Koi carp (Cyprinus carpio var. koi) are popular ornamental fish, and their complex mottling and patterning are ideal models for studying the regulatory mechanisms of pigmentation. However, there are few studies addressing the influence of epigenetics, especially DNA methylation on koi coloration and phenotype formation. In this study, we focused on three phenotypes of Kohaku offspring, namely the Rs group (all red-skinned), the Rw group (red-white-skinned) and the Ws group (all white-skinned), each of which underwent DNA methylation and transcriptome sequencing. A comprehensive analysis revealed that the genes in the differentially methylated regions and the differentially expressed genes (DEGs) were significantly enriched in pathways such as retinol metabolism and melanogenesis. The highest number of DEGs was observed in the Rs and Rw groups, while key genes involved in color differentiation, such as mitf, gch2 and bco1, were hypermethylated and regulated in the Rs group. Vivo experiments also showed that inhibition of methylation led to a significant increase in the expression of genes related to the retinol and pteridine pathway (e.g. pnp4a, gch2 and bco2) in the dorsal skin but not in the ventral skin. The results of in situ hybridization of carotenoid metabolism genes (bco1 and bco2) also suggest that DNA methylation is involved in the regulation of different color phenotypes and coloration in various parts of the body. These findings could deepen the understanding of the dynamic changes in DNA methylation that are crucial for the differentiation and variation of skin color in koi, thus revealing the potential influence of epigenetics on pigmentation.

The Eastern Equatorial Pacific hosts complex current systems that generate widespread mesoscale eddies, profoundly shaping primary productivity and marine ecosystems. Using the Angular Momentum Eddy Detection and Tracking Algorithm (AMEDA), this study analyzed spatiotemporal patterns of mesoscale eddies from 2016 to 2021 and their correlation with Dosidicus gigas distribution during March–August each year. A total of 929 anticyclonic eddies (AEs) and 1,047 cyclonic eddies (CEs) were identified. AEs concentrated near the equator, overlapping with the Equatorial Undercurrent and Equatorial Countercurrent, whereas CEs were mainly distributed within 3°–5°S and 3°–5°N, corresponding to the southern and northern equatorial surface currents. Significant differences in D. gigas distribution were observed inside and outside the two eddy types, with abundance markedly higher in AEs than in CEs. The population favored the northeastern eddy core (0–R) of AEs and the northern and southwestern margins (R) of CEs, with peak abundance concentrated at the one-radius (R) edge for both types. Suitable environmental ranges for D. gigas were 25–26°C (SST), 0.1–0.2 m (SSH), 34–36 (SSS), and 0.25–0.30 mg/m3 (CHLA). Dense D. gigas regions within AEs featured low temperature, low salinity, high CHLA, and high SSH, while those within CEs exhibited low SST, low salinity, low CHLA, and high SSH. This study suggests that relatively low temperatures within both eddy types provide suitable thermal habitats for equatorial D. gigas to avoid high surface temperatures, and high SSH in the northern regions of both eddy types enhances mixing efficiency through accelerated currents and upwelling, thereby promoting nutrient aggregation and prey supply. These findings reveal regulatory mechanisms of eddy type, structure, and environmental patterns on D. gigas habitat, offering mesoscale dynamic indicators for fisheries resource prediction in this region.

In order to investigate the molecular mechanisms of muscle fiber development underlying locomotion differences between two common carp (Cyprinus carpio) strains cultured in a rice-fish symbiosis system, we conducted comparative transcriptomic and proteomic analyses of muscle tissues collected from indolent Congjiang (CJ) and active FFRC No. 2 (FR) strains cultured under the identical paddy field conditions. RNA-seq revealed 3,708 differentially expressed genes (DEGs), while proteomic analysis identified 108 differentially expressed proteins (DEPs). Functional enrichment and protein-protein interaction (PPI) network analyses highlighted key genes (psma3, ppargc1a, ube3a) and proteins (Myh, Ckmt2b, Suclg2) involved in proteasome activity, adipocytokine signaling, and ubiquitin-mediated protein degradation. Quantitative real-time PCR (q-PCR) analysis of ubiquitin proteasome pathway related genes validated significantly elevated expression levels in the muscle tissue of CJ compared to FR. After a 21-day interference experiment, ube3a knockdown increased average muscle fiber area and diameter as well as reduced muscle fiber density in juvenile CJ, indicating that ube3a knockdown might promote muscle development in common carp. These results provided molecular insights into fish locomotion capacity related to behavioral adaptation in agroecological systems.

During trawl operations, the accumulation of catch within the codend can significantly alter the hydrodynamic characteristics of the gear, leading to increased drag and energy consumption, while also affecting catch quality. Existing trawl drag models have mainly focused on empty-net conditions and have failed to systematically account for the coupled effects of catch load and key codend structural parameters, such as codend length and terminal mesh size, thereby constraining the development of low-energy trawl gear and the precise control of fishing operations. This study aimed to investigate the mechanisms by which catch load, codend length, terminal codend mesh size, and flow velocity influence trawl drag, and to establish an integrated trawl drag model based on parametric descriptors of gear characteristics. Flume tank experiments were conducted in which codend length, terminal codend mesh size, catch load, and flow velocity were systematically controlled, and trawl drag data were collected to develop regression models using the least-squares method. The results showed that drag increased significantly with increasing catch load. Under conditions of constant codend mesh size, increasing codend length reduced trawl drag, and the drag change rate decreased as flow velocity increased. Under conditions of constant codend length, increasing the terminal codend mesh size also reduced drag, and this drag-reduction effect was more pronounced at lower catch loads and lower flow velocities. The proposed drag model showed a high goodness of fit for absolute drag values (D) (R² = 0.9199 and 0.962), and all parameters passed the significance test (p < 0.05). However, the predictive consistency at the level of the dimensionless drag coefficient (Cd) was relatively weaker, indicating that there is still room for improvement in the selection of characteristic area and in the model structure. This study reveals the nonlinear influence mechanisms of codend length and mesh size on drag, clarifies the quantitative relationships between catch filling ratio, codend structural parameters, and drag prediction, and provides a theoretical basis and engineering reference for the design of low-energy trawl gear and the intelligent regulation of trawl fishing operations.

Acrossocheilus wenchowensis is a lukewarm-water fish found in southern Chinese mountain streams, valued for both ornamental and edible purposes. We assembled a near telomere-to-telomere (T2T) genome using HiFi, ONT, Hi-C and Illumina data. The assembly is approximately 870.69 Mb with a contig N50 of about 21.28 Mb. Among these, 14 chromosomes in Hap1 and 15 chromosomes in Hap2 have reached T2T levels. A total of 24,909 protein-coding genes were predicted in Hap1 and 24,496 in Hap2, with BUSCO scores of 97.4% and 97.6%, respectively. A conserved centromeric satellite sequence (262 bp) derived from an LTR transposon was identified. Comparative genomics showed that Acrossocheilus and Onychostoma diverged approximately 13.7 million years ago (Mya), while A. wenchowensis diverged from A. fasciatus about 5.25 Mya. Resequencing of four geographic populations of A. wenchowensis revealed distinct genetic structure in the LY group compared to the other populations based on SNP and InDel analysis. This genome provides a framework for diploid T2T studies in fish and supports further functional genomics research.

The fish community structure of the Zhoushan Fishing Ground is undergoing change due to overfishing, climate variability, and other anthropogenic stressors. To investigate community-level environmental responses and interspecific associations in this region, we used 11 consecutive years (2014-2024) of spring bottom trawl survey data from the Zhoushan Fishing Ground and integrated environmental covariates to build a two-part hurdle model within the Hierarchical Modelling of Species Communities (HMSC) framework. The results showed that the spatial random effect had the highest contribution (41%), followed by the interannual trend (18%), indicating that community occurrence patterns are primarily shaped by the superposition of stable spatial structuring and long-term change. Depth was significant for more species, whereas salinity was significant for the fewest. Residual correlations further revealed that the focal fish species could be partitioned into two assemblages with one linking species. Meanwhile, within the two-part hurdle model, the direction and significance of responses to the same covariate were not always consistent, supporting that species occurrence probability and positive biomass are governed by different ecological processes. Overall, this study provides a transferable quantitative framework for community assessment in coastal fishing grounds and offers a more operational chain of evidence for ecosystem-based fisheries management.

Grass carp (Ctenopharyngodon idella) has an important economic value in the world. In order to meet increasing high quality nutritional demands, there is an urgent need for genetic selection in breeding programs to improve fish muscle quality. Body weight (BW) and muscle unsaturated fatty acid (UFA) content are economically important traits in fish. In this study, we conducted a genome-wide association study (GWAS) based on whole-genome resequencing to identify single nucleotide polymorphisms (SNPs) and candidate genes potentially associated with BW and muscle UFA content in grass carp. A total of 4315,253 high-quality SNPs were identified and mapped onto 24 chromosomes. We identified 9, 4, 7 and 6 SNPs significantly associated with BW, UFA, polyunsaturated fatty acids (PUFA), and docosahexaenoic acid (DHA) content of fish muscle, respectively. Within the 100 kb upstream and downstream range of these significant SNPs, 51 candidate genes were associated with BW, while 48, 88 and 113 candidate genes were linked to muscle UFA, PUFA, and DHA content, respectively. Notably, nfatc2a, mylk4a, ext2 associated growth, st6galnac5, hmgcra, Rab8a and ptges3a associated with lipid metabolism. The findings of this study will facilitate the breeding of higher muscle UFA content new varieties of grass carp in the future.

The red tilefish Branchiostegus japonicus is an economically important demersal fish species with high-quality. However, research on its reproductive biology and population structure characteristics is limited. To better understand the reproductive biological features of B. japonicus, a study was conducted on 461 individuals collected from the East China Sea (27°00′–31°00′N, 122°30′–127°30′E) from March to December in 2021. This study analyzed the relationship between standard length and the body weight, and detected the sex ratio, length at first sexual maturity, reproductive period, fecundity, and spawning type of this species. The results revealed a power function relationship between body weight (W) and standard length (L) in the samples as the following regression equation: W = 0.000014 L3.16 (R2 = 0.956). The sex ratio was close to 1:1 (χ2 = 1.11, P > 0.05), and the sex ratio exhibited significant differences according to different standard lengths. Using the logistic equation, we estimated that 50

The koi carp is a highly valued ornamental fish with a variety of skin color patterns that play an important role in survival and reproduction, but the molecular basis of these conspicuous colors remains obscure. Here, we generated a single-cell atlas of the red and white skin of Kohaku koi. We found that the skin tissue could be divided into 10 cell types, of which epithelial cells, endothelial cells, fibroblasts and xanthophores were present in higher proportions. Interestingly, pseudotime analysis revealed that pigment cells developed from white to red skin, and genes related to the uptake and degradation of carotenoids were significantly upregulated in red skin. Functional studies using TEM, HPLC, ISH, immunofluorescence, RNAi, cell culture, gene editing, RNA-seq and gene family analysis showed that k-bco2 could access more substrates than k-bco1, and that the two genes do not interact directly but may act synergistically via the calcium-ion signaling pathway. These insights enhance our understanding of pigment cell development and differentiation in fish, and the scRNA-seq transcriptome profiles offer valuable implications for future molecular breeding strategies.

Cold stress due to overwintering is considered a major issue limiting the development of the red tilapia (Oreochromis spp.) industry. This study was the first to systematically investigate the effects of cold stress on skin color, immuno‐antioxidant function, muscle compositions, and intestinal microbiota of red tilapia during overwintering. Fish (initial weight: 72.71 ± 1.32 g) were divided into the cold stress group (cold) and the control group. In the control group, the water temperature (WT) was maintained at 20°C, which is consistent to with the overwintering WT indoors or greenhouse in the local area. In the cold group, the WT was decreased from 20°C to 8°C by 2°C per day during the experiment. At the end of the experiment, we found that the L∗ value of fish ventral skin in the cold group was lower than that in the control group (p < 0.05). The superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), catalase (CAT), and total antioxidant capacity (T‐AOC) activities were higher, but complement 3 (C3) and complement 4 (C4) activities were lower in the liver of cold group fish than those in the control group (p < 0.05). For the gill tissue, the SOD, MDA, and GSH activities were higher, but the C3 activity was lower in the cold group than those in the control group (p < 0.05). The total amino acid (TAA) content in the muscle of fish in the cold group was higher than that in the control group (p < 0.05). 16 s rRNA analysis showed that the intestinal microbial abundance and alpha diversity of fish in the cold group decreased (p < 0.05). Component analysis revealed a significantly higher relative abundance of Cetobacterium spp. in the fish of the cold group. The findings of this study will provide a valuable understanding of fish cold stress during overwintering, which will contribute to facilitating the breeding of new cold‐resistant varieties of red tilapia in the future.

The common carp (Cyprinus carpio) is an economically important freshwater fish species for aquaculture, and the FFRC No.2 strain common carp has recently become widespread in China. A differentiation of skin color exists during the breeding practice of FFRC No.2 strain common carp, where most individuals are gray, occasionally accompanied by a small number of red individuals. To further clarify the growth and morphological variation between individuals with different skin colors and the effects of phenotypic measurements on body weight, six growth-related traits (body weight BW, total length TL, body length BL, head length HL, body thickness BT, and body height BH) and 19 truss measurements (pairwise linear distances between nine landmarks, such as Dis12, Dis13, and Dis14) were measured for 50 individuals randomly selected with different skin colors at three and six months of age, respectively. The mean comparisons, principal component analysis (PCA) and path analysis were further performed using morphological data. The results showed that the gray population was significantly higher than the red population in six growth traits at three and six months of age (P＜0.05). Meanwhile, 17 and 13 phenotypic parameters (ratio of distance measurements to BL) significantly differed between gray and red populations at three and six months of age, respectively. Among these, four head-related phenotypic parameters (HL/BL, Dis12/BL, Dis14/BL, and Dis24/BL) and six trunk-related phenotypic parameters (BH/BL, Dis16/BL, Dis23/BL, Dis34/BL, Dis36/BL, and Dis46/BL) in the gray population were significantly lower than those in the red population (P＜0.05). In contrast, Dis68/BL in the gray population was significantly higher than that in red population (P＜0.05) at three and six months of age. PCA was performed based on phenotypic parameters, those with significant differences were observed between the gray and red populations at three and six months of age. Scatter plots of PC1 and PC2 showed that most individuals with different skin colors were distinguishable in distribution, with a small number of overlapping individuals at three and six months of age. In addition, significantly positive correlations (P＜0.01) were detected between the growth traits of the different populations at three and six months of age, with correlation coefficients (r) ranging from 0.434 to 0.984. The path analysis was performed using a stepwise linear regression algorithm. The results showed that TL, BT, and BH of the gray population at three months of age, BL, BT, and BH of the gray population at three months of age and the red population at six months of age, and BL and BT of the red population at six months of age had significant effects on BW, with determinant coefficients (R2 ) ranging from 0.935 to 0.967. Differences were observed in the path coefficients of morphological traits on BW for different populations at different stages. The highest direct path coefficients on BW were found in TL of the gray population at three month of age (0.611), and BL of the gray population at six months of age (0.633), and BL of the red population at three and six months of age (0.654 and 0.764, respectively). The study revealed significant differences in growth and morphological characteristics between individuals with different skin colors of FFRC No. 2 strain common carp; the specific selection programs of growth traits in the subsequent breeding process for different skin color populations should be considered.

The alteration of water temperature influences fishery productivity. The aim of the present study was to investigate the impact of water temperature on the growth performance, gonad development, immunity, and antioxidant functions of hybrid red tilapia (Oreochromis niloticus × Oreochromis aureus). The experimental fish were reared at four different temperatures (22, 25, 28, and 31 ℃). The fish reared at 28 ℃ had the highest weight gain and the highest specific growth rate, but a lower feed conversion ratio. Increasing the water temperature to 28 ℃ promotes the development of the gonads of this fish; however, lower temperatures (22 ℃) can inhibit its development. The fish reared at 28 ℃ had the highest gonad somatic index (P < 0.05). Malondiadehyde, lysozyme, and complement (C3) in the gills and liver of hybrid red tilapia (O. niloticus × O. aureus) were significantly decreased at 31 ℃, indicating the immune system was influenced at a higher temperature. However, the total antioxidant capacity, superoxide dismutase, and glutathione in the gills and liver of the fish were significantly higher (P < 0.05) at rising temperatures. The fish reared at 25 ℃ showed better liver health. We conclude that thermal stress may increase oxidative stress and reduce immune function in red tilapia, leading to impaired fish growth, and reproduction. Knowledge of the effects of temperature on fish species is critical for sustainable fishery management, and it may improve the production of these species and contribute to genetic breeding programs.

Cephalopods are predominantly short-lived marine organisms, and their habitats are more susceptible to the effects of climate change. Modelling and predicting the distribution of potential habitats of cephalopods and their changing habitat spatial patterns under climate change scenarios can provide an essential scientific foundation for cephalopod habitat conservation and fisheries ecosystem management in the context of climate change. The trawl survey data collected along Zhejiang offshore in the spring and autumn of 2017-2023, in conjunction with marine environmental data including sea surface temperature (SST), sea surface salinity (SSS), dissolved oxygen concentration (DO) and chlorophyll-a concentration (CHLA), collected by temperature-salt-depth instrument, were employed to simulate and predict the potential habitat distribution of Uroteuthis duvauceli, Abralia multihamata, and Sepiella maindroni in the four RCP climate scenarios in 2100 by random forest as a species distribution model. The results demonstrated that the Random Forest predictions were accurate and reliable, with an AUC exceeding 0.8 for each group and a standard deviation below 0.05. The main environmental factors affecting the habitat distribution of three cephalopod species are SST and SSS, with an average contribution rate of 0.28 in spring and 0.33 in autumn. The average contribution rate of SSS in spring is 0.32, and in autumn it is 0.29. The response curves demonstrated that the three cephalopod species exhibited varying degrees of response to changes in SST and SSS. During the spring period, the optimal habitat for cephalopods was characterised by SST ranging from 18 °C to 20 °C, and SSS exceeding 28 ‰. In contrast, in autumn, S. maindroni exhibited a preference for warmer water compared to U. duvauceli and A. multihamata. The potential habitat suitability zones of cephalopods under high gas emission scenarios were found to mainly extend to the southern and northern coast of Zhejiang. Among them, the area of the high adapted zone of S. maindroni increased by 352 % in the RCP4.5 scenario, the area of the high adapted zone of U. duvauceli increased by 69 % in the RCP4.5 scenario, and the area of the high adapted zone of A. multihamata increased by 69 % in the RCP8.5 scenario. The centroid changes of the three species of cephalopods were not found to be significant in the high suitability zones of the three cephalopod species in different climatic scenarios. The present study proposes that climate change will result in alterations to the potential habitat of cephalopods offshore Zhejiang, which is a significant consideration for the future conservation and management of cephalopod fisheries.

Ghrelin (ghrl) and its receptor gene ghsr (growth hormone secretagogue receptor) regulate numerous physiological functions, including growth hormone secretion and food intake. In the present study, we investigated the sequences and expression characteristics of these two genes in bighead carp (Hypophthalmichthys nobilis). The ghrl and ghsr genes encoded 106 and 346 amino acids, respectively, and were 1208 bp and 2239 bp in length. Early blastocysts exhibited the highest levels of ghrl and ghsr expression throughout early development (P < 0.01). The gut exhibited the highest levels of ghrl expression, whereas significantly higher levels of ghsr (P < 0.01) were detected in the brain. Significantly higher levels of ghrl and ghsr expression were detected in the intestine and muscle in summer compared to the levels in winter (P < 0.05). Furthermore, the significantly higher levels of ghrl and ghsr expression were detected in the muscle of individuals with big size compared to the levels of individuals with small size (P < 0.05). In situ hybridization analyses revealed that the intestine ghrl expression signals were more pronounced than intestinal ghsr expression signals, whereas the ghsr expression signals were more intense than those of ghrl in brain tissues. Finally, the co-expression patterns of related genes in the growth hormone synthesis, secretion, and action pathway (ko04935) and the cAMP signaling pathway (ko04024) indicated that ghrl and ghsr potentially regulate feeding and associated energy metabolism activities in bighead carp, in addition to influencing growth performance.

In order to select the fish varieties that are suitable for rice–fish system in terms of nutrition and field adaptability, we compared the muscle characteristics between two common carp varieties, namely, the Congjiang strain (CJ) and FFRC No. 2 strain (FR) to illustrate their nutrition and movement differences when farmed in the paddy field. The nutritional composition analysis of muscles revealed that the protein content of FR was significantly higher than that of CJ (P < 0.01). Conversely, the fat content of CJ was significantly higher than that of FR (P < 0.01). Both varieties contained 16 amino acids and 21 fatty acids. The essential amino acid index of FR was higher than that of CJ. The contents of n-3 and n-6 fatty acids in CJ muscle were significantly higher than those in FR muscle (P < 0.05). Muscle texture and structure analysis showed that FR exhibited significantly higher hardness, chewiness, gumminess, and resilience than CJ (P < 0.01). Additionally, CJ had significantly smaller muscle fiber diameter and area than FR (P < 0.01). However, CJ displayed significantly higher muscle fiber density than FR (P < 0.01). Finally, the fluorescence detection results showed that the content of reactive oxygen species (ROS) in FR muscle cells was significantly higher than that in CJ muscle cells (P < 0.01). The results indicated that both carp varieties were excellent sources of protein and fat, with reasonable amino acid composition and rich beneficial fatty acid content. The muscle characteristics affected movement capacity of fish. It is conceived that the crossbreed of these two varieties may be a promising variety for the rice–fish symbiosis system because it could provide more favorable nutrition and overcome the shortage of each parent fish (low growth rate in CJ and high escape potential in FR).

As a globally renowned ornamental fish, the body color and patterns of koi carp play a decisive role in their market value. Although genetic factors drive color diversity, the non-coding regulatory mechanisms underlying koi color variation are poorly understood. This study focused on two color patterns (red and black) in Hi-Utsuri koi. Histological analysis revealed that black skin primarily consists of dendritic melanocytes, whereas red skin contains numerous granular erythrophores. Whole transcriptome and small RNA sequencing identified many differentially expressed non-coding RNAs (lncRNAs, circRNAs, miRNAs) and mRNAs associated with skin pigmentation. Key regulatory factors involved in pigment differentiation and formation were identified, including lncRNA_89636, asip, mc1r, miR-200a and miR-144. A combination of bioinformatic analysis and experimental techniques (in situ hybridization, dual luciferase reporter assays, cell vector construction, gene editing, lentiviral vector construction, qPCR and western blotting) was used to investigate the molecular regulatory mechanisms among lncRNA_89636, miR-200a and asip. The results showed significantly higher expression of lncRNA_89636 and asip in red skin compared to black skin, while miR-200a was markedly elevated in black skin relative to red skin. A key finding was that lncRNA_89636 regulates asip expression by competitively binding to miR-200a, thereby influencing melanocyte function. Gene editing experiments confirmed that knockout the asip gene disrupts melanocyte distribution and alters the expression levels of both lncRNA_89636 and miR-200a. This work preliminarily elucidates the molecular mechanism regulating skin pigmentation in koi carp via the lncRNA_89636/miR-200a/asip axis and provides a theoretical basis for breeding superior Hi-Utsuri koi.

Understanding the seasonal dynamics of the fisheries and crustacean communities are of crucial ecological significance. To investigate the structural characteristics of these communities and their seasonal dynamics in the offshore of the Zhoushan Archipelago Seas, China, this study conducted a four seasons’ trawl survey to collect fisheries data in spring, summer, autumn, and winter of 2022. A normalized abundance size spectrum approach was applied to investigate the seasonal variation in regressed parameters (slope and intercept) for fish-only and fish-plus-crustacean communities. Our study found that average values of the slope of the size spectrum for fish and fish-plus-crustacean were −1.36 and −1.53, respectively; the overall adding effect with crustaceans in all seasons was more negative (a steeper slope). The results also showed that the adding effect of crustaceans in the fisheries communities were season-specific and region-specific. Temporally, adding crustaceans into fisheries communities contributed to more/less negative slopes in temperate/warm seasons, respectively. Regionally, the inclusion of crustaceans induced a reverse distribution pattern (nearshore–offshore) for fish abundance, as well as the re-scaled intercept, which could indicate the abundance in all seasons except in summer. It was assumed that although fish dominated the overall community structure, crustaceans contributed a compensatory effect by regulating the size distribution across trophic levels. This study provides valuable insights for the dynamic assessment and scientific management of fisheries and crustacean resources in the whole ecosystem.

Illex argentinus is an important cephalopod species widely distributed in Patagonian waters of the southwest Atlantic Ocean. Its distribution is influenced by various environmental factors, as well as mesoscale eddies which are important marine dynamic processes that regulate the environment in this region. However, the mechanism by which eddies affect the distribution of I. argentinus remains unclear. This study analyzed the relationship between the distribution of I. argentinus and both cyclonic (CE) and anticyclonic (AE) eddies, with focus on environmental shifts in sea surface temperature (SST), water temperature at 200 m depth (T200m), and chlorophyll-a concentration (Chl-a). We constructed a Habitat Suitability Index (HSI) model to explore how eddies regulate the distribution of I. argentinus. The results showed that I. argentinus abundance was negatively correlated with SST and T200m, but positively correlated with Chl-a. There was a significantly higher abundance of squid in CEs than in AEs which was mainly distributed on the western periphery side of CEs. Squid abundance showed differing trends in each eddy type between January and April, with an initial increase and then a decrease within CEs, and an overall gradual increase within AEs. The HSI in CEs was significantly higher than that in AEs, and high-HSI areas coincided with the distribution pattern of high abundance of I. argentinus. Therefore, this study indicates that eddies in Patagonian waters have a significant impact on the abundance and distribution of I. argentinus, and the environmental conditions characterized by lower temperatures and higher productivity in CEs are more conducive to yield suitable habitat of this species.

High temperatures are one of the most important abiotic stressors affecting the survival and growth of American shad (Alosa sapidissima). Building on previous omics sequencing studies of A. sapidissima liver and gills under high temperature stress, this study focused on investigating the regulatory role of miR-1236-3p and its target gene hsp90b1. The results indicate that the full-length cDNA of the hsp90b1 gene is 2023 bp and comprises a 5’ end of 58 bp, a 3’ end of 84 bp, and a coding region of 1881 bp, encoding 626 amino acids. Sequence alignment and phylogenetic tree analysis reveal that the hsp90b1 sequence is highly conserved across species. In situ hybridization showed that hsp90b1 is mainly localized in the cytoplasm. Software prediction identified a potential binding site between miR-1236-3p and hsp90b1. Through the construction of wild-type and mutant 3’UTR hsp90b1 dual luciferase reporter plasmids, the targeted relationship between the two was confirmed. In addition, the spatiotemporal expression levels of the hsp90b1 was found to be highest in the multicellular stage and liver tissue at a cultivation temperature of 27 °C; miR-1236-3P was highly expressed in the hatching stage and heart tissue at 30 °C. These findings provide a theoretical foundation for further investigating the regulatory role of non-coding RNA in A. sapidissima heat stress and offer data for subsequent molecular breeding studies.