Larval Anisakid Infections in Marine Fish from Three Sea Areas of the Republic of Korea

The present study was performed to determine the infection status of anisakid larvae in marine fish collected from 3 sea areas of the Republic of Korea. Total 86 marine fish (8 species) collected from the East Sea (Goseong-gun, Gangwon-do), 171 fish (10 species) from the South Sea (Sacheon-si, Gyeongsangnam-do), and 92 fish (7 species) from the Yellow Sea (Incheon Metropolitan City) were examined by both naked eyes and artificial digestion method. Among the total of 349 fish examined, 213 (61.0%) were infected with 8 species of anisakid larvae, i.e., Anisakis simplex, 6 types of Contracaecum spp., and Raphidascaris sp., and the mean larval density was 13.8 per infected fish. Anisakid larvae were detected in 45 fish (52.3%) from the East Sea, 131 fish (76.6%) from the South Sea, and 37 fish (40.2%) from the Yellow Sea. The average numbers of larvae detected were 4.0, 16.6, and 15.9, respectively. Anisakis simplex larvae were detected in 149 fish (42.7%), and the mean larval density was 9.0 per infected fish. They were found in 26 fish (30.2%) collected from the East Sea, 96 fish (56.1%) from the South Sea, and 27 fish (29.3%) from the Yellow Sea. The average numbers of larvae detected were 2.9, 10.3, and 10.5, respectively. Conclusively, the present study suggests that the infection rate and density of anisakid larvae are more or less higher in the fish from the South Sea than those from the East Sea or the Yellow Sea.     

Fish assemblage structure in the East China Sea and southern Yellow Sea during autumn and spring

Based on bottom trawl surveys in autumn 2000 and spring 2001, the fish assemblage structure in the southern Yellow Sea and the continental shelf of the East China Sea was analysed. Four groups of fishes were identified for each season by the two-way indicator species analysis (TWIA). Although seasonal migration caused a slight difference in fish assemblages between autumn and spring, two major groups of fishes, corresponding to the Yellow Sea and East China Sea were identified. Inshore and offshore groups were subsequently separated. Changes in water depth may be most important in the separation of the groups in the offshore waters of the East China Sea. Temperature affected the groupings between north and south, particularly in the central part of the Yellow Sea. Here, the cold water mass affected the species composition which was low in diversity and different from the other areas.     

Molecular Analysis of Anisakis Type I Larvae in Marine Fish from Three Different Sea Areas in Korea

Anisakiasis, a human infection of Anisakis L3 larvae, is one of the common foodborne parasitic diseases in Korea. Studies on the identification of anisakid larvae have been performed in the country, but most of them have been focused on morphological identification of the larvae. In this study, we analyzed the molecular characteristics of 174 Anisakis type I larvae collected from 10 species of fish caught in 3 different sea areas in Korea. PCR-RFLP and sequence analyses of rDNA ITS and mtDNA cox1 revealed that the larvae showed interesting distribution patterns depending on fish species and geographical locations. Anisakis pegreffii was predominant in fish from the Yellow Sea and the South Sea. Meanwhile, both A. pegreffii and A. simplex sensu stricto (A. simplex s.str.) larvae were identified in fish from the East Sea, depending on fish species infected. These results suggested that A. pegreffii was primarily distributed in a diverse species of fish in 3 sea areas around Korea, but A. simplex s.str. was dominantly identified in Oncorhynchus spp. in the East Sea.     

再议中国近海小黄鱼种群的划分问题

以往认为,中国近海小黄鱼可划分为3个种群.本研究从地理隔离、数量动态、形态解剖,分子遗传学和海洋水文等不同方面,重新审视了我国近海小黄鱼（Larimichthys polyactis Bleeker）种群的划分问题.研究表明：中国近海小黄鱼仅仅存在两个种群,即黄海南部和东海小黄鱼种群及渤海和黄海北部小黄鱼种群.主要证据有三：其一,分析1965年至今小黄鱼不同种群形态解剖学和分子遗传学重要文献,发现这些文献的结果仅仅支持黄海南部和东海小黄鱼是一个种群的结论;其二,依据1971-1982年我国10多个主要渔业公司小黄鱼捕捞统计资料,黄海南部和东海的小黄鱼在地理分布上几乎不存在隔离的现象.在冬季外海,黄海南部和东海小黄鱼栖息于同一个越冬场.进入春季后,它们从该越冬场分别向舟山渔场、鱼山渔场和吕泗渔场产卵洄游.同时,东海南部近海越冬场的小黄鱼向北作产卵洄游,在舟山渔场汇入外海来的小黄鱼鱼群中.从5-8月,黄海南部至东海仅存在一个小黄鱼索饵群体.而黄海北部和渤海小黄鱼群体与上述群体存在明显的地理隔离;其三,黄海南部和东海,近年来小黄鱼产量增长趋势一致,而同期的渤海和黄海北部小黄鱼资源量恢复不大.     

Distribution of Anisakis species larvae from fishes of the Japanese waters

Human anisakiasis is caused by the consumption of raw, marinated or undercooked fish and squid infected with nematodes of the genus Anisakis Dujardin, 1845. In view of food safety, this study was carried out to examine the distribution of Anisakis species in marine fishes within Japanese waters. Seven fish species from six localities were collected and examined for Anisakis infection. Morphological and molecular (ITS region and mtDNA cox2 gene) characterization revealed the presence of two, among the three sibling species of Anisakis simplex, viz. A. simplex sensu stricto (s.s.) and A. pegreffii. Distribution data were collated with the results from the previous researches to better understand Anisakis distribution in Japanese waters. Distributions of Anisakis species were found to be locality-specific rather than host-specific, particularly between the two major species, A. simplex s.s. and A. pegreffii. Anisakis simplex s.s. is mainly found in fishes from northern Japan to Pacific sides, whereas A. pegreffii is in fishes from the Sea of Japan to East China Sea sides.     

Morphological and molecular characterization of Anisakis larvae (Nematoda: Anisakidae) in Beryx splendens from Japanese waters

The third-stage (L3) larvae of Anisakis, which are the etiological agents of human anisakiasis, have been categorized morphologically into Anisakis Type I larvae and Anisakis Type II larvae. Genetic analysis has allowed easy identification of these larvae: Anisakis Type I larvae include the species Anisakis simplex sensu stricto, Anisakis pegreffii, Anisakis simplex C, Anisakis typica, Anisakis ziphidarum, and Anisakis nascettii, whereas Anisakis Type II larvae include the species Anisakis physeteris, Anisakis brevispiculata, and Anisakis paggiae. Since human consumption of raw fish and squid is common in Japan, we investigated Anisakis L3 larvae in 44 specimens of Beryx splendens from Japanese waters. A total of 730 Anisakis L3 larvae collected from B. splendens were divided morphologically into 4 types: Type I, Type II, and 2 other types that were similar to Anisakis Type III and Type IV described by Shiraki (1974). Anisakis Type II, Type III, and Type IV larvae all had a short ventriculus, but their tails were morphologically different. In addition, data from genetic analysis indicated that Anisakis Type II, Type III, and Type IV larvae could be identified as A. physeteris, A. brevispiculata, and A. paggiae, respectively. Therefore, A. physeteris, A. brevispiculata, and A. paggiae can be readily differentiated not only by genetic analysis but also by morphological characteristics of L3 larvae.     

Genetic analysis of the populations of Japanese anchovy Engraulis japonicus from the Yellow Sea and East China Sea based on mitochondrial cytochrome b sequence

Japanese anchovy Engraulis japonicus was not only a commercial species but also a key link in the marine food chain in the Yellow Sea and East China Sea. However, in recent years, E. japonicus experienced a deep recession caused by over fishing. Therefore, determination of population genetic structure is essential to underpin resource recovery and to aid delineating and monitoring populations for fishery management. In this study, sequence variation of a 402-bp fragment of mitochondrial cytochrome b (cyt b) gene from ten populations of E. japonicus in the Yellow Sea and East China Sea was determined, detecting 73 haplotypes. Haplotype diversities and nucleotide diversities for the ten populations ranged from 0.4706 ± 0.1177 (D) to 0.9935 ± 0.210 (WH), and from 0.0014 ± 0.0013 (D) to 0.0090 ± 0.0053 (WH), respectively. Analysis of molecular variance (AMOVA) showed no significant differences at all hierarchical levels, and almost all F_ST values were non-significant, indicating no significant population genetic structure in the Yellow Sea and East China Sea. Two indistinct clades with low support values were detected and the analysis of haplotype frequency distribution showed no significant geographic differences among populations. These results supported the null hypothesis that E. japonicus within the Yellow Sea and East China Sea constituted a panmictic mtDNA gene pool. Based on the present study, the existence of separate genetic stocks in the Yellow Sea and East China Sea were not detected. Strong dispersal capacity of planktonic larvae, and ocean current could be the reasons for genetic homogeneity in this species in the Yellow Sea and East China Sea.     

Infection status of larval anisakids in Astroconger myriaster collected from the Southern Sea near Pusan]

A study was presented on the anisakid larvae in Astroconger myriaster which were caught at the Southern Sea and saled at Pusan area. The nematodes were morphologically classified into Anisakis sp. and Contracaecum sp. after fixation in 70% ethanol and clearing in lactophenol. Total of 1,768 larval anisakids were collected from 259 (67.8% positive rate) out of 382 examined A. myriaster. Total 642 larvae of Anisakis sp. were obtained from 94 (24.6%) and 1,126 Contracaecum sp. were recovered from 165 (43.1%) fish. The average number of worms per infected fish was 4.6. The infection rate increased according to the length of fish, and all of the fish over 71 cm were found infected. The numbers (proportions) of recovered worms by the organs were 1,440 (80.5%) in the omentum, 166 (9.4%) in the intestine, 107 (6.0%) in the stomach, 32 (1.8%) in the skin, 18 (1.0%) in the muscle, 13 (0.7%) in the liver, and 2 (0.1%) in the head. The larvae in the muscle may infect the humans who are enjoying raw sliced meat of the fish.     

黄海和东海营养盐分布及其对浮游植物的限制

根据1997～1999年黄海和东海4个季节的现场调查资料,分析探讨了黄海、东海的营养盐分布特征及其对浮游植物生长的限制状况．结果表明,在长江口以东及其东北部海域终年存在一个范围很大的营养盐高值区．分析表明,这些营养盐主要来自长江冲淡水的扩展及苏北沿岸流的输送．此外,还获得了1998年长江流域特大洪水期间,迄今被观测到的长江冲淡水中营养盐的最大扩展范围,计算并研究了黄海、东海上层水中Si／N／P比值,结果表明,黄东海上层水中Si／N比值较高,Si不会成为黄东海浮游植物生长的限制因子;但在南黄海南部尤其是西南部、东海近岸及长江口以东海域,N／P比值很高(>30),说明与一般海洋环境的情况不同,黄海、东海有很大一部分海域浮游植物的生长受磷限制,而不是受氮限制．     

Molecular identification of Ammodytes (PISCES, Ammodytidae) larvae, with ontogenetic evidence on separating populations

A total of ten larval Ammodytes were collected from the Yellow (5 specimens) and Bering Seas (5), and a 638 base pair sequence from their mitochondrial DNA COI genes was analyzed for species identification. Sequences were compared with those of adult Ammodytes personatus from the East (4), the Yellow (2) and the East China Seas (2), and Japan (3). Average genetic distance was 0.064 between the Yellow Sea larvae and the Bering Sea larvae, but was 0.0043 between the Yellow Sea larvae and all the adult A. personatus except two individuals from the East Sea. NJ-tree showed that five Yellow Sea larvae were closely clustered with adult A. personatus, except for two individuals. The five Bering Sea larvae were located distantly from adult A. personatus, and are thought to be A. hexapterus. We found morphological differences among two populations of A. personatus larvae and A. hexapterus larvae in morphometric characters and pigmentation. Our results indicated that the East Sea population of A. personatus is closer to A. hexapterus than to the Yellow Sea population of A. personatus, suggesting the East Sea population may be part of separate species.     

Length–weight relationships of 22 fish species from the East China Sea

Estimated length–weight relationships are presented for 22 commercially important marine fish species representing nine families, found in the East China Sea. A total of 2776 specimens were caught by otter trawl on the continental shelf in the East China Sea between 2009 and 2013. Information pertaining to length–weight relationships should lead to a better understanding of fish communities in the East China Sea.     

Infestation by larvae of Anisakis simplex A and Anisakis physeteris in fish species of the Italian seas

Data on the occurrence of larvae of Anisakis simplex A and Anisakis physeteris in marine fishes from Italian waters are reported. The larvae have been identified by multilocus electrophoresis using biochemical keys. Considerations on the life-history pattern of these species in the Mediterranean Sea are advanced.     

A concept to protect fisheries recruits by seasonal closure during spawning periods for commercial fishes off Taiwan and the East China Sea

The 72 most important commercial fish species as well as nine unidentified fish groups representing hundreds of fish species as the major and minor target species caught in waters off Taiwan and the East China Sea were selected from the ‘Fisheries Yearbook Taiwan Area.’ All available published and grey literature as well as the Fish Database of Taiwan and Fishbase websites were thoroughly reviewed for a total of 108 fish species, including 51 out of 72 major and 57 minor target fish species, on their reproductive periods in waters off Taiwan and the East China Sea. The spawning periods from these commercial fish species were then summarized. An imperative adjustment was recommended for the established fishing season closure, i.e. for an earlier start, from April to June, in the southern East China Sea. This suggested correction corresponded with the spawning period of most fishes so as to maximize the protection of spawning cohorts for at least 68 major and minor target fish species, which would account for over 53% of the total fish yield in Taiwanese offshore fisheries.     

Anisakid parasites of the pouting (Trisopterus luscus) from the Cantabrian Sea coast, Bay of Biscay, Spain

An epidemiological survey was undertaken of anisakids in 139 specimens (length: 13.2-24.5 cm) of pouting or bib (Trisopterus luscus) captured off the coast of northern Spain in the Cantabrian Sea. Third-stage larvae of two species of nematodes, Anisakis larvae type I and Hysterothylacium aduncum, were isolated. One adult female H. aduncum was also detected in the intestine of one pouting. Total prevalence of anisakids was 88.5%. Hysterothylacium aduncum and Anisakis showed, respectively, prevalence of 87.8% and 22.3%, mean intensity of 19.7 and 3.5, and mean abundance of 17.3 and 0.8. Analysis of infection parameters as a function of host length revealed a much higher prevalence in pouting specimens with length < 20 cm (94.4% for H. aduncum; 28.0% for Anisakis) than in those with length > or = 20 cm (65.6% for H. aduncum; 3.1% for Anisakis). The high mean intensity of Anisakis in muscle of parasitized pouting (5.9) may pose human health risks, although these are minimized by eating only thoroughly cooked pouting, as is the custom in Spain.     

Ascaridoid parasites infecting in the frequently consumed marine fishes in the coastal area of China: A preliminary investigation

Marine fishes represent the important components of the diet in the coastal areas of China and they are also natural hosts of various parasites. However, to date, little is known about the occurrence of ascaridoid parasites in the frequently consumed marine fishes in China. In order to determine the presence of ascaridoid parasites in the frequently consumed marine fishes in the coastal town Huizhou, Guangdong Province, China, 211 fish representing 45 species caught from the South China Sea (off Daya Gulf) were examined. Five species of ascaridoid nematodes at different developmental stages were detected in the marine fishes examined herein, including third-stage larva of Anisakis typica (Diesing, 1860), third and fourth-stage larvae of Hysterothylacium sp. IV-A of Shamsi, Gasser & Beveridge, 2013, adult and third-stage larvae of Hysterothylacium zhoushanense Li, Liu & Zhang, 2014, adults and third-stage larvae of Raphidascaris lophii (Wu, 1949) and adults of Raphidascaris longispicula Li, Liu & Zhang, 2012. The overall prevalence of infection is 18.0%. Of them, Hysterothylacium sp. IV-A with the highest prevalence (17.5%) and intensity (mean = 14.6) of infection was the predominant species. The prevalence and intensity of A. typica were very low (1/211 of marine fish infected with an intensity of one parasite per fish). The morphological and molecular characterization of all nematode species was provided. A cladistic analysis based on ITS sequence was constructed in order to determine the phylogenetic relationships of these ascaridoid parasites obtained herein. The present study provided important information on the occurrence and diagnosis of ascaridoid nematodes in the commercially important marine fishes from the South China Sea. The low level of infection and the species composition of ascaridoid nematodes seem to indicate the presence of low risk of human anisakidosis when local population consumed these marine fishes examined herein.     

Significant genetic differentiation between the Yellow Sea and East China Sea populations of cocktail shrimp Trachypenaeus curvirostris revealed by the mitochondrial DNA COI gene

The cocktail shrimp Trachypenaeus curvirostris is an ecologically and economically important shrimp species in the Yellow Sea and East China Sea. However, there is no information about its population genetic structure. The population genetic structure and level of gene flow of T. curvirostris from the Yellow Sea and the East China Sea were studied with a 658-bp segment of mtDNA COI gene. In total, 85 individuals were collected from five locations and 13 haplotypes were obtained. The genetic variation of COI gene in five populations was moderate, giving an overall haplotype diversity of 0.6888 ± 0.0432 and nucleotide diversity of 0.0069 ± 0.0038. Conflicting to our expectation, significant genetic differentiation was detected in this species. The result revealed two genetically divergent lineages, displaying clear different geographical distributions in the studied area. The significant genetic differentiation between the Yellow Sea and East China Sea populations might be caused by the Yangtze River outflow. Mismatch distribution revealed that T. curvirostris had undergone population range expansion, possibly before 103,400–109,700 years ago in the last interglaciation, rejecting the sudden demographic expansion.     

Anisakis spp. larvae in three mesopelagic and bathypelagic fish species of the central Mediterranean Sea

In this work 437 fish samples of species belonging to the families Myctophidae (Electrona risso and Diaphus metopoclampus) and Phosichthyidae (Vinciguerria attenuata) were examined for the presence of Anisakidae larvae. The study was performed with fishes in the central Mediterranean Sea, particularly in the Strait of Sicily and in the Strait of Messina. The visual inspection and chloro-peptic analysis revealed the presence of nematode parasites with prevalence values between 2.9% in Electrona risso samples and 5.4% in Vinciguerria attenuata samples. A positive correlation was found between standard length (SL) and prevalence of infestation in D. metopoclampus samples (p < 0.05). The larvae examined were morphologically ascribed, at genus level, to Anisakis morphotypes I and II and molecularly identified as Anisakis pegreffii, Anisakis ziphidarum and Anisakis physeteris, in 67%, 9% and 24% of the fish samples examined. Overall, A. pegreffii and A. ziphidarum larvae were isolated in 14 and 2 specimens of D. metopoclampus respectively, A. physeteris larvae were found in 3 E. risso and 2 V. attenuata. A positive correlation was found between standard length and prevalence of infestation in D. metopoclampus samples (p < 0.05). First information is provided on the presence of Anisakis spp. larvae of the myctophid fish species E. risso, D. metopoclampus and V. attenuata from the Central Mediterranean. It is also confirmed the role of lanternfishes (Myctophidae) as paratenic hosts for Anisakis spp.     

Species composition and distribution of ichthyoplankton in the White Sea in July 2003

On the basis of an ichthyoplankton survey made in July 2003 in Kandalaskha Gulf, the Basin, the Gorlo Strait, and the Voronka the species composition and distribution of fish eggs and larvae are investigated. The ichtyoplankton comprises 17 fish species, of which the majority (11) were boreal forms. Other fish were represented by arctic species (2) and arctic-boreal species (4). The traits of distribution of abundantly caught species are considered in detail: larvae of the White Sea oligovertebrate herring Clupea pallasii marisabli, eggs of the dab Limanda limanda, larvae of the northern sand lance Ammodytes marinus, and of the capelin Mallotus villosus villosus. The presence of all larvae of White Sea herring only within Kandalaskha Gulf is considered to be evidence supporting the hypothesis suggested by Dmitriev (1946) on the absence of their drift beyond large gulfs of the White Sea. The natural barrier for mutual exchange with early developmental stages of fish between the White Sea and the Barents Sea in summer may be a developed hydrologic front in the boundary area of the Basin and Gorlo Strait, discovered in the course of the survey. This front causes their death by thermohaline shock in the abrupt gradient zone.     

Anisakis pegreffii Larvae in Sea Eels (Astroconger myriaster) from the South Sea,Republic of Korea

Anisakis simplex sensu stricto (s.s.), Anisakis pegreffii, Anisakis berlandi (=A. simplex sp. C), and Anisakis typica are the 4 major species of Anisakis type I larvae. In the Republic of Korea (Korea), A. pegreffii, A. berlandi, and A. typica larvae in fish hosts has seldom been documented. In this study, molecular analysis was performed on Anisakis larvae from the sea eels (Astroconger myriaster), the major source of human anisakiasis in Korea, collected from Tongyeong City, a southern coastal area of Korea. All 20 sea eels examined were infected with Anisakis type I larvae (160 larvae; 8 per fish). Their species were analyzed using PCR-RFLP patterns and nucleotide sequences of internal transcribed spacers (ITS1, 5.8 subunit gene, and ITS2) and mitochondrial cytochrome c oxidase 2 (cox2). Most (86.8%; 112/129) of the Anisakis type I larvae were A. pegreffii, and 7.8% (10/129) were A. typica. The remaining 5.4% (7/129) was not identified. Thus, A. pegreffii is the major species of anisakid larvae in sea eels of the southern coast of Korea.     

Characteristics of the localization of Ancyrocephalus paradoxus (Monogenea) on the pike perch Stizostedion lucioperca

In one summer old fishes of the pike perch, caught in the K urish Gulf of the Baltic Sea in August-September of 1984, at 100% infection with A. paradoxus 94% of monogeneans were localized under the lower anterior angle of the operculum on the lateral surface of the intergill space (isthmus). In fishes 1+ on the isthmus there were found 52%, in pike perches 2+ 42%, and in fishes 3+ 67% of worms. In older fishes (4-10+) the number of worms on the isthmus accounts for 5% of their total number while others are localized on gill filaments. Variability of sizes, chitinoid structures and microlocalization of worms depending on the age of fish were established.