Abstract:黄河口西南侧潮下带是渤海中国明对虾[Fenneropenaeus chinensis (Osbeck,1765)]重点增殖放流区。本研究于 2020 年 4—12 月采用定点设站结合生产调研对此海域内小岛河河口中国明对虾放流迁移进行跟踪调查, 研究增殖放流中国明对虾在放流早期迁移和入海后的分布特点及放流效果, 为优化放流技术策略、提高增殖放流效率提供实践参考。结果显示, 小岛河河口放流虾苗开闸后进入河道, 沿河道向外迁徙, 3~7 d 进入海域, 未发现对虾个体溯河上游; 不同大小的幼虾出闸、滞留放流通道时长不同, 小个体虾出池慢、滞留河道时间长, 大个体虾出池快、入海时间短; 潮下带开阔海区内, 仅在进入放流期后的 6—8 月出现中国明对虾, 且其数量逐月减少, 8 月开捕后中国明对虾分布数量和范围急剧减少至基本不出现。上述结果进一步证实黄河口西南侧潮下带区现存中国明对虾应来源于当年增殖放流群体, 建议在类似小岛河河口的开阔河口区, 增殖放流中国明对虾时选用相对大规格的虾苗, 以缩短开闸放流滞留时间, 获得更高放流效率。

Abstract:Large yellow croaker (Larimichthys crocea) is an important commercial marine fish endemic to China. It has long been ranked as one of four major seafood items in China. Unfortunately, overfishing, pollution of the ocean environment, and other factors have led to a severe decline in the natural resources of large yellow croaker. Enhancement release of large yellow croaker has been conducted since 1987 and is considered an effective fishery management measure. Although the traditional tagged method can indirectly assess the effect of enhancement release, it has numerous disadvantages, such as high cost, complicated operation, tags easily falling off, and fish body damage, which obstruct the effectiveness of the assessment. Furthermore, few strategies and methods have previously been proposed to precisely assess the effect of enhancement release of large yellow croaker. Through mixing “labeled” individuals with a known parental origin and the released population at a certain proportion, andidentifying “labeled” individuals through parentage identification after recapturing, microsatellite marker technology calculates the rate of recapture with a higher precision, and is becoming more popular in the enhancement release assessment. To assess the applicability of microsatellite markers in evaluating the effect of enhancement releasing programs in Larimichthys crocea, this study used a total of 8 microsatellite loci with rich polymorphism to conduct parentage identification for 100 parents of released offspring and 295 individuals recaptured from Guanjingyang sea water. In addition, this study also proposed a method for evaluating the recapture effect of large yellow croaker enhancement programs based on microsatellite molecular markers. In total, 78 alleles were detected at the 8 microsatellite loci. The values of observed heterozygosity and excepted heterozygosity were 0.511–0.939 (mean 0.764) and 0.643–0.897 (mean 0.781), respectively, and the polymorphism information content of the 8 loci was 0.587–0.883 (mean value was 0.751). The results of simulated analysis using Cervus 3.0.7 software showed that the combined exclusion probability of individuals at the 8 microsatellite loci reached 99.99% or more with a confidence level greater than 95%. Among the 190 large yellow croakers recaptured from Guanjingyang sea water in July, only five were identified as the offspring of the 100 released parents, accounting for 2.63% of all recaptures. This study estimated that the proportion of the large yellow croaker from released individuals to the recaptured ones should be approximately 60.53% in July. The recapture rate of large yellow croaker released by Fufa company was around 0.0038% in July, while the marked individuals failed to be detected in the recaptured samples in August and September. The recapture rate of 0.0038% is lower than that of the traditional tagged release. Compared with traditional tags that have visible external-scale tags to assist with identification and recapture by fishermen, it was difficult to include the internal markers in the statistics, as the captured individuals were not detected by visual identification. Microsatellite markers can efficiently and “autonomously” implement numerous permanent carrying markers based on genetic characteristics, and will not damage the marked individuals. Therefore, the proportion of released individuals to recaptured samples, which was calculated through the microsatellite method, is closer to the real data as opposed to traditional tagged release calculations. All the marked individuals detected in this study were recaptured in water with a slow current on both sides of Guanjingyang, which further confirmed that Guanjingyang is a suitable feeding ground for large yellow croaker juveniles. Nevertheless, this study also found that no marked individuals were detected in August and September. This could be attributed to the small proportion of recaptured individuals and the wider range of release of the population at that time. This study provides a new method for assessing the effect of stock enhancement, and affirms that enhancement release can restore the wild stock of large yellow croaker to a certain extent.

Abstract:In order to breed the all-female largemouth bass (Micropterus salmoides) population, 15-day old largemouth bass, with an average length of (15.1±0.09) mm, were fed dietary supplements containing 0 (MT0), 50 (MT50), and 100 mg/kg (MT100) 17α-methyltestosterone (MT). After continuous feeding for 60 days, the effects of MT on the growth, sex differentiation, hormone levels, and gene expression variations in largemouth bass were analyzed. The body lengths and weights of largemouth bass in the MT50 and MT100 groups were significantly lower than those in the MT0 group (P＜0.05). The male sex ratio in both MT50 and MT100 groups was 100%, which was significantly higher than that in the MT0 group (45%) (P＜0.05). Histological sections of the gonads indicated that the gonadal structures of MT-induced physiological males were similar to those of wild-type males. The concentration of estradiol in the physiological males of the MT50 and MT100 groups was significantly lower than that in the wild-type females of MT0 group (P＜0.05), while the concentration of testosterone in physiological males of the MT50 group was significantly higher than that in the females of MT100 and MT0 groups (P＜0.05). Additionally, compared to the wild-type females, the expressions of Dmrt1 and Gsdf were upregulated, while the expressions of Foxl2 and Cyp19a1a were downregulated in the gonads of physiological males in the MT50 and MT100 groups. In conclusion, dietary supplementations of 50~100 mg/kg MT could effectively induce the 15-day-old female largemouth bass sex-reversal into physiological males. This study establishes a physiological male induction method and provides valuable information for the breeding of all-female largemouth bass population.

Abstract:Learning and memory play important roles in species obtaining new foraging skills and food preferences. In order to study the influence of learning and memory pathways on the regulation of feeding in Chinese perch Siniperca chuatsi, an overexpression vector of learning and memory related genes c-fos and zif268 was constructed, and pcDNA3.1- EGFP was chosen as the reporter plasmid and transferred into Chinese perch brain cells by electroporation. The optimal electroporation conditions were determined by testing the transfection efficiency with different voltages, plasmid amounts, transfection times, and numbers of shocks. The results showed that learning and memory overexpression vector pcDNA3.1-c-fos-EGFP, pcDNA3.1-zif268-EGFP was successfully constructed. The maximum electroporation efficiency was achieved under the following conditions: in a 0.2 cm electroporation cuvette containing brain cells (1×106 /mL), electric voltage 240 V, pulse time 5 ms, 6 μg of plasmid, one electric shock, and transfection time of 48 h. We demonstrated that pcDNA3.1-EGFP was successfully transfected into Chinese perch brain cells in vitro. The mRNA expression levels of the appetite genes agrp, pomc, mch, npy were detected after overexpression of learning and memory genes. After overexpression of the c-fos gene, the mRNA expression of the appetite genes pomc and mch was significantly higher. After overexpression of the zif268 gene, there were no significant changes in the mRNA expression levels of the agrp, mch, npy and pomc genes in vitro. In summary, the results confirm that social learning can promote the acquisition of feeding habits in Chinese perch through the c-fos signaling pathway. As a transcription factor, c-Fos is likely to regulate the expression of appetite genes pomc and npy.

Abstract:Hypoxia is one of the main environmental stress factors affecting the growth, reproduction, and survival of fish in aquaculture. In addition to the antioxidant defense system, the mechanism of hypoxia tolerance in fish also includes many regulatory factors that play an important role in hypoxia signal transduction. The calcium-sensing receptor (CaSR) is a transmembrane receptor belonging to the G-protein-coupled receptor (GPCRs) superfamily, and is widely conserved in mammals, fish, and other vertebrates. CaSR can participate in a variety of important physiological processes by regulating different signal pathways under the stimulation of Ca²⁺ and other agonists. Apoptosis is an important physiological activity in most organisms, and under normal conditions it promotes the development of the organism and helps maintain homeostasis. Oxidative stress induced by hypoxia can induce cell apoptosis. It was found that hypoxia upregulated the expression of CaSR, and increased CaSR promoted intracellular calcium overload, which induced endoplasmic reticulum stress, and could affect cell apoptosis genes in specific pathways, leading to downstream apoptosis. However, the regulation of CaSR on cell apoptosis under anoxic conditions is primarily observed in mammals and has rarely been reported in fish. The aim of this study was to investigate the characteristics of the CaSR gene and its regulatory mechanism involved in apoptosis during hypoxia stress in Genetically Improved Farmed Tilapia (GIFT). The cDNA full-length sequence of the CaSR gene of GIFT was cloned by RT-PCR. Quantitative real-time PCR (qRT-PCR) was used to analyze the expression pattern of CaSR in different tissues, and further detected expression changes in CaSR and the mRNA of other apoptosis-related genes in the liver under hypoxic conditions (0.55 mg/L). Finally, ELISA was used to detect changes in activities of antioxidant enzymes in the liver, while morphological changes and apoptosis in the liver were observed by HE and TUNEL staining, respectively. The results showed that the cDNA full-length sequence of the CaSR gene in GIFT was 3265 bp in length, including 21 bp at the 5′-UTR, 421 bp at the 3′-UTR, and a 2823 bp open reading frame (ORF) encoding 940 amino acids. The predicted protein structure contained a seven-transmembrane domain unique to the GPCRs superfamily. Multiple sequence comparisons of CaSR proteins indicated that CaSR has the highest similarity with the corresponding protein in tilapia. CaSR gene mRNA was found to be expressed in nine tissues, with the highest expression in muscle, followed by kidney. Hypoxic stress could lead to structural damage of liver and promote apoptosis of liver cells. Compared with the control group (5.0 mg/L), hypoxic stress could enhance the activity of SOD, CAT and GSH-Px antioxidant enzymes and maintain them at high levels, and could also significantly upregulate the expression of CaSR mRNA and cause mRNA expression changes in Bcl-2, Caspase-3, and P53, all of which are apoptosis genes. The results suggest that hypoxic stress could induce oxidative stress and cause damage in the tissues of GIFT, and that activated CaSR might participate in the process of hypoxia signal transduction through mediating Ca²⁺ to affect the expression of key genes in the apoptosis pathway under oxidative stress, thus leading to the apoptosis of fish hepatocytes.

Abstract:In the commercial production of Litopenaeus vannamei, the reproductive performance of female shrimp and the development of larval offspring have been used as important indicators to measure the quality of shrimp. In order to evaluate the reproductive performance and larval development of different strains of Litopenaeus vannamei, 103 families were constructed by selecting 90 wild female shrimp, 166 female shrimp of strain P and 115 female shrimp of strain S under the same culture conditions. There were 56 wild population families, 28 P families, and 19 S families. The experiment lasted for 30 days. Reproductive parameters such as mating rate, spawning rate, hatching rate, metamorphosis duration, and survival rate were recorded for each female shrimp. The results showed that compared with the P and S strains, the wild population had significantly more desirable mating and hatching rates. In terms of female spawning performance, the spawning volume of the P strain was significantly lower than that of the other two strains (P＜0.01), and the spawning cycle was significantly higher than that of the other two strains (P＜0.01). In terms of larval development, the wild population showed certain advantages in terms of larval survival rate and metamorphosis duration. By analyzing the correlation between reproductive traits of Litopenaeus vannamei, it was found that there was a significant positive correlation between body weight and egg number in all three strains (P＜0.05). The correlation coefficients between body weight and egg number of the wild population, P, and S strains were 0.364, 0.278, and 0.553, respectively. In addition, this study also found that the hatching rate of fertilized eggs of Litopenaeus vannamei was significantly negatively correlated with duration of metamorphosis (Z_Ⅰ→P₁) (P＜0.05), and the correlation coefficient was –0.211 which indicated that the higher the hatching rate of fertilized eggs, the shorter the metamorphosis development time of the larvae. The results showed that the breeding performance of females of different strains of Litopenaeus vannamei carry significant potential for manipulation. During the process of selecting parental shrimp strains with high breeding performance, it is possible to select according to the reproductive capacity of female shrimp and the development of larval offspring.

Abstract:为掌握凤鲚(Coilia mystus)早期资源在长江口的时空分布特征, 于 2019 年 5—10 月在长江口沿岸水域设置 10 个调查站点, 对凤鲚的仔、稚鱼及其环境因子进行逐月采样, 统计分析了凤鲚的体长、发育期及丰度等数据, 研究了凤鲚在长江口的主要繁殖时间及早期个体分布情况, 并利用 GAM 模型分析了丰度分布与环境因子的相关性。结果表明, 5—10 月是长江口凤鲚的主要繁殖期, 其中 5—8 月为繁殖盛期。长江口北支的东旺沙-北八滧-启隆乡沿岸水域为凤鲚仔稚鱼主要分布水域, 为长江口凤鲚的重要育幼场。GAM 分析结果表明, 长江口凤鲚仔稚鱼的分布主要受盐度、温度和溶解氧的影响, 3 个环境因子均对凤鲚仔稚鱼丰度的影响显著(P＜0.05), GAM 最优模型偏差解释率为 65.50%。凤鲚仔稚鱼的最适盐度在 5~12, 温度在 20~28 ℃时相对适宜, 凤鲚仔稚鱼生长适宜的溶解氧为 5.2~8.0 mg/L。

Abstract:Small yellow croaker, Larimichthys polyactis is one of the most important fishery resources in China. The phenotypes of different geographical groups are influenced by their migration patterns and may exhibit adaptive changes. To explore the morphological differentiation of small yellow croaker in different geographic populations, the reproductive and non-reproductive populations in the south Yellow Sea and the south-central East China Sea were used as the research objects. The analysis methods t-test, principal component analysis and the difference coefficient were used to systematically analyze 31 phenotypic traits of the small yellow croaker populations. The results indicated that the phenotypic traits of the south Yellow Sea population and the south- central East China Sea population vary widely. The average coefficients of variation during the reproductive period were 7.77% and 6.48%, respectively, and the coefficients of variation during the non-reproductive period were 8.65% and 7.62%, respectively. The variation intensity of the south Yellow Sea population was higher than that of the south-central East China Sea population, and the difference coefficient was primarily measured on the horizontal axis. Significant differences were detected between 15 traits in the reproductive periods and 16 traits in the non-reproductive periods (P＜0.05). There were significant differences among 7 traits in both periods, while the differences of these traits remained relatively stable within the population. The results of principal component analysis indicated that the cumulative contribution rate of the four principal component variances during the reproductive period was 48%, and the scores of PC2 and PC3 reached extremely significant levels (P＜0.01) when detecting population difference, and the traits with higher factor loading were primarily head, dorsal fin, anal fin, and abdomen. The cumulative contribution rate of the four principal component variances in the non-reproductive period was 46.61%, and the scores of PC1 and PC2 reached extremely significant levels (P＜0.01) when detecting population difference. The traits with higher factor loading were primarily head, body height, dorsal/pelvic fins, and anal fin length. The head and trunk traits of the two populations could be differentiated, as the dorsal and anal fins were longer and the upper margin and abdomen were shorter in the south-central East China Sea group than in the Yellow Sea group. This morphological variation may be attributed to the specialization of phenotypic traits induced by migratory life history strategies. The results of this study support the theory that migration behavior and complex habitats improve environmental adaptability, and aid in improving our understanding of the ecological characteristics and evolutionary trends of species.

Abstract:Engraulis japonicus is a small warm-water pelagic fish commonly found along the coast of China. It is mainly distributed along the coasts of the East China Sea, the Yellow Sea, and the Bohai Sea, which are regions with abundant resources. Unlike adult E. japonicus, which is commonly used in the bait breeding market, juvenile E. japonicus can be dried and processed into a delicious and nutritious food, which has a higher market value. When E. japonicus spawns from April to June, fishermen along the coast of Zhejiang use nets and bag seines to catch juvenile E. japonicus. In 2018, the closed fishing season in the East China Sea begins from May 1 instead of June 1. In order to develop and utilize fishery resources rationally, the Ministry of Agriculture and Rural Affairs implemented special fishing concessions for this fishery, and local fishery administrative departments introduced and implemented a scientific observation system for this fishery. This study aimed to analyze the quantitative distribution of juvenile E. japonicus and its relationship with environmental factors. Scientific observation was conducted from April to June 2019 and the fishing activities of juvenile E. japonicus were recorded. The environmental factors were selected using Pearson’s correlation analysis to determine whether they were significantly correlated and to verify that the variables in the model were independent. Thereafter, the best model was determined by a minimum Akaike information criterion (AIC). The results indicated that the relative abundance of juvenile E. japonicus exhibited monthly variations, with the highest relative abundance in May and the lowest in April. GAM analysis revealed that the main factors influencing the resource density and distribution of juvenile E. japonicus were latitude, salinity, chlorophyll and dissolved oxygen along the Zhejiang coast. There was a multi-peak nonlinear relationship between the resource density of juvenile E. japonicus and the latitude, salinity at 0.5 m water depth, and dissolved oxygen at 0.5 m water depth. There was a positive linear relationship between chlorophyll at 0.5 m water depth and the resource density of juvenile E. japonicus. The results of this study provide a basis for the special concession fishing management of juvenile E. japonicus along the Zhejiang coast, and also provide a reference for resource assessment and study of adult E. japonicus.

Abstract:Gender and age are important biological characteristics of Oratosquilla oratoria, and may affect the habitat distribution and the responses to crucial environmental factors. In order to study the role of these biological characteristics in influencing its spatial distribution and the relationships with environmental factors, we developed the BP neural network models to predict the distribution of O. oratoria based on the data collected from the Shandong offshore trawl survey in May 2017. The samples of O. oratoria were classified according to their gender and age, and the relative biomass of females/males and individuals of current/non-current year were used as the response variables in the model to compare the differences in spatial distribution and environmental adaptability of different genders and ages. The results showed that both female and male O. oratorias were mainly distributed in the coastal waters in spring. Meanwhile, the current-year individuals tended to be evenly distributed among survey stations, whereas the non-current individuals tended to concentrate nearshore. Longitude, surface temperature, surface salinity and water depth were selected as the key environmental factors that had important effects on relative biomass of O. oratorias, according to the stepwise selection method. The relative biomass of female O. oratorias is higher than that of male, within the longitude range of 120.5°E–121.5°E and within the range of high water salinity; meanwhile, relatively low temperature and water depth favored male more than female. At the same time, the non-current-year individuals were more suitable to the changes of key environmental factors. The current-year individuals were more suitable to the low longitude than the non-current-year individuals, but were poorly suited to higher longitude and shallow water depth. We compared the differences of spatial distribution among genders and ages, and analyzed the suitability of environmental factors and the impact of biological characteristics of O. oratorias, in order to provide references for the protection of O. oratorias habitat and the rational utilization of resources.

Abstract:Exploring the synchronization of species habitat changes within an area is beneficial to the effective utilization and management of multiple associated species resources. In this study, we used fisheries and environmental (including sea surface height anomaly (SSHA), sea surface salinity (SSS), and 400 m water layer temperature (Temp_ 400 m) data on Dosidicus gigas in the autumns of 2011–2016, and fisheries and environmental (including sea surface temperature (SST), mixed layer depth (MLD), and 400 m water layer temperature (Temp_ 400 m) data on Trachurus murphyi in the autumns of 2013–2016 to construct habitat models with different weights. The optimal habitat models were selected and validated by data from 2017. Based on the highest performing model, the habitat suitability indices of Trachurus murphyi and Dosidicus gigas were predicted from 1950 to 2017, with differences in habitat changes between the species further examined under different ENSO events. The results showed that the optimal model of Trachurus murphyi and Dosidicus gigas could accurately predict their potential distribution. During the El Ni?o years, the sea surface temperature was higher, the sea surface height decreased from northeast to southwest, the mixed layer depth was shallow, and the sea surface salinity concentration in the north of Chile were higher than those in the South; the species distribution results showed that suitable habitats for Trachurus murphyi significantly increased and the gravity center of the optimal HSI moved westward, while suitable habitats for Dosidicus gigas decreased and the gravity center of the optimal HSI moved southeast. During the La Ni?a years, sea surface temperature was lower, the sea surface height increased from northeast to southwest, the mixing layer depth was increased, and the sea surface salinity was similar to that during El Ni?o years, though the difference was not significant; under tHSI climate conditions, suitable habitats for Dosidicus gigas increased significantly in a latitudinal direction and the gravity center of HSI moved northeastward, while the suitable habitats for Trachurus murphyi decreased significantly in a southwesterly direction and the optimal HSI weight was heavy, indicating a core habitat shifts to the southeast. Our findings suggest that variations in the suitable habitats of Trachurus murphyi and Dosidicus gigas under different ENSO events may be related to current distributions in the Southeast Pacific Ocean and prey biomass prey.

Abstract:We investigated the uptake and elimination of cadmium (Cd) and explored the effects of calcium (Ca) on Cd accumulation in Portunus trituberculatus using a two-compartment model. The Cd exposure concentrations were 1 μg/L, 5 μg/L, and 50 μg/L, respectively. We determined the uptake rate constant (k₁), elimination rate constant (k₂), bioconcentration factor (BCF), and biological half-life (B_1/2) using the two-compartment model with non-linear curve fitting. The results showed that the BCF of Cd in hepatopancreas tissue was significantly higher than that in muscle tissue. Both BCF and k1 in hepatopancreas tissues increased with the increase of Cd concentration in water, and the BCF of Cd in hepatopancreas tissue was 12.16, 112.77 and 260.11, respectively. The uptake rate constant (k₁) and elimination rate constant (k₂) in muscle tissue increased with the increase of Cd concentration in water, while the BCF of Cd in muscle tissue from the low to high concentration group was 1.85, 2.45, and 1.97, respectively. The target hazard quotient (THQ) was used to assess the possible health risks to the hepatopancreas and muscle of P. trituberculatus. The results showed that THQs differed in these two tissues; when the exposure concentrations were between 1 μg/L and 50 μg/L, the THQs of Cd in muscles were less than 1; however, the THQs of the hepatopancreas were ＞1 except at 1 μg/L. The results indicated that Cd accumulation in P. trituberculatus muscle posed no significant health risk, but there were serious health risks associated with Cd accumulation in the hepatopancreas unless the Cd exposure concentrations were ＜1 μg/L. In addition, Ca can decrease the accumulation of Cd in the hepatopancreas and muscle of P. trituberculatus, and promote the elimination of Cd from the hepatopancreas. Our findings help to improve the understanding of the control technology and consumption of P. trituberculatus.

Abstract:An investigation was conducted to determine spatial distribution characteristics of the monogenean parasite Dactylogyrus simplex (Bychowsky, 1936) on the gill filaments of the cyprinid freshwater fish Diptychus maculatus (Steindachner, 1866) in the Yarkand River Basin, Xinjiang, from May 2019 to June 2020 through three sampling surveys. The infection and spatial distribution characteristics of D. simplex were analyzed using statistical methods. A total of 3994 D. simplex parasites were detected in 325 D. maculatus individuals, with a total infection rate of 67.7% and an average infection abundance of 12.3±1.2. The infection rates of the left and right gills were 59.4% and 57.2%, respectively, with no significant difference in infection abundance between them (P＞0.05). For the gill slice, the average infection abundance of gill I (the gill slice closest to operculum) and gill II was significantly higher than that of gill IV (P＜0.01). With the growth of the host, the infection rate, abundance, and intensity of D. simplex first increased and then decreased, reaching the highest values at 13＜S≤18 cm body length; however, no significant difference in infection was detected among the body length groups (P＞0.05). The results indicated that D. simplex had no preference for size, left and right gill, or age of the host, but preferred to parasitize gills I and II on the gill slices. The D. simplex population exhibited an aggregated distribution gills of the host. The findings of this study provide basic data for fish parasitic disease prevention and control in the Yarkand River Basin.

Abstract:Chemokines are small cytokines with the molecular weights of only 8–10 kD, which can be expressed and secreted by macrophages, fibroblasts, T cells and B cells. Chemokines can be classified into constitutive and inducible types according to their physiological functions. Constitutive chemokines are usually involved in the migration and localization of lymphocytes, and immune surveillance, while inducible chemokines are secreted and then induced the migration of leukocytes to the inflammatory sites upon infection or inflammatory stimulation. According to the arrangement of the first two cysteines in their amino acid sequences, chemokines can be divided into four categories: the CXC subfamily, CC subfamily, C subfamily and CX3C subfamily. So far, there is no report on CX3C subfamily chemokines in fish, while a fish special CX subfamily has been identified. In addition to recruiting and activating leukocytes, fish chemokines also play important roles in immune and stress responses, embryogenesis, and angiogenesis. The present study reviewed the classification, identification, structure, expression, and functions of fish chemokines.

Abstract:Antarctic krill (Euphausia superba) has become a key species in the Antarctic ecosystem due to its abundant biomass and important position in the food web; therefore, its ecological role and feeding activities have garnered increasing attention. Antarctic krill is a typical phytophagous zooplankton, but also exhibits a certain degree of omnivorous behavior, as its feeding composition differs owing to the varying dominance of phytoplankton in the sea, thus having the potential to be a natural sampler of phytoplankton. The study of stomach content analysis has a long history, but those studies have significant spatiotemporal differences and the study areas were sparse and uneven with regard to circumpolarly. With the application of emerging approaches in the study of feeding habits, stomach content analysis has lacked necessary attention in recent years, due to being time-consuming, labor-intensive, and requiring a high-level of professional knowledge. However, as a direct way to examine the short-term feeding activity of Antarctic krill, the limitation of this single approach could be overcome by combining the traditional method, i.e. stomach content analysis, with lipid biomarker analysis, stable isotope analysis, PCR, and other emerging methods. Such practice will provide more accurate and comprehensive data on the feeding ecology of Antarctic krill for future studies. This paper summarized and concluded the research status of the stomach contents of krill, methods and applications, major gastric species, and seasonal, sea area, and ontogenetic differences, and further explored the potential of stomach content analysis of krill as a natural sampler of phytoplankton in the Southern Ocean. The results provide new scientific ideas for further study of the trophic dynamics of the Antarctic marine ecosystem.