioxidant capacity (T-AOC), hydroxyl radical scavenging capacity (HFR-SC), reduced glutathione (GSH) levels, and catalase (CAT) activity in the serum of A. japonica. Notably, T-AOC and CAT activities in the 0.3 m/s group were significantly higher than in the still water group, while GSH levels peaked at 0.2 m/s. In terms of liver enzyme activity, glutamate dehydrogenase (GDH) activity increased with velocity, peaking at 0.2 m/s before declining. Meanwhile, pyruvate kinase (PK) activity was significantly higher in the 0.3 m/s group compared to the still water group (P<0.05). These findings suggest that appropriate flow training (0.2–0.3 m/s) enhances the antioxidative capacity and energy metabolism efficiency of A. japonica, promoting healthier growth and improving survival in natural environments. This study provides valuable guidance for health management during A. japonica aquaculture and flow training design prior to stock enhancement.

• Habitat use history of Coilia nusus in Oujiang River Estuary based on otolith microchemistry

  XIAO Zeyu, LIU Mingzhi, SHAN Xiaoluan, JIANG Rijin, YIN Rui, LI Zhenhua, JIANG Tao, ZHU Shuailin, WANG Haoran, SHEN Jiarong

  2025,49(7):079308-079308, DOI: 10.11964/jfc.20241114782

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  Coilia nasus, an ecologically and economically important anadromous fish species in China, exhibits a typical riverine migratory life-history strategy. The Oujiang River Estuary, a representative macrotidal estuary in southern Zhejiang Province, is characterized by highly dynamic hydrological and salinity gradients, which exert significant influence on the habitat selection and life-history strategies of C. nasus. To elucidate the "habitat use history" of this species and better understand its migratory and developmental patterns, this study employed electron probe micro-analysis (EPMA) to analyze the microchemical composition of strontium (Sr) and calcium (Ca) in the otoliths of 15 C. nasus specimens collected from the estuary. The results demonstrated substantial variation in Sr/Ca ratios, encompassing low values (Sr/Ca≤3) indicative of freshwater environments, intermediate values (3<Sr/Ca≤7) corresponding to estuarine brackish waters, and high values (Sr/Ca>7) reflective of marine habitats. All otolith core regions exhibited Sr/Ca values below 3 (1.78~2.61), indicating that spawning and hatching occurred in freshwater. While all individuals exhibited an overall anadromous pattern, variations in individual migratory trajectories were evident, including the presence of a distinct population that overwinters in freshwater. Otolith Sr mapping results were consistent with those obtained from quantitative line transect analyses. Based on early freshwater life-history characteristics, individuals were categorized into two types: the short freshwater early life history type (Type SF) and the long freshwater early life history type (Type LF). Further analysis of Sr/Ca variation suggested the potential existence of three ecologically distinct population groups within the estuary. One-Way ANOVA of the freshwater coefficient (F_C) between Type SF and Type LF revealed significant differences, indicating divergent degrees of freshwater reliance during early life stages. These findings suggest that the complex and variable environmental conditions of the Oujiang River Estuary have shaped unique migratory behaviors and habitat selection patterns in C. nasus, demonstrating the species' adaptive responses to local environmental heterogeneity. This study, through otolith microchemical analysis, not only provides a detailed reconstruction of the habitat use history of C. nasus in the Oujiang River Estuary but also offers a scientific foundation for understanding its ecological traits and informing effective conservation and management strategies.

• Artificial intelligence fish-monitoring links Gymnocypris przewalskii migration to river environment

  HUANG Zhenli, WEN Hao, QI Hongfang, YE Guanzhong, LI Haiying, WANG Luhai, FU Shengyun, ZHONG Nanchang, LIU Jun

  2025,49(7):079309-079309, DOI: 10.11964/jfc.20241114755

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  The naked carp (Gymnocypris przewalskii) is a keystone and anadromous species in Qinghai Lake, but its annual reproductive migration to rivers is not well understood due to insufficient monitoring tools. Here, we introduced a ″fish optical video + artificial intelligence″ technology, developed an artificial intelligence fish detection (AI-Fish) algorithm and intelligent monitoring equipment for shallow rivers. We also established a standard growth model for G. przewalskii to estimate the age of fish and applied it to a 30-metre-wide section of the lower Quanji River. From 2021 to 2024, monitoring data revealed the migration dynamics and environmental interactions of G. przewalskii in Qinghai Lake. The annual migration comprises three phases: early (upstream migration), middle (breeding), and late (downstream migration). River flow and water temperature primarily influence migration timing, with a critical flow rate of 2.5 m3/s promoting upstream migration in the Quanji River, peaking at 10 m3/s. Upstream migration aligns with daily water temperature rhythms, peaking in the afternoon (15:00-16:00) and evening (20:00-21:00), with a daily maximum of 362,000 individuals. Notably, not all migrants spawn, exhibiting 'non-reproductive accompanying migration.' Migration is geographically limited by natural barriers and altitude. Big data analysis of over 700 000 individuals showed a normally distributed age structure, dominated by 3-7 years old, with distinct male and female distributions influenced by sex ratio. Our results indicate that the developed equipment effectively can be used for all-weather and real-time monitoring of the migratory population of G. przewalskii in Qinghai Lake, with an identification accuracy of more than 90%, and can obtain biological parameters such as the number of fish, direction of migration, full length, and age structure. By establishing a monitoring network in the main rivers of Qinghai Lake, we can quickly and accurately collect comprehensive 'big data' on the migrating population each year, providing robust scientific support for their future conservation.

• Effects of physical enrichment and predator stress on growth, behavior and respiratory metabolism of juvenile marbled rockfish (Sebastiscus marmoratus)

  GUO Haoyu, XUE Xianglong, HUA Yujie, LIU Haoyu, Lü Chenhang, QI Yulu, CHAI Xuejun, ZHANG Xiumei

  2025,49(7):079610-079610, DOI: 10.11964/jfc.20241114762

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  Stock enhancement based on hatchery-reared fish has become one of the most common forms of management practices in marine fisheries resource restoration. However, a lack of environmental stimulation contributes to the poor survival adaptability of hatchery-reared fish in the wild, with negative consequences for post-release performance in natural environments. To investigate whether incorporating physical enrichment and predator stress into aquaculture environments can enhance the survival adaptability of hatchery-reared fish, this study conducted a two-factor interaction experiment to examine the effects of predator stress and physical enrichment on the growth, behavior, and respiratory metabolism of juvenile marbled rockfish (Sebastiscus marmoratus).The findings are as follows: ① Physical enrichment significantly improved the final body weight of the juveniles (P<0.05), demonstrating its positive effect on growth in controlled environments. On the other hand, prolonged predator stress inhibited fish growth, leading to decreased final body weight, weight gain rate, and specific growth rate, highlighting the potential trade-offs of predator stress on growth. ② Predator stress did not have a significant impact on the activity or boldness of juvenile marbled rockfish but did significantly reduce their exploratory behavior, suggesting a specific behavioral adjustment under stressful conditions. ③ In the presence of predators, physical enrichment could increase activity of juvenile fish, indicating its role in promoting active behaviors even in predator-present environments. ④ Physical enrichment did not significantly impact predator avoidance behavior responses, but long-term coexistence with predators significantly reduced the cumulative duration spent in risky areas by the juvenile fish. This indicates the potential of predator stress to shape risk-avoidance strategies over time. ⑤ Physical enrichment markedly reduced the oxygen consumption rate of juvenile fish (P<0.01), suggesting a reduction in metabolic stress or enhanced energy efficiency. In contrast, predator stress significantly increased oxygen consumption (P<0.05), reflecting heightened metabolic demands associated with stress responses. ⑥ Both physical enrichment and predator stress had significant interaction effects on the exploratory behavior, activity levels, and respiratory metabolism of the juveniles. These interactions provide critical insights into the mechanisms through which environmental enrichment influences fish growth and behavioral adaptability. Based on these findings, this study recommends incorporating physical enrichment and controlled predator stress exposure as part of the pre-release acclimation process for hatchery-reared marbled rockfish. Such practices could effectively improve the environmental adaptability of hatchery-reared marbled rockfish, thereby potentially enhancing their survival performance after releasing into the wild.

• Flow tolerance of juvenile Lateolabrax maculatus

  LIU Qiqing, HUANG Liuyi, LUO Yan, LIU Xiao, LIU Bo, WANG Run, BI Chunwei, YOU Xinxing

  2025,49(7):079511-079511, DOI: 10.11964/jfc.20250314905

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  Sea cage aquaculture is an important industry for marine fish production in China. With the compression of offshore cage farming space and the requirements of ecological and environmental protection, the development of deep-sea cage culture is an inevitable trend to promote the high-quality development of mariculture industry. Flow velocity has an important impact on fish behavior, physiology and growth. Studying the swimming performance of fish is of great significance for the optimal stocking specifications of deep-sea aquaculture species, improving the design and operation of aquaculture facilities, and promoting the high-quality and orderly development of deep-sea aquaculture. Lateolabrax maculatus is an important aquaculture species in offshore and deep-sea cages in northern China. However, due to its own swimming ability research and the influence of flow on its swimming behavior is not clear, it is impossible to provide scientific basis for the site selection, breeding equipment design and stocking specifications of deep-sea cages for the fish. To evaluate the flow tolerance of juvenile Lateolabrax maculatus, this study investigated critical swimming speed (U_crit), burst swimming speed (U_burst), endurance swimming time, and their correlations with 14 morphological traits using a fish behavioral experimental circulating flume with specimens of (9.61±0.74) cm body length. Through ethological research methods, we analyzed tail beat frequency, swimming states, and swimming trajectories under varying velocities. Results demonstrated that absolute U_crit and U_burst were (0.69±0.05) m/s and (0.86±0.05) m/s respectively, while relative values reached (7.12±0.4) BL/s and (9.09±0.48) BL/s (BL represents the body length of experimental fish, BL/s indicates the swimming speed in body lengths per second). The endurance swimming time was measured (200.83±45.73) min at 0.6 m/s, but showed dramatic decline at 0.7 m/s. Significant positive correlations (P<0.05) were identified between swimming performance (absolute U_crit and U_burst) and most morphological traits, except for first dorsal fin length, second dorsal fin length, ventral fin length, and caudal fin length (P>0.05). Tail beat frequency exhibited significant positive correlation with velocity (P<0.05). When the flow velocity was ≥ 4 BL/s, the relative swimming distance of Lateolabrax maculatus decreased significantly, the proportion of countercurrent forward swimming time decreased significantly, the proportion of countercurrent static swimming time increased, and the proportion of downstream backward time decreased with the increase of flow velocity. The swimming area of the experimental fish was reduced, and it could only move in the corner of the flume at high flow velocity (6 BL/s). Based on swimming performance analysis, we recommend considering partial morphological traits (tail length, head length, and trunk length) alongside body length for stock selection. For juvenile L. maculatus aquaculture facilities, maximum flow velocity should not exceed 6.24 BL/s, while behavioral considerations suggest maintaining velocities below 4 BL/s. The results of this study can provide a reference for the site selection of sea cage aquaculture, the design and construction of breeding facilities and the determination of stocking specifications of L.maculatus farming.

• Preliminary study on acoustic barrier efficacy against Schizothorax prenanti under varied acoustic parameters and hydraulic conditions

  MU Xicheng, LI Jiaxin, LI Feng, ShI Xiaotao, YU Lixiong, WANG Min, ZHANG Shenwei, CHEN Xiaolong, ZHENG Daiqing, YANG Ji, CHEN Jun, ZHANG Hengbin, ZHANG Xin, LI Xinyu, LIU Guoyong

  2025,49(7):079512-079512, DOI: 10.11964/jfc.20250414958

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  To investigate whether acoustic deterrence technology can enhance fish passage efficiency under hydrodynamic conditions at fishway entrances, this study established a 1∶50 scaled physical model of the Xianghe Hydraulic Complex in a laboratory flume. Underwater speakers were deployed upstream of the fishway entrance in the river channel to evaluate the efficacy of predator vocalizations and pulsed sounds in obstructing upstream migration and improving fishway entrance passage rates, with Schizothorax prenanti as the test species. The results demonstrated that: ① Tested acoustic signals experienced waveform distortion under hydrodynamic conditions, yet retained spectral characteristics exceeding ambient noise levels while remaining within the frequency reception range of cyprinids. ② All acoustic stimuli induced significant negative phonotaxis in test fish, with the sound field exhibiting a “central amplification-peripheral attenuation” pattern characterized by faster lateral attenuation than longitudinal dissipation. ③ Optimal deterrence effects were achieved with 130 dB pulsed sounds at river current velocity 0.15 m/s and fishway entrance velocity 0.4 m/s, whereas 130 dB Chinese alligator (Alligator sinensis) vocalizations showed superior efficacy at 0.15 m/s river flow and 0.6 m/s fishway entrance velocity. ④ At 0.4 m/s fishway entrance velocity, both 130 dB alligator vocalization and pulsed sound experimental groups demonstrated significantly higher passage rates compared to the control (P<0.05). Two-Way ANOVA revealed significant main effects of sound type (P<0.05) and fishway entrance velocity (P<0.05), with a significant interaction between these factors (F=3.273, P=0.04). This study confirms that acoustic deterrence technology can effectively impede upstream migration in fluvial environments under specific hydrodynamic conditions. The findings provide scientific evidence and technical references for engineering applications of acoustic fish guidance systems and optimization of ecological operations in hydropower facilities.

• Effects of hydrodynamic-schooling interaction on upstream migration behaviour of juvenile Hypophthalmichthys molitrix

  YANG Zijing, LIN Chenyu, SHI Xiaotao, DING Haoyu, LIANG Zezhang, SHI Shangshang, LI Zhimin, RONG Guiwen, LUO Jia, REN Kaiyuan

  2025,49(7):079513-079513, DOI: 10.11964/jfc.20241214788

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  Elucidating the hydrodynamic-fish motion response relationship during the upstream migration of schooling fish is fundamental for designing fish passage in hydropower infrastructure. The current study quantified the upstream movement patterns of individual and group (ten individuals) juvenile Hypophthalmichthys molitrix, an economically significant fish species in China, under the combined hydrodynamic-schooling influence in non-fatigued flow fields with varying turbulence levels. We concluded that: ① In the low-turbulence flow field, individual juvenile H. molitrix achieved a 100% passing rate with an average time expenditure of (40±27) s, exhibiting uniform movement distribution without a clear velocity preference. ② Within the locally high-turbulence flow field, individual juvenile H. molitrix tended to linger in areas of lower velocity and turbulence, utilising the Kármán vortex street to minimise instantaneous energy cost, leading to a significantly increased time expenditure [(84±54) s, P<0.001)]. ③ The swimming trajectories of juvenile H. molitrix in school were relatively concentrated, with the attraction and guidance effects between neighbour fish promoting their linear formations along the primary flow. ④ In locally high-turbulence flow field, the inter-individual repulsion effect of juvenile H. molitrix in school hindered their effective avoidance of high-speed, high-turbulence flowing areas, causing impeded upstream movement, with passing rate dropping significantly to 54% (P<0.05) and time expenditure extending to (88±12) s. The study indicates that the movement distribution of juvenile H. molitrix during upstream migration is primarily influenced by the combined effects of flow velocity and turbulence intensity, with a tendency to avoid high-turbulence areas. During schooling, the attraction and guidance between individuals help optimize the upstream path and reduce energy expenditure, while the repulsion effect may decrease migration efficiency and hinder the full utilization of favorable water flow conditions by individual fish. The findings offer theoretical foundations and data support for optimising the design and enhancing the operational efficiency of fish passage by regulating fish school size and developing characteristic flow fields.

• Effects of light environment on behavioral traits and upstream swimming activeness of juvenile Hypophthalmichthys molitrix

  ZHANG Jinyu, SHI Xiaotao, LIN Chenyu, XIANG Lulu, HUANG Jie, SHI Shangshang, YANG Zijing, LI Weidong, WEI Lang

  2025,49(7):079514-079514, DOI: 10.11964/jfc.20230614038

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  Abstract:

  This study investigates the effects of phototaxis and behavioral traits of fish under different light conditions on their upstream swimming activeness to facilitate fish migration past dams and improve the efficiency of fish passage facilities in China. The experiment used juvenile Hypophthalmichthys molitrix, a key economic fish species in China, as the test subject. By analyzing their phototaxis, stress degree, activeness, and light-oriented activeness under varying light wavelengths and illuminance levels, we assessed how these factors influence upstream swimming activeness at different flow velocities. ① Under red light, the preferred illuminance range for H. molitrix was 3.268-5.444 lx; under blue light, the acceptable illuminance range was 0.033-10.511 lx; under green light, the acceptable and preferred illuminance ranges were 0.367-74.489 lx and 3.776-9.833 lx, respectively; under white light, no distinct preference or acceptable illuminance range was observed. ② The stress degree of H. molitrix under red and green light initially increased and then decreased with rising illuminance, whereas under blue light, it increased monotonically. The activeness of H. molitrix under red and green light increased steadily with illuminance, while under blue light, it exhibited a fluctuating upward trend. ③ The upstream swimming tendency of H. molitrix was primarily influenced by light preference and stress degree. When stress degree was low, upstream swimming activeness increased with higher light-oriented activeness; conversely, when stress degree was high, upstream swimming activeness decreased as light-oriented activeness increased. To optimize fish passage efficiency, we recommend: a 10 lx red light source at the facility entrance can attract fish. Shaded areas inside the passage, combined with intermittent 1 000 lx green light sources, can promote sustained upstream movement. Near hazardous turbine intake zones, a combination of 1 000 lx blue light and a 0.35 m/s flow velocity can deter fish from approaching. This study provides theoretical and data-driven support for optimizing fish protection engineering in various fish passage scenarios.

• Fighting behavior of Eriocheir sinensis and Procambarus clarkii under different polyculture conditions

  TU Wen, HUANG Jin, LI Jinghao, WU Le, LI Jiayao, XI Yewen

  2025,49(7):079615-079615, DOI: 10.11964/jfc.20220313358

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  Abstract:

  Eriocheir sinensis and Procambarus clarkii are two important economic aquatic products in China, the development of the two ecological polyculture can not only make full use of the bait resources, but also promote the transformation from traditional culture model to modern culture model. However, in actual production, the attacking and fighting behavior caused by problems such as breeding density, stocking size, sex ratio and other issues greatly reduce the survival rate of E. sinensis and P. clarkii. Thus, in order to explore the key factors influencing the aggressive and fighting behaviors of E. sinensis and P. clarkii under different polyculture conditions, several indoor behavioral observation experiments were carried out to analyze the effects of size, density, gender on the fighting behavior between E. sinensis and P. clarkii. The results showed that the number of attacks and fights between E. sinensis and P. clarkii increases as their size increases. When the size of E. sinensis and P. clarkii are different, the size of E. sinensis showed a significant role in the intensity of their fighting. The bigger E. sinensis get, they attacked and fought with each other more frequent. In polyculture mode, light had no significant effect on their fighting behavior. As the density of P. clarkii increased, the frequency and intensity of fights first increased and then decreased. There was a positive correlation between the content of lactic acid in hemolymph and cheliped muscle and the times of fighting The male of E. sinensis and P. clarkii are more aggressive, as male fights more than female at all density groups. In conclusion, in the practice of polyculture, the culture density and size of E. sinensis had a significant effect on fighting behavior, the traditional mode which releasing P. clarkii before E. sinensis can reduce the coexistence time of large E. sinensis and P. clarkii, thus mitigating the impact of fighting between E. sinensis and P. clarkii. Meanwhile, a proper gender proportion and feeding management can alleviate the cannibalism between E. sinensis and P. clarkii. This study can provide some theoretical guidance and reference for practical production.

• Acoustic signal classification methods of Macrobrachium rosenbergii based on improved residual network

  CAO Zhengliang, JIANG Qianqing, JIANG Shan, WANG Zixian, LI Zhaocheng, JIN Yuxue, HU Qingsong

  2025,49(7):079616-079616, DOI: 10.11964/jfc.20241214825

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  The precise identification of shrimp behavior in aquaculture is of great significance for optimizing feeding and disease prevention. In view of the limitations of traditional optical monitoring methods in complex aquaculture environments, with integrated passive acoustic technology, this research acquires the acoustic information associated with different behaviors of the Macrobrachium rosenbergii and proposes a deep learning-based method for behavior recognition in M. rosenbergii. The acoustic signals of three behaviors (i.e., feeding, moving, and fighting) were collected and converted into Mel spectrograms as the dataset. Then the classification effects of CNN, ResNet18, and VGG16 neural network models were compared. The results showed that ResNet18 in terms of recognition accuracy (97.67%) outperforms VGG16 and CNN. After introducing the Batch Normalization (BN) algorithm, the recognition accuracy of BN-ResNet18 increased to 99.00%, representing a 1.33% enhancement relative to the baseline ResNet18 model. In addition, BN-ResNet18 showed the best classification performance in the 14.0-44.1 kHz frequency band, which further proved that the synergistic optimization of residual connection and BN module could effectively enhance model performance. BN-ResNet18 demonstrates high accuracy and robustness in feature classification of complex behavioral acoustic signals. This study provides technical support for intelligent recognition based on the acoustic signals of shrimp behaviors and has potential application value in the refined management of aquaculture.

• Design and effect evaluation of tube fishway for low head dams

  SHI Xiaotao, WANG Nannan, XU Jiawei, LUO Jinmei, LI Dongqing, JI Huaiyao, ZHU Mengna, CHEN Wei, LU Jianyu, KE Senfan

  2025,49(7):079517-079517, DOI: 10.11964/jfc.20240114304

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  There is a huge demand for fish passing through low head dams in China, and there is an urgent need to build low-cost portable fishways without construction. In view of this, this study independently designed a tube fishway to assist fish migration, analyzed the fish passing effect of Hypophthalmichthys molitrix through portable tube fishways at three tube angles and two charge conditions, obtained evaluation indicators for the fish passing effect of new tube fishways, and constructed a risk proportional regression model based on attempt rate, passage rate, and maximum ascent distance to identify the key factors affecting the fish passing effect of tube fishways. The results showed that: ① The optimal attempt rate model found that charge is a key factor affecting the attempt of hypophthalmichthys molitrix to enter the fishway; There is a significant negative correlation between charge and ascent migration attempt rate of hypophthalmichthys molitrix in tube fishways. ② The highest passage rate of the tube fishways can reach 90.5%. Through the optimal passage rate model, it was found that the angle of the tube, water temperature, and number of attempts are key factors affecting the passage of hypophthalmichthys molitrix through the fishway; The lowest passage rate occurs when the tube angle is 90°. There is a significant negative correlation between the number of attempts and the ascent passage rate of hypophthalmichthys molitrix; There is no significant difference in the ascent passage rate under the conditions of tube angle of 30° and 45°, but both are significantly higher than 90°. ③ The optimal maximum ascent distance model found that water temperature and tube angle are key factors affecting the probability of hypophthalmichthys molitrix passing through the maximum ascent distance; there is a significant positive correlation between water temperature and the probability of the maximum ascent distance that hypophthalmichthys molitrix can pass through; the probability of the maximum ascent distance that hypophthalmichthys molitrix can pass through is not significantly different under tube angles of 30° and 45°, but both are significantly higher than 90°.