Hairtail (Scombriformes: Trichiuridae) have always ranked first in single-species production in Chinese marine fishery. However, due to the confusion of species identification, in official statistics, data on hairtail production and economic value are a combination of all the different species of Trichiuridae. In this study, based on sampling along China’s coastal areas, the composition and distribution of common hairtail species, as well as their age, growth, and trophic traits, are discussed. Six species of four genera and two subfamilies were identified, and largehead hairtail (Trichiurus japonicus) and Savalai hairtail (Lepturacanthus savala) were the most important populations that constituted catch production. The growth parameter b could be divided into two groups, with values in species mostly inhabiting northern parts of Chinese seas higher than those in southern parts. Most individuals were 1–2 years of age, suggesting species sexual precocity and individual miniaturization under multiple stresses. Species of Trichiuridae are at the top of the food web and play a bottom-up role in regulating the trophic dynamics of marine food webs. Largehead hairtail showed the highest stability and the greatest impact on the stability of the trophic structure. Despite temporary resource maintenance under fishery-induced evolution, the effective recovery and reasonable utilization of hairtail resources are still the main focuses of attention for Chinese marine fishery.

Trichiurus nanhaiensis is one of the most important commercial fish species in the South China Sea. This study aimed to investigate the level of genetic variation and population genetic structure of T. nanhaiensis in the South China Sea for the first time, using 281 individuals collected from seven locations along the coast of mainland China, Taiwan, and Hainan Island. A high level of haplotype diversity and low nucleotide diversity were detected in the mitochondrial DNA cyt b gene and nuDNA RYR 3 gene. The overall expected heterozygosity (He = 0.693) among the seven populations ranged from 0.681 to 0.706 in microsatellite DNA data, which revealed high levels of genetic diversity. Significant genetic differentiation was found in Taidong populations in Taiwan, revealing the prevention of gene flow caused by the Kuroshio Current. Two major lineages based on the cyt b gene suggested that the Taiwan Strait acted as a geographic barrier for T. nanhaiensis during the glacier periods in the late Pleistocene. The Bayesian skyline plot also revealed that population demographic expansion of T. nanhaiensis was estimated to have occurred in 0.1 Mya. Our results indicated that all populations of T. nanhaiensis had experienced a recent genetic bottleneck following recent expansion based on ABC analysis.

Understanding dietary behavior during the individual development of marine predators and its temporal variations elucidates how species adapt to changes in marine resources. This is crucial for predicting marine predators’ habitat selection and the natural population’s responses to environmental changes. The authors conducted a comparative analysis of dietary shift strategies and trophic level variations in Greater lizardfish (Saurida tumbil) in the Beibu Gulf during two distinct periods (2010 and 2020) using stomach content and stable isotope analysis methods. Possible driving factors for these changes were also explored. Changes in the fishery community structure and the decline in the abundance of primary prey resources have led the S. tumbil population to diversify their prey species, utilize alternative resources, and expand their foraging space. However, the species’ foraging strategy, characterized by chasing and preying on schooling and pelagic prey, promoted stability in their feeding behavior across spatial and temporal scales. The main prey items remained demersal and pelagic fish species, followed by cephalopods and crustaceans. Similar to other generalist fish species, ontogenetic dietary shifts (ODSs) indicated a partial transition towards larger prey items. However, the timing and magnitude of the ODSs varied between the two periods, reflecting life-history variations and adaptive adjustments to environmental changes. In comparison to 2010, the population’s mean body length (BL) increased in 2020, and the proportion of the population feeding on pelagic–neritic prey significantly increased. However, the δ¹⁵N values were lower, indicating that the shift in the ecological niche of preferred prey from demersal to pelagic–neritic was the primary cause of the decrease in trophic levels. In the future, we will conduct further quantitative research integrating the spatiotemporal data of both predators and prey to clarify the relationships between marine predators’ feeding behavior, trophic levels, and changes in prey community structure.

Benthic–pelagic coupling is a key approach to studying the structure and energy dynamics of shallow marine food webs. The movement and foraging patterns of consumers are major drivers of nutrient and energy distribution in ecosystems and are critical for maintaining ecosystem stability. To better understand the energy coupling of consumers between coastal marine habitats, this study employed a Bayesian mixture model using SC and SI data. By classifying functional groups based on taxonomy, morphological traits, and feeding ecology similarities, we constructed a trophic network and analyzed the changes in fish feeding patterns and the dynamics of benthic–pelagic coupling across environmental gradients. The results show that the primary carbon sources in the Beibu Gulf are phytoplankton, particulate organic matter (POM), and sediment organic matter (SOM), with phytoplankton contributing the most. Pelagic food subsidies dominate the food web. Small sized, abundant planktivorous and benthivorous fish act both as predators and important prey, transferring carbon and energy derived from both benthic and pelagic zones to higher trophic-levels. Larger, higher-trophic-level piscivorous fish serve as key energy couplers, preying on organisms from various habitats. Depth and chlorophyll–a (Chl–a) are the two key variables influencing the trophic structure of fish, with opposite gradient patterns observed for each. Along the depth gradient, fish exhibit clear adaptive foraging strategies. As water depth increases, fish tend to forage more within their specific habitat (either benthic or pelagic), with prey types continually changing, leading to a gradual reduction in the strength of benthic–pelagic trophic coupling. This study reveals the spatial resource utilization patterns and adaptive foraging strategies of fish in the Beibu Gulf, providing deeper insights into the structure and spatial variation of food webs. It also enhances our understanding of ecosystem responses to human pressures and global changes, offering valuable perspectives for predicting these responses.

The study of trophic relationships among closely related species plays an important role in deepening our understanding of the resource utilization characteristics, differentiation patterns, and population dynamics of co-occurring species in the same habitat. This research uses two congeneric fish species, Pennahia pawak and Pennahia anea, as examples. Based on a stomach content analysis and a carbon–nitrogen stable isotope analysis, a comparative analysis of their feeding habits and trophic niches is conducted. Additionally, a spatial niche analysis is employed to explore the coexistence and competitive mechanisms between these two closely related fish species. The results show that specialized feeding habits mitigate intraspecific competition as the population densities increase. The carbon and nitrogen stable isotope analysis reveals variations in the feeding habits and trophic levels with body length, indicating adaptive shifts in prey selection. Despite similar food resources, niche differentiation arises due to differences in dominant prey, facilitating coexistence. Differences in spatial niche further contribute to niche separation and coexistence. In resource-limited environments, species such as Pennahia utilize trophic and spatial niche differentiation to collectively exploit resources and achieve coexistence, with implications for fishery management favoring Pennahia resource occupancy capabilities.

Parupeneus biaculeatus, also known as pointed goatfish, belongs to the family Mullidae and is distinguished by its unique hyoid barbels containing sensory organs and a specialized foraging strategy, setting it apart from other fish species and making it an ideal model for studying biological adaptations and evolutionary processes. In this study, we present a high-quality chromosome-level genome assembly for P. biaculeatus using HiFi long reads and Hi-C data. The assembled genome has a total length of 657.58 Mb with a contig N50 of 9.35 Mb, organized into 22 chromosomes covering 99.34% of the genome. A total of 22,490 protein-coding genes were predicted, of which 98.37% were functionally annotated. Repeat analysis revealed that 34.83% of the genome consists of repetitive sequences. The genome assembly achieved an estimated completeness of 99.30% according to BUSCO analysis. This genomic resource provides new opportunities for understanding the biological traits, adaptive mechanisms, and evolutionary history of P. biaculeatus, and lays a foundation for further genomic studies within the family Mullidae.