Conger Myriaster Research Articles

Age-structured otolith chemistry profiles revealing the migration of Conger myriaster in China Seas

Conger myriaster is an eel species of considerable economic value in China Seas and around the Korean Peninsula and Japan, but its migration pattern remains largely unknown. This study used otolith microchemistry to investigate the migration and spawning of C. myriaster in the Yellow Sea and East China Sea. Samples were collected from three geographic regions, i.e. Middle Yellow Sea (QD), South Yellow Sea (DS) and East China Sea (ZS), and the micro-chemical compositions of otoliths were analyzed using laser ablation inductively coupled plasma mass spectrometry to produce continuous life history profiles of 4-year classes. The ratios of trace elements were analyzed with growth rings of otoliths to infer age-specific life-history profiles. Hierarchical cluster analysis showed no obvious partitioning in otoliths cores among samples, suggesting a similar environment at birth in these fish. The chemical compositions showed non-significant differences among sampling areas from core to metamorphosis zone, beyond which Ba:Ca ratio showed significant differences in the QD compared to other regions within the first year. This suggested that individuals might experience similar environmental conditions in the early life stages, and, during metamorphosis, QD individuals separated from the population and moved toward coastal waters of Shandong peninsula. The ZS and DS individuals shared similar chemical composition within the first year but differed in Ba:Ca and Sr:Ca ratios afterwards, suggesting a separation of the two groups at ages 1−2. The chemical signatures of the otoliths provide information on the spawning and separation of C. myriaster, which may contribute to the management of the eel fisheries.

Effect of dietary moisture content on growth and feed intake in conger eel Conger myriaster

Effect of dietary moisture content on growth and feed intake in conger eel <I>Conger myriaster</I>

Identification of keystone predators in Haizhou Bay food web based on the revised SURF index

Keystone predator species play an important role in regulating the number, richness and distribution of prey species. Based on the bottom trawl surveys in Haizhou Bay, keystone predator species in fish communities were identified by the revised SURF (supportive role to fishery ecosystems) index. Conger myriaster, Saurida elongata, Hexagrammos otakii, Chelidonichthys spinosus, and Larimichthys polyactis were the keystone predators in the fish community. They had high number of nodes degree, and were also the main predators of many species. Further, they had strong ability of clustering. The fluctuations of their density would have great impacts on ecosystem energy flow and food web structure. The method not only considered the feeding ratio between species, but also took the amount of catch and abundance of species as important factors in the identification of keystone predators. Compared with the traditional method, this method had great improvement and provided a new one for the identification of key predators. Our results showed that the strong inter-specific interactions played an important role in maintaining the structure and function of food webs. Protection of key predators would benefit the stability of biological communities and species diversity. Therefore, ecosystem-based fisheries management (EBFM) should give priority to the protection of key species. The important economic fish species, C. myriaster and L. polyactis, should be protected with high priority as they suffered from higher fishing pressure.

Nutritional Characteristics of Seasoned Laver Pyropia yezoensis with Conger Eel Conger myriaster Seasoning Sauce

Nutritional Characteristics of Seasoned Laver Pyropia yezoensis with Conger Eel Conger myriaster Seasoning Sauce

Relationships Between Community Structure and Environmental Factors in Xixiakou Artificial Reef Area

The construction of artificial reefs has unparallelly developed for a few decades in China. Artificial reefs can be used to manage and conserve commercially exploited fish and crustacea. However, their suitability as ecological niche is poorly characterized. Therefore, in this study, we detected the seasonal variation of community biodiversity and the corresponding driving environmental factors. We also explored the relationships between dominant species and environmental factors to identify appropriate ecological niche areas. Different statistical analysis methods were used to assess species distribution within an artificial reef area in Xixiakou during nine sampling events in four seasons between 2017 and 2018. Non-metric multidimensional scaling (NMDS) and cluster analysis results indicated that the components of community can be divided into two clusters. Complexity of community, which is exhibited by species number, biodiversity, and catch per unit effort (CPUE), was significantly higher in summer than in other seasons. Generalized additive model (GAMs) results revealed the significant effects of temperature and chlorophyll a on the community structure. Sebastes schlegelii, Hexagrammos otakii, Conger myriaster and Charybdis japonica were the dominant species in four seasons. GAMs results indicated that temperature, dissolved oxygen (DO), pH and chlorophyll a affect the CPUE of dominant species significantly. The distinct suitable ecological niche for each dominant species was found in this study. For example, Charybdis japonica preferred to live in the area with 20.7–22.1 °C, dissolved oxygen 7.07–7.15 mg L−1 and salinity 31.8–31.9. The results of this study are beneficial to resource conservation and fishery management.

High levels of genetic diversity and connectivity of whitespotted conger Conger myriaster in the East China Coast

Genetic diversity and population structure are fundamental to studying population dynamics and understanding demographic history, playing a key role in marine organism conservation. To study the genetic diversity and population structure of whitespotted conger Conger myriaster, an important commercial marine species, broadly distributed in Asia, a total of 197 individuals were collected from six locations along the East China Coast. Around 655 bp sequence of mitochondrial control region was used to assess the genetic diversity, population differentiation, and demographic history of C. myriaster populations. A high level of haplotype diversity was detected. No significant population structure was observed by using analysis of molecular variance (AMOVA), consistent with the results of discriminant analysis of principal components (DAPC) and Mantel tests. Bayesian phylogenetic tree revealed three distinct lineages, which diverged during the Pleistocene. Mismatch and Bayesian skyline analyses supported that all geographical populations as well as three evolutionary lineages had experienced demographic expansions. This genetic assessment would give an important contribution to revealing the interaction between phylogeographic history and demographic history and future utilization and conservation of this species.

The complete mitochondrial genome sequence of Rhynchoconger ectenurus (Anguilliformes: Congridae)

The complete mitochondrial genome of Rhynchoconger ectenurus was sequenced by high-throughput sequencing method. The length of this genome is 17,716 bp, containing 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and 2 large non-coding regions. ND6 and 8 tRNA genes are encoded by L-strand, and others are encoded by H-strand. Phylogenetic tree based on 13 protein-coding genes shows that the clade of Rhynchoconger ectenurus is closely clustered with that of Conger japonicus, and families Anguillidae and Synaphobranchidae have the closer relationship to Congridae, compared to Muraenidae.

Spatial analyses of the influence of autocorrelation on seasonal diet composition of a marine fish species

Spatial autocorrelation is common in environmental factors, species distributions, and predator-prey interactions. Spatially autocorrelated distribution of prey and strong prey selectivity by predators may cause spatial autocorrelation of the fish diet shown as higher similarity among diets of fish caught nearby or in the same trip. We explore the importance of spatial autocorrelation analysis in understanding the fish diet composition and predator-prey interaction in diet analysis based on one example fish whitespotted conger (Conger myriaster) in the Yellow Sea and its prey species that have been monitored across seasons. Among the spatial estimators, the cluster-based estimator is used to quantify fish diet similarity from the same trip, and the spatial Gaussian and exponential autocorrelated estimators are used to test the hypothesis that fish diet similarity decreases over distance. The two types of spatially autocorrelated estimators performed better than spatially-independent and cluster-based estimators, with lower mean square errors in a cross-validation procedure. Prey selectivity related to the prey availability, and the spatial overlap between predator and prey were likely important factors affecting seasonal and spatial variations in diet composition of the example fish species. Cross-variograms indicated that whitespotted conger and some of its dominant prey species were positively spatially autocorrelated, which suggested fishes generally aggregated in areas of high prey density. Our study provides a practical basis for considering the effect of spatial characteristics in quantifying the diet composition likely linked to the environmental driven distributions of both fishes and their prey.

진해만에서 각망에 어획된 어류의 종조성 및 계절변동

Seasonal fluctuation in abundance and species composition of fish in coastal waters off Jinhae bay were investigated using seasonal samples collected by a fyke net from July, 2010 to April, 2011. A total of 1,869 fishes were sampled and classified into 23 species, 18 families, and 7 orders. The dominant species were Sebastes inermis (184 individuals, 9.8%), Nuchequula nuchalis (158 individuals, 8.5%), and Konosirus punctatus (143 individuals, 7.7%). The highest number of individuals was found in Fall (572 individuals), while the lowest number of individuals was found in Winter (416 individuals). The diversity index was the highest in winter (H’=3.005) and the lowest in fall (H’=2.953). The dominance index was the highest in fall (D=21.0%) and the lowest in spring (D=16.5%). The economically important species in Jinhae bay were Conger myriaster, Engraulis japonicus, Konosirus punctatus, Sebastes inermis, Lateolabrax japonicus, Acanthopagrus schlegelii, and Paralichthys olivaceus.

양념 첨가 붕장어통조림의 제조 및 품질특성

This study was carried out to investigate the quality characteristics of three types of canned conger eel Conger myriaster added seasoning sauce. The canned products of Sample-1 (Canned conger eel added Kochujang sauce), Sample-2 (Canned conger eel added Chokochujang sauce) and Sample-3 (Canned conger eel added tomato paste sauce) were made. After removing all intestines of the conger eel including head, fins and scales, 100g of conger eel meat was washed, filled into cans (Can No. ; 301-3) added with seasoning sauce 50g (Sample-1 ; Kochujang sauce, Sample-2 ; Chokochujang sauce, Sample-3 ; tomato paste sauce), respectively. All samples were seamed by using a vacuum seamer, and then sterilized at 118℃ for 40minutes using a steam system retort. Parameters such as microbial growth, proximate composition, pH, volatile basic nitrogen (VBN), thiobarbituric acid (TBA) value, amino-N content, salinity, color value (L, a, b), texture profile, total amino acid content, free amino acid content, mineral content and sensory evaluation of the 3 types of canned product were analysed according to the general methods. The moisture contents of Sample-1, Sample-2 and Sample-3 were ranged from 60.3 to 77.1g/100g, the crude protein content were 10.7 to 12.9g/100g, the crude lipid content were 3.8 to 5.6g/100g, respectively. Amino-N contents of Sample-1, Sample-2 and Sample-3 were 157.4, 172.8 and 186.3mg/100g, free amino acid content of samples were 366.6, 403.7 and 467.7mg/100g, respectively. As a result of the sensory evaluation, the shape, color and texture of Sample-1, Sample-2 and Sample-3 tend to be similar. But odor, taste and overall acceptance of Sample-3 were not estimated to be better than others.

Population status and distribution of whitespotted conger (Conger myriaster) in Yellow Sea: An important migratory species along coastal China with limited data

AbstractWhitespotted conger (Conger myriaster) is a marine migratory species with important economic and ecological values in Northwestern Pacific. The population status and distribution of whitespotted conger may have changed in the eastern coastal water of China owing to the intensive fishing pressure and human activities in the past few decades. There have been miscellaneous concerns about its population trend and potential environment‐driven variations in spatiotemporal distribution. Delta‐generalized linear models, generalized linear mixed models, and a set of correlation analyses were performed to answer the above concerns, and a stratified random sampling‐designed bottom trawl survey from 2011 to 2017 in Haizhou Bay of the central Yellow Sea was conducted to collect samples. Our study suggested that whitespotted conger remained a relatively stable population status with slight fluctuations likely caused by climate variability during 2011–2017. The hierarchical generalized linear mixed models with spatial random effect performed better than the generalized linear model and the common generalized linear mixed models. Spatiotemporal differences of whitespotted conger were significantly associated with bottom water salinity, depth, sampling time, and space, which were probably mainly influenced by a combination of the Cold Water Mass, the Yellow Sea Warm Current, and the Yellow Sea Coastal Current. The predicted spatiotemporal distribution of whitespotted conger has a monthly variation matching its seasonable migration and an overall higher abundance in the deeper water than that in the neritic areas in Haizhou Bay.

조미 붕장어통조림의 제조 및 품질특성

This study was carried out to investigate the quality characteristics of canned seasoned conger eel Conger myriaster. The canned products of Sample-1 (Canned seasoned conger eel added Teriyaki sauce), Sample-2 (Canned seasoned conger eel added spicy sauce) and Sample-3 (Canned seasoned conger eel added seasoning sauce) were made. After removing all intestines of the conger eel including head, fins, and scales. 100g of conger eel meat was washed, filled into cans (Can No. ; 301-3) added with additive material 50g (Sample-1 ; Teriyaki sauce, Sample-2 ; spicy sauce, Sample-3 ; seasoning sauce), respectively. All samples were seamed by using a vacuum seamer, and then sterilized at 118℃ for 40 minutes using a steam system retort. Parameters such as microbial growth, proximate composition, pH, volatile basic nitrogen (VBN), thiobarbituric acid (TBA) value, amino-N content, salinity, color value (L, a, b), texture profile, total amino acid content, free amino acid content, mineral content, sensory evaluation of the 3 kinds of canned product were measured. The moisture contents of Sample-1, Sample-2 and Sample-3 were ranged from 68.9 to 74.4g/100g, the crude protein content were 12.6 to 12.9g/100g, the crude lipid content were 8.7 to 15.7g/100g, the ash content were 1.9 to 2.4g/100g. And pH, VBN content, TBA value, amino-N content and salinity of Sample-1, Sample-2 and Sample-3 tend to be similar. As a result of the sensory evaluation, the shape, color and texture of Sample-2 were similar to those of Sample-3, while odor, taste and overall acceptance of Sample-1 were not estimated to be better than others.

Artificial reefs can mimic natural habitats for fish and macroinvertebrates in temperate coastal waters of the Yellow Sea

The deployment of artificial reefs to enhance the abundance of reef-associated species in the coastal waters of China occurs on a very large scale. However, the ability of these artificial structures to mimic natural habitats for fauna has not been evaluated. This study examined the benthic fish and macroinvertebrates assemblages (sampled using trap nets) of artificial reef complexes deployed in shallow, nearshore (9–11 m) and deeper, offshore waters (20–30 m) in the Lidao artificial reef zone (Yellow Sea, China) to determine whether they differed from assemblages on adjacent habitats: i.e. natural reefs in nearshore and bare substratum in offshore waters. It also investigated the extent of any temporal variation in these assemblages. A greater total number of taxa were identified in offshore than nearshore waters, but nearshore waters supported higher total mean numbers and biomass. No significant differences were detected in the characteristics of the benthic fish and macroinvertebrate fauna between artificial reefs and their corresponding natural habitats in both depths. Faunal composition in both depths showed strong patterns of temporal variation, mainly due to changes in the abundance of some transient fish species such as Conger myriaster and Pseudopleuronectes herzenstein, which matched seasonal patterns in water temperature and clarity. The similarity of community structure between nearshore artificial reefs and natural habitats implies that the artificial reefs are mimicking natural habitats, which facilitates functional connectivity. Thus, in the Lidao artificial reef zone, artificial reefs and natural habitats can be considered as integrated habitat management units. In the offshore waters, however, the lack of a difference in composition between habitats possibly reflects the observed sinking of the artificial reefs. This highlights the importance of detailed site assessments before the deployment of artificial reefs, particularly in silty sediments.

Description of Two New Species of Philometra Costa, 1845 (Nematoda: Philometridae) from Marine Fishes off Japan, with Notes on Philometroides seriolae (Yamaguti, 1935).

Philometrid nematodes (Philometridae) represent a group of more than 200 species parasitic in the body cavity and various body tissues of fishes. Due to morphological and biological peculiarities, the majority of them are known only by their large females. Generally, the fauna of these parasites remains little known. Occasional helminthological examinations of three species of marine fishes in Japan revealed two new and one insufficiently known species of these tissue-dwelling parasites. These were studied with the use of light and scanning electron microscopy. All three nematode species are described. Philometra ostorhinchi sp. nov. (males and females) from the ovary of Ostorhinchus semilineatus (Temminck et Schlegel) (Apogonidae, Perciformes) is characterized mainly by the lengths and structure of spicules and the gubernaculum (spicules 108-120µm long, length of the gubernaculum 78-87µm); it is the only species of philometrids parasitic in a fish belonging to the Apogonidae. The gravid females of Philometra tenuis sp. nov. (only females available) from the head subcutaneous tissues of Conger myriaster (Brevoort) (Congridae, Anguilliformes) differ from congeners mainly in an unusual shape of the anterior oesophageal bulb. Some new data on the morphology of an insufficiently known species Philometroides seriolae (Ishii, 1931), collected from the body musculature of Seriola quinqueradiata Temminck et Schlegel (Carangidae, Perciformes), are provided; the number and arrangement of cephalic papillae in subgravid females of P. seriolae were found to be similar to those in females of the majority of other philometrid species. The present study extends the knowledge of the species composition of philometrids parasitizing marine fishes and of the morphology of P. seriolae, the type species of Philometroides Yamaguti, 1935.

붕장어 기름담금통조림의 제조 및 품질특성

붕장어 기름담금통조림의 제조 및 품질특성

Fishery biology of whitespotted conger Conger myriaster (Brevoort, 1856) in the Yellow Sea and East China Sea

Whitespotted conger Conger myriaster is a commercially important species in the seas around China, Korea and Japan. The coastal waters of China serve as an important feeding ground for congers, but the spatio-temporal variations in the fishery and biological characteristics of the population have been rarely evaluated and less well understood in this area. We studied the growth, spawning and feeding characteristics of C. myriaster on the basis of samples collected from October 2016 to April 2017 in the Yellow Sea and East China Sea. A total of 529 specimens were collected, with ages ranging from 1 to 6 years and total length ranging from 132 mm to 834 mm. The parameters of von Bertalanffy growth equation L∞ and k were 1 026 mm and 0.226 a−1, respectively; the sex ratio was 88:0 (female: male) in the East China Sea and 2.67:1 in the South Yellow Sea; the development stage of ovary ranged from peri-nucleolus stage to secondary yolk globule stage, and the testis of two males was at mid-meiotic stage; Crustacean was the major prey for conger of small length, and food source shift to fish with somatic growth. The results showed substantial differences from previous studies in Japan and Korean waters, as well as from China seas in the 1980s, suggesting potential spatiotemporal changes in the biological characteristics of C. myriaster. This study may improve current understanding of the fishery biology of C. myriaster in the Yellow Sea and East China Sea.

Residual concentrations of human chorionic gonadotropin in female whitespotted conger reared under low water temperatures after a single injection

To develop methods for inducing maturation of female whitespotted conger, Conger myriaster, a single injection of human chorionic gonadotropin (hCG; 2.5 IU/g body weight, BW) was administered to each of 7 females, which had ovarian oocytes with a larger diameter than 560 μm at a water temperature of 10 °C. Subsequent changes in the serum concentration of hCG and estradiol-17β (E2) and in their BW index [(BW/BW before the injection) × 100] were measured once a week until 9 weeks after the injection was administered. The serum concentration of hCG reached a peak value of 3.68 ± 0.37 IU/ml after one week, followed by a rapid decrease to 4 weeks later and then a gradual decrease thereafter, expressing its lowest value (0.1 ± 0.02 IU/ml) 9 weeks later. A week after administration, the serum E2 concentration rose to 6.1 times that before the administration and remained at that level for 3 weeks. Thereafter, the serum E2 concentration decreased sharply and reached approximately the pre-administration level after 8 weeks. Their BW index increased until 5 weeks after administration at a constant rate to 130% of the weight before injection and then gradually decreased. A booster injection of hCG (0.5 IU/g BW) was administered to each of 4 females exhibiting maximum ovarian oocyte diameter exceeding 850 μm at 9 weeks after the injection, followed by an injection of 17α-hydroxyprogesterone (2 μg/g BW) one day later for induction of ovulation. One of the females ovulated within 67 h of the final injection. These results indicate that a single injection of hCG (2.5 IU/g BW) has effects on promoting the maturation of female whitespotted conger eels for at least one month. In addition, the results suggest the possibility of developing a new method that reduces handling stress for females by increasing the dosing interval by one month or more.

보일드 붕장어통조림의 제조 및 품질특성

보일드 붕장어통조림의 제조 및 품질특성

A New Method for Bone Softening and Texture Enhancement of Conger Eel (Conger myriaster) Kabayaki

The purpose of this study was to develop a processing method to soften intramuscular bones, such as ribs, while maintaining the taste and physical properties of traditional conger eel kabayaki. The steamed product produced by one of the methods for processing kabayaki was evaluated, and it was found that the ribs were hardly softened, and the sensation of foreign bodies in the mouth due to bones was clearly felt. However, the sensory evaluation of the retort products showed that there was no bone-related foreign body sensation, and the ribs of some products were so soft that they could not be detected. In oven-cooked products, the ribs were softened when the oven temperature was set to 140°C and 150°C but not at 130°C. Products manufactured in a 150°C oven were found to be overdry on the surface and burnt. The size of the conger eel needed to be less than 253 g to soften the ribs in the 140°C oven (oven-140 product). The moisture content of the retort product was 84.0%, which was relatively higher than that of steamed (65.7%) and oven-140 (66.8%) products. Total free amino acids were the highest when using the retort method to soften bones. The physical properties of conger eel products showed that the oven-140 product is different from the retort product and is similar to the steam product. The sensory evaluation of the products also showed that the sensory properties of the oven-140 product were those of the steamed product but were distinctly different from those of the retort product.

Mucosal galectin genes in all freshwater eels of the genus Anguilla.

In this study, we determined the genomic DNA sequences of the mucosal galectin-encoding genes from all 19 species and subspecies of the genus Anguilla. The nucleotide sequences of the galectin genes were c. 2.3-2.5 kb long and the organisation of their four exons and three introns was conserved in all species. An unusual sequence was found in the fourth exon of Anguilla reinhardtii, resulting in a unique deduced amino-acid sequence at the C-terminus. All six amino-acid residues important for β-galactoside binding were conserved in three species, while one residue (R73 ) was substituted to K73 in the other 16 species-subspecies, including Anguilla marmorata. However, this substitution did not appear to affect the sugar-binding ability of galectins because the galectin of A. marmorata was previously shown to bind to lactose. We also discuss the molecular evolution of galectins among Anguilla spp. and the homologues previously identified in Conger myriaster.