Top PDF Use of otolith Sr:Ca ratios to study the riverine migratory behaviors of Japanese eel Anguilla japonica

Use of otolith Sr:Ca ratios to study the riverine migratory behaviors of Japanese eel Anguilla japonica

Use of otolith Sr:Ca ratios to study the riverine migratory behaviors of Japanese eel Anguilla japonica

Type 3 measurements differed from Types 1 and 2 in not having consistent low or high Sr:Ca ratios. Fig. 3d –i illustrate the diversi- fied temporal changes of Sr:Ca ratios in the otoliths of Type 3 eels. For example, Case 1: the Sr:Ca ratio be- yond the elver check gradually decreased from 7 × 10 – 3 at the elver check to less than 4 × 10 – 3 at the otolith edge (Fig. 3d,e), indicating that the eel after the elver stage gradually migrated to freshwater. Case 2: the Sr:Ca ratios decreased gradually after the elver check to a low level less than 4 × 10 – 3 at ages-1 and -2, and then increased to reach a peak approximately 8.0 × 10 – 3 at age-3. After age-3, it decreased to less than 4 × 10 – 3 again (Fig. 3f). This indicated that the eel migrated into freshwater at ages-1 and -2, rather than migrating out the river into the seawater at age-3 and re-invading the river again. Case 3: the Sr:Ca ratios after the elver check decreased to less than 4 × 10 – 3 from 1 to 4 yr old, then increased to greater than 5 × 10 – 3 thereafter (Fig. 3g,h,i). This indicated that these eels had migrated to freshwater during young yellow eel stage, rather than migrating into seawater, and did not re-entry the river until collected. These phenomena indicated a di- versified habitat use and flexible migratory behavior in the yellow phase. Type 3 eels were further divided into
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Salinity preference of silvering Japanese eel Anguilla japonica: evidence from pituitary prolactin mRNA levels and otolith Sr:Ca ratios

Salinity preference of silvering Japanese eel Anguilla japonica: evidence from pituitary prolactin mRNA levels and otolith Sr:Ca ratios

salinity transfer is only approximately 1 d (Suzuki & Hirano 1991, Suzuki et al. 1991b). In the present study, the yellow and silver stage eels were caught and exposed to the same salinity regimes for about half a day before being sacrificed. However, the silver eels showed a lower PRL expression value than the yellow ones (Fig. 5). There are 2 possible explanations. First, in eels, although the relationship between salinity and PRL expression is valid, the lower PRL transcript levels in silver eels than in yellow eels may also include a maturity response in addition to a salinity response. However, when the freshwater- reared yellow eels were induced to become silver eels by repeated injection of human chorionic gonado- tropins, no significant difference was observed for the expression of PRL mRNA levels between the yellow and silver eels (Y. S. Han et al. unpubl. data). This may partially exclude the maturation-related change in the PRL expression of the eel. Alternatively, the more pos- sible reason may be that the exposure time for the eels in the same salinity regime was not long enough to eliminate the different expression patterns of the PRL mRNA between yellow and silver eels. That is, the true difference of PRL mRNA expression between yellow and silver eels may be even larger than the observed value in the present study.
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Salinity preference of silvering Japanese eel Anguilla japonica: evidence from pituitary prolactin mRNA levels and otolith Sr: Ca ratios.

Salinity preference of silvering Japanese eel Anguilla japonica: evidence from pituitary prolactin mRNA levels and otolith Sr: Ca ratios.

salinity transfer is only approximately 1 d (Suzuki & Hirano 1991, Suzuki et al. 1991b). In the present study, the yellow and silver stage eels were caught and exposed to the same salinity regimes for about half a day before being sacrificed. However, the silver eels showed a lower PRL expression value than the yellow ones (Fig. 5). There are 2 possible explanations. First, in eels, although the relationship between salinity and PRL expression is valid, the lower PRL transcript levels in silver eels than in yellow eels may also include a maturity response in addition to a salinity response. However, when the freshwater- reared yellow eels were induced to become silver eels by repeated injection of human chorionic gonado- tropins, no significant difference was observed for the expression of PRL mRNA levels between the yellow and silver eels (Y. S. Han et al. unpubl. data). This may partially exclude the maturation-related change in the PRL expression of the eel. Alternatively, the more pos- sible reason may be that the exposure time for the eels in the same salinity regime was not long enough to eliminate the different expression patterns of the PRL mRNA between yellow and silver eels. That is, the true difference of PRL mRNA expression between yellow and silver eels may be even larger than the observed value in the present study.
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Identification and growth rates comparison of divergent migratory contingents of Japanese eel (Anguilla japonica)

Identification and growth rates comparison of divergent migratory contingents of Japanese eel (Anguilla japonica)

This study is to identify the different migratory contingents of the eel by their otolith Sr/ Ca ratios and to compare their growth rates among different contingents. 2. Material and method A total of 212 Japanese eels were collected from China, Japan and Taiwan, respectively (Table 1). The eels were collected for artificial maturation and thus all of them were silver eels except those collected from Taiwan. The Pearl River is the third largest river in China, and has a large freshwater volume for eels. The eels from China were collected at Fan-Yu in the lower Pearl River (113j30VE and 23jN), ca. 200 – 250 km from South China Sea, in the fall of 1996 during their downstream spawning migration (Tzeng et al., 2000a). The eels from Japan were collected from the brackish Mikawa Bay (137jE and 34j45VN) on the east coast and from freshwater Shinjiko lake and brackish Naka-umi inland sea (132j45V – 133j45VE and 35j 30V – 35j35VN) on the north coast of western Japan, in June 1998 to June 1999. Mikawa means three rivers in Japanese, because there are three small rivers flowing into the bay. The eels from Taiwan included yellow and silver eels.
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Sex-dependent habitat use by the Japanese eel Anguilla japonica in Taiwan

Sex-dependent habitat use by the Japanese eel Anguilla japonica in Taiwan

Data analyses. Differences in frequency distribution of the wild Japanese eels among habitat contingents were tested for significance by the chi-square test of homogeneity using χ 2 contingency table. Differences in the mean age, TL and BW among eel groups of unknown sex, yellow and silver females and silver males were examined by 1-way ANOVA followed by Tukey’s HSD multiple comparison tests. The differ- ence of the mean otolith Sr:Ca ratios for each sex between 200 and 400 µm and beyond the elver check were measured by Student’s t-test for paired compar- isons.
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Use of the Sex Ratio as a Means of Resource Assessment for the Japanese Eel Anguilla japonica: A Case Study in the Kaoping River, Taiwan

Use of the Sex Ratio as a Means of Resource Assessment for the Japanese Eel Anguilla japonica: A Case Study in the Kaoping River, Taiwan

Giving the unique character of the eel sex ratio in relationship to population density, long-term changes in the eel sex ratio may reflect long-term changes in the eel resource. In conclusion, the use of the sex ratio as an indicator of the eel resource status may be helpful for eel conserva- tion. An analysis of the latest 5 yrs of eel sampling found that the sex ratio was strongly skewed towards females, which contrasts with historic information, suggesting imminent danger to the eel resource in the Kaoping River. The hypothesis that the variation in sex ratio in conjunction with different growth strategies for each sex serves to maximize the adaptive fitness of the eel might turn out to be hazardous when eel sex ratios in all habi- tats significantly shift toward females.
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Disparities in habitat use and migratory behavior between tropical eel Anguilla marmorata and temperate eel A. japonica in four Taiwanese rivers

Disparities in habitat use and migratory behavior between tropical eel Anguilla marmorata and temperate eel A. japonica in four Taiwanese rivers

4 Present address: Institute of Fisheries Sciences, National Taiwan University, Taipei, Taiwan 106, ROC ABSTRACT: Strontium (Sr):calcium (Ca) ratios in otoliths of the eels Anguilla japonica and A. mar- morata caught in 4 Taiwanese rivers were examined to reconstruct their migratory environmental history. In all sampling locations, each eel species preferred a different environment and all were dif- ferently distributed in the river. A. japonica was more abundant than A. marmorata in the lower reach, accounting for 76 to 86% of the eel population. In contrast, A. marmorata was more abundant than A. japonica in the upper reach, accounting for 76 to 100% of the eel population. A. japonica con- sisted of diversified migratory contingents, including freshwater, brackish-water and seawater eels, but A. marmorata tended to reside in freshwater and seemed to avoid seawater during the yellow eel stage. This disparity in migratory behaviors and habitat use between species may reflect interspecific competition and adaptive radiation. The flexible migratory behavior and adaptation to different salinities of A. japonica may be an advantageous evolutional fitness when facing competition, heavy fishing pressure and environmental stress. The freshwater-restricted A. marmorata is more easily threatened by both fishing pressure and continuous habitat degradation than A. japonica.
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The sex-ratio reversal of the Japanese eel Anguilla japonica in the Kaoping River of Taiwan: The effect of cultured eels and its implication

The sex-ratio reversal of the Japanese eel Anguilla japonica in the Kaoping River of Taiwan: The effect of cultured eels and its implication

Otolith elemental signatures determined by SB- ICPMS and LA-ICPMS methods showed similar pat- terns, indicating a higher Mn/Ca ratio and lower Sr/Ca ratio in cultured eels than in wild eels. The concentrations of minor and trace elements in the otolith may be in- fluenced primarily by environmental conditions, al- though physiological processes may also contribute (Kalish, 1989, 1991). Thus, the migratory life history of the fish is recorded in the otoliths (Campana and Neilson, 1985; Campana, 1999). We found that Mn/Ca and Sr/Ca ratios can discriminate between eels from culture ponds and the wild. The constant lower Sr/Ca ratio in the WC/S2 eels than in the W1 eels from LA- ICPMS data may be because the water for the culture ponds was mostly well water, which might have lower Sr concentration compared with estuary water where the W1 eels habituated. The concentration of the Sr/Ca ratio is greatest in seawater, middle in the estuary, and lowest in
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Salinities, not diets, affect strontium/calcium ratios in otoliths of Anguilla japonica

Salinities, not diets, affect strontium/calcium ratios in otoliths of Anguilla japonica

the effects of salinity and diets on otolith Sr/Ca ratios before it is used to study the migratory environmental history of eels. The incorporation of element from the environment into the otoliths is a multi-stage process and is characterized by a sequence of more or less independent barriers. Elements pass by ion transport from blood plasma into the endolymph and are finally precipitated on to the otolith surface (Campana, 1999). The partition coefficients for elements transported from the ambient environment to otolith differ across different barriers. In most otolith studies, the partition coefficients of otolith elements were directly related to the ambient water because of difficulties in measuring concentrations in the endolymphatic fluid surrounding the otolith (Bath et al., 2000; Milton and Chenery, 2001; Kraus and Secor, 2004). The partition coefficient of Sr/Ca ratios from ambient water to otolith for the Japanese Eel, however, is still unclear.
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Migratory life history of European eel Anguilla anguilla from freshwater regions of the River Asi, southern Turkey and their high otolith Sr:Ca ratios

Migratory life history of European eel Anguilla anguilla from freshwater regions of the River Asi, southern Turkey and their high otolith Sr:Ca ratios

Academia Sinica, Nankang, Taipei, Taiwan and Department of Biology, Ondokuzmayis University, Samsun, Turkey (Received 10 May 2010, Accepted 24 December 2010) Otolith Sr:Ca ratios from 32 of 34 European eel Anguilla anguilla collected from three freshwater sites in the River Asi, southern Turkey, indicated that they were resident in fresh water without apparent exposure to salt water since the elver stage. The Sr:Ca ratio criterion indicative of residence in fresh water was more than twice that of values from other European countries. Otolith Sr:Ca ratios of A. anguilla from fresh waters can vary among regions, possibly reflecting regional-specific water chemistry. Hence, the use of Sr:Ca ratios determined in one region to interpret results from a different region might lead to misclassification of migratory life-history types. © 2011 The Authors Journal of Fish Biology © 2011 The Fisheries Society of the British Isles
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Use of otolith microchemistry to investigate the environmental history of European eel Anguilla anguilla.

Use of otolith microchemistry to investigate the environmental history of European eel Anguilla anguilla.

Peak SrICa ratio in the otolith nucleus Regardless of whether the otoliths were removed from natural eels from brackish waters or stocked eels from fresh water lakes, all sh[r]

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Migratory environmental history of the grey mullet Mugil cephalus as revealed by otolith Sr: Ca ratios.

Migratory environmental history of the grey mullet Mugil cephalus as revealed by otolith Sr: Ca ratios.

0.001). The mullet generally spawned offshore and recruited to the estuary at the juvenile stage; therefore, these data support the use of Sr:Ca ratios in otoliths to reconstruct the past salinity history of the mullet. A life-history scan of the otolith Sr:Ca ratios indicated that the migratory environmen- tal history of the mullet beyond the juvenile stage consists of 2 types. In Type 1 mullet, Sr:Ca ratios range between 4.0 × 10 – 3 and 13.9 × 10 – 3 , indicating that they migrated between estuary and offshore waters but rarely entered the freshwater habitat. In Type 2 mullet, the Sr:Ca ratios decreased to a minimum value of 0.4 × 10 – 3 , indicating that the mullet migrated to a freshwater habitat. Most mullet beyond the juvenile stage migrated from estuary to offshore waters, but a few mullet less than 2 yr old may have migrated into a freshwater habitat. Most mullet collected nearshore and offshore were of Type 1, while those collected from the estuaries were a mixture of Types 1 and 2. The mullet spawning stock consisted mainly of Type 1 fish. The growth rates of the mullet were similar for Types 1 and 2. The migratory patterns of the mullet were more divergent than indicated by previous reports of their catadromous behavior.
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Temporal analysis of population genetic composition in the overexploited Japanese eel Anguilla japonica

Temporal analysis of population genetic composition in the overexploited Japanese eel Anguilla japonica

Ming-Iu Lai, Student Member, IEEE, Tzung-Yu Wu, Jung-Chin Hsieh, Chun-Hsiung Wang, and Shyh-Kang Jeng, Senior Member, IEEE Abstract—In this paper a compact switched-beam antenna is proposed. The antenna is composed of a four-element antenna array based on L-shaped quarter-wavelength slot antenna ele- ments. Such an antenna element is a planar structure and presents a directional radiation pattern in the azimuth plane. Its maximum radiation direction is toward near the direction of the open end of the slot. As a result, the open ends of the four slot antennas are arranged toward 0 2 , and 3 2, respectively. The statuses of these antennas are controlled by some diodes. Con- sequently, by carefully controlling the diodes, an antenna with several switchable patterns can be achieved. To prove the concept, a 2.4–2.5 GHz switched-beam antenna for WLAN applications is designed and implemented. Its size is 52 mm in square. The antenna possesses eight directional patterns and many nearly omnidirectional patterns in the azimuth plane. The experiment results fully demonstrate the performance of the proposed design.
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Effects of salinity and ontogenetic movements on strontium:calcium ratios in the otoliths of the Japanese eel, Anguilla japonica Temminck and Schlegel

Effects of salinity and ontogenetic movements on strontium:calcium ratios in the otoliths of the Japanese eel, Anguilla japonica Temminck and Schlegel

The relationship between Sr/Ca ratios in the otoliths of reared eels and ambient salinity (Fig. These data also validate the use of Sr/Ca ratios in otoliths as [r]

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Effects of salinity and ontogenetic movements on strontium: calcium ratios in the otoliths of the Japanese eel, Anguilla japonica Temminck and Schlegel.

Effects of salinity and ontogenetic movements on strontium: calcium ratios in the otoliths of the Japanese eel, Anguilla japonica Temminck and Schlegel.

The relationship between Sr/Ca ratios in the otoliths of reared eels and ambient salinity (Fig. These data also validate the use of Sr/Ca ratios in otoliths as [r]

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The sex ratios and growth strategies of wild and captive Japanese eels Anguilla japonica

The sex ratios and growth strategies of wild and captive Japanese eels Anguilla japonica

The role of gender and sexual differences in the growth histories of Japanese eel Anguilla japonica were linked with respect to the sex ratio and growth rate of wild eels collected from Taiwanese rivers. The sex ratio of wild eels was compared with that of eels semi-intensively cultured in a pond and intensively cultured in an aquarium. The sex ratio of wild eels from a low-density river habitat was dominated by females (86.4% of sex-determined eels), slightly dominated by males (57.1%) in a cultured pond, and dominated by males (90.0%) in an aquarium. This evidence supported the hypothesis that the sex of eels is determined by population density. The parameters of the von Bertalanffy growth equation demonstrated that males grew faster to reach a smaller asymptotic length than did females. We propose that the variation in eel sex ratio interacts with sex-linked differences in growth strategy to play an important role in density-dependent population regulation.
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Timing of metamorphosis and estuarine arrival across the dispersal range of the Japanese eel Anguilla japonica.

Timing of metamorphosis and estuarine arrival across the dispersal range of the Japanese eel Anguilla japonica.

The mean increment widths of the otoliths from the outer core to the metamorphosis check for the elvers collected at the 6 estuaries showed a geographic cline that dec[r]

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Gonadotropin Induced Synchronous Changes of Morphology and Gonadal Development in the Japanese Eel Anguilla japonica

Gonadotropin Induced Synchronous Changes of Morphology and Gonadal Development in the Japanese Eel Anguilla japonica

Abstract In a previous study, we had observed synchronous changes of morphology and gonadal development in wild Japanese eel during the silvering process. In this study, we aimed to clarify if gonadotropin is the key hormone responsible for this phenomenon. Yellow eels captured in the Kaoping River were repeatedly injected with human chorionic gonadotropin (HCG), and changes of morphology and gonadal development were examined. After five weekly injection of HCG at a dosage of 0.75 IU/g body weight, eels was classified into well-responsive and poor-responsive groups according to skin coloration. Approximately 50 % of males and 20 % of females were responsive to become silver eels. Mean age, total length, body weight, condition factor, gonadosomatic index (GSI), fin-index (FI), hepatosomatic index (HSI) and ocular index (OI) were significantly higher in well-responsive eels than in poor-responsive eels. The mean digestosomatic index (DSI), in contrast, significantly decreased in well-responsive eels compared to poor ones. OI was positively correlated and DSI was negatively correlated with the GSI in both sexes. These results indicated that well developed eels are more sensitive to HCG treatment, and the skin color, eye size, gonadal development and digestive tract shrinkage were synchronous after HCG injection. The pituitary – gonad axis plays important role on eel silvering.
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The silvering of the Japanese eel Anguilla japonica: season, age, size and fat

The silvering of the Japanese eel Anguilla japonica: season, age, size and fat

2 Taiwan Fisheries Research Institute, 199 Hou-Ih Road, Keelung, Taiwan Abstract This study aims to understand the changes in age, total length, body weight, and muscle fat content in the Japanese eel Anguilla japonica during silvering, from yellow to silver eels, and their physiological significances. Eels were collected from the downstream of the Kaoping River of southern Taiwan from November 1998 through November 1999. The female eels were classified into three developmental stages based on external skin coloration and oocyte diameter, namely yellow, pre-silver and silver eel stages. The male eels were classified into yellow and silver eel stages only.
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Synchronous changes of morphology and gonadal development of silvering Japanese eel Anguilla japonica.

Synchronous changes of morphology and gonadal development of silvering Japanese eel Anguilla japonica.

Abstract The gonadal development of Japanese eel Anguilla japonica during silvering was examined via gonadal histology and morphometric characteristics. Specimens were collected from the Kaoping River of Taiwan between November 1998 and November 2001. Female eels predominated, constituting 87.6% of the sex-determined eels. The degree of gonadal development was assessed by skin coloration, with female eels divided into yellow, pre-silver, and silver phases. Males were divided into yellow and silver phases because of small sample size. Silver phase eels predominated in the winter. Mean ( F S.E.) total length of silver-phase eels was significantly larger in females (642.2 F 10.4) than males (564.8 F 14.6) ( p < 0.001). The mean ( F S.E.) gonadosomatic index (GSI) of females increased significantly from 0.27 F 0.01 for yellow phase, to 0.55 F 0.03 for pre- silver and 1.32 F 0.07 for silver phase. Oocyte development progressed from the chromatin nucleolus stage in the yellow phase eel, through the peri-nucleolus stage in the pre-silver phase eel and to the oil-drop stage in the silver phase eel. Spermatogenesis was active for silver phase males which had a larger mean GSI (0.15 F 0.01) than yellow phase males (0.07 F 0.02), but the gonadal development of males was slower than that of females. GSI, ocular index (OI), and fin-index (FI) were positively correlated, and gut-index (GI) was negatively correlated with total length in both sexes. Residual analysis of the regression of the indices GSI, OI, FI, and GI on TL indicated that the variation of the indices with growth was greatly influenced by the developmental phase of the eel.
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