Fatty acid composition of <Emphasis Type="Italic">Euphausia superba</Emphasis>, <Emphasis Type="Italic">Thysanoessa macrura</Emphasis> and <Emphasis Type="Italic">Euphausia crystallorophias</Emphasis> collected from Prydz Bay,Antarctica

The information of trophic relationship is important for studying the Southern Ocean ecosystems. In this study, three dominant krill species, Euphausia superba, Thysanoessa macrura and Euphausia crystallorophias, were collected from Prydz Bay, Antarctica, during austral summer of 2009/2010. The composition of fatty acids in these species was studied. E. superba and T. macrura showed a similar fatty acid composition which was dominated by C14:0, C16:0, EPA (eicosapentenoic acid) and DHA (decosahexenoic acid) while E. crystallorophias showed higher contents of C18:1(n-9), C18:1(n-7), DHA and EPA than the former two. Higher fatty acid ratios of C18:1(n-9)/18:1(n-7), PUFA (polyunsaturated fatty acid)/SFA (saturated fatty acid), and 18PUFA/16PUFA indicated that E. crystallorophias should be classified as a typical omnivore with a higher trophic position compared with E. superba and T. macrura.     

Distribution of dominant zooplankton species along a latitudinal gradient in China sea during spring

Dominant species of zooplankton community vary with latitude. Though China possesses a vast coastal area in northwestern Pacific, studies on the latitudinal dominant species gradient are rare. We collected zooplankton samples from Haizhou Bay(34.56?–35.19?N, 119.51?–120.30?E), Yueqing Bay(28.14?–28.38?N, 121.10?–121.21?E) and Dongshan Bay(23.65?–23.90?N, 117.45?–117.60?E) in May 2012 and May 2013 to preliminarily characterize the latitudinal dominant species distribution. All the samples were collected vertically using a 0.505 mm mesh plankton net with 0.8 m in mouth diameter from bottom to surface. Calanus sinicus, Aidanosagitta crassa, Labidocera euchaeta, Zonosagitta nagae, Acartia pacifica and Paracalanus parvus were found to be dominant. C. sinicus was the most dominant species and the unique one occurred in all three bays. With latitude decreasing, both the abundance and proportion of C. sinicus declined sharply. Cluster analysis showed that the 6 dominant species could be divided into 3 groups, based on their occurrences in the three bays. Our results suggested that the distribution of dominant species along the coast of China has a significant latitudinal gradient. C. sinicus which widely distributes in the coastal water of the northwestern Pacific can well adapt to the temperature at different latitudes. The high abundance in Haizhou Bay indicated that C. sinicus was an exemplary warm-temperate species, and more commonly occurs in the north of China seas. The ecological characteristics of dominant species change from warm-temperate type in high-latitudinal bays to warm water type in low-latitudinal bays.     

A real-time PCR targeted to the upstream regions of HlyB for specific detection of Edwardsiella tarda

Edwardsiella tarda has become one of the most important emerging pathogens in aquaculture industry.Therefore,a rapid,reproducible,and sensitive method for detection and quantification of this pathogen is needed urgently.To achieve this purpose,we developed a TaqMan-based real-time PCR assay for detection and quantification of E.tarda.The assay targets the hemolysin activator HlyB domain protein of E.tarda.Our optimized TaqMan assay is capable of detecting as little as 40 fg of genomic DNA per reaction.A standard curve was generated from the threshold cycle values(y) against log10(E.tarda genomic DNA concentration) as x.The intra-and inter-assay coefficient of variation(CV) values were less than 2.06% and 1.05% respectively,indicating that the assay had good reproducibility.This method is highly specific to E.tarda strains,as it shows no cross-reactivity to Edwardsiella ictaluri,a member of the same genus,or to nine other fish-pathogenic bacteria species belonging to three other genera.This sensitive and specific real-time PCR assay provides a valuable tool for diagnostic quantitation of E.tarda in clinical samples.     

Genetic diversity and population structure of Eleutheronema rhadinum in the East and South China Seas revealed in mitochondrial COI sequences

Eleutheronema rhadinum is a potential commercial fisheries species and is subject to intense exploitation in China. Knowledge on the population structure of E. rhadinum in Chinese coastal waters, which is important for sustainable exploitation and proper resource management, is lacking. In the present study, the genetic diversity and population structure of E. rhadinum were evaluated using a 564-base pair fragment of the mitochondrial cytochrome c oxidase subunit I （COl） gene. A total of 76 specimens were collected from three localities around the East （Qidong and Zhoushan） and South China Seas （Zhuhai）. Among these individuals, nine polymorphic sites were detected and 1 l distinct haplotypes were defined. High levels ofhaplotype diversity （h=0.759i0.035） and low levels of nucleotide diversity （re=0.001 98i0.003 26） were observed in these populations, Hierarchical analysis of molecular variance （AMOVA） indicated that 96.72% of the genetic variation occurred within the populations, whereas 3.28% occurred among populations. No significant genealogical branches or clusters were recognized on the neighbor-joining tree. Intra-group variation among populations was significant （~0~t=0.032 85, P〈0.01）. These results suggest that E. rhadinum populations in the East and South China Seas have developed divergent genetic structures. Tests of neutral evolution and mismatch distribution suggest that E. rhadinum may have experienced a population expansion. The present study provides basic information for the conservation and sustainable exploitation of this species.     

A preliminary phylogenetic analysis of Luidia (Paxillosida: Luidiidae) from Chinese waters with cytochrome oxidase subunit I (COI) sequences

Luidia Forbes (Paxillosida: Luidiidae) are common soft bottom sea stars with 49 described species. Because of substantial morphological diversity, the taxonomy of the genus is complex and hasn’t been resolved definitely. In order to resolve general taxonomic issues, and determine species boundaries and phylogenetic relationships within the genus Luidia, the sequences of cytochrome oxidase subunit I (COI) gene from 24 specimens of Luidia, belonging to eight taxa in Chinese waters, were studied. Three sequences of two species in genus Luidia from GenBank were used to analyze the phylogenetic relationships. The molecular phylogeny exhibited three main clades, each with strong bootstrap support: Clade A including Luidia quinaria from the Sea of Japan; Clade B including seven nominal species (L. quinaria von Martens, L. yesoensis Goto, L. changi Liu, Liao and Li, L. orientalis Fisher, L. avicularia Fisher, L. longispina Sladen and L. hardwicki Gray) from Chinese waters; and Clade C including L. maculata Müller & Troschel from Chinese waters. Our molecular phylogeny results support the morphological Quinaria-Group and Alternata-Group assigned by Döderlein. Seven nominal species we sampled do not exhibit genetic distances that are large enough to recognize them as separate species. Cryptic species may exist in’ Luidia quinaria’ from the Yellow Sea and the Sea of Japan. Meaningful morphological characters need further investigation in Luidia.     

Enhancing the culturability of bacteria from the gastrointestinal tract of farmed adult turbot Scophthalmus maximus

Eighteen agar media were tested for the culture of gut-associated bacteria from farmed adult turbot(Scophthalmus maximus),including 16 agar media with or without 1% gastrointestinal(GI)supernatant,or with 2% or 4% GI supernatant.A total of 1 711 colonies were analyzed and 24 operational taxonomic units(OTUs)were identifi ed.The greatest bacterial diversity was isolated on Zobell 2216E/Zobell 2216E+ agar media,whereas MRS/MRS+ agar media produced a low diversity of colonies.Agar media with GI supernatant(1%,2%,or 4%)showed increased diversity and yielded different profi les of OTUs from the corresponding original media,suggesting that GI supernatant provides substances that enhance the culture effi ciency of bacteria from the turbot GI tract.The large majority of the colonies(82%)were γ-Proteobacteria,whereas 15.6% and 2.4% of colonies were Firmicutes and Actinobacteria,respectively.At the genus level,49.4% of all colonies were assigned to Vibrio.Other potential pathogens,including Pseudomonas,Photobacterium,and Enterobacter,and potential probiotics,including Bacillus,Paenibacillus,and Pseudomonas,were also isolated on agar media.Most cultured bacteria belonged to species that were fi rst described in the turbot GI tract.The impact of these species on turbot physiology and health should be investigated further.     

Molecular identification based on ITS sequences for Kappaphycus and Eucheuma cultivated in China

The systematic classification of the Eucheumatoideae is difficult because of their variable morphology and interpretation of reproductive structures. Kappaphycus and Eucheuma specimens cultivated on the Hainan and Fujian coast of China were introduced from Vietnam, the Philippines and Indonesia. Combined with morphological characteristics, all Kappaphycus and Eucheuma cultivated strains were identified by internal transcribed spacer (ITS) sequences. The phylogenetic tree was constructed using neighbor-joining and maximum likelihood methods. The results indicate that different ITS sequence lengths occurred in the different genera and species. An obvious difference in morphology could be found in the protuberance shape between Kappaphycus and Eucheuma. The protuberance in Eucheuma was thorn-like and in Kappaphycus was wartlike or papillate. Their ITS sequence lengths differed significantly in nucleotide variation rates up to 58.55%-63.90%. All nucleotide variations occurred in the ITS1 and ITS2 regions except for five nucleotide transversions in the 5.8S rDNA region. In addition, the difference was at the branches among congeneric species. Kappaphycus sp. had branches with small buds, while K. alvarezii did not have such a feature. The nucleotide variation rates varied from 7.02% to 7.48% among species; within the same species of the clades it was <1.20%. Eucheumatoideae algae cultivated in China consisted of three clades, K. alvarezii, Kappaphycus sp., and E. denticulatum. The results indicate that ITS sequence analysis was an effective way for identification of interspecies and intraspecies phylogenetic relationships and might provide a clue for molecular identification of algal Eucheumatoideae.     

Comparison of stem taper models for the four tropical tree species in Mount Makiling,Philippines

This study was conducted to evaluate the performance of six stem taper models on four tropical tree species, namely Celtis luzonica (Magabuyo), Diplodiscus paniculatus (Balobo), Parashorea malaanonan (Bagtikan), and Swietenia macrophylla (Mahogany) in Mount Makiling Forest Reserve (MMFR), Philippines using fit statistics and lack-of-fit statistics. Four statistical criteria were used in this study, including the standard error of estimate (SEE), coefficient of determination (R ²), mean bias \(( \bar E )\), and absolute mean difference (AMD). For the lack-offit statistics, SEE, \(\bar E\) and AMD were determined in different relative height classes. The results indicated that the Kozako2 stem taper model offered the best fit for the four tropical species in most statistics. The Kozako2 model also consistently provided the best performance in the lack-of-fit statistics with the best SEE, \(\bar E\) and AMD in most of the relative height classes. These stem taper equations could help forest managers and researchers better estimate the diameter of the outside bark with any given height, merchantable stem volumes and total stem volumes of standing trees belonging to the four species of the tropical forest in MMFR.     

Long-term changes in sedimentary diatom assemblages and their environmental implications in the Changjiang (Yangtze) River estuary,China

Long-term data on diatom assemblages in a sediment core （60 cm） obtained from the Changjiang （Yangtze） River estuary were analyzed in order to assess the environmental changes that took place in the approximately 38 years （as determined by 210pb measurements）, i.e., between 1974 and 2012, of sediment accumulation. From the sediment core, 62 diatom taxa and genera were identified. The diatom biomass in the core generally increased beginning in the mid-1990s （core depth： 35 cm）, accompanied by a shift in the dominant species from Podosira stelliger and two species of Cyclotella （C. stylorum and C. striata） to Paralia sulcata, three species of Thalassiosira （ T. eccentria, I＂. oestrupii, and T. excentrica）, Actinoptychus undulates, and Thalassionema nitzschioides. The changes in both species diversity and abundance suggested that since the 1980s the estuary has undergone extensive eutrophication. This conclusion was supported by the increased proportion of planktonic species, another indicator of high nutrients inputs, in the Changjiang River estuary.     

Three tropical seagrasses as potential bio-indicators to trace metals in Xincun Bay, Hainan Island, South China

Concentrations of the trace metals Cu,Cd,Pb,and Zn were measured in seawater,rhizosphere sediments,interstitial water,and the tissues of three tropical species of seagrasses (Thalassia hemprichii,Enhalus acoroides and Cymodocea rotundata) from Xincun Bay of Hainan Island,South China.We analyzed different environmental compartments and the highest concentrations of Pb and Zn were found in the interstitial and seawater.The concentrations of Cd and Zn were significantly higher in blades compared with roots or rhizomes in T.hemprichii and E.acoroides,respectively.A metal pollution index (MPI) demonstrated that sediment,interstitial water,and seagrasses in the sites located nearest anthropogenic sources of pollution had the most abundant metal concentrations.There was obvious seasonal variation of these metals in the three seagrasses with higher concentrations of Cu,Pb and Zn in January and Cd in July.Furthermore,the relationships between metal concentrations in seagrasses and environmental compartments were positively correlated significantly.The bioconcentration factors (BCF) demonstrated that Cd from the tissues of the three seagrasses might be absorbed from the sediment by the roots.However,for C.rotundata,Zn is likely to be derived from the seawater through its blades.Therefore,the blades of T.hemprichii,E.acoroides and C.rotundata are potential bio-indicators to Cd content in sediment,and additionally Zn content (C.rotundata only) in seawater.     

First record of Biecheleria cincta (Dinophyceae) from Chinese coasts, with morphological and molecular characterization of the strains

The presence of Biecheleria cincta (=Woloszynskia cincta) in the Chinese coasts is reported for the first time. In scanning electron microscope, three to five series of vesicles and an elongated apical vesicle (EAV) were visible in the epicone, and both the hypocone and the cingulum had three series of vesicles each. Thin sections revealed that B. cincta possesses stalked pyrenoids and an unusual eyespot consisting of a stack of cisternae with brick-like materials (type E), thus supporting its transfer from Woloszynskia to Biecheleria. Spiny cysts formed spontaneously in culture, with an encystment rate of around 20%. Both large subunit ribosomal DNA (LSU rDNA) and internal transcribed spacer region (ITS) sequences in 12 strains from the Chinese coasts were determined. Phylogenetic analyses based on LSU rDNA and ITS sequences using Bayesian inference and maximum likelihood revealed two distinct ribotypes (referred to as ribotype A and B) in B. cincta. ITS region pairwise distances within B. cincta ranged from 0.024 to 0.072, suggesting the existence of a complex of cryptic species.     

Ulva and Enteromorpha (Ulvaceae, Chlorophyta) from two sides of the Yellow Sea: analysis of nuclear rDNA ITS and plastid rbcL sequence data

Ulvacean green seaweeds are common worldwide; they formed massive green tides in the Yellow Sea in recent years, which caused marine ecological problems as well as a social issue. We investigated two major genera of the Ulvaceae, Ulva and Enteromorpha, and collected the plastid rbcL and nuclear ITS sequences of specimens of the genera in two sides of the Yellow Sea and analyzed them. Phylogenetic trees of rbcL data show the occurrence of five species of Enteromorpha (E. compressa, E. flexuosa, E. intestinalis, E. linza and E. prolifera) and three species of Ulva (U. pertusa, U. rigida and U. ohnoi). However, we found U. ohnoi, which is known as a subtropical to tropical species, at two sites on Jeju Island, Korea. Four ribotypes in partial sequences of 5.8S rDNA and ITS2 from E. compressa were also found. Ribotype network analysis revealed that the common ribotype, occurring in China, Korea and Europe, is connected with ribotypes from Europe and China/Japan. Although samples of the same species were collected from both sides of the Yellow Sea, intraspecific genetic polymorphism of each species was low among samples collected worldwide.     

Screening and isolation of the algicidal compounds from marine green alga <Emphasis Type="Italic">Ulva intestinalis</Emphasis>

Twenty species of seaweed were collected from the coast of Zhejiang, China, extracted with ethanol, and screened for algicidal activity against red tide microalgae Heterosigma akashiwo and Prorocentrum micans. Inhibitory effects of fresh and dried tißsues of green alga Ulva intestinalis were assessed and the main algicidal compounds were isolated, purified, and identified. Five seaweed species, U. intestinalis, U. fasciata, Grateloupia romosissima, Chondria crassicaulis, and Gracilariopsis lemaneiformis, were investigated for their algicidal activities. Fresh tissues of 8.0 and 16.0 mg/mL of U. intestinalis dissolved in media significantly inhibited growth of H. akashiwo and P. micans, respectively. Dried tissue and ethyl acetate (EtOAc) extracts of U. intestinalis at greater than 1.2 and 0.04 mg/mL, respectively, were fatal to H. akashiwo, while its water and EtOAc extracts in excess of 0.96 and 0.32 mg/mL, respectively, were lethal to P. micans. Three algicidal compounds in the EtOAc extracts were identified as 15-ethoxy-(6z,9z,12z)-hexadecatrienoic acid (I), (6E,9E,12E)-(2-acetoxy-β-D-glucose)-octadecatrienoic acid ester (II) and hexadecanoic acid (III). Of these, compound II displayed the most potent algicidal activity with IC₅₀ values of 4.9 and 14.1 µg/mL for H. akashiwo and P. micans, respectively. Compound I showed moderate algicidal activity with IC₅₀ values of 13.4 and 24.7 µg/mL for H. akashiwo and P. micans, respectively. These findings suggested that certain macroalgae or products therefrom could be used as effective biological control agents against red tide algae.     

Seasonal variations of net-phytoplankton community structure in the southern Yellow Sea

Based on the field survey data of four cruises in 2011, all phytoplankton communities in the southern Yellow Sea (SYS) were investigated for the species composition, dominant species, abundance and diversity indices. A total of 379 species belonging to 9 phyla were identified, of which the most abundant group was Bacillariophyta (60.9%), followed by Pyrrophyta (23.7%) and Haptophyta (6.9%). The seasonal distribution of abundance was: summer (4137.1×10³ ind m^?3) > spring (3940.4×10³ ind m^?3) > winter (3010.6×10³ ind m^?3) > autumn (340.8 ×10³ ind m^?3), while the horizontal distribution showed a decreasing tendency from inshore to offshore regions. The dominant species of phytoplankton varied in different seasons. The dominant species were Thalassiosira pacifica, Skeletoema spp. and Chaetoceros cinctus in spring, Chaetoceros debbilis, Chaetoceros pseudocurvisetus and Chaetoceros curvisetus in summer, Thalassiosira curviseriata, Alexandrium catenella and Ceratium fusus in autumn, Paralia sulcata, Phaeocystis sp. and Bacillaria paradoxa in winter, respectively. In SYS, the group of temperate coastal species was the major ecotype, and the groups of the central SYS species and oceanic species were also important constituents. The average values of Shannon-Weaver diversity index (H’) and Pielou evenness index (J) were 2.37 and 0.65 respectively. The indices H’ and J in the open sea were higher than those in coastal waters. Obvious co-variation tendencies between H’ and J were observed in all but the summer cruise of this survey.     

Are Acila divaricata and Acila mirabilis One Species or Two Distinct Species?Evidence from COI Mitochondrial DNA

Acila divaricata (Hinds, 1843) and A. mirabilis (Adams and Reeve, 1850) are common benthic bivalves in China. A number of researchers have proposed that the latter species is a junior synonym of the former species. Because of morphological similarities, it is difficult to distinguish these two species based on visual examination only. For better understanding of their taxonomy, the mitochondrial COI gene fragments of five individuals of A. divaricata from the East China Sea and six individuals of A. mirabilis from the Yellow Sea were sequenced in this study. The phylogenetic relationships of the obtained COI sequences, together with nineteen sequences of three species of the genus Nucula, were analyzed. The pairwise intra- and inter-specific distances for the COI sequences ranged from 0.002 to 0.017 and from 0.128 to 0.134, respectively, and no overlap was found. Phylogenetically, A. divaricata and A. mirabilis form distinct clades and cluster into a sister to all other Nucula species. The results indicated that A. divaricata and A. mirabilis are two distinct species. The differences in the morphology and distribution between the two species were briefly discussed.     

Composition and distribution of planktonic ciliates in the southern South China Sea during late summer: Comparison between surface and 75 m deep layer

Ciliates are very important components in most marine ecosystem.They are trophic link between the microbial food web and grazing food chain.In this study,ciliates were collected from 11 sites in the southern South China Sea(SCS) during August 25 to September 28,2011.Their composition and distribution at the surface and 75 m deep depth of the ocean were studied.A total of 30 species belonging to 22 genera were identified,and 22 species of 15 genera were Tintinnids.Eutintinnus fraknoii and E.stramentus were the most common species.The other dominants were strombidiids ciliates including Strombidium conicum and S.globosaneum,which were followed by the tide form,Mesodinium pulex.Ciliates abundance ranged from 46 ind L~(-1) to 368 ind L~(-1) in the open sites,46–368 ind L~(-1) at surface and 73–198 ind L~(-1) at 75 m deep layer.In the Yongshu reef,ciliates abundance ranged from 167 ind L~(-1) to 365 ind L~(-1) in the water column,similar to that in Sanya coral reef waters.Ciliates composition showed obvious difference between surface and 75 m deep layer at station S2(P 0.05),while no similar result was observed at other sites.At 75 m deep layer,salinity was negatively related to mixed layer depth(P 0.05),but positively to chlorophyll a concentration(P 0.05),indicating that the change of vertical mixing in water column influenced vertical distribution of ciliates in the southern SCS.     

Seasonal variation in community structure and body length of dominant copepods around artificial reefs in Xiaoshi Island, China

This study aims to investigate the seasonal variations in copepod community structure and prosome length of dominant species from March 2009 to January 2010 around artificial reefs in Xiaoshi Island,Yellow Sea,Weihai,China.Samples were collected using two types of plankton net(Model I and Model II) for different-sized copepods.The number of taxon was calculated from the data of both the net types,while the copepod abundance was done using the samples from Model II only.Sixteen species of planktonic copepods,including 5 dominant species,were recorded.Results reveal that Oithona similis was the first dominant species from March to June,and was replaced by Paracalanus parvus in September;both dominated the copepod community in January.Acartia hongi was the second dominant species from March to September.Centropages abdominalis was the third dominant species from March to June,and was replaced by O.similis in September and Corycaeus affinis in January.C.affinis was the fourth dominant species in September.Population density of the dominant copepods was compared with that of other similar regions.We found that the dominant species were mostly small copepods(<1 mm) except for adult Centrapages abdominalis.Seasonal variation in prosome length of O.similis,C.abdominalis,and C.affinis,and their copepodites were studied for the first time in China.For P.parvus and A.hongi,seasonal trends in prosome length variation were similar with those in Jiaozhou Bay,Yellow Sea,Qingdao,China,in a similar temperate domain.The results are helpful for future calculation of copepod biomass and production,and for investigation of the relationship between copepods and fish resources.     

Fouling acorn barnacles in China—a review

We review the species composition,distribution, and seasonal variation of fouling acorn barnacles in Chinese waters-from Bohai Sea and Yellow Sea to East and South China Seas. Thirty-two species of acorn barnacles were found, of which, the dominant species are Amphibalanus amphitrite, A. reticulatus, A. variegates, Balanus trigonus, Fistulobalanus kondakovi, Megabalanus tintinnabulum, Striatobalanus amaryllis, and Eurapha withersi in the fouling communities. A. amphitrite is the dominant species in the coastal waters of Bohai Sea and Yellow Sea and A. reticulatus is dominant in the East and South China Seas. The settlement period of fouling acorn barnacles is usually in summer and autumn. From north to south with the decrease of latitude, their settlement period obviously extends, even to the whole year, and the species number also increases.0ther environmental factors, such as salinity and distance from shore, also play an important role in the distribution of fouling acorn barnacles.     

Effect of UV-B irradiation on interspecific competition between Ulva pertusa and Grateloupia filicina

We report the effect of UV-B irradiation (9.6 kJ m^?2 day^?1) on interspecific competition between two species of macroalgae, Ulva pertusa (U) and Grateloupia filicina (G), in co-culture. Growth of U. pertusa and G. filicina was inhibited by UV-B irradiation in mono-culture and specific growth rate (μ) declined as a result. Interspecific competition between U. pertusa and G. filicina was closely related to the initial weights when co-cultured. When initial ratios of U. pertusa (U) to G. filicina (G) were U:G=1.2:1 and 1:1, U. pertusa was the dominant algae. When the initial U:G ratio was 1:1.2, G. filicina was competitively dominant in the earlier stage, but U. pertusa grew faster, superseding G. filicina in the later stage. At initial ration U:G = 1:1.4, G. filicina was predominant. Under UV-B irradiation, the competitive ability of G. filicina was weakened and the interspecific competitive balance favored U. pertusa, which suggests that G. filicina was more sensitive to UV-B irradiation. We also probed the potential allelopathic effects between the two species, which led to mutual growth inhibition.     

Quantitative trait loci detection of <Emphasis Type="Italic">Edwardsiella tarda</Emphasis> resistance in Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> using bulked segregant analysis

In recent years, Edwardsiella tarda has become one of the most deadly pathogens of Japanese flounder (Paralichthys olivaceus), causing serious annual losses in commercial production. In contrast to the rapid advances in the aquaculture of P. olivaceus, the study of E. tarda resistance-related markers has lagged behind, hindering the development of a disease-resistant strain. Thus, a marker-trait association analysis was initiated, combining bulked segregant analysis (BSA) and quantitative trait loci (QTL) mapping. Based on 180 microsatellite loci across all chromosomes, 106 individuals from the F1333 (♀: F0768 ×♂: F0915) (Nomenclature rule: F+year+family number) were used to detect simple sequence repeats (SSRs) and QTLs associated with E. tarda resistance. After a genomic scan, three markers (Scaffold 404-21589, Scaffold 404-21594 and Scaffold 270-13812) from the same linkage group (LG)-1 exhibited a significant difference between DNA, pooled/bulked from the resistant and susceptible groups (P <0.001). Therefore, 106 individuals were genotyped using all the SSR markers in LG1 by single marker analysis. Two different analytical models were then employed to detect SSR markers with different levels of significance in LG1, where 17 and 18 SSR markers were identified, respectively. Each model found three resistance-related QTLs by composite interval mapping (CIM). These six QTLs, designated qE1–6, explained 16.0%–89.5% of the phenotypic variance. Two of the QTLs, qE-2 and qE-4, were located at the 66.7 cM region, which was considered a major candidate region for E. tarda resistance. This study will provide valuable data for further investigations of E. tarda resistance genes and facilitate the selective breeding of disease-resistant Japanese flounder in the future.