Acanthogobius Flavimanus Research Articles

Distribution and diets of larval and juvenile fishes: Influence of salinity gradient and turbidity maximum in a temperate estuary in upper Ariake Bay, Japan

We investigated the fish assemblage and distribution, diversity, and diets in relation to copepod prey communities along the Chikugo estuarine gradient in the Ariake Bay, Japan. Larval and juvenile fish samples, ambient copepod samples were collected and major hydrographic parameters were recorded at seven selected sampling stations (salinity range: 0.4–28.8 psu) during four sampling cruises in spring 2001. A zone of estuarine turbidity maximum (ETM) was identified in the upper part of the estuary which was characterized by low salinity. Two different fish and copepod communities based on the spatial distribution patterns were identified: the oligohaline community in the upper estuary, which was associated with the ETM; and the euryhaline community in the lower estuary, downstream of the ETM. The oligohaline fish community was composed of Acanthogobius flavimanus, Acanthogobius hasta, Coilia nasus, Neosalanx reganius, and Trachidermus fasciatus while the euryhaline community was composed of Engraulis japonicus and Sebastes inermis. Lateolabrax japonicus was distributed over wide spatial areas. Sinocalanus sinensis was the single dominant member of the oligohaline copepod community while the euryhaline community was dominated by Oithona davisae, Acartia omorii and Paracalanus parvus. Strong dietary relationships were identified between fishes and copepods in the same community. ETM appears to have significant influence on the distribution and abundance of the oligohaline copepod S. sinensis and this prey copepod appears to have strong influence on the fishes in the oligohaline regions. Most of the fishes were distributed in the low saline upper estuary where they foraged on the single dominant copepod S. sinensis which contributes the majority of the copepod standing biomass of the estuary and thus appear to support nursery for fishes. It was concluded that the ETM-based copepod S. sinensis plays a key role in survival and distribution of larval and juvenile fishes in Chikugo estuary.

Heterophyid metacercarial infections in brackish water fishes from Jinju-man (Bay), Kyongsangnam-do, Korea

Heterophyid metacercarial infections in brackish water fishes, i.e., perch, shad, mullet, redlip mullet, and goby, of Jinju-man (Bay), Kyongsangnam-do, Korea, were investigated using a digestion technique. Among 45 perch (Lateolabrax japonicus), the metacercariae of Heterophyopsis continua were found in 55.6% (18.5 metacercariae per fish), Stictodora spp. in 28.9% (3.6), and Metagonimus takahashii in 6.7% (17.0). The metacercariae of H. continua were detected in 23 (65.7%) of 35 shad (Konosirus punctatus). Among 15 mullet (Mugil cephalus), the metacercariae of Pygidiopsis summa were found in 100% (105.9 metacercariae per fish), Heterophyes nocens in 40.0% (8.5), H. continua in 13.3%, and Stictodora spp. in 6.7%. Among 12 redlip mullet (Chelon haematocheilus), the metacercariae of P. summa were detected in 91.7% (1,299 metacercariae per fish), H. nocens in 16.7%, and Stictodora spp. in 16.7%. Among 35 gobies (Acanthogobius flavimanus), the metacercariae of Stictodora spp. were found in 82.9% (44.5 metacercariae per fish), and H. continua in 25.7% (2.8). The adult flukes recovered from a cat experimentally infected with metacercariae from perches were compatible with M. takahashii. The results confirm that the estuarine fish in Jinju-man (Bay) are heavily infected with heterophyid metacercariae. Furthermore, it was found for the first time that the perch acts as a second intermediate host for M. takahashii.

Ontogenetic diet shift, feeding rhythm, and daily ration of juvenile yellowfin goby Acanthogobius flavimanus on a tidal mudflat in the Tama River estuary, central Japan

To ascertain the feeding habits of benthic juvenile yellowfin goby Acanthogobius flavimanus, the gut contents of 599 specimens (15–41 mm in standard length, SL), collected on a tidal mudflat in the Tama River estuary throughout the diel cycle, were examined. The major prey items changed from harpacticoid copepods to errant and sedentary polychaetes at ca. 20 mm SL. Prey width increased with fish size. Fish of 26–28 mm SL fed mainly from sunset to morning, with highest feeding intensity during twilight hours and/or high tide. Based on the gut evacuation rate estimated from a forced feeding experiment in the laboratory and data for the diel change of mean gut-content volume in the field, the daily ration of juvenile yellowfin goby (26–28 mm SL) was calculated to be 13.8 mm3 fish−1 day−1. This volume is approximately equivalent to 3.9 individuals of the errant polychaete Ceratonereis erythraeensis (9.7 mm in body length, BL) or 8.1 individuals of the sedentary polychaete Prionospio japonica (14.8 mm BL), both species occurring abundantly on the mudflat during the study.

문절망둑(Acanthogobius flavimanus)의 생식소 발달과 혈중 성 스테로이드호르몬 농도 변화

Changes of sex steroid hormones in the plasma of yellowfin goby, Acanthogobius flavimanus were investigated in relation to the gonadosomatic index (GSI), the hepatosomatic index (HSI) and gonadal development. The GSI in females rose rapidly in November and remained high from December to May <TEX>$(7.26\pm0.89­6.62\pm0.02)$</TEX>. The Male's GSI also increased gradually from November and was highest in May <TEX>$(0.16\pm0.08)$</TEX>. The HSI in both sexes was in reverse correlation with the GSI, and the HSI was low during the spawning season (February-May). In females, the <TEX>$estradiol-17{\beta}\;(E_2)$</TEX> level increased during vitellogenesis (November and December) and reached its maximum <TEX>$(8.13\pm2.87 ng/mL)$</TEX> at the maturing period, in January. <TEX>$17{\alpha},\;20{\beta}$</TEX>-dihydroxy-4-pregnen-3-one<TEX>$(17{\alpha}20{\beta}OHP)$</TEX> gradually increased from October <TEX>$(0.063{\pm}0.02ng/mL)$</TEX> to March <TEX>$(0.16{\pm}0.02ng/mL)$</TEX> and increased rapidly in May. The level of testosterone (T) showed a similar tendency of <TEX>$E_2$</TEX>. In males, T increased gradually during spermatogenesis from September to December <TEX>$(0.14{\pm}0.06­0.26{\pm}0.10ng/mL)$</TEX> and peaked in January <TEX>$(0.36{\pm}0.29 ng/mL)$</TEX> when the spermatozoa filled the testis. 11-KT also rose markedly in January and then decreased. On the other hand, <TEX>$17{\alpha}29{\beta}OHP$</TEX> in males did not show any clear tendencies.

Larval and juvenile fishes occurring with flood tides on an intertidal mudflat in the Tama River estuary, central Japan

Intertidal movements of fish larvae and juveniles on a mudflat in the Tama River estuary, central Japan, were investigated by comparing the abundance and sizes of fishes caught in the intertidal zone during flood tides with those in the subtidal zone during low tides. A total of 28 465 individuals, belonging to 9 families and 20 species, were collected by small purse seine. Among the abundant species, planktonic larvae and juveniles of gobiids and Konosirus punctatus were more abundant in the intertidal zone at flood tide than the subtidal zone at low tide. Similar occurrence patterns were found in juvenile Plecoglossus altivelis altivelis and Lateolabrax japonicus, having fully developed swimming abilities. In contrast to these species, much higher abundances of epibenthic juveniles of 2 gobiids (Acanthogobius flavimanus and Gymnogobius macrognathos) were found in the subtidal zone at low tide, although they also utilized the intertidal zone at flood tide.

MtDNA singletons as evidence of a post-invasion genetic bottleneck in yellowfin goby Acanthogobius flavimanus from San Francisco Bay, California

Yellowfin goby, a fish native to East Asia, was first reported in northern California (San Francisco Bay) in 1963 and in southern California (Los Angeles Harbor) in 1979. Over the past 4 decades, it has spread to other northern and southern California estuaries, respectively. The docu- mented expansion of yellowfin goby in California provided an opportunity to study potential founder effects in a marine invasive fish by seeking evidence of reductions in mtDNA singleton haplotypes consistent with an expected loss of overall genetic diversity. We obtained samples of yellowfin goby from San Francisco Bay in northern California, from 2 small estuaries in southern California, and from Tokyo Bay, Japan, the presumed source population. The mtDNA control region was fully sequenced and analyzed for a total of 216 specimens, where the numbers of singleton haplotypes relative to the total number of haplotypes in each sample were compared to predictions from a regression analysis of singletons on total haplotypes. AMOVA comparisons among haplotype frequencies were also per- formed. Singleton haplotypes were significantly fewer than predicted among yellowfin goby of San Francisco Bay, indicating some loss of genetic diversity in that invasive population. Singletons were not significantly fewer than prediction among yellowfin goby of Tokyo Bay or of southern California. ΦST values were not significantly different between San Francisco and Tokyo bays, but were different between San Francisco Bay in northern California and southern California locations, suggesting separate introductions to California.

Catch efficiency of a small seine for benthic juveniles of the yellowfin goby Acanthogobius flavimanus on a tidal mudflat

Experimental hauls of a small seine for juvenile yellowfin goby, Acanthogobius flavimanus, were carried out on a tidal mudflat in the Shinhama Lagoon, central Japan, between April and June 2001. Immediately before each haul, visual censuses were conducted to evaluate whether juvenile densities estimated from the catches accurately reflected real densities in the area. The densities estimated from the net samples were significantly lower than those determined by visual censuses throughout the study period. The catch efficiency of the small seine for juveniles of ca. 17–40 mm in standard length was estimated as 23–71%, a negative relationship between efficiency and fish length being found.

Myxobolus buri, the myxosporean parasite causing scoliosis of yellowtail, is synonymous with Myxobolus acanthogobii infecting the brain of the yellowfin goby

: Myxobolus buri Egusa, 1985, is a well-documented myxosporean parasite that causes the scoliosis of cultured yellowtail Seriola quinqueradiata. A similar parasite has been described as Myxobolus acanthogobii Hoshina, 1952, from the brain of the yellowfin goby Acanthogobius flavimanus, although this parasite is not associated with skeletal abnormalities in host fish. The present study aimed to re-examine the identification of these two parasites by morphological and molecular analyses. Morphological characteristics (e.g. presence of the intercapsular processes and several folds on the sutural ridges) and spore dimensions were not distinguishable between the two species and were consistent with those in the original descriptions. Molecular analysis indicated that small subunit rRNA gene sequences shared 100% identity between the two parasites. Consequently, it can be concluded that M. buri is synonymous with M. acanthogobii, and thus this parasite can be reassigned as M. acanthogobii.

Effects of endocrine-disrupting chemicals on expression of ubiquitin C-terminal hydrolase mRNA in testis and brain of the Japanese common goby

We investigated the effects of endocrine-disrupting chemicals (EDCs) on the expression of ubiquitin C-terminal hydrolase (UCH) mRNA in the testis and brain of the Japanese common goby, Acanthogobius flavimanus. The cDNA sequence of goby UCH contained an open reading frame encoding 220 amino acid residues ( M r = 24,223) with 51.3% overall sequence identity with human and mouse UCHL1. A competitive PCR assay was used to quantify the levels of UCH mRNA in the testis and brain of male gobies after exposure to bisphenol A, nonylphenol, or estradiol-17β for 3 weeks. Exposure to estradiol-17β at a nominal concentration of 100 ng/L induced significant increase in UCH mRNA levels in both testis and brain ( P < 0.05), whereas exposure to nonylphenol induced a significant decrease in UCH mRNA levels in the testis ( P < 0.01). These results suggest that EDCs can either positively or negatively regulate UCH mRNA levels.

Morphological and functional development of characters associated with settlement in the yellowfin goby, Acanthogobius flavimanus

Morphological and functional development of characters from pelagic larval to benthic juvenile periods in the yellowfin goby, Acanthogobius flavimanus, were examined on the basis of 275 specimens (9.4–25.9 mm in standard length) collected in shallow water in the Tama River estuary, central Japan. Judging from the development of osteological features, late pelagic juveniles possessed fully developed swimming and feeding abilities. Rapid changes in various characters, including the formation of a loop-shaped gut, increases in condition factor and teeth number, broader upper-field view capability, and extended scaly area and pigmentation development, occurred during the transition from late pelagic to early benthic periods. Most of the changes were associated with structural and functional aspects enabling more efficient use of benthic resources or the avoidance of predators in the benthic habitat.

Deduced primary structure of two forms of vitellogenin in Japanese common goby ( Acanthogobius flavimanus)

Complete nucleotide sequences of two forms of vitellogenin (Vg) cDNA in Japanese common goby were determined from a liver cDNA library of E 2-treated male fish. These two Vg cDNAs contained complete open reading frames encoding 1664 and 1238 amino acid residues including signal peptides, respectively. From comparison of the deduced amino acid sequences of both Vgs and the partial amino acid sequences of the yolk proteins, the longer sequence was concluded to be cDNA of the Vg-530 and the shorter one was that of the Vg-320 of the Japanese common goby which were reported in our previous paper. The deduced sequence of Vg-530 without signal peptide was arranged by lipovitellin heavy-chain (LvH), phosvitin (Pv), lipovitellin light-chain (LvL), and β ′-component (β ′-c) domains from the N-terminus, and showed a range of 40–45% sequence identity to those of other fish. Furthermore, the deduced sequence of Vg-320 showed no obvious Pv domain, has a shortened C-terminal coding region after the LvH domain, and showed a close similarity to the phosvitin-less Vg of zebrafish. Moreover, biochemical analysis of the yolk proteins verified that Vg-530 cleaves into the Lv–Pv complex (molecular mass: 470 kDa) and β ′-c (33 kDa), while Vg-320 showed no change when incorporated into oocytes. The present study demonstrated the existence of the two different forms of Vgs at both the cDNA and protein level, and showed molecular alteration of the two Vgs during vitellogenesis. Two Vg sequence data will aid in designing nucleotide probes for detecting Vg gene expressions as a biomarker of environmental estrogens.

Estrogenic activity in coastal areas around Japan evaluated by measuring male serum vitellogenins in Japanese common goby Acanthogobius flavimanus

: Surveys of the estrogenic activity in coastal areas of Japan were performed by using two serum vitellogenins (Vg-530 and Vg-320) of male Japanese common goby Acanthogobius flavimanus as biomarkers. To evaluate the relationship between the Vg concentrations in the serum of male fish and the concentrations of environmental estrogens in seawater, 3 week exposure experiments were performed using estradiol (E2), nonylphenol (NP) and bisphenol A (BPA). From the results of the E2 exposure, mean concentrations of the Vg and the ratio of Vg-positive fish increased from actual concentration at 10.5 ng/L E2 treatment. Exposure of NP and BPA showed that the 19.0 µg/L NP treatment induced the Vg but 133.7 µg/L BPA did not. As for the survey of the estrogenic activity in coastal areas, the mean Vg concentrations and ratio of Vg-positive fish in some urban areas were similar to values of the 10.5 ng/L E2 treatment. Although E2 and NP were detected in the seawater from urban areas, the concentrations were concluded as not sufficient to independently induce the Vg. Considering these results, it is concluded that the total estrogenic activity in some urban areas is dependent not only on E2 but synergistically with other environmental estrogens.

Development of enzyme-linked immunosorbent assays for two forms of vitellogenin in Japanese common goby ( Acanthogobius flavimanus)

Two vitellogenins (Vgs) were detected in serum from estradiol-17β (E 2)-injected Japanese common goby ( Acanthogobius flavimanus). Vitellogenins with molecular masses of 530 kDa (Vg-530) and 320 kDa (Vg-320) were purified, and used to raise specific antisera in rabbits. Sandwich enzyme-linked immunosorbent assays (ELISAs) for Vg-530 and Vg-320 were developed using the antisera and the isolated Vgs. The sensitivity ranges of these ELISAs were 1.25–160 ng/ml for Vg-530 and 0.26–66 ng/ml for Vg-320, and very low cross-reactivity was found with the alternate Vg in each assay. Treatment of male gobys with E 2 by injection and immersion induced both Vgs in sera in a dose-dependent manner. The mean concentrations of the Vgs increased from 10 ng/L E 2 exposure for three weeks. Serum concentrations of the two Vgs in field-collected maturing females increased in accordance with increment of E 2 level and ovarian development, and the mean concentrations of Vg-530 were higher than those of Vg-320 in maturing female. These results indicate that the sandwich ELISAs for Vg-530 and Vg-320 developed in the present study is useful as an assay system for surveys of estrogenic activity in coastal areas of Japan.

낙동강 하구역 어류의 종조성 변화

Species composition and seasonal variations in abundance of fishes in the Nakdong River estuary were investigated using an otter trawl seasonally from September 2001 to July 2002. These data were compared with those obtained before the construction of the estuary barrage in 1987. A total of 3,648 fishes that comprised 30 species in 21 families were collected. Acanthogobius flavimanus and Leiognathus nuchalis predominated, and they were responsible for in the number of individuals and biomass, respectively. The next abundant fish species were Platycephalus indicus and Liparis tanakai. Compared with data obtained before the construction of the estuary barrage in 1987, abundances of Acanthogobius flavimanus, Platycephajus indicus, Liparis tanakai, Tridentiger trigonocephalus and Lateolabrax japonicus increased, while those of Pholis fangi, Repomucenus valenciennei, Sardineila zunasi and Scomber japonicus decreased. These results seems to be related to change of sediment environment caused by irregular discharge of freshwater with variation of sea water movement in the Nakdong River estuary.

Expression of ubiquitin C-terminal hydrolase is regulated by estradiol-17β in testis and brain of the Japanese common goby

The effect of endocrine-disrupting chemicals (EDCs) on the expression of ubiquitin C-terminal hydrolase (UCH) mRNA in the Japanese common goby, Acanthogobius flavimanus, was investigated by competitive PCR assay. Exposure of fish to estradiol-17β (E2) induced significant increase in the UCH mRNA in testis and brain, but exposure to bisphenol A and nonylphenol did not. This result suggests that expression of the UCH gene is E2-inducible.

Identification of Acanthotrema felis (Digenea: Heterophyidae) metacercariae encysted in the brackish water fish Acanthogobius flavimanus.

The metacercariae of Acanthotrema felis Sohn et al., 2003 (Digenea: Heterophyidae) were discovered in a species of the brackish water fish, Acanthogobius flavimanus, in the Republic of Korea. They were experimentally fed to kittens, and adult flukes were harvested 7 days later. The adults were morphologically characterized by the presence of a bipartite seminal vesicle, the ventral sucker associated with a ventrogenital sac enclosing 3 sclerites (2 long and pointed, and 1 short and thumb-like), and an unarmed gonotyl. The adult flukes were identified as A. felis Sohn et al., 2003, and the brackish water fish A. flavimanus has been verified as one of its second intermediate hosts.

가덕도 주변 해역 어류의 종조성과 계절 변동 -3. 꽃게통발에 의해 채집된 어류-

가덕도 주변 해역에 서식하는 어류의 종조성과 계절 변동을 알아보기 위해 꽃게통발을 이용하여 어류를 채집하였다. 1998년 1월부터 12월까지 매월 소조기에 채집된 어류는 26과 49종이었다. 붕장어 (Conger myriaster)가 가장 많이 채집되었으며, 그 다음으로 볼락 (Sebastes inermis), 쥐노래미 (Hexagrammos otakii), 노래미(H. agrammus), 쥐치 (Stephanolepis cirrhifer), 문절망둑 (Acanthogobius flavimanus) 등이 많이 채집되었는데, 이들 6종이 전체채집 개체수와 생체량의 <TEX>$67.1\%$</TEX>와 <TEX>$69.4\%$</TEX>를 차지하였다. 그 밖에도 말쥐치 (Thamnaconus modestus), 복섬 (Takifugu niphobles), 그물코쥐치 (Rudarisu ercodes), 그물베도라치 (Dictyosoma burgeri), 횐꼬리볼락 (Sebastes longispinis), 능성어 (Epinephelus septemfasciatus) 등이 비교적 많이 채집되었다. 채집 종수는 11월에 28종으로 가장 많았고, 7월에 14종으로 가장 적었다. 개체수와 생체량은 모두 3월에 가장 높은 값을 보였으며, 개체수는 7월에 생체량은 9월에 가장 낮은 값을 나타냈다. 종다양도지수는 연중 큰 변동이 없는 편이었으나, 채집 어종수가 적고 쥐치와 말쥐치가 극우점하였던 8월에 가장 낮은 값을 보였다. The monthly collected fish samples by crab pots were analyzed in order to study the species composition and seasonal variation of fish assemblage in the coastal water off Gadeok-do, Korea in 1998, During the study period, 49 species of fishes representing 26 families were collected, The dominant species were Conger myriaster, Sebastes inermis, Hexagrammos otakii, H. agrammus, Stephanolepis cirrhifer and Acanthogobius flavimanus. These 6 dominant species accounted for <TEX>$67.1\%$</TEX> and <TEX>$69.4\%$</TEX> in the number of individuals and biomass, respectively. The secondary importance species were Thamnaconus modestus, Takifugu niphobles, Rudarius ercodes, Dictyosoma burgeri, Sebastes longispinis and Epinephelus septemfasciatus. The highest number of species was collected in November, and the number of individuals and biomass were highest in March. But the lowest numbers of species and individuals were collected in July and the lowest biomass in September, Although the species diversity indices varied little monthly, the lowest value was recorded in August because of small number of species and predominance of 5. cirrhifer and T. modestus.

Plasticity in vertical migration by native and exotic estuarine fishes in a dynamic low‐salinity zone

We investigated the degree of flexibility in retention strategies of young fishes in the low‐salinity zone (LSZ) of the San Francisco Estuary during years of highly variable river flow. We conducted depth‐stratified sampling over three full tidal cycles in each year from 1994 to 1996. In 1994, exotic striped bass (Morone saxatilis), native longfin smelt (Spirinchus thaleichthys), and exotic yellowfin goby (Acanthogobus flavimanus) migrated tidally, occurring near the surface on flood tides and near the bottom on ebb tides. This strategy may have facilitated retention, because landward residual currents were absent in this drought year. During 1995, this behavior persisted for striped bass and yellowfin goby, even though landward residual currents were present under high river‐flow conditions. In moderate river‐flow conditions (1996), longfin smelt again migrated tidally, whereas at another station adjacent to shallow bays, longfin smelt, striped bass, and native delta smelt (Hypomesus transpacificus) migrated on a reverse diel cycle, occurring near the surface by day and at depth by night. Reverse diel migration may facilitate horizontal transport and retention. Therefore, young fishes appeared to be behaviorally flexible in different environmental conditions to maximize retention. Vertical migrations may also enhance feeding success because zooplankton prey similarly migrated in the LSZ. Our study underscores the value of interdisciplinary studies in a variety of environmental conditions to decipher the range of organism behaviors promoting transport and retention in optimal habitats.

Species composition and seasonal occurrence of fish larvae and juveniles in the Shimanto Estuary, Japan

To clarify the characteristics of the larval and juvenile fish community in a Japanese estuary, monthly collections were conducted in the shallow waters of the Shimanto Estuary, Japan from July 1985 to June 1987. A total of 49 101 fishes of more than 100 species from 44 families were sampled over the 2-year period. Numerically, Gerres equulus was most common, accounting for 20.02% of the total abundance. Rhyncopelates oxyrhynchus was ranked second, followed by Acanthopagrus latus, Acanthogobius flavimanus, Mugil cephalus cephalus, Parioglossus dotui, and Acanthopagrus schlegeli. Thus, fishes observed in the estuary were mostly marine species that spawn in the sea. The majority of these fish first appeared within the estuary at late postlarval and/or early juvenile stages. Based on their utilization of the shallow waters in the estuary, the majority of species could be categorized as residents. In the Shimanto Estuary, shallow waters are studded with shelters, especially eelgrass beds, which serve as important nursery grounds for coastal and euryhaline fishes.

Diversity and evolution of life histories of gobioid fishes from the viewpoint of heterochrony

The ontogenies of the gobioid fishes are matched against a framework of age-based heterochrony and their life-history strategies are discussed on the basis of published reports. Deceleration was observed in Leucopsarion, Crystallogobius and some species of Luciogobius from temperate or cold waters. Hypomorphosis was observed in Schindleria, Paedogobius and another species of Luciogobius, the former two genera maturing at one month or two after hatching throughout the year in tropical environments. Acceleration was observed in oxudercines, soft bottom-dwellers in intertidal areas and mangrove swamps, during larval and juvenile periods. Their acceleration, based on warm conditions allowing fast metamorphosis, may be an adaptation allowing immediate recruitment to a littoral life style. Hypermorphosis was observed in Acanthogobius flavimanus, which develops more slowly than other congeners. Isomorphosis by acceleration and hypomorphosis was observed during the larval and juvenile periods in fluvial Rhinogobius spp. and Acentrogobius viridipunctatus. This developmental shift, with truncation of the larval period, seems to be an important event among gobioid fishes, facilitating their survival in severe environments such as spates in rivers or on mudflats.