中国刀鲚研究现状、未解科学问题与创新实用解决思路：文献及日本鳗鲡产卵场研究比较

… migratory patterns of Osbeck’s grenadier anchovy Coilia mystus in the Yangtze estuary and the estuarine tapertail anchovy Coilia ectenes … The present study suggests that the spawning …

Anadromous Coilia ectenes was sampled from the Yangtze estuary at Chongming and two of the primary upstream spawning grounds at Jingjiang and Anqing in April, May, June and August 2006. Gonad development was analyzed for females. In April, fish were collected in the estuary and at Jingjiang, but not at Anqing. No female was mature (gonad at stages IV or V) at either location. In May, 45% of the females were mature in the estuary, 9% at Jingjiang and 5% at Anqing. In June, 86% were mature in the estuary, 83% at Jingjiang and 7% at Anqing. In August, C. ectenes was absent at Jingjiang. No female was mature in the estuary, and all females were mature at Anqing. Absolute fecundity (AF) increased significantly with standard length (SL) by a power function AF=2.27×10−6×SL2.67(r2=0.57, n=48, P<0.05). Mature females in the estuary were smaller than those at Jingjiang and Anqing. Conservation of spawners in the upstream spawning grounds is important because they have a size-related fecundity advantage over the smaller spawners in the estuary.

In order to elucidate the transformation rule of fatty acids in body of female Coilia nasus during the spawning migration process, the fatty acid content and its components were …

… nasus in the Yangtze River during spawning migration process, the components and … and ovary of Coilia nasus were determined from three aspects of migration distance, ovarian …

… Adults migrate to the middle and lower reaches … ectenes are very similar in morphology to Coilia mystus. Both species distribute and spawn in the Yangtze Estuary with similar spawning …

… Mature individuals migrate upriver and spawn in the lower and middle reaches of … ectenes may also spawn in lakes adjacent to the Yangtze River, such as Poyang and Taihu Lakes, …

… Mature individuals migrate upriver and spawn in the lower and middle reaches of the Yangtze … ectenes may also spawn in lakes adjacent to the Yangtze River, including Poyang and …

… ectenes migrates from near ocean waters to freshwater areas every year during the spawning season, and the mature migrate upriver and spawn in the lower and middle reaches of the …

… To understand the seasonal migration of the anadromous Coilia nasus, we … for spawning migration in the estuary in spring and early summer and returned to the estuary after spawning …

Simple Summary The Japanese grenadier anchovy (Coilia nasus), a valuable anadromous fish that migrates up the Yangtze River to reproduce, is endangered due to severe overfishing. To aid its recovery, a comprehensive 10-year fishing moratorium is now in effect. To assess the population’s status during this critical period, we studied over 1100 individuals along their 2024 spawning migration route. Our research revealed significant differences between the sexes: females grow larger and live longer, likely a strategy to maximize reproductive output, while males mature earlier. Crucially, we discovered a clear pattern of size-dependent migration, where larger fish travel farther upstream to spawn. These findings underscore the importance of protecting upstream spawning habitats, as they support larger, more mature individuals. This study provides important baseline data for conservation managers to evaluate the effectiveness of the fishing moratorium and inform this culturally significant species’ recovery efforts.

The estuarine areas provide necessary spawning habitat, nursing habitat, and migratory for a variety of fishes and the environmental conditions are of significant heterogeneity. Coilia mystus is the key commercial fish that spawns in the Yangtze Estuary and the yield has declined sharply in the past 30 years. In order to understand the spawning habitat selection mechanism of C. mystus, the geographically weighted regression (GWR) model was applied to explore the non-stationary effect of environmental variables [e.g., the sea surface temperature (SST) and the sea surface salinity (SSS)] and geographical variables [e.g., the distance to the coast (DTC) and the depth (DEP) of water] on the egg density distribution of C. mystus. The data were derived from the spring and summer ichthyoplankton surveys carried out from 2019 to 2020 in the Yangtze Estuary, China. The GWR model results showed that the key variables in different seasons had spatial non-stationary effects on the distribution of spawning habitat of C. mystus, which were mainly caused by regional rise in temperature and saltwater intrusion of the South Branch. In the spring, the SSS, the DTC, and the DEP were the main impact factors and saltwater intrusion in the South Branch might lead to the trend that the spawning habitat moved further upstream to the Changxing Island. The SST was most important in the summer and the relatively lower SST was more crucial in the spawning habitat selection than the DTC and the DEP. The GWR model performed well in the study of C. mystus potential spawning habitat in the Yangtze Estuary. We recommend that more attention should be paid in regional variation of environmental factors to explore fish potential spawning habitat in the estuarine areas.

… River, which is the migration channel for Coilia nasus. Recent … May and June were the peak spawning months for C. nasus in … nasus spawning. It is speculated that the waters in Lvhua …

Coilia nasus is a typical anadromous migratory fish found in the lower reaches of the Yangtze River. Every year, C. nasus clusters offshore and swims upstream along the Yangtze River into the tributaries and lakes in the middle and lower reaches of the Yangtze River to breed. In this study, female C. nasus were collected as study subjects from the Chongming section of Shanghai, the Taizhou section of Jiangsu, and the Anqing section of Anhui. Their ovaries were used to examine tissue sections and investigate gene expression, including the follicle-stimulating hormone receptor (fshr), the luteinizing hormone receptor (lhr), kisspeptin-1 (kiss1), and forkhead box l2 (foxl2), which are related to reproductive development, while the serum levels of estrogen (including estradiol, E2) and progestins (including 17α,20β-dihydroxy-4-pregenen-3-one, 17α,20β-DHP) were also analyzed. Our results showed that, first, the growth period of the oocytes was small in stage II of ovarian development, in which both E2 and 17α,20β-DHP levels and gene expression were low. Then, in stage III, the growth period of the oocytes became large, and the yolk granules and oil droplets began to appear. Simultaneously, E2 and the expression of kiss1 and foxl2 were significantly elevated. Finally, stage IV was the period of a large amount of accumulation of nutrients in the oocytes, and 17α,20β-DHP levels and the expression of fshr and lhr were significantly elevated. These results enrich the theoretical study of ovarian development in the natural population of C. nasus, supplementing the biological basis of C. nasus reproduction and scientifically supporting the study of C. nasus population ecology and resource conservation.

… To investigate genetic structure and differentiation of four lake populations of Coilia ectenes, a total of eighty-one individuals … ectenes have not developed significant genetic structure. …

Coilia nasus are an important fish resource in the Yangtze River, and the Yangtze River Estuary is a crucial migration pathway for them. In this study, we used otolith microchemistry to analyze the strontium/calcium (Sr/Ca) ratios and Sr contents in the sagitta otolith of C. nasus from the south branch (SB) and north branch (NB) of the Yangtze River Estuary and obtained the diversity of migration patterns and spawning ground distribution for C. nasus. The results indicate that C. nasus from both branches include two types of habitat history: freshwater (F)–brackish water (B) (Type I) and F-B seawater (S) (Type II), with Type I being dominant at 62.50% in both branches. The C. nasus from the SB comprise six migration patterns, while that from the NB has seven migration patterns. The C. nasus from both branches hatch in F habitats. At the time of capture, the C. nasus from the SB predominantly remain in F, accounting for 62.5%, while C. nasus from the NB primarily stay in B, accounting for 87.5%. Throughout the migration process, C. nasus from both branches switch between different habitats, with C. nasus from the NB exhibiting more frequent transitions between F and B, showing a greater reliance on the estuarine brackish habitat. The radius of the first blue region near the core (Lf) and freshwater coefficient (Fc) of the otolith for C. nasus from both branches are divided into three groups: long-distance freshwater dependence (LD), medium-distance freshwater dependence (MD), and short-distance freshwater dependence (SD), with the LD only appearing in the SB, while the NB is primarily represented by MD. There is a correlation between the differences in Lf among different groups of C. nasus and the differences in the distance from the spawning grounds of C. nasus in different sections of the Yangtze River to the estuary (DYRE), reflecting the distribution pattern of C. nasus spawning grounds in different sections of the Yangtze River. This study provides theoretical guidance for the protection of migration pathways and maintenance of spawning grounds for C. nasus, which have significant practical value in the precise management of C. nasus resources in the Yangtze River Estuary.

To reconstruct the life history of Coilia nasus in the Shandong section of the Yellow River, an electron probe microanalyzer (EPMA) was employed to analyze the Sr and Ca values in the otoliths of 12 individuals collected from Pangkou Bay. The results indicated that the life history of C. nasus is complex and diverse, the individuals in this study can be categorized into five distinct patterns. Pattern I includes P1, P2, P3, and P4, whose life history tracks indicate hatching in brackish water near the Yellow River estuary; after approximately 1 year, they begin to migrate along the Yellow River to Pangkou Bay for spawning. Pattern II encompasses P9, P12, and P13, which hatch in freshwater habitats; as these individuals grow, there is an abrupt change from Stage 1 to Stage 2, but their life history does not extend to marine habitats with high Sr/Ca values, and after about 1 year, they migrate along the Yellow River to Pangkou Bay for spawning. Pattern III includes P6, P8 and P10, which also hatch in freshwater habitats and experience abrupt changes; however, the mapping analysis reveals a large area of red and yellow concentric rings, indicating a history of seawater habitat and an extension of their life history to Laizhou Bay. Pattern IV is represented by P11, whose living environment was relatively stable, with no significant abrupt changes and no migratory life history characteristic, which presumed to be a freshwater settlement type that passively entered the Yellow River due to the flood season of Dongping Lake. Pattern V is exemplified by P7, whose analysis results show two trips to freshwater and brackish water habitats, both of which produced significant pattern changes which indicates that it conducted a reproductive migration at the first instar, swam to the Yellow River estuary after spawning, and migrated to Pangkou during the reproductive period of the following year to lay eggs until it was captured. This study demonstrates that most individuals in Pangkou Bay are of the migratory type. Compared with the sexual maturity of individuals in other waters of the Yangtze River basin, Pangkou Bay is identified as an important spawning ground for the migratory type of C. nasus.

… ectenes taihuensis lacks anadromous behavior, and can independently grow and … to investigate the genetic diversity and population structure of C. ectenes taihuensis. Sixty-eight …

The genetic structure and genetic variation of three populations of Coilia ectenes taihuensis in … mean nucleotide diversity(π) of the populations of different lakes are 0.9646 and 0.0097, …

… attributed to between population differences, and lack of genetic structure. Our results supported that C. e. taihuensis is a geographical population of C. ectenes; their difference has not …

… These polymorphic microsatellites will provide useful tools for the study of genetic diversity and population structure of genus Coilia. This knowledge will help the development of …

… ectenes for use in breeding programs, elite microsatellite-… applied to genetically detect wild populations. Out of 92 randomly … and genetic structure of a wild population collected from the …

… ectenes fishery resources, some scientists have studied the population structure and variation of C. ectenes using morphological, biochemical and molecular markers (Yuan et al. …

… We found very low levels of genetic partitioning, with less than 0.1% of the total variation attributed to between population differences, and lack of genetic structure, thus supporting the …

… The changes of the catch and age structure of lake anchovy and the relationship with environ⁃ mental variation in Lake Taihu. Journal of Fisheries of China, 2008, 32(2): 229⁃235. [13] …

… Coilia ectenes, also called Coilia nasus, is an ecologically … ectenes has declined dramatically in the recent decades. Thus… ectenes based on the transcriptome database and …

… and between populations is referred as the genetic population structure of the species. Coilia … ectenes were successfully utilized in stock structure analysis of C. mystus (Ma et al. 2011), …

… freshwater populations. Therefore, it is important to understand the population structure of C. … Reconstructing habitat use of Coilia mystus and Coilia ectenes of the Yangtze River estuary…

… populations in Northwestern Pacific. We used mtDNA control region to assess the factors in shaping the genetic structure of Japanese grenadier anchovy, Coilia … population structure …

Coilia nasus is found in the Yangtze River and the coastal waters of China, Korea, and Japan. Two ecotypes (anadromous and freshwater-resident populations) are distributed throughout the Yangtze River basin based on their ecology and behavior, but relatively little is known about the population structure of this species. Analysis of short interspersed element (SINE) insertions, which vary among individuals, has been acknowledged to provide a unique way to study population divergence. SINEs isolated from C. nasus were characterized, and this enabled analysis of the SINE insertion pattern in six populations distributed throughout the Yangtze River basin. In all populations, four SINE loci displayed individual polymorphism, and two SINE loci showed a stochastic loss in all individuals of two resident populations. The correlation between genetic and geographic populations indicated a degree of genetic isolation in this species. In contrast with Coilia grayii and Coilia mystus, two SINE loci appeared only in C. nasus. Sequencing analysis indicated that the high insertion variability of SINEs was attributed mainly to the tails, which contained various repeat copies. The results in this study will be useful for sustainable management of fishery resources and conservation of this species.

Simple Summary Coilia nasus is a migratory fish species with high nutritional and economic value, and naturally inhabits the middle and lower reaches of the Yangtze River and offshore China. Since the 1970s, the continuous deterioration of the habitat environment and continuous high-intensity fishing have led to a sharp decline in the germplasm resources of the Coilia nasus, which has been listed in the Red List of Threatened Species by the International Union for Conservation of Nature. Artificial farming has gradually become an important way to protect and utilize the germplasm resources of Coilia nasus, but limited germplasm sources and unscientific breeding strategies have put the germplasm resources and genetic diversity of Coilia nasus at risk, which limits its resources protection and utilization. The aim of this study was to assess the germplasm resources of Coilia nasus by analyzing the genetic diversity and genetic structure of its natural and farmed populations. In conclusion, the present study provides a reference for germplasm conservation and breeding strategy optimization in Coilia nasus, and contributes to the healthy development of Coilia nasus aquaculture. Abstract Coilia nasus is a threatened migratory species in the Yangtze River Basin. To reveal the genetic diversity of natural and farmed populations of C. nasus and the status of germplasm resources in the Yangtze River, the genetic diversity and structure of two wild populations (Yezhi Lake: YZ; Poyang Lake: PY) and two farmed populations (Zhenjiang: ZJ; Wuhan: WH) of C. nasus were analyzed using 44,718 SNPs obtained via 2b-RAD sequencing. The results indicate that both the wild and farmed populations had low genetic diversity, and germplasm resources have undergone varying degrees of degradation. Population genetic structure analyses indicated that the four populations may have come from two ancestral groups. Different amounts of gene flow were identified among WH, ZJ, and PY populations, but gene flow among YZ and other populations was low. It is speculated that the river–lake isolation of Yezhi Lake is the main cause of this phenomenon. In conclusion, this study revealed that genetic diversity reduction and germplasm resource degradation had occurred in both wild and farmed C. nasus, suggesting that conservation of its resources is of great urgency. This study provides a theoretical basis for the conservation and rational exploitation of germplasm resources for C. nasus.

… omnivorous fish called lake anchovy, Coilia ectenes taihuensis. The main purposes were to … Guo, LG, Studies on fisheries ecology in a large euthrophic shallow lake, Lake Chaohu, …

… the ecological patterns and intra-interspecific variations in Coilia. Furthermore, it contributes to the application of ecological … ectenes taihuensis, was sampled from Taihui Lake (TH). …

… markers will be useful in studies on population genetics, conservation genetics, and fishery management and in the construction of genetic linkage maps of C. ectenes and C. mystus. …

… ectenes transcriptome and polymorphic microsatellite loci obtained in this study will facilitate further studies on the population genetic management and conservation of C. …

… ” of Coilia nasus (which has declined sharply) and Coilia … Here, we studied the genetic structure of these species by … analysis showed two distinct genetic clusters that corresponded to C. …

The estuarine tapertail anchovy Coilia nasus is distributed throughout the Dayang River. However, the life history and habitat use of this fish remain unknown. Here, the microchemistry patterns of Sr and Ca in 23 otoliths collected from the lower reaches of the Dayang River were analyzed using an X-ray electron probe microanalyzer. The anchovies were divided into two patterns: (1) with low Sr/Ca ratios (<3.0) and a single bluish Sr concentration map, indicating that it only experienced a freshwater habitat during its whole life, and (2) with Sr/Ca ratios fluctuating between low and high (>3.0) phases and Sr concentration maps showing various colors, including blue, green, yellow, and red, from the core to the edge of otoliths, whose larvae hatched in freshwater and spent their first winter in brackish or sea waters. The juveniles then stayed in estuarine water areas for further growth and feeding until sexual maturity, when the mature adults returned to the spawning grounds in the river. The co-existence of freshwater residents and anadromous C. nasus in the Dayang River has been studied for the first time, and its possible spawning ground was discovered. These findings provide essential information to effectively protect this species and guide its rational, sustainable utilization.

Loss of valued diadromous fishes and their habitats is one of the most critical problems in aquatic habitat connection and resource management worldwide. In China, the Poyang, Dongting, Gaobao, Gucheng, Dongping, and Taihu lakes were known to be historical migratory spawning sites of the anadromous estuarine tapertail anchovy Coilia nasus. However, except for Poyang Lake, it is believed that these lakes are no longer used by anadromous fish owing to overfishing, water pollution, and loss of connectivity. To confirm this assumption, we used an electron probe microanalyzer to analyze elemental strontium (Sr) and calcium (Ca) microchemical patterns in the otoliths of C. nasus individuals sampled from these lakes, in accordance with our previous analysis of the otolithic patterns of the same species sampled from habitat areas characterized by different salinity gradients. The results of line transect analysis of Sr/Ca ratios and Sr X-ray intensity maps of the otoliths indicated that all individuals from Dongting, Gaobao, Gucheng, Taihu, and Dongping lakes were characterized by a freshwater-resident life history. In contrast, individuals from Poyang Lake exhibited both freshwater-resident and anadromous life histories. The findings of this pilot study suggest that anadromous C. nasus can be found in Poyang Lake but are unlikely to be found in Dongting, Gaobao, Gucheng, Dongping, or Taihu lakes, despite these lakes being historical distribution areas or even spawning sites. This anchovy can possibly be used as a good model species for understanding the aforementioned global problem. Given that C. nasus is a commercially important species, restoration of its natural habitats and maintenance of their connections are recommended for its management and conservation.

… Reconstructing habitat use of Coilia mystus and Coilia ectenes of the Yangtze River estuary, and of Coilia ectenes of Taihu Lake, based on otolith strontium and calcium [J]. Journal of …

At present, the resources of anadromous fish in the world are drastically reduced and one of the solutions to promote its recovery may be to identify and protect its feeding grounds. To determine whether the feeding grounds of anadromous Coilia nasus in the Yangtze River are still in the sea area, the quantitative line analysis of Sr and Ca contents (Sr/Ca ratios) and the area distribution analysis of Sr content in the otoliths of C. nasus in three water areas (Poyang Lake, Yangtze River estuary and Shengsi Sea area) were carried out by electron probe microanalysis (EPMA) to analyze the habitat use and the migratory patterns of different estuarine C. nasus. These results showed that the Sr/Ca ratios of all otoliths fluctuated significantly. By comparison, it was found that C. nasus of Yangtze River might exist in the Shengsi Sea area, and the Shengsi Sea area might be one of the feeding grounds of migratory C. nasus. Therefore, it is urgent to carry out a comprehensive investigation on the distribution of related groups in the Shengsi Sea area and the influence of potential threat factors, such as fishing and harsh habitat, to effectively protect the resources and habitats of C. nasus in the Shengsi Sea area.

… applied to investigate the otolith microchemistry characteristics of 10 … Coilia mystus and Coilia ectenes of the Yangtze River estuary, and of Coilia ectenes of Taihu Lake, based on otolith …

… Otolith microchemistry was chosen in this study because the application of otolith chemical … The evidence on this was revealed by analyzing otoliths of C. nasus individuals from …

Otolith microchemistry are widely applied in the field of fish migration ecology. However, the extraction of otoliths … a nonlethal substitute for otoliths for effective microchemical “fingerprint” …

… Fluctuation of Sr/Ca in otoliths of Coilia nasus in the Yangtze River … Coilia mystus and Coilia ectenes of the Yangtze River estuary, and of Coilia ectenes of Taihu Lake, based on otolith …

… Coilia mystus and Coilia ectenes of the Yangtze River estuary, and of Coilia ectenes of Taihu Lake, based on otolith … This study, through otolith microchemical analysis, not only provides …

The habitat use and the migratory patterns of different estuarine tapertail anchovy Coilia nasus populations along the Chinese coast were studied by examining the environmental signatures of strontium and calcium in their otoliths using electron probe microanalysis (EPMA). The results showed that the life patterns were quite similar between the individuals from the Huanghe (Yellow) River and Changjiang (Yangtze) River and considerably different from those of the Qiantang River and Oujiang River. Most of the anchovies were typical anadromous fish, but several individuals were brackish–water residents. Our results also suggest that C. nasus may probably be a natal homing fish.

A recent study based on gonad histology revealed that the existence of the spawning grounds for Gray's grenadier anchovy (Coilia grayii) and Osbeck's grenadier anchovy (C. mystus) in the Min River Estuary, the largest in Fujian Province, southern China. Further confirming their natal sources and migratory patterns is essential to understand their life histories. We used otolith microchemistry to assess the origins and habitat uses of 23 C. grayii and 22 C. mystus, collected the Min River Estuary and the adjacent waters. The results showed that C. grayii spawned in both freshwater (n‍ = 14) and brackish water (n = 9), and C. mystus spawned mainly in brackish water (n‍ = 20) with minor in freshwater (n‍ = 1) and marine water (n‍ = 1). The migratory patterns of C. grayii (four types) and C. mystus (five types) were diverse, mainly exhibiting anadromous and semi-anadromous behaviors. The first migratory behavior of C. grayii and C. mystus occurred within the age of the first year. The findings have significant implications for fishery stock management of the Min River Estuary and its adjacent waters.

… Reconstructing habitat use of Cailia mystus and Coilia ectenes of the Yangtze River estuary, and of Coilia ectenes of Taihu Lake, based on otolith strontium and calcium [J]. Journal of …

Owing to the asynchronous deposition of trace elements between paired left and right otoliths within individual fish, researchers must consciously and uniformly use only single otoliths (especially the left one) for microchemical studies. To ensure reliability of unilateral otolith data for inferring the same habitat experiences of individual fish, this study focused on Coilia nasus as a representative case to validate whether the microchemical composition was consistent between left and right sagittal otoliths. Electron probe microanalysis was employed to determine microchemical profiles of Sr and Ca in both otoliths of 20 wild C. nasus specimens of the same age. At the individual level, Sr/Ca ratios in corresponding micro-regions (e.g., core and edge) of bilateral otoliths showed highly significant positive correlations, with approximately 92.59% of paired comparisons showing no significant differences at equivalent life-history stages, demonstrating that microchemical signals recorded by either otolith are highly consistent in both spatial distribution and elemental concentration levels. This study provides evidence of fundamental concordance in microchemical composition between bilateral otoliths within an individual, providing critical references on the methodological foundation for reliably using either the left or right otolith in future studies on otolith microchemistry of fish population connectivity, migration characteristics, and life history reconstruction.

The estuarine tapertail anchovy, Coilia nasus, is a migratory fish with high economic value in China. We collected fish from the Changjiang River (the Yangtze River) estuary, the Qiantang River estuary, and the southern Yellow Sea, and studied their relationships using otolith elemental and stable isotopic microchemistry signatures to assess the population connectivity of C. nasus. Results show that, in addition to Ca, other elements were present in the otolith core. The δ18O, Na/Ca, Fe/Ca, and Cu/Ca values of the Qiantang population were significantly higher than those of the others, whereas its δ13C and Ba/Ca values were found to be significantly lower. Otolith multi-element composition and stable isotope ratios differed significantly between the Qiantang and Changjiang estuary groups (p < 0.05); however, no difference was observed between the latter and the Yellow Sea group. Cluster analysis, linear discriminant analysis, and a self-organizing map strongly suggest possible connectivity between the fish populations of the Changjiang estuary and Yellow Sea, while the population of the Qiantang River estuary appears to be independent. Notably, results suggest a much closer connectivity between the fish populations of the Changjiang River and the Yellow Sea.

The Japanese grenadier anchovy Coilia nasus Temminck & Schlegel, 1846 belongs to the family Engraulidae of the order Clupeiformes. This species is widely distributed in China, Japan, and Korea and in Northwest Pacific Ocean. In China, C. nasus is found in the Bohai Sea, the Yellow Sea, the East China Sea, and the middle and lower reaches and the estuaries of some main rivers, such as the Liao River, the Yellow River, and the Yangtze River. The life history of C. nasus is diverse and it is found to have three main ecological types (i.e., anadromous migratory, freshwater resident, and freshwater landlocked), indicating its strong adaptability to different habitats. Because of its commercial importance in China, C. nasus has been heavily exploited for years. Due to the significant decline of the wild stocks and the degeneration of freshwater spawning grounds in its distribution region, C. nasus was listed in the IUCN Red List of Threatened Species as "Endangered" category in 2018.Currently, the exact distribution boundary of C. nasus to the southern limit of China is unclear. Based on the fishery surveys in the southern Zhejiang Province for the past 15 years, the adjacent waters of Ou River estuary in Wenzhou are the known southernmost distribution area for C. nasus. The distribution of C. nasus in Fujian waters, both freshwater and seawater was documented from 1960—2008; however, the sampled individuals were very rare. It is impossible to understand the habitat history and life history pattern of C. nasus using traditional fishery survey methods. In this study, three C. nasus individuals were collected by trawl net, set net, and gill net in Fuzhou and Ningde waters in 2017—2019 during various fishery surveys along the coastline of Fujian. To reconstruct the life history of C. nasus in Fujian waters, the X-ray electron probe micro-analysis (EPMA) approach was used to analyze otolith (sagitta) microchemistry patterns of the fish for the first time. Otolith microchemistry is an effective tool for revealing the anadromous pattern and the spatial and temporal distribution of fishes. The otolith Sr/Ca ratios are powerful indicators for identifying freshwater, brackish water, and seawater habitats throughout the life history of fish.The results of this study showed that the Sr/Ca ratios of the otolith core areas of all three C. nasus individuals were less than 3, and the core areas exhibited a blue pattern in the X-ray intensity maps of Sr content. Both results indicated that the three individuals originated from freshwater and hatched in freshwater habitat. Among the three individuals, the individual collected in Fuzhou waters was more dependent on freshwater at its early life stage and did not enter brackish water until it was almost 1-year-old. Combined with the sampling site and the adjacent water of Min River, it is deduced that it might have originated from the pure freshwater habitat of Min River. Two individuals collected in Ningde waters were less dependent on freshwater habitat at their early life stage. Combined with the sampling sites, i.e., the outer water of Sansha Bay, it is deduced that the two individuals from Ningde might have originated from the pure freshwater habitat of Jiao Brook in Ningde, Ou River in Wenzhou, or Min River in Fuzhou. According to the fluctuations of the Sr/Ca ratio from the core to the edge of the otoliths and X-ray intensity maps of Sr content through the otolith core, all three C. nasus individuals were confirmed to be typically anadromous ecological types. The habitat history of the only one C. nasus individual in Fuzhou was a freshwater-brackish type; its hatching and early life stage were also associated with freshwater habitat, and then it entered the brackish water habitat and traveled back and forth between brackish water and freshwater habitats to grow out until it was captured. The habitat history of the other two C. nasus individuals in Ningde was freshwater-brackish-seawater type; their hatching and early life stage were associated with freshwater habitat, and then they entered high salinity habitat and traveled back and forth between brackish water and seawater habitats for growth until captured. Moreover, we found that the higher salinity in the capture waters of the three C. nasus individuals did not correspond to the Sr/Ca ratio at the edge of the otoliths, indicating a certain time delay in otolith responding to the salinity of their most present living habitats.This study not only revealed the diversity of C. nasus life history patterns and habitat histories but also confirmed the current distribution of anadromous C. nasus in Fujian waters. Since February 2019, the Yangtze River, the most important habitat for C. nasus and many endangered fishes and mammals has initiated a new management measure, i.e., a 10-year fishing ban plan. However, there is still a lack of sufficient understanding of the distribution, the locations of spawning grounds and the population size of C. nasus in Fujian waters. Further studies on the key habitats of C. nasus such as spawning ground and ecological type are needed to formulate effective management measures for its natural resource conservation in Fujian waters.

… the life history of tapertail anchovy between its Coilia nasus and C. brachyg⁃ nathus which … to analyze the micro⁃ chemistry patterns of element Sr and Ca in otoliths of these two fishes …

Coilia grayii is the anadromous form of anchovy that is distributed in the East and South China Seas. It is a common fish species in the estuarine area of the Pearl River. Nevertheless, freshwater populations appear upstream in the Pearl River, but the migratory pathway has been mostly impeded by dam construction. Behavioral differences and constrained habitat within tributaries are suspected of promoting genetic divergence in these populations. In this study, we investigated the migratory behavior and genetic divergence of six populations of C. grayii fragmented by dams based on the otolith strontium/calcium (Sr/Ca) ratio, mitochondrial DNA, and microsatellite genotyping. All populations were in freshwater with low Sr/Ca ratios, except the estuarine population (Humen population) hatched in brackish water. Reduced nucleotide diversity corresponding to distance was observed. Populations from distant hydrological regions exhibited a decline in genetic diversity and a significant difference with the remaining populations after fitting the isolation by distance model. Pairwise fixation indices confirmed these results and moderate and significant differentiation was found between Hengxian site and downstream sites. Furthermore, STRUCTURE analyses revealed that all separated populations exhibited an admixed phylogenetic pattern except for individuals from the Hengxian locality. The upstream sites showed significantly increased resistance to gene flow from the estuarine population because of isolation by the dam. The results of the neutrality test and Bayesian skyline plots demonstrated complex demography—individuals’ experienced historical expansion and partial upper-dam populations had recently undergone a colonization, forming a new genetic structure. Accordingly, this study demonstrates differences in the migration pattern and genetic differentiation of C. grayii as a consequence of demographic history and current processes (habitat fragmentation and colonization).

… 1.2 总 DNA 提取 总 DNA 提取参照《分子克隆实验指南》[16]中 的酚-氯仿抽提方法进行.使用 1%的琼脂糖凝胶电 泳检测 DNA 质量, 并将浓度稀释至 5 ng. 1.3 PCR 扩增及序列测定 mtDNA Cyt …

The Pleistocene climate oscillations have been proven to have profound influences in the evolutionary processes of marine species and left significantly tractable footprints in genomes of marine fauna. However, such history remains unknown for the Japanese grenadier anchovy Coilia nasus, a relatively large fish found in marine, freshwater and brackish water. In order to provide insight into the phylogeographic pattern and historical demography of C. nasus, we employed the mtDNA D-loop and Cyt b as molecular markers to estimate the genetic variation among populations of C. nasus. We took samples from 18 populations throughout the distribution of C. nasus. Partial sequences of mtDNA D-loop (n = 424) and Cyt b (n = 129) were obtained. Four phylogeographic lineages were revealed by the mtDNA D-loop analysis. Frequency changes of the four lineages throughout the species’ distribution indicated limited genetic exchange among three major geographic regions. Patterns of isolation-by-distance were detected among the populations. Neutrality test, mismatch distribution, and network analyses consistently showed that all the four lineages had populations with relatively stable over time and then subjected to sudden expansion during the late-Pleistocene era (c. 20,000–75,000 years ago). The phylogeographic and demographic history of C. nasus was highly influenced by climatic fluctuations in the Pleistocene. Geographic isolation resulted from Pleistocene climatic fluctuations might have profound impacts on the distribution pattern of genetic variation of C. nasus. Our result also indicated that the population expansion event for C. nasus occured along with habitat continuous expansion during the inter-glacial period.

Abstract The estuarine tapertail anchovy (Coilia nasus) is a small anadromous fish mainly distributed in the northwest and western Pacific, extending southward toward Guangdong in southeastern China and northward to the Ariake Sound of southwestern Japan. This important commercial anchovy has suffered from population decline in both Japan and China, and the taxonomic status of the populations from Japan and China has been disputed. To ascertain the taxonomic status of the populations from Japan (C. nasus) and China (once named C. ectenes), the genetic diversity was comparatively analyzed between Cyt b gene and D-loop sequences of C. nasus from Rokkaku River in Ariake Sound, Japan, and those of C. nasus in waters of China downloaded from GenBank. The results showed that the nucleotide diversity of Cyt b haplotypes of C. nasus from Rokkaku River was 0.0033, and the nucleotide diversity based on D-loop analysis was 0.0061. The level of fixation index (Cyt b: 0.2861/D-loop: 0.2890) between C. nasus from Japan and China were relatively high, and the level of genetic distance (Cyt b: 0.0052 ± 0.0014/D-loop: 0.0168 ± 0.0038) was lower than that between C. nasus and C. mystus. The phylogenetic trees and haplotype network constructed based on Cyt b gene and D-loop sequences indicated that C. nasus populations from Japan and China failed to form monophyletic clades respectively, suggesting that the anchovies from Japan and China should be the same species but from populations that had separated from each other.

Different ecotypes exhibit distinct life histories and occupy various environmental conditions for local adaptation. Coilia nasus, an anadromous fish, resides in offshore waters of the Pacific Northwest and reproduces in connected rivers and lakes, including the middle-lower Yangtze River. Populations of C. nasus have differentiated into two ecotypes: migratory and landlocked.This study examined the spatiotemporal distributions of these ecotypes and the environmental conditions of their habitats by analyzing environmental DNA collected from Poyang Lake and Tai Lake during 2020–2021.A total of 157 eDNA samples were obtained, with 62 yielding positive results, including 23 from Poyang Lake and 39 from Tai Lake. The migratory population exhibited seasonal movements in Poyang Lake, entering the Yangtze River-Poyang Lake channel in spring, migrating southward during summer, and returning to the channel in autumn. In contrast, the spatial distribution of the landlocked population remained relatively stable throughout the seasons. Partial least squares structural equation modeling (PLS-SEM) analysis indicated that the distribution patterns of the migratory population were not significantly associated with environmental factors. In contrast, the distribution of the landlocked population was significantly affected by lower water turbidity and reduced conductivity.The findings suggest that temporal variations in the spatial distribution of C. nasus in Poyang Lake primarily reflect its migratory reproductive life history. Conversely, the distribution of the landlocked C. nasus population resembles that of resident fish populations and is mainly influenced by a preference for higher water quality. The results imply that differences in life histories and adaptation to local environmental conditions may have contributed to the formation of the two ecotypes. This study also shows the effectiveness of eDNA technology in assessing fish population distribution and dynamics.

… Monitoring the anadromous fish Coilia nasus using conventional methods is hindered by … Here, we developed a species-specific environmental DNA (eDNA) assay and integrated it with …

Accurate differentiation between Coilia brachygnathus and Coilia nasus is imperative for the effective management of fisheries, the conservation of aquatic ecosystems, and the mitigation of commercial fraud. Current morphological identification remains challenging due to their high morphological similarity—particularly for processed samples—while conventional molecular methods often lack the speed or specificity required for field applications or high-throughput screening. In this study, a novel integrated approach was developed and validated, combining TaqMan quantitative real-time PCR (qPCR). for precise genotyping of C. brachygnathus and C. nasus with Recombinase Polymerase Amplification coupled with Lateral Flow Dipstick (RPA-LFD) for rapid on-site screening. First, species-specific RPA-LFD assays were designed to target the mitochondrial COI gene sequence. This enabled visual detection within 10 min at 37 °C, with a sensitivity of 102 copies/μL, and required no complex equipment. A dual TaqMan MGB qPCR assay was further developed by validating stable differentiating SNPs (chr21:3798155, C/T) between C. brachygnathus and C. nasus, using FAM/VIC dual-labeled MGB probes. Results showed that this assay could distinguish the two species in a single tube: for C. brachygnathus, Ct values in the FAM channel were significantly earlier than those in the VIC channel (ΔCt ≥ 1), with a FAM detection limit of 125 copies/reaction; for C. nasus, only VIC channel amplification was observed, with a detection limit as low as 12.5 copies/reaction. Validation with 171 known tissue samples demonstrated 100% concordance with expected species identities. This integrated approach effectively combines the high accuracy and quantitative capacity of TaqMan qPCR for confirmatory laboratory genotyping with the speed, simplicity, and portability of RPA-LFD for initial field or point-of-need screening. This reliable, efficient, and user-friendly technique provides a powerful tool for resource management, biodiversity monitoring, and ensuring the authenticity of high-quality C. brachygnathus and C. nasus.

… structure in three Chinese estuary populations of Coilia mystus: 21 individuals from ChangJiang … The results of this study suggest that the three Coilia mystus populations, especially the …

… animal genomic DNA extraction kit (SANGON, Shanghai, China, # Cat: B518251). Integrity of extracted DNA was checked with agarose gel electrophoresis. Concentration of DNA was …

… 2 The proportions of anadromous Coilia ectenes with sagittal otolith of straight and curved … class of females and males anadromous Coilia ectenes collected in the Yangtze Estuary …

Fishery harvest of Coilia mystus in the Yangtze Estuary has declined dramatically since the late 1990s. A full understanding of the reproductive biology of this species is essential for effective management of the population. A total of 1072 females of C. mystus collected from the Yangtze Estuary area between May 2006 and September 2007 were analyzed to reveal the general reproductive biology of the population. Females with increased gonadosomatic index (GSI) and gonads developed to stages IV and V occurred mainly from March through August, indicating a major spawning season in this period; there were also a few females with increased GSI and developed gonads observed in November and January. Absolute fecundity (AF) ranged from 3093 to 36 786; and increased with both body weight (BW) and age. The relationship of AF to BW was fitted to a linear function AF = 924.72 x BW-414.17 (r(2) = 0.82, n = 134, P l 0.05). Relative fecundity was 871 eggs per gram. Oocyte diameter (OD) of mature females ranged from 0.55 to 0.90 mm with a mean (+/- SD) of 0.71 +/- 0.05 mm (n = 3927), independent of BW. The frequency distribution of OD showed a single mode and histological examination demonstrated that the development of oocytes was synchronous within an ovary, suggesting that C. mystus is a single spawner. Compared to previous studies, females in this study tended to produce more but smaller eggs. This increased fecundity may represent biological compensation for the decline in abundance of the population due to overexploitation.

The comprehensive 10‐year fishing moratorium implemented in the Yangtze River Basin since 2021 provides a unique opportunity to evaluate the recovery of threatened fish populations. This study assessed the recovery status of Coilia nasus in the lower reaches of the Yangtze River during the fourth year of the moratorium through analysis of age structure, growth parameters, and sex ratio. Field investigations were conducted at two strategic locations (Chongming and Taizhou) during the migration season (May–June 2024), yielding 3077 specimens. Results revealed significant improvements in population parameters, including increased mean age (2.64 years) and standard length (28.5 cm), alongside a higher proportion of age 3 and age 4 individuals (63.3%). Sex ratio analysis showed a pronounced female bias (3.19:1), with spatial variations between estuarine (4.99:1) and upstream (2.04:1) sites. Growth parameter analysis indicated a shift toward natural growth dynamics, with increased asymptotic length (L∞) and altered growth rates (k) compared to premoratorium periods. Despite these positive indicators, the absence of five‐year‐old individuals and lower average length compared to historical records suggest incomplete recovery. Our findings provide evidence for the effectiveness of the fishing ban while highlighting the need for continued protection.

An assessment of the stock status and historical changes in abundance of Coilia mystus and C. nasus in the Yangtze River Estuary, China, was carried out based on field surveys conducted in 2019–2020 and published length-frequency (L/F) data from earlier periods. These two species’ current and past relative biomasses (B/BMSY) were estimated using a length-based Bayesian biomass estimation method (LBB). The LLB method also estimated their asymptotic lengths (Linf), current and optimum mean lengths at first capture (Lc; Lopt_c), and their ratios of natural and fishing mortality to growth (M/K; F/K). In response to increasing fishing pressure, both species’ maximum lengths declined, along with their B/BMSY ratio, which declined for C. mystus from 1.7 in 1982 to 0.47 in 2020 and for C. nasus from 1.7 in 2006 (or earlier) to 0.17 in 2020. These assessments show that both of the two Coilia species are overfished, with C. nasus impacted more severely than C. mystus. The prospect for the recovery of these two species is briefly discussed. This contribution will help toward the management of the population of these two Coilia species and provides a basis for evaluating the effect of the 10-year fishing ban in the Yangtze River.

The implementation of the 10-year fishing ban in the Yangtze River has provided a crucial opportunity for the recovery of rare and endangered diadromous species, such as Coilia nasus.In this study, we utilized electronic length–frequency analysis (ELEFAN) and length-based Bayesian biomass estimation (LBB) method to fit the body length data of C. nasus from the Yangtze River Estuary and its adjacent sea areas before and after the fishing ban (2019-2023), and the resource changes of C. nasus population were evaluated. Additionally, combined the catch production monitoring data from 2020 to 2022, we comprehensively analyzed the impact of the Yangtze River fishing ban on the recovery of C. nasus resources.The results showed that: (1) The proportion of quantity, weight and occurrence frequency of C. nasus in catches showed a significant increasing trend year by year. (2) 4,994 C. nasus were caught from 2021–2023, with body lengths ranging from 13–410 mm. In 2023, the average body length and weight of C. nasus had increased by 39.93% and 133.89%, respectively, from those in 2021. (3) ELEFAN estimated that the growth parameters after fishing ban, including asymptotic length, growth coefficient, and the theoretical age at length zero, were determined to be 42.92 cm, 0.43 year-1, and -0.31 year, respectively. The total mortality rate, fishing mortality rate, and exploitation rate were determined to be 1.47 year-1, 0.79 year-1, and 0.54, respectively. (4) LBB estimated that the relative fishing mortality of C. nasus before the fishing ban increased from 1.22 in 2019 to 2.65 in 2020, while the relative biomass decreased from 0.34 to 0.22. After the fishing ban, the relative fishing mortality decreased from 0.85 in 2021 to 0.06 in 2023, and the relative biomass increased from 0.26 in 2021 to 0.90 in 2023, with a significant increase in 2022, indicating a clear recovery trend in C. nasus resources.By quantifying the resource characteristics of C. nasus before and after the 10-year fishing ban on the Yangtze River, this research revealed the impact of the ban and provided a reference for future systematic evaluations of the C. nasus population.

… The information on the biology of Coilia dussumieri was outdated, and this study provides … genus, may contribute significantly to the management of Coilia stocks in tropical waters. …

Background: Coilia nasus was one of the important economic fish in the Yangtze Estuary. The meat of C. nasus is tender and delicious, which is deeply loved by people. With the ban on fishing in the Yangtze River, a large number of “C. nasus from the sea” have appeared in the market. At present, the nutritional status and its true source are not clear. Therefore, the nutritional composition and quality of offshore C. nasus were analyzed to identify its source and evaluate its development and utilization potential according to its nutritional quality in the future. Methods: The muscle nutritional components and quality of offshore C. nasus were analyzed according to the methods of national standards of China. Result: The content of essential amino acids (EAA) in dry sample was 57.06%±7.39%. The first limited amino acid was tryptophan (Trp), the essential amino acids index (EAAI) was 83.05 and the F-value was 2.37. The total content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in fatty acids were 10.67%±0.46%, the ratio of DHA/EPA was 1.74%±0.05%. This investigation indicates that the muscle of C. nasus from offshore of the Yangtze Estuary contained rich amino acid such as glutamate (Glu) and lysine (Lys) and sufficient polyunsaturated fatty acids such as DHA and EPA.

As an important fishery resource and endangered species, studying the habitat of Coilia nasus (C. nasus) is highly significant. This study used fishery survey data from southern Zhejiang coastal waters from 2016 to 2020, employing a maximum entropy model (MaxEnt) to map the habitat distribution of C. nasus. Model performance was evaluated using two metrics: the area under the curve (AUC) of the receiver operating characteristic curve for the training and test sets and true skill statistics (TSS). This study aimed to predict the habitat distribution of C. nasus and explore how environmental variables influence habitat suitability. The results indicated that the models for each season had strong predictive performance, with AUC values above 0.8 and TSS values exceeding 0.6, indicating that they could accurately predict the presence of C. nasus. In the study area, C. nasus was primarily found in brackish or marine waters near bays and coastal islands. Among all environmental factors, salinity (S) and bottom temperature (BOT) had the highest correlations with habitat distribution, although these correlations varied across seasons. The findings of this study provide empirical evidence and a reference for the conservation and management of C. nasus and for the designation of its protected areas.

To assess the status of Coilia nasus resources in the Yangtze River Estuary and support evaluation of fishing ban effectiveness, this study integrated fishery resource survey data and environmental variables collected from 2023 to 2025. A generalized additive model (GAM) was applied to examine post-ban recovery patterns of C. nasus and the environmental drivers shaping its spatiotemporal distribution. The results revealed pronounced seasonal variation in biomass, with autumn (November) values significantly higher than those in spring and summer. Biomass peaked in autumn 2024, forming a persistent and highly concentrated aggregation. Spatial analyses further indicated that high-biomass areas were consistently distributed within the brackish-water mixing zone of the outer estuary, corresponding to migratory pathways and foraging requirements of the species. GAM results demonstrated that the spatiotemporal distribution of C. nasus was jointly regulated by multiple environmental factors. In spring, temperature, depth, transparency, pH, dissolved oxygen (DO), and chlorophyll-a (Chl-a) exerted significant effects; in summer, salinity and pH were the dominant drivers; and in autumn, temperature, pH, salinity, DO, ammonium (NH4+–N), nitrate (NO3−–N), and phosphate (PO43−–P) showed significant influences. This study provides scientific evidence to support the management of C. nasus resources, particularly in the brackish-water mixing zone of the outer Yangtze River Estuary, and to improve evaluation of fishing-ban effectiveness.

The proximate composition and fatty acid profile in 3 tissues (muscle, liver and ovary) of wild female Coilia mystus in breeding stage were analyzed using the national standard method. The results indicated that: (1) The total fat contents in muscle, liver and ovary were 2.04% ± 0.22%, 11.96% ± 0.77% and 28.46% ± 0.63%, respectively. (2) The muscle contained the most content of saturated fatty acids (SFA) and the least content of mono-unsaturated fatty acids (MUFA) (p less than 0.05). The content of SFA and MUFA between liver and ovary showed no significant differences (p>0.05). The content of poly unsaturated fatty acids (PUFA) was significantly different among these 3 tissues (p less than 0.05): highest in the ovary and the lowest in the muscle. Within PUFAs, the docosahexaenoic acid (DHA) was highest, reaching 8.41% ± 1.18%, 7.64% ± 0.12% and 10.46 % ± 0.45% in muscle, liver and ovary, respectively. PUFA, n-3PUFA, DHA and eicosapentaenoic acid (EPA) were all highest in the ovary.

… The southward shift of the spawning area associated with a southward movement of the … the spawning location and the salinity front functions as a landmark for the spawning migration …

… Study area in East Asia for the spawning migration of Anguilla japonica. Their spawning area is shown ( ) that includes the areas where genetically identified adult fish were collected in …

… River eels occurred only in autumn and early winter during the spawning migration season, but at least a few sea eels or estuarine, eels occurred throughout the year, with their …

Kim, H., Kimura, S., Shinoda, A., Kitagawa, T., Sasai, Y., and Sasaki, H. 2007. Effect of El Niño on migration and larval transport of the Japanese eel (Anguilla japonica). – ICES Journal of Marine Science, 64: –. To clarify the effect of an El Niño on the migration of Japanese eels (Anguilla japonica) in the western North Pacific, differences in migration patterns of eel larvae (leptocephali) in El Niño and non-El Niño years were compared qualitatively through a numerical particle-tracking model. Depending on interannual meridional displacements of the salinity front and bifurcation of the North Equatorial Current, transport of Japanese eel larvae to the Kuroshio was much less than to the Mindanao Current in an El Niño year, and recruitment to coastal habitats in Japan decreased in those years. In non-El Niño years, transport to the Kuroshio was twice as high, and recruitment to coastal habitats increased. If the spawning area of eels was independent of El Niño, transport differences between the two currents were not clear. In the western North Pacific, mesoscale eddies also played a significant role in dispersing eel larvae and prolonging their migration. Consequently, the changing oceanic conditions associated with climate change have resulted in decreased recruitment of Japanese eels, and the eddy effect on migration of the Japanese eel larvae needs to be added into the North Equatorial Current–Kuroshio system.

… its spawning migration out of continental waters (Aoyama et al. 2002; Okamura et al. 2002). The onset of spawning migration of … for starting migration. Body size and age at the onset of …

The European and Japanese eel populations have declined significantly in recent decades. To effectively manage and conserve them, gaining a better understanding of their migratory life cycles is important. Previous research on the spawning ecology and larval dispersal of European and Japanese eels has led to many significant discoveries and advancements for their migratory life cycles. However, different scholars hold varying views on their migratory life cycles, especially concerning the European eel, therefore this article aims to provide a comprehensive review of research from multiple disciplines concerning the spawning ecology and larval dispersal of European and Japanese eels and to propose migratory life cycles of these two species. The migratory life cycle of the European eel is as follows: European silver eels undertake a year-long spawning migration from September to January to reach the Sargasso Sea for spawning before the next spawning season, typically between December and May. After hatching, European eel leptocephali are transported by the Gulf Stream, Frontal Countercurrents, North Atlantic Current, and Azores Current and return to Europe and North Africa for growth. Recruitment of European glass eels mainly occurs between October and June of the following year, and the recruiting season is more concentrated in countries closer to the spawning area and more dispersed in countries farther away. The consistent recruitment pattern and the growth rate of leptocephali suggest a larval transport period, also called larval duration, of around 1 year. Understanding the migratory life cycle of European eels can facilitate the evaluation or development of their conservation measures.

… All of the river eels as well as estuarine and sea eels were caught during the same spawning migration season in the present study. The GSI values of some of the female river eels …

… These findings strongly suggested that Anguilla japonica has a flexible migration strategy … river eels that contribute to the spawning population of Anguilla japonica each year. However, …

… in the process of migrating to the spawning area in the same way as eels from freshwater that exhibit the typical life history pattern of Anguilla japonica. Possible migratory pathway for …

Growth extent varies considerably among recruiting cohorts of Japanese eels Anguilla japonica. However, the effects of oceanic variation on their growth, particularly during the larval stage, remain unclear. We sampled glass eels in northeast Taiwan from 2010 to 2019 and investigated the effects of sea surface temperature (SST), salinity, chlorophyll a (chl a) concentration, and El Niño-Southern Oscillation (ENSO) events on the total length (TL) of these eels by developing a generalized additive model. The results revealed that mean SST between 21 and 24.5°C in the spawning area was associated with TL. Larger TL values were observed from 0.03-0.07 mg m-3 in the spawning area, and along the migration routes TL was greatest when chl a was &gt; 13 mg m-3. Other variables, including mean SST and salinity along the migration route, influenced TL but contributed less than 4.5%. Larger and smaller A. japonica glass eels were observed during El Niño and La Niña years, respectively. Specifically, El Niño years exerted the greatest influence (67.1%) on TL, and this was followed by mean SST (12%) and accumulated chl a concentration (11.4%) within the spawning area. Our results indicated that environmental factors within the spawning area influenced the TL of A. japonica glass eels to a greater extent than did those along the migration routes, and climatic ENSO events exerted an additional important effect regarding changes in TL. Taken together, our results provide fundamental ecological information and a basis for fisheries to more effectively manage A. japonica.

… Anguilla japonica were captured in the southern part of the West Mariana Ridge, the presumed spawning … 6 mo) spawning migration and retain the initial isotopic values of where they …

… was in the silver stage (early maturing stage), and the eel was confirmed to have just begun spawning migration to the open ocean from Tokyo Bay based on the otolith Sr:Ca ratios, …

… spawning migration. Accordingly, we believed that the ratios of life-history types of the silver eels collected in the estuary can represent those of the whole river system. The estuarine …

… eel Anguilla japonica and the tropical giant mottled eel Anguilla … japonica larvae during nine surveys from 1991 to 2007 … use and migratory behavior between tropical eel Anguilla …

… downstream migration of adult eels, because the downstream migration occurs at the onset of the spawning migration. Profiles of reproductive hormones during the downstream …

… ABSTRACT: The migratory history of the Japanese eel Anguilla japonica collected in Otsuchi … migration into the ocean and back out to the spawning area where they spawn and die. …

Eel aquaculture, though thriving nowadays, is totally dependent on the successful capture of wild eel fry and glass eels for its seedlings. The declination of eel resources in recent years has resulted in an urgent need for technology development in artificial seedlings production on an aquaculture basis, in order to protect natural resources and to stabilize the eel supply in the farming industry. Since the life history of the eel holds many mysteries, artificial hatching and rearing of larvae has long been regarded as an extremely difficult task. However, in recent years, the spawning ground of the Japanese eel has finally been located after continuous effort with intensive marine surveys, in which wild parental eels were captured, followed by the collection of fertilized eggs and the harvest of newly hatched preleptocephali. Meanwhile, through the collaborative efforts of many researchers, progress has also been made in improving technologies for artificial maturation of parental eels, which do not mature naturally in captivity, as well as in the technology for artificial hatching. Moreover, a technology for producing feed-rearing eel hatchlings, the most challenging process of all, has advanced rapidly after suitable feed was developed in the 1990s. Then, in 2002, for the first time in the world, larvae were successfully reared up to the glass eel stage, and second generation artificial hatchlings were born in 2010. In this way, eel farming technology that is not reliant on natural resources has been developed. There are strong hopes now for a technology for stable mass production of glass eels to be developed in the near future.

Scientists have long sought to uncover the secrets of the migration of anguillid eels, genus Anguilla. As catadromous fishes, anguillid eels spend most of their lives in freshwater until they return to their spawning grounds in the tropics, although part of the population never enters freshwater and instead resides in brackish and marine areas close to coastlines. Molecular phylogenetic research suggests that anguillid eels originated from deep-ocean midwater marine anguilliform species and that tropical eels originating from the Indo-Pacific region are the most basal species of anguillid eels. Anguillid eels left the tropical ocean to colonize temperate areas. The yearly spawning of tropical species and constant larval growth throughout the year extend to periods of recruitment in continental habitats to last all year for tropical eels. Tropical eels such as A. celebesensis and A. borneensis have relatively short migrations periods of less than 100 km to their spawning grounds. Conversely, the temperate European eel A. anguilla travels the longest distances and migrates more than 5000 km across the Atlantic Ocean to spawn in the Sargasso Sea. The ancestral state of migration in the genus Anguilla may have been local, short-scale and nonseasonal spawning migration throughout the year as defined in tropical eels. With the expansion of dispersion of global oceanic migration across the world, migration scales can gradually change. Temperate anguillid eels migrate thousands of kilometres from spawning areas to coastal and inland water habitats while retaining spawning areas in tropical areas, accompanied by seasonal downstream and spawning migrations with consequences for seasonal recruitment. Recent advances and the availability of electronic tags such as pop-up satellite archival tag could reconstruct the entire spawning migration from continental growth habitats to spawning sites with detailed migration behaviours and routes. Migration ecology and mechanisms throughout the life of anguillid eels have gradually been revealed in recent decades.