《近海渔业资源可持续利用专刊》序言

• Data-driven assessment of coastal fisheries resources

  SHAN Xiujuan, CHEN Zuozhi, REN Qingqiang

  2026,50(4):049301-049301, DOI: 10.11964/jfc.20260315415

  Abstract(0) HTML(0) PDF(4.75 M)( 0) Collect

  Abstract:

  Coastal fisheries resources serve as a critical foundation for high-quality animal protein supply and the blue economy in China. Under the combined pressures of intensified human activities and climate change, these resources are facing challenges including impaired recruitment capacity, increased population fluctuations, and heightened community structure changes, underscoring an urgent need for more accurate assessments to support science-based management. This Special Issue focuses on the core requirements for sustainable utilization of coastal fisheries resources and systematically presents recent advances across the key processes of “monitoring-assessment-management”. Conceptually, they expand from single-stock dynamics to integrated analyses of community structure and habitat processes, thereby promoting a shift in management objectives toward an ecosystem perspective. Technically, they highlight the development of multi-source, multi-dimensional, and low-disturbance monitoring systems, and advocate reducing ecological impacts through improved understanding of fishing-gear selectivity and optimization of operational practices. For decision-making, in response to growing demands for data-driven governance, they introduce models and algorithms that strengthen uncertainty analysis and facilitate strategy evaluation, providing methodological support for risk-constrained, fine-scale, and adaptive management.

PAPERS

• Population dynamics and its driving factors of small yellow croaker (Larimichthys polyactis) in the Yellow and Bohai Seas

  HAN Qingpeng, SHAN Xiujuan, WU Qiang, JIN Xianshi, TENG Guangliang, WANG Leyan

  2026,50(4):049302-049302, DOI: 10.11964/jfc.20260115302

  Abstract(0) HTML(0) PDF(6.14 M)( 0) Collect

  Abstract:

  Accurate assessment of fishery population dynamics and their driving factors is fundamental to the scientific management of fishery resources. The Yellow and Bohai Seas serve as crucial habitats for numerous fishery organisms, underpinning the sustainable productivity of the ‘marine granary’ in northern China. The small yellow croaker (Larimichthys polyactis) is an economically important fish species in the Yellow and Bohai Seas, and has long been a primary target for fishing. This study aims to accurately assess the spatio-temporal dynamics of the L. polyactis population in the Yellow and Bohai Seas, thereby providing a scientific basis for the management of the fishery resources. Based on survey data of L. polyactis in the Yellow and Bohai Seas and publicly available information from 2001 to 2025, this study employed spatiotemporal modelling and spatial clustering analyses to characterize the spatiotemporal distribution patterns and long-term changes in stock abundance of L. polyactis. In addition, population dynamics were systematically evaluated using a data-rich stock assessment model, and the driving mechanisms underlying stock fluctuations were further elucidated through structural equation modelling. The results showed that the L. polyactis mainly overwinters in waters deeper than 50 m, with a small number distributed in the 30-50 m water range and very few in waters shallower than 30 m. In addition to the central and southeastern Yellow Sea, the waters deeper than 50 m in the northern Yellow Sea also serve as an important overwintering ground. The interannual distribution of L. polyactis population density exhibits significant spatial heterogeneity. In the winter of 2001, L. polyactis displayed extensive and continuous high-density distribution areas, followed by a decline in resource abundance and contraction of distribution hotspots. By 2025, the center of gravity of L. polyactis population had shifted westward, and the distribution hotspots in the central and southern Yellow Sea had achieved a certain degree of recovery. Interannual variability in population density further revealed an uneven and spatially unbalanced recovery across regions. Results from the stock assessment model indicated that L. polyactis recruitment exhibited high interannual variability. Fishing pressure on this species remained low during 2001-2005, with its stock status in a healthy condition. After 2005, high fishing pressure led to a decline in the spawning stock biomass and impaired recruitment potential. However, with the reduction in fishing pressure in recent years, the population has shown signs of recovery. From 2023 to 2025, the fishing mortality coefficient (F) and spawning potential ratio (SPR) of L. polyactis performed better than their respective target reference points. Structural equation modelling clearly revealed the dominant drivers of stock dynamics. Fishing pressure is the primary cause of the decline in L. polyactis resources in the Yellow and Bohai Seas, with its impact far exceeding other factors (path coefficient of F: –1.26). Nevertheless, existing management measures (path coefficient: 0.30) and climatic conditions (path coefficient: 0.27) have supported resource conservation and recovery. The stock recovery of L. polyactis is constrained by the characteristics of unstable recruitment and spatial imbalance. The impacts of fishing pressure and climatic factors on the stock dynamics of L. polyactis are often exerted through their spatial distribution pattern. As a non-spatial approach, the stock assessment model used in this study is only capable of characterizing the temporal variations of stock status indicators of L. polyactis in the Yellow and Bohai Seas, and cannot reflect the spatial differences in stock status. Integrating spatiotemporal distribution patterns with stock status indicators suggests that relying solely on reference points (such as F or SPR thresholds) for management may mask the risk of localized resource decline. Without accounting for the spatial structural characteristics of the L. polyactis population, the recovery of the overall stock status in recent years indicated by the stock assessment model may mask the differences in recovery among distinct subpopulations, which could potentially lead to inappropriate management adjustments, such as the misallocation of fishing effort. Conducting resource assessments that incorporate spatial dimensions and implementing regionally differentiated resource management are key approaches to maintaining the productivity of L. polyactis populations in the Yellow and Bohai Seas and enhancing their resource sustainability. This study presents a novel integrated analytical framework that couples spatio-temporal distribution with stock status and their driving factors, which can be extended and applied to the analysis of population dynamics and the formulation of management strategies for exploited fish species in the Yellow and Bohai Seas and even global marine waters.

• Discussion on constraining mechanisms of population recruitment and resource sustainability of anchovy (Engraulis japonicus) in the Yellow Sea

  LIU Shufang, WANG Xinliang, WANG Ruixiang, WAN Ruijing, ZHUANG Zhimeng

  2026,50(4):049303-049303, DOI: 10.11964/jfc.20260115360

  Abstract(0) HTML(0) PDF(5.48 M)( 0) Collect

  Abstract:

  The anchovy (Engraulis japonicus) is a key species in the Yellow Sea and East China Sea ecosystems, playing a vital role in energy flow and fishery resources. Since its severe collapse in the late 1990s under intense fishing pressure, the population has shown slow growth, and its resource sustainability remains a major concern despite recent signs of increase. This review aims to systematically elucidate the multidimensional mechanisms constraining the effective recruitment of the Yellow Sea anchovy population, thereby providing a scientific basis for sustainable resource management. By integrating findings from stock assessment, early life history biology, ecophysiology, population genetics, and climate change research, this paper identifies and analyzes key constraints on E. japonicus recruitment from the perspectives of spawning stock biomass, reproductive traits, critical bottlenecks during early development, genetic structure, and environmental stressors. The E. japonicus biomass in the Yellow Sea plummeted from 4.10 million tons in 1993 to a low of 0.11 million tons in 2003. More than two decades later, the current population size remains far below historical levels. Key mechanisms constraining effective recruitment include: ① Severe depletion of spawners and eggs: In May 2010, E. japonicus egg abundance in the Yellow Sea was only 6.01% of that in May 1986, and dropped to 0.05% in the same comparable area. ② Decreased egg quality: Natural mortality rates of eggs in major spawning grounds increased from 64.10% during the initial exploitation phase to 80%-91% post-collapse, accompanied by a general trend towards smaller egg size. ③ Small mouth size of first-feeding larvae: At 3.7 mm total length, larval mouth size is only about 250 μm, significantly smaller than most marine fish species. ④ Short PNR window: Under 23.0-24.8°C, the mixed feeding stage lasts only one day, with the Point of No Return (PNR) occurring at 6 days post-hatching. ⑤ Low swimming capacity: Cruising speeds of northern anchovy (E. mordax) larvae are only 0.3-0.5 cm/s, much lower than those of clupeids. ⑥ Climate warming stress: Rising sea temperatures lead to smaller egg size, shorten the mixed feeding stage, and may shift conditions away from the optimal growth temperature window of 21-22°C for larvae and juveniles. ⑦ Genetic constraints: The population exhibits a pattern of high haplotype diversity but low nucleotide diversity with strong gene flow, suggesting potential cryptic erosion of genetic diversity under high fishing pressure, which may undermine its evolutionary potential. E. japonicus recruitment in the Yellow Sea is jointly constrained by insufficient spawning stock biomass, multiple vulnerabilities in early life history, potential genetic structure limitations, and superimposed climate stressors, posing multiple bottlenecks to resource sustainability. This study reveals the multidimensional constraints on the recruitment dynamics of small pelagic fish and provides important theoretical insights for developing ecosystem-based fishery management strategies.

• Identification, evolution, expression pattern and ecological adaptation strategies of the FABP gene family in Japanese anchovy (Engraulis japonicus)

  WANG Ruixiang, WANG Huan, LIU Shufang, ZHUANG Zhimeng

  2026,50(4):049304-049304, DOI: 10.11964/jfc.20260115362

  Abstract(0) HTML(0) PDF(6.19 M)( 0) Collect

  Abstract:

  The Japanese anchovy (Engraulis japonicus), a keystone lipid-rich species in the Yellow and East China Seas ecosystems, plays a vital role in energy flow, and its lipid metabolism mechanisms significantly influence population dynamics. The fatty acid-binding protein (FABP) gene family is central to lipid metabolism regulation. This study aimed to systematically identify the FABP gene family members in E. japonicus and analyze their molecular characteristics and expression profiles, thereby providing a foundation for elucidating the molecular mechanisms of lipid metabolism and ecological adaptation in this species. Based on the chromosome-level genome of the E. japonicus, FABP gene family members were screened using Hidden Markov Model (HMM) and homology BLAST searches. Their phylogenetic relationships, gene structures, conserved motifs, chromosomal locations, gene duplication events, and three-dimensional protein structures were analyzed through bioinformatics approaches. Transcriptome data from different tissues (heart, liver, muscle, gonad), sexes, and body length groups were utilized to analyze gene expression profiles. A total of 14 FABP genes belonging to 7 subtypes (FABP1, FABP2, FABP3, FABP4, FABP6, FABP7, FABP10a) were identified in the E. japonicus genome, unevenly distributed across 9 chromosomes. Phylogenetic analysis classified these genes into three distinct clades. Synteny and tandem duplication analyses revealed that FABP1 genes (FABP1.1 and FABP1.2) originated from segmental duplication, while four FABP3 genes (FABP3.1-3.4) formed a tandem duplication cluster on chromosome 9. All FABP proteins possess the typical β-barrel tertiary structure, although some FABP7 genes showed deletions of conserved motifs. Transcriptome analysis demonstrated that FABP gene expression exhibited significant tissue specificity (e.g., high expression of FABP1 and FABP10a in liver), sex specificity (e.g., specific high expression of FABP7 in testis), and certain correlations with body length. Notably, multi-copy genes (e.g., different paralogs of FABP3 and FABP7) showed markedly divergent expression patterns across tissues, suggesting potential functional differentiation. This study presents the first systematic identification and characterization of the FABP gene family in the E. japonicus. Gene duplication events, particularly the tandem duplication of FABP3, and the subsequent expression divergence may enhance the capacity for lipid uptake, transport, and utilization in E. japonicus, representing an adaptive molecular evolution in response to its high-lipid diet and periodic migratory life history. These findings provide novel theoretical insights for understanding the pivotal role of E. japonicus in energy flow within marine ecosystems at the molecular level and for the sustainable utilization of fishery resources.

• Study on the management strategies evaluation for Oratosquilla oratoria in the Bohai Sea

  REN Qingqiang, SHAN Xiujuan, DING Qi, WU Qiang

  2026,50(4):049305-049305, DOI: 10.11964/jfc.20260115336

  Abstract(0) HTML(0) PDF(5.01 M)( 0) Collect

  Abstract:

  Fishery resources in the Bohai Sea have declined markedly due to overfishing and habitat degradation, leading to an increasing dominance of invertebrate species such as the mantis shrimp Oratosquilla oratoria. Here, we estimated growth parameters of O. oratoria using ELEFAN GA method with Bootstrap resampling based on length–frequency data collected in 2014, 2015 and 2024, and conducted a management strategy evaluation (MSE) while propagating uncertainty through alternative natural mortality coefficient (M) estimates. The results indicated that the length-weight relationship in 2014 and 2015 was W=0.0148·L^2.94 and estimated growth parameters were asymptotic body length (L_inf) of 20.14 cm and growth coefficient (K) of 0.74, respectively. In 2024, the length-weight relationship was W=0.0228·L^2.78, and L_inf and K were 20.19 cm and 0.73, respectively. A total of 16 management practices (MPs) were identified as feasible MPs for the management of O. oratoria in the Bohai Sea, including 9 input controls and 7 output controls. Across all M-setting scenarios, input controls generally performed better than output controls in maintaining stock status and yield and avoiding overfishing performance metrics. Moreover, only curE80 (80% of current effort level) consistently provided the best overall trade-off between conservation and exploitation among all M scenarios. Our results therefore recommend curE80 as a priority MP for O. oratoria in the Bohai Sea, while emphasizing that management outcomes remain sensitive to M estimates.

• CPUE standardization of small yellow croaker (Larimichthys polyactis) in the East China Sea using an INLA-based Bayesian spatio-temporal model and multi-source data

  LIU Zunlei, YANG Linlin, YUAN Xingwei, JIN Yan, CHENG Jiahua

  2026,50(4):049306-049306, DOI: 10.11964/jfc.20251215273

  Abstract(0) HTML(0) PDF(6.93 M)( 0) Collect

  Abstract:

  Fishery-dependent and independent data each have strengths and limitations for estimating abundance indices. Commercial catch-per-unit-effort (CPUE) offers broad spatio-temporal coverage but suffers from gear selectivity and preferential sampling, while scientific surveys provide standardized sampling but limited coverage. Integrating these data sources is particularly challenging in mixed fisheries where multiple gear types with different selectivity patterns operate concurrently. Small yellow croaker (Larimichthys polyactis) in the East China Sea represents such a complex fishery, supporting important commercial fisheries while exhibiting strong spatio-temporal dynamics influenced by environmental conditions and gear-specific catchability. This study aimed to develop a robust CPUE standardization approach for small yellow croaker by integrating multi-gear commercial fishery data and scientific survey data within a Bayesian spatio-temporal modeling framework, evaluating alternative spatial structures and data integration strategies to obtain more reliable abundance indices for stock assessment. We analyzed 39 434 commercial fishing records from 158 vessels operating in September during 2010-2023, covering three major gear types: trawl, gillnet, and stow net, complemented by scientific survey data from 90-120 stations annually. An INLA-based Bayesian spatio-temporal generalized linear mixed model with gamma distribution and log-link was developed, incorporating year effects, gear effects, environmental covariates (depth, distance to coast, bottom temperature, bottom salinity), and their interactions. Models with independent spatial fields substantially outperformed shared spatial field models for both commercial and survey data, with the optimal model (M1) including independent spatial fields, linear environmental effects, and gear-environment interactions achieving the lowest DIC (7 786) and WAIC (7 838) values. Gamma distribution provided superior predictive performance (R²=0.76, RMSE=616) compared to lognormal distribution (R²=0.65, RMSE=784). Gear-environment interactions significantly improved model fit, revealing differential environmental responses: salinity positively affected all gears but most strongly influenced trawl catch rates (effect size 0.262), while distance to coast showed negative effects on trawl (-0.259) and stow net (–0.129) but negligible effects on gillnet. Spatial random effects revealed persistent positive anomalies in the northern East China Sea (30-33°N), indicating this region as core habitat not fully explained by environmental covariates. Annual abundance indices from integrated modeling showed pronounced interannual variability, with peaks in 2015 and notable declines during 2016-2020, followed by recovery in 2022-2023. The INLA-GLMM framework with independent spatio-temporal fields effectively disentangles gear-specific catchability, environmental effects, and true abundance variation, providing a robust foundation for stock assessment and fisheries management of this important species.

• Length-based stock assessment of small yellow croaker (Larimichthyspolyactis) in the Zhoushan Fishing Ground

  ZOU Xintai, MA Luyao, WANG Jing, XU Yongjiu, ZHANG Chang, LI Yuru, LIU Baogui, JU Peilong

  2026,50(4):049307-049307, DOI: 10.11964/jfc.20251215276

  Abstract(0) HTML(0) PDF(5.66 M)( 0) Collect

  Abstract:

  Assessing the current stock status of the Larimichthys polyactis, a fish species of high ecological and economic value, in the Zhoushan Fishing Ground is crucial for ensuring the sustainable utilization of its resources. In response to the decline in L. polyactis resources and the long-term lack of systematic statistical data in the Zhoushan Fishing Ground, this study employs stock assessment methods that require only short-term length-frequency data to clarify the current stock status and exploitation level of this population, thereby providing a scientific basis for its management and conservation. Based on length data from 772 individuals collected during four surveys from 2019 to 2024, growth parameters (the asymptotic length, L_inf, and the growth coefficient, K) were estimated using ELEFAN methods, while the natural mortality coefficient (M) was estimated using six empirical formulas. Different parameter combination scenarios were set up, applying both the Length-Based Spawning Potential Ratio (LB-SPR) and the Length-Based Bayesian Biomass (LBB) assessment methods. Sensitivity analyses were performed on input parameters, and results from both methods were integrated to evaluate stock status. The LB-SPR assessment indicated that the average relative fishing mortality (F/M) was 6.70, while the average spawning potential ratio (SPR) was only 0.05. The LBB assessment revealed that the average F/M was 9.97, the average relative biomass (B/B_MSY) was 0.09, and the ratio of mean length at first capture to optimal length at first capture (L_c/L_{c_opt}) was 0.70. Sensitivity analyses demonstrated that while quantitative results varied with input parameters, the conclusion regarding the stock status remained robust. All indicators consistently showed that the L. polyactis stock in the Zhoushan Fishing Ground is subject to extremely high fishing pressure, with critically low spawning potential and biomass, alongside significant population miniaturization. L. polyactis resource in the Zhoushan Fishing Ground has suffered severe overexploitation. Furthermore, the stock assessment methods and procedure used in this study demonstrate strong applicability and robustness under data-limited conditions, providing a methodological reference for stock assessment research in similarly data-limited fisheries.

• Quota assessment of Nemipterus virgatus in the Northern South China Sea based on catch survey data

  FENG Bo, CHEN Wenyang, WANG Feng, LI Zhonglu

  2026,50(4):049308-049308, DOI: 10.11964/jfc.20251015178

  Abstract(0) HTML(0) PDF(5.03 M)( 0) Collect

  Abstract:

  The allowable catch of Nemipteridae family in the northern South China Sea has been assessed, but management parameters for specific species are lacking. It is necessary to conduct a quota evaluation of Nemipterus virgatus to obtain more practical reference points for output control. Applying the CMSY++ approach, we analyzed the catch time series of N. virgatus reconstructed from stratified sampling survey data together with sixteen catch-per-unit-effort time series (CPUE). CMSY and BSM models were run to estimate biological reference points such as carrying capacity k, resilience r, catchability coefficient q, and maximum sustainable yield (MSY). Residual analysis was conducted to verify the applicability of CPUE datasets. Representative CPUE datasets were selected, the exploitation status of N. virgatus across different fishing methods was compared based on the trends of B/B_MSY and F/F_MSY, and the overall exploitation status of N. virgatus in 2023 was evaluated using the Kobe plot. The resilience r of N. virgatus in the northern South China Sea was estimated at 0.79-0.89, carrying capacity k at 704.47-817.20 thousand tons, the catchability coefficient at 0.03×10^–3-2.63×10^–3，and MSY at 151.66-164.71 thousand tons. The three CPUE datasets were identified as unsuitable for CMSY++ analysis through runs test of residuals and outlier diagnosis of residuals. Three B/B_MSY and F/F_MSY trajectories were similar from 2008 to 2018 that represented trawl, gillnet, and longline fisheries respectively. The B/B_MSY curve for gillnets began to recover in 2019 and rose above the safe level of 1.0 by 2022, whereas the corresponding curves for the other two gear types remained below 1.0. The F/F_MSY for gillnets dropped markedly after 2019 and fell below 1.0, while the F/F_MSY ratios for the other two gear types stayed above 1.0. Based on the risk probability indicated by the Kobe plot, the N. virgatus stock was considered to be overfished in 2023. A total allowable catch (TAC) of 132 thousand tons is recommended for the current stage. Statistical analysis based on catch surveys enables the understanding of stock exploitation status from multiple perspectives, and the design and long-term implementation of a sound catch survey program, along with the acquisition of accurate fishery production data derived therefrom, will contribute to the stock assessment and management of mixed fisheries.

• Comparison of fish diversity in the adjacent waters of the Yellow and Yangtze River Estuaries based on environmental DNA

  LÜ Ding, LIU Chengbin, HU Yulong, SHAN Xiujuan, WANG Weiji

  2026,50(4):049309-049309, DOI: 10.11964/jfc.20260115334

  Abstract(0) HTML(0) PDF(5.29 M)( 0) Collect

  Abstract:

  To systematically compare the differences in fish community composition and diversity patterns, and to evaluate the applicability of environmental DNA (eDNA) metabarcoding technology for monitoring estuarine fishery ecosystems, this study collected water samples from nine stations in each of the two major estuaries during the spring of 2025. eDNA was extracted, and a fragment of the fish 12S rRNA gene was amplified and subjected to high-throughput sequencing. After quality control and taxonomic annotation of the sequencing results, species composition and diversity were assessed. The results revealed a total of 57 fish species identified across both estuarine regions, with the number of fish species in the Yangtze River Estuary (43 species) being significantly higher than that in the Yellow River Estuary (30 species). The community structure in the Yellow River Estuary showed a pattern dominated by a single dominant species (Trachurus japonicus), whereas the Yangtze River Estuary was co-dominated by multiple species such as Coilia mystus, T. japonicus, and Engraulis japonicus, exhibiting a more even distribution. Alpha diversity indices indicated that species richness, the Shannon index, and Pielou's evenness were all significantly higher in the Yangtze River Estuary than in the Yellow River Estuary. Non-metric multidimensional scaling (NMDS) analysis showed large differences in community composition among stations and high spatial heterogeneity within the Yellow River Estuary, while stations in the Yangtze River Estuary exhibited higher similarity. This study demonstrates that fish diversity in the Yangtze River Estuary is higher than in the Yellow River Estuary during spring, with significant differences in dominant species patterns and spatial heterogeneity between the two, which may stem from differences in their hydrological environments and habitat complexity. The findings provide a new data perspective for the baseline assessment and management of fishery resources in the Yellow River and Yangtze River estuaries, and offer an empirical case study and methodological reference for the application of eDNA technology in the routine monitoring of biodiversity in China's coastal waters.

• Seasonal and interannual dynamics of fish community structure in the Yangtze River Estuary and adjacent waters based on environmental DNA metabarcoding analysis

  SU Shengfa, AN Changting, LI Ang, ZHANG Jianlong, LIU Shufang

  2026,50(4):049310-049310, DOI: 10.11964/jfc.20260115367

  Abstract(0) HTML(0) PDF(5.41 M)( 0) Collect

  Abstract:

  Human activities and global climate change are posing ongoing threats to fish diversity, leading to imbalances in community structure and a decline in ecosystem functions, thereby endangering the sustainable utilization of fishery resources. Under the combined pressure of multiple stressors, accurately understanding the spatiotemporal dynamics of fish diversity has become a critical issue that urgently needs to be addressed for ecological conservation and resource management. To validate the suitability of environmental DNA (eDNA) metabarcoding for monitoring fish diversity in the Yangtze River Estuary, and to reveal the spatiotemporal dynamics of fish community structure in this area, this study employed eDNA metabarcoding technology to investigate the fish biodiversity in the Yangtze River Estuary and its adjacent waters during the spring and autumn seasons of 2022 and 2024. Through filtration of seawater samples, DNA extraction, amplification with MiFish primers, high-throughput sequencing, and a stringent bioinformatics pipeline coupled with taxonomic annotation against the MitoFish database. This study obtained 17,477,708 raw sequences, and after quality control, 16,690,083 high-quality sequences were obtained, with sequencing quality values (Q30) all above 85%. A total of 219 fish species were identified, belonging to 2 classes, 21 orders, and 87 families, with a matching rate of 84.93% compared to historical literature records. In terms of species composition, Perciformes was the dominant group (102 species, accounting for 46.58%). Analysis of alpha diversity indices (Shannon, Simpson, Pielou) revealed significant seasonal variations in fish community structure, with species richness and diversity indices in spring 2024 significantly lower than those in spring 2022. Beta diversity analysis (NMDS) further elucidated the seasonal differentiation pattern of the community structure. The composition of dominant species indicated a community shift towards miniaturization and lower trophic levels. This study, utilizing environmental DNA (eDNA) metabarcoding, has revealed the seasonal dynamics and interannual variation trends of fish community structure in the Yangtze River Estuary. It confirms the effectiveness of this technology for monitoring fish diversity in this region, providing critical data to support biodiversity conservation and adaptive management in the area.

• Spatiotemporal distribution of Portunus trituberculatus in north-central Zhejiang coastal waters based on environmental DNA (eDNA)

  MAO Mengqi, ZHOU Yongdong, ZHANG Hongliang, XU Kaida, JIANG Rijin, WANG Haoxue, YUAN Xia, ZHAO Yunhao, WANG Xiaoyan

  2026,50(4):049311-049311, DOI: 10.11964/jfc.20251115229

  Abstract(0) HTML(0) PDF(6.49 M)( 0) Collect

  Abstract:

  Portunus trituberculatus is one of the most important marine economic crab species in China, supporting coastal fisheries and regional economies. However, wild populations have experienced persistent declines in recent decades due to overfishing, habitat degradation, and environmental change, highlighting the urgent need for efficient and reliable approaches to assess its spatial and seasonal distribution. Conventional fishery-dependent surveys, such as bottom trawl investigations, are often constrained by sampling selectivity, labor intensity, and spatial coverage, which may limit their ability to resolve fine-scale population dynamics; in this context, environmental DNA (eDNA) has emerged as a promising, non-invasive tool, although its applicability to benthic crustaceans in open marine environments remains insufficiently evaluated. Here, an eDNA-based quantitative detection framework for P. trituberculatus was established and applied to the north-central coastal waters of Zhejiang Province during the summer and autumn of 2024. Species-specific primers and a TaqMan probe targeting P. trituberculatus were designed and validated, and a quantitative real-time PCR (qPCR) assay was developed for sensitive and specific detection in environmental samples. A total of 157 seawater samples were collected from 29 stations across two seasons, covering surface, middle, and bottom water layers, and bottom trawl surveys were conducted concurrently to provide fishery-independent reference data. The developed primers and probe exhibited high specificity, with no cross-amplification detected in closely related crustacean species. Horizontally, P. trituberculatus eDNA displayed pronounced spatial heterogeneity in both seasons, with consistently elevated concentrations in the Yushan Fishing Ground, indicating this area as a key habitat and aggregation zone. Vertically, distribution patterns differed between seasons: in summer, eDNA concentrations did not differ significantly among layers, suggesting strong vertical mixing and rapid dispersion, whereas in autumn, eDNA concentrations were significantly enriched in the middle layer and clear stratification was observed, reflecting seasonal changes in water-column stability and species behavior. Furthermore, both the mean eDNA concentration and detection rate in autumn were significantly higher than those in summer, consistent with seasonal migration and increased population aggregation. Compared with bottom trawl surveys, eDNA analysis provided a more comprehensive indication of species presence and distribution, particularly where trawl efficiency may be limited; the combined application of eDNA monitoring and trawl surveys enabled a refined assessment of the spatial and seasonal distribution patterns of P. trituberculatus. Overall, this study demonstrates the effectiveness and sensitivity of eDNA techniques for monitoring benthic crab resources in open marine systems and provides a robust scientific basis for resource assessment, ecological conservation, and the sustainable management of P. trituberculatus fisheries.

• A comparison of fish diversity results based on eDNA metabarcoding and trawl net: a case study of the southern coastal waters of Zhejiang Province

  CHEN Zhi, JIANG Rijin, LU Zhanhui, ZHANG Yazhou, LIU Shanshan, GAO Tianxiang, LI Pengfei

  2026,50(4):049312-049312, DOI: 10.11964/jfc.20251115231

  Abstract(0) HTML(0) PDF(6.92 M)( 0) Collect

  Abstract:

  To compare the similarities and differences in fish diversity between eDNA metabarcoding and trawl net, this study, taking the southern coastal waters of Zhejiang Province as a case area, analyzed the fish composition, species dominance, and community diversity index of the two survey methods using bioinformatics, traditional morphological identification, non-metric multidimensional scaling analysis, significance test of differences and linear regression analysis. The results are as follows: ① A considerable number (19.92%) of non-indigenous fish OTUs (e.g., freshwater fish, deep-sea fish, tropical coral reef fish) were detected in the high-throughput sequencing results; although the sampling water layer (surface, mid-depth, bottom) did not affect the number of fish OTUs detected by eDNA (P≥0.073), it did influence the composition of fish OTUs (stress=0.138, R=0.117, P=0.001); increasing sampling density (number of replicates, number of water layers) significantly increased the number of fish OTUs (P≤1.1×10^-3); a significant proportion (24.402%) of fish OTUs in this area were in a low annotation state, and some fish sequences exhibited interspecific identity or intraspecific variation. ② The number of fish species detected by eDNA was much higher than that by trawl net (152 species vs. 75 species), and there was a significant linear correlation between the two survey methods (P=0.049 7, r_Pearson=0.381, R²=0.153). ③ When all fish species were analyzed, the two survey methods showed a significant difference in species dominance (P=0.034); for many shared fish species and dominant/keystone dominant species, such as Engraulis japonicus and Nibea albiflora, the species dominance differed by 1-2 orders of magnitude between the two survey methods. ④ Among the 12 frequently occurring fish species, only Harpadon nehereus and Ctenotrypauchen chinensis showed a linear correlation between sequence abundance and individual counts/weight, while the r_Pearson values in the fitted models for the remaining species were low or even negative. ⑤ The community diversity index measured by the two survey methods differed considerably, and their linear correlation was also very low (P≥0.087). This study demonstrates that: ① eDNA has considerable uncertainty. ② Except for some indicators, species, or stations, it is difficult to model and predict the corresponding values of one survey method based on the results of the other. ③ The two survey methods cannot replace each other but rather have a complementary and cross-validating relationship. This study provides a basis for understanding the advantages and disadvantages of eDNA metabarcoding and for the rational use of different survey methods.

• A combined morphological and DNA barcoding approach for large-scale analysis of fish egg communities and its application in the seagrass bed-coral reef seascapes of eastern Hainan

  LIU Yanghao, MIAO Zhongbo, LU Ying, ZHANG Lu, XIA Wentong, XIE Songguang

  2026,50(4):049313-049313, DOI: 10.11964/jfc.20251215256

  Abstract(0) HTML(0) PDF(6.38 M)( 0) Collect

  Abstract:

  This study analyzed the species composition and community structure of fish eggs in a specific seagrass bed–coral reef habitat in eastern Hainan, and evaluated its function as a spawning ground, providing valuable information for fisheries resource management and conservation. Fish eggs were identified using an integrative approach combining DNA barcoding and morphology. A workflow for determining species composition and abundance in large egg-sample datasets based on morphological–molecular integration was established: ① fish eggs were assigned to distinct morphological groups and additional subgroups according to typical morphological characteristics and subtle differences; ② each morphological group/subgroup was counted and subsampled, and each subsampled egg was photographed to record morphological traits and then molecularly sequenced to determine species identity. Species composition and abundance of the community were determined by integrating the above results. A total of 96 fish-egg samples (86 596 eggs) were collected from the nearshore seagrass bed-coral reef seascape off Wenchang, Hainan, during April–May 2024, and 20 morphological groups were delineated. COI sequences were successfully obtained from 1 208 eggs, identifying 66 species belonging to 8 orders, 29 families and 45 genera. Perciformes had the highest species richness (30 species, 45.5%), followed by Scorpaeniformes (13 species, 19.7%). Scorpaenidae contained the most species (11 species, 16.7%), followed by Labridae (8 species, 12.1%). The correspondence between morphological groups and taxonomic groups was further established. These results confirm the seagrass bed–coral reef seascape as an important spawning habitat for these fishes. This study provides a practical and scalable framework for community-level analyses of large fish-egg datasets, offering a robust methodological foundation for fisheries resource assessment and marine ecological conservation.

• Fish community structure and functional diversity in the southern offshore waters of the Shandong Peninsula

  LI Jinhan, LIU Shude, DONG Xiuqiang, LIU Chunqiao, WANG Zhiyang, TANG Yongzheng, WANG Lei

  2026,50(4):049314-049314, DOI: 10.11964/jfc.20251115208

  Abstract(0) HTML(0) PDF(9.00 M)( 0) Collect

  Abstract:

  The fish community is a critical component of aquatic ecosystems, playing an irreplaceable role in maintaining ecological balance and biodiversity. Functional diversity, which reflects the variation in species' traits and ecological niches, provides a valuable perspective for assessing ecosystem functioning and stability. To understand the current state of the fish community structure and the spatiotemporal patterns of functional diversity in the offshore waters of the southern Shandong Peninsula, this study conducted four seasonal bottom trawl surveys in the southern offshore waters of the Shandong Peninsula during spring (May), summer (August), autumn (October), and winter (December) of 2024. Using the dominance index and abundance-biomass comparison (ABC) curves, we analyzed the species composition, dominant species, and the level of community disturbance of fish in this area. Twelve functional traits from three categories (feeding, locomotion, and habitat adaptation) were selected. Using methods such as the community-weighted mean (CWM) and functional diversity indices, the spatiotemporal variations of fish functional diversity in the study area have been investigated. A total of 51 fish species were collected, belonging to 49 genera, 33 families, and 10 orders across 2 classes. The fish biomass was highest in summer and lowest in winter, whereas the abundance peaked in summer and reached its minimum in autumn. Although the dominant species fluctuated across seasons, they were consistently dominated by small-bodied fishes. The fish community was subjected to varying degrees of disturbance across the four seasons, with a moderate level of disturbance observed in autumn, while severe disturbance was recorded in the remaining seasons. CWM index analysis showed that, across all four seasons, the dominant functional traits were typical of fishes with moderate-to-high resilience, small adult body size, numerous but small offspring, rapid development, and low trophic levels. Functional diversity indices showed no significant differences among seasons but exhibited substantial spatial variation. In the Southern offshore waters of the Shandong Peninsula, the fish community was dominated by r-selected opportunistic species, making the assemblage susceptible to disturbance and the ecosystem relatively fragile. The functional space occupied by fishes remained relatively stable across seasons, with no significant edge expansion or contraction. This study can provide a scientific basis for the assessment of fish resources and the sustainable utilization of fishery resources in the Southern offshore waters of the Shandong Peninsula.

• Community structure of early life stage fish resources and its relationship with environmental factors in the western waters of Sishili Bay, Yantai

  LI Xun, BIAN Xiaodong, SUN Ming, SHAN Xiujuan, LI Xuening, ZHANG Haiting, XU Xilong

  2026,50(4):049315-049315, DOI: 10.11964/jfc.20260115291

  Abstract(0) HTML(0) PDF(7.33 M)( 0) Collect

  Abstract:

  Sishili Bay, Yantai, is located in the northern waters of Laishan District, Yantai City, adjacent to the North Yellow Sea, bordered by Zhifu Bay to the northwest and connected to the Yangma Island waters to the east. It is one of the important coastal bays in the Yantai-Weihai coastal area. To investigate the environmental driving mechanisms governing the dynamics of fish early life stages and to evaluate the effects of artificial habitat modification on recruitment processes in Sishili Bay, Yantai, this study was based on ichthyoplankton survey data from nine cruises conducted between 2024 and 2025. We employed the relative importance index, species turnover rate, and diversity indices to analyze intra-annual variations in community structure; utilized Canonical Correspondence Analysis (CCA) and Mantel tests to examine the spatiotemporal distribution patterns of fish eggs and larvae and their relationships with environmental factors; and applied Mann-Whitney U tests to analyze differences in basic environmental parameters between artificial reef and control areas, while comparing species dominance and average resource density to assess the current impacts of artificial reef construction on the distribution of fish early life stages. Results showed that a total of 21 fish egg taxa and 33 larval fish taxa were recorded, with the primary spawning period occurring from May to July. The dominant spawning species included Kareius bicoloratus, Paralichthys olivaceus, Konosirus punctatus, Engraulis japonicus, Sillago japonica, Sebastes vulpes, Sardinella zunasi, Hyporhamphus sajori, Hypoatherina valenciennei, Strongylura anastomella and Hexagrammos otakii, totaling 20 species. Species composition, resource density, and species turnover rates all exhibited distinct monthly variations, with inter-monthly turnover rates remaining no less than 47%. Cold-temperate and warm-temperate fish species coexisted from March to May, warm-temperate and warm-water species dominated from June to August, and a transition from warm-water to cold-temperate species was observed from September to November. For fish eggs, both the Shannon-Wiener diversity index (H′) and Pielou's evenness index (J′) displayed trends of initial decrease, followed by increase, and subsequent decrease, while the Simpson's diversity index (D) peaked in May and then fluctuated downward. For larvae, H′ exhibited an increasing then decreasing trend, D showed an initial decrease followed by increase and then continuous decline, whereas J′ peaked sharply in September before dropping rapidly. Sea surface temperature and salinity were identified as the key environmental drivers of the spatiotemporal patterns of fish early life stage communities. Current artificial reef construction demonstrated significant associations with the aggregation of early life stages of certain reef-associated species (Acanthopagrus schlegelii and Sebastes vulpes). These findings provide scientific basis and ecological data support for the assessment and conservation of fish early life stages and the evaluation of ecological benefits of artificial reefs in the western waters of Sishili Bay.

• Effects of rare species on fish community stability and functional characteristics in the Zhoushan Fishing Ground

  YAN Chenchen, WANG Jing, LI Yuru, WANG Yingbin, JU Peilong, LIU Baogui

  2026,50(4):049316-049316, DOI: 10.11964/jfc.20250915140

  Abstract(0) HTML(0) PDF(5.67 M)( 0) Collect

  Abstract:

  The persistent decline of marine biodiversity, driven by synergistic global and anthropogenic pressures, highlights an urgent need to understand the functional roles of all ecosystem components—particularly overlooked rare species. Focusing on the depleted Zhoushan Fishing Ground in the East China Sea, this study applied a trait-based framework and conducted a virtual removal experiment to quantify the multifaceted impacts of rare species—identified using the Rabinowitz index—on fish community dynamics. Analysis of four seasonal surveys revealed that removing rare species consistently and significantly reduced total community biomass by an average of 6.73%. It also led to a substantial contraction in the community’s functional space (declines ranging from 14.92% to 34.77%) and a significant 5.20% reduction in functional redundancy, underscoring their critical role in expanding ecological strategies and enhancing functional insurance. Notably, while community stability increased significantly by 8.20% following rare species removal in spring 2025, changes in other seasons were non-significant, indicating temporally variable dynamics in which rare species can contribute to ecological variability. For methodological consistency and comparability of results, nonparametric statistical analyses were uniformly adopted for all four functional indicators (stability, biomass, functional redundancy, functional space): Kruskal-Wallis tests were used to examine overall seasonal variations, and Wilcoxon signed-rank tests to assess the significance of paired differences in each indicator before and after rare species removal. These findings clearly demonstrate the dual role of rare species: although their unique ecological strategies may introduce short-term fluctuations—as evidenced by the observed increase in stability upon their removal due to reduced interspecific asynchrony—they are essential for long-term resilience by uniquely supporting functional diversity and redundancy. This study provides robust empirical evidence that conserving rare biodiversity is not only ecologically meaningful but also a practical imperative for sustaining ecosystem multifunctionality and stability, offering a crucial scientific foundation for integrating rare species into ecosystem-based fisheries management in China and similar marine systems worldwide.

• Shrimp resource dynamics and environmental drivers in the Zhoushan Fishing Ground

  WANG Ziqi, ZHANG Yazhou, JIANG Rijin, HE Zhouting

  2026,50(4):049317-049317, DOI: 10.11964/jfc.20251015171

  Abstract(0) HTML(0) PDF(5.34 M)( 0) Collect

  Abstract:

  This study investigated spatiotemporal variability in the major shrimp resources of the Zhoushan Fishing Ground from 2020 to 2024 and evaluated the development status of the beam trawl shrimp fishery, with the aim of providing a solid scientific basis for future fisheries policy development. Using contemporaneous beam trawl logbook data and remote-sensing-derived environmental variables-dissolved oxygen (DO), sea surface temperature (SST), sea surface salinity (SSS), and chlorophyll-a (Chl.a) concentration-we applied center-of-gravity analysis and generalized additive models (GAMs) to quantify distribution patterns of major shrimp resources and their associations with environmental drivers.The shrimp catch composition was dominated by Metapenaeopsis barbata (23.30%) and Solenocera crassicornis (23.24%). The centers of gravity of these two shrimp resources were located within 30°10′-30°51′N and 124°40′-125°01′E. The centers of gravity exhibited limited variability during 2020–2021 and 2023–2024, whereas they shifted southwestward from 2021 to 2022 and subsequently turned northeastward from 2022 to 2023. Resource density was significantly associated with year, month, longitude, and latitude. For S. crassicornis, the key environmental factors were SST, DO, and Chl.a, with optimal ranges of 14-23°C, 200-250 mmol/m³, and 0-40 mg/m³, respectively. In contrast, M. barbata was primarily influenced by SST and Chl.a, with optimal ranges of 15-30 °C and 30-50 mg/m³, respectively. Overall, shrimp resources remained generally stable from 2020 to 2024, and both catch and CPUE increased markedly following the seasonal fishing moratorium.Extreme weather events and oceanographic variability may substantially affect shrimp distribution and yield. The observed fluctuations in the distributional center of gravity may reflect the combined effects of environmental forcing and fisheries management policies. The CPUE of the two shrimp species showed pronounced spatiotemporal variability, closely related to their reproductive periods and growth cycles. Collectively, the results indicate that SST, Chl.a, and DO are dominant drivers of shrimp distribution and abundance in the Zhoushan Fishing Ground, and that environmental variability together with fisheries management jointly shapes the spatiotemporal dynamics of shrimp resources.

• Seasonal spatio-temporal distribution characteristics of Coilia nasus in the Yangtze River Estuary and adjacent waters

  GUO Hongyi, ZHANG Xuguang, LIU Shouhai, TANG Wenqiao, LIU Kai

  2026,50(4):049318-049318, DOI: 10.11964/jfc.20260115355

  Abstract(0) HTML(0) PDF(5.44 M)( 0) Collect

  Abstract:

  The Yangtze River Estuary, situated at the boundary of the Yellow Sea and the East China Sea, is a typical large-scale estuarine system on the western Pacific coast. Coilia nasus (Clupeiformes: Engraulidae) is a representative anadromous species in this system. Over recent decades, C. nasus has experienced marked population declines driven by overfishing, wetland loss, altered hydrodynamics, and reduced sediment discharge. A 10-year fishing ban took effect across key Yangtze waters in 2021, yet the habitat use patterns of different age groups within the estuary remain poorly understood. This study aimed to reveal the spatio-temporal distribution characteristics of age-specific groups of C. nasus in the Yangtze River Estuary and adjacent waters, and to evaluate the nursery function of the estuarine mouth zone and its environmental drivers. Bottom trawl surveys were conducted during spring (May), summer (August), and autumn (November) of 2024 and 2025 across 55 fixed stations (121°-124°E, 31°-32°N), totalling six seasonal cruises. All captured C. nasus were measured for standard length (SL, cm) and assigned to Young-of-the-year (YOY) (age 0) or non-YOY (age ≥ 1) groups based on overwintering bands on scales. Abundance was standardized as numerical density (ind./km²). Density-weighted centres of gravity, inertia ellipses, and the global index of collocation (GIC) were computed for each year × season × age-group combination. Bottom salinity and temperature were recorded at each station, and their effects on density were evaluated using Spearman rank correlations and negative binomial generalized linear models. Salinity fronts were identified within a latitudinal band covering the mouth zone by locating the maximum longitudinal salinity gradient. A total of 12 025 specimens were collected. Population composition shifted markedly across seasons: non-YOY individuals dominated in spring (78.6%), while YOY prevailed in summer (62.1%) and autumn (74.3%), reflecting the life-history pattern of spring spawning migration and subsequent summer–autumn juvenile recruitment. YOY density increased from (335 ± 757) ind./km² in spring to (1 454 ± 3 027) ind./km² in autumn, whereas non-YOY density declined from (1 680 ± 2 753) ind./km² in spring to (485 ± 1 085) ind./km² in autumn. Despite these contrasting trends, density-weighted centres of gravity of both groups remained within the estuarine mouth zone (approximately 122°E, 31.2°-31.4°N) across all cruises. Spatial overlap was highest in spring (GIC = 0.996) and declined in summer and autumn (GIC ≈ 0.940), indicating progressive spatial segregation while retaining a shared distribution core. Bottom salinity was the primary environmental constraint: density of both groups was negatively correlated with salinity across all seasons (Spearman ρ: -0.508 to -0.807, all P < 0.001). Salinity fronts were consistently located between 122.1° and 122.5°E, coinciding spatially with YOY distribution centres. The estuarine mouth zone functions as a stable nursery for C. nasus juveniles, as evidenced by consistently high densities and a spatially persistent distribution centre across seasons. Bottom salinity gradients and salinity front dynamics appear to be primary factors regulating the age-specific spatial distribution of C. nasus in the estuary. These results offer a quantitative basis for delineating critical nursery habitats and developing habitat-oriented management measures in the context of the ongoing fishing ban.

• Diversity and spatial distribution characteristics of fish communities in river networks in the Pearl River Delta

  JIA Qiuju, LI Jie, LIU Yaqiu, XIA Yuguo, ZHANG Yingqiu, CHEN Weitao, ZHU Shuli, SHUAI Fangmin

  2026,50(4):049319-049319, DOI: 10.11964/jfc.20251215269

  Abstract(0) HTML(0) PDF(8.11 M)( 0) Collect

  Abstract:

  The Pearl River Delta river network (PRDRN), with its unique subtropical geographical pattern of "three rivers converging and eight outlets to the sea", is one of the most fish-diverse waters in the world. In order to understand the fish diversity and spatial distribution patterns in the river network of the Pearl River Delta, and to provide data support for the conservation and sustainable development of river network fish diversity, this study calculated the Shannon-Wiener diversity index, Pielou's evenness index, and Margalef richness index to characterize fish diversity. Non-metric multidimensional scaling (NMDS) and redundancy analysis (RDA) were used to explore the distribution characteristics of fish in the Pearl River Delta river network and their relationships with environmental factors. The results showed that a total of 157 fish species were collected, belonging to 16 orders 57 families 124 genera, with Perciformes being the most numerous (78 species), accounting for 49.68% of the total fish species, followed by Cypriniformes (30 species), accounting for 19.11% of the total. A total of 17 alien fish species were surveyed, among which Oceochromis nilotica had the highest numerical proportion and Prochilodus lineatus had the highest weight proportion. Among all sampling sites, the Hengmen River section in Zhongshan had the highest diversity index (3.37), evenness index (0.78), and richness index (8.56). NMDS results showed that fish in the Pearl River Delta river network can be divided into three communities: Community 1, dominated by pelagic and demersal-pelagic fish such as Hemiculter leucisculus, Megalobrama terminalis, Hypophthalmichthys molitrix, Aristichthys nobilis and Squaliobarbus curriculus; Community 2, composed mainly of benthic fish including Misgurnus anguillicaudatus, Glossogobius giuris and Cynoglossus trigrammus; Community 3, represented by typical estuarine fish such as Clupanodon thrissa and Coilia grayii. RDA results indicated that salinity, precipitation, and water temperature had significant effects on fish communities. This suggests that the fish resources in the Pearl River Delta river network are abundant and fish diversity is relatively good, but species invasion is relatively severe, and the relative historical resource quantity has decreased considerably. Fish populations in the river network are divided into three groups, and salinity, precipitation, and water temperature are the main factors influencing the spatial differences of fish communities in the Pearl River Delta river network. The study clarified the fish diversity, spatial distribution patterns of communities, and related influencing environmental factors in the Pearl River Delta, providing a scientific basis for the conservation of fishery resources and sustainable development.

• Optimal design of survey stations for inshore fishery resources: a case study of the inshore waters of the Northern Shandong Peninsula

  ZHENG Xiang, LI Fan, XU Bingqing, YANG Yanyan

  2026,50(4):049320-049320, DOI: 10.11964/jfc.20260115369

  Abstract(0) HTML(0) PDF(5.92 M)( 0) Collect

  Abstract:

  Coastal ecosystems in the Bohai Sea and the Yellow River Estuary support vital fishery resources but are increasingly threatened by environmental degradation and anthropogenic pressures, which necessitating reliable and cost-effective monitoring. To establish an accurate and efficient fishery resource monitoring system and address the contradiction of "insufficient accuracy" and "high cost" in traditional surveys of the coastal waters of the Bohai Sea and the Yellow River Estuary, this study utilized the fishery resource survey data from May and August in 2023 to 2025, compared the efficacy of three sampling methods: simple random sampling, cyclic systematic sampling, and stratified random sampling, and through quantitative analysis using the multi-objective comprehensive evaluation index (C_REE), determined the optimal sampling scheme that balances accuracy and economy. The study found ① the ranking of sampling method efficacy is consistent, with stratified random sampling having the lowest C_REE and the strongest stability; ② the stratification criteria are determined by region and season, in May of the Bohai Sea coastal area, it is ≤10 m、10-20 m、>20 m; in August, it is ≤8 m, 8-18 m, >18 m; in May of the Yellow River Estuary, it is ≤8 m, 8-18 m, >18 m; in August, it is ≤6 m, 6-16 m, >16 m; ③ under the high accuracy standard of C_REE ≤10%, approximately 35 stations were needed for the Bohai Sea coastal area in May and August of a single year; for the Yellow River Estuary in May and August of a single year, approximately 18 stations were needed; if the conventional standard of C_REE ≤15% is adopted, the number of stations can be reduced by approximately 37.5%. The findings provide technical support for the construction of a long-term monitoring system for fishery resources in the Bohai Sea coastal area and the Yellow River Estuary, and also provide scientific basis for the optimization of sampling schemes for the river-mouth-nearshore coupled ecosystem in the north.

• Impact of extended fishing moratorium on life-history parameters of different-sized fishes in the Bohai Sea via coupled aLBI-LBB methods

  LIANG Yaowei, SHAN Xiujuan, HAN Qingpeng, ZHAO Jie, WU Qiang, LI Zhongyi, DAI Fangqun

  2026,50(4):049321-049321, DOI: 10.11964/jfc.20260115368

  Abstract(0) HTML(0) PDF(6.63 M)( 0) Collect

  Abstract:

  The summer fishing moratorium (SFM) aims to protect spawners and larvae for fishery resource conservation. To evaluate the conservation effectiveness of an extended SFM in the Bohai Sea, this study compared the population status and biological parameters of fish species with different body shapes before and after the policy adjustment. Bottom trawl survey data from late August were analyzed across two periods that before (2014-2016) and after (2017-2019) the SFM adjustment. Nine representative species across six body shapes were selected: compressed (Konosirus punctatus, Thryssa kammalensis, Engraulis japonicus, Sardinella zunasi), ribbon-like (Enedrias fangi), depressed (Callionymus beniteguri), eel-like (Chaeturichthys stigmatias), asymmetrical (Cynoglossus lighti), and fusiform (Scomber japonicus). Kernel density estimation was used to compare length-frequency distributions. Allometric growth parameters b were analyzed using length-weight power functions. Biological priors, including asymptotic length (L_inf), length at first maturity (L_mat), and optimum length (L_opt), were estimated using the aLBI (a length-based indicators) method. The robustness of L_inf estimates across different bin sizes (0.50–3.00 cm) was measured by relative error (RE). Finally, L_inf and L_mat were used as priors for the LBB (length-based bayesian biomass) model to estimate and compare resource indicators, such as relative biomass (B/B₀) and the ratio of natural mortality to growth (M/K). Results showed significant differences in responses to the extended SFM among fish species. Body lengths showed an increasing trend for T. kammalensis, S. zunasi, and K. punctatus, while a decreasing trend was observed for E. fangi, C. beniteguri, C. lighti and S. japonicus. Changes in body length for C. stigmatias were not significant. The extension of the summer fishing moratoria resulted in species-specific responses in the allometric growth parameter b. Specifically, for E. fangi, T. kammalensis, and E. japonicus the parameter b was significantly greater than 3 (P<0.001) across both periods, indicating positive allometric growth. RE increased with larger bin sizes; for K. punctatus and C. beniteguri, RE increased and L_inf was overestimated when bin sizes exceeded 1.25 cm. B/B₀ showed an improving trend for K. punctatus, E. fangi, C. stigmatias, E. japonicus, and S. zunasi, but declined for C. beniteguri, C. lighti, and S. japonicus. M/K values remained relatively stable, fluctuating around 1.5 for most species. In conclusion, the effectiveness of the extended SFM varies by species, and assessment models are highly sensitive to bin size settings. Practical applications should optimize bin sizes based on biological traits and sample sizes. Although the extended SFM helps improve the population structure of pelagic fishes, the miniaturization of demersal fishes and the insufficient spawning biomass in certain populations warrant further attention.

• Optimizing the special fishing license system during a summer fishing moratorium in the Bohai and Yellow seas: a study based on the perspective of fishers

  DING Qi, SHAN Xiujuan, JIN Xianshi, SUN Jiting

  2026,50(4):049322-049322, DOI: 10.11964/jfc.20251215277

  Abstract(0) HTML(0) PDF(5.03 M)( 0) Collect

  Abstract:

  The special fishing license system during a summer fishing moratorium has been implemented in China since 2017, aiming to achieve rational utilization of fishery resources whilst improving fishers' incomes. Fishers are the implementing entity of the special fishing license system. Assessing their satisfaction with fisheries management policies is crucial for evaluating policy effectiveness, understanding fishers’ needs, and promoting system optimization. Using a Partial Least Squares Structural Equation Modelling (PLS-SEM) approach on data gathered via semi-structured interviews and online surveys, we measure fishers’ satisfaction with the special fishing license system and its influencing factors, with a focus on the Japanese common squid (Todarodes pacificus) and the mantis shrimp (Oratosquilla oratoria). Our results demonstrated that fishers were generally satisfied with the special fishing license system. The mean overall satisfaction score for the T. pacificus fishery was 4.7 out of 5, which is higher than that for the O. oratoria fishery (4.1 out of 5). Overall, satisfaction with the special fishing license system in the T. pacificus fishery is higher than that in the O. oratoria fishery in all aspects. Satisfaction directly promoted willingness to participate in both fisheries, with an effect size of 0.168 and 0.518 for T. pacificus and O. oratoria fisheries. Socio-economic benefit has a significant influence on both satisfaction and willingness to participate. Fishers in the O. oratoria fishery expressed much lower willingness to participate due to the relatively low scores on the fishing period, the fishing area, and the impact on fishers' income. The optimization of the special fishing license system should take into account both the characteristics of fishery resources and socio-economic factors. To improve the fairness and practicability of the special fishing license system and promote high-quality development of marine fisheries, it is suggested to implement measures including carrying out ongoing fishery resource surveys and fishing monitoring, enabling flexible adjustment of fishing operations, and strengthening the organizational management of fishing vessels.

• Quota proportion of coastal fishery resources based on three weighting schemes: the case of seven coastal cities in Shandong Province, China

  LI Shaowen, DING Qi, YU Ning, CUI Guangxin, WANG Tiantian, SHAN Xiujuan, LI Fan

  2026,50(4):049323-049323, DOI: 10.11964/jfc.20251015173

  Abstract(0) HTML(0) PDF(5.13 M)( 0) Collect

  Abstract:

  Focusing on seven coastal prefecture-level cities in Shandong, the research employed data on catch volume, social indicators, and efficiency indicators from 2017 to 2023. The weights of these indicators and the corresponding quota proportion for each city were analyzed using three weighting schemes: the Equal Weighting Method, the Kakwani Relative Deprivation Coefficient Method, and the Entropy Weight Method. The fairness of three weighting schemes was evaluated using the Gini coefficient. The results indicated that under the Equal Weighting Method, Yantai City received the highest quota proportion (26.90%), while Dongying City received the lowest (6.80%). Under the Kakwani Relative Deprivation Coefficient Method, Yantai City again received the highest allocation (37.09%), and Dongying City the lowest (3.72%). Compared to the Equal Weighting Method, this scheme increased quota shares for Yantai and Weihai by 10.18 and 3.97 percentage points, respectively, while reducing the shares of the other cities, with Binzhou City experiencing the largest decrease (6.85 percentage points). Under the Entropy Weight Method, Weihai City received the highest quota proportion (30.29%), and Dongying City the lowest (5.45%). Relative to the Equal Weighting Method, Weihai's share increased the most (+5.54 percentage points), while Binzhou City's share decreased the most (-3.80 percentage points). Fairness analysis based on the Gini coefficient showed that all three weighting schemes resulted in coefficients below 0.2. The allocation derived from the Entropy Weight Method yielded the smallest Gini coefficient (0.097), indicating the highest level of fairness among the three schemes. Under this optimal scheme, the weights for the catch volume, social, and efficiency indicators were 0.436, 0.406, and 0.158, respectively. The corresponding quota proportions for the cities were as follows: Qingdao 12.91%, Dongying 5.45%, Yantai 27.31%, Weifang 7.39%, Weihai 30.29%, Rizhao 9.60%, and Binzhou 7.05%. Based on these proportions, the approximate fishing quotas for the seven coastal cities were estimated as: Qingdao 220.4 thousand tons, Dongying 93.0 thousand tons, Yantai 466.1 thousand tons, Weifang 126.2 thousand tons, Weihai 516.9 thousand tons, Rizhao 163.9 thousand tons, and Binzhou 120.3 thousand tons. This study can provide insights for marine fisheries management.

• Size selectivity of T90 mesh codends in stow net for Coilia mystus and Metapenaeus joyneri in the South China Sea

  YAN Lei, LI Jie, YANG Bingzhong, WANG Teng, CHEN Zuozhi, ZHANG Peng

  2026,50(4):049324-049324, DOI: 10.11964/jfc.20251215266

  Abstract(0) HTML(0) PDF(5.18 M)( 0) Collect

  Abstract:

  Stow net fishery is one of the most important components in coastal waters of China, characterized by simple gear structure, low energy consumption and stable economic benefits. In the South China Sea, two-stick stow net is widely used to harvest small fish and crustaceans, especially Coilia mystus and Metapenaeus joyneri. However, traditional stow net usually employ small mesh sizes and diamond-shaped meshes, resulting in poor size selectivity and high bycatch rates of juveniles, which pose serious threats to sustainable exploitation of coastal fishery resources. Codend structure, particularly mesh size and mesh orientation, plays a key role in determining the geometric configuration, hydrodynamic performance and selective properties of stow net. Compared with conventional diamond meshes, T90 meshes (diamond meshes rotated by 90°) have been proven to maintain more stable opening geometry and better selectivity in trawl fisheries, but their effectiveness in passive stow net systems remains insufficiently quantified. The objective of this study was to quantify the size selectivity of T90 mesh codends with different mesh sizes used in two-stick stow net fisheries in the South China Sea, and to evaluate their effects on the selective properties for C. mystus and M. joyneri, providing a scientific basis for codend design optimization and mesh size regulation. Field selectivity experiments were conducted using the covered method with T90 mesh codends of three mesh sizes (30, 35, and 40 mm). Catch data from the codend and the cover net were collected and sorted by size. Logistic and Richards models were applied to fit the size selectivity curves for C. mystus and M. joyneri, and selectivity parameters, including the 50% selection length (L₅₀), were estimated using the maximum likelihood method. The relationship between L₅₀ and mesh size was further analyzed to estimate the minimum appropriate mesh size for each target species. The results showed a clear increase in size selectivity with increasing mesh size. For C. mystus, the estimated L₅₀ values were 130.88 mm, 134.04 mm, and 142.72 mm for the 30, 35, and 40 mm T90 mesh codends, respectively. For M. joyneri, the corresponding L₅₀ values were 70.75 mm, 79.93 mm, and 90.10 mm. In both species, L₅₀ increased consistently with mesh size, indicating enhanced release of smaller individuals. Based on the linear relationship between L₅₀ and mesh size, the minimum appropriate mesh sizes were estimated to be 28.20 mm for C. mystus and 29.51 mm for M. joyneri. Considering the body shape characteristics of the target species and the selectivity results, it is recommended that the minimum mesh size of T90 codends used in two-stick stow net fisheries in the South China Sea should not be less than 30 mm. Compared with traditional diamond meshes, T90 mesh codends can maintain higher opening stability and significantly improve the release efficiency of juvenile fish and shrimp. These findings demonstrate that adopting T90 mesh structures is an effective technical measure to improve stow net selectivity and contribute to the sustainable management of coastal fishery resources in the South China Sea.