Academic literature on the topic 'Glass eels'
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Journal articles on the topic "Glass eels"
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Budiharjo, Agung, Tjut Sugandawaty Djohan, Djumanto Djumanto, and Jusup Subagja. "UMUR GLAS EEL (Anguilla spp.) YANG MASUK MUARA SUNGAI PROGO, YOGYAKARTA." Berkala Penelitian Hayati 14, no. 2 (June 30, 2009): 179–83. http://dx.doi.org/10.23869/bphjbr.14.2.200910.
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The leptocephalus drift with sea currents and moving from spawning area into coastal area near mouth of Progo River. In the coastal area, leptocephalus metamorfosed into glass eel, after that glass eel migrated to river. The aims of this research were to estimate glass eels age and predict hatching dates. Glass eels sampled on new moon during Februari 2007–Mei 2009 at mouth of Progo River. Glass eel ages estimated using their otolith microstructure. Hatching dates predicted with back calculation of glass eels age. We collected 1.082 glass eels. The ages of glass eel at recruit ranged from 58 to 190 days, and divided into 5 age groups. Glass eels are migrated to river hatched on new moon from July to January. Glass eels are migrated to river during October–January hatched during July–October. Glass eels are migrated to river during February–Juny hatched during November – January.
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Budiharjo, Agung. "KOMPOSISI JENIS LARVA SIDAT (Anguilla spp.) YANG BERMIGRASI KE MUARA SUNGAI PROGO, YOGYAKARTA." Berkala Penelitian Hayati 15, no. 2 (June 30, 2010): 121–26. http://dx.doi.org/10.23869/bphjbr.15.2.20104.
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Progo River is one of the rivers on the Java Island, which empties into the Indian Ocean, are became the entrance of the glass eels from the ocean. Glass eels were entering the river consists of several species. The aim of this research was to study of the species composition of glass eels that migrated into the estuary of the Progo River. Glass eels collected in the estuary in the year 2007–2009 at the lunar date 28 on at 20:00 until 04:00. In the period of 3 years, was successfully collected as many as 1.110 glass eels, which consisted of 3 species of Anguilla marmorata (31.17%), Anguilla bicolor bicolor (64,32%), and Anguilla nebulosa nebulosa (4.50%). Glass eels migrated into the estuary of Progo River during September to June. Glass eel of A. marmorata migrated to the estuary during September to June, A. bicolor bicolor migrated during October to June, and A. nebulosa nebulosa migrated to the estuary only during February to June.
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Cresci, Alessandro, Caroline M. Durif, Claire B. Paris, Cameron R. S. Thompson, Steven Shema, Anne Berit Skiftesvik, and Howard I. Browman. "The relationship between the moon cycle and the orientation of glass eels ( Anguilla anguilla ) at sea." Royal Society Open Science 6, no. 10 (October 2019): 190812. http://dx.doi.org/10.1098/rsos.190812.
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Links between the lunar cycle and the life cycle (migration patterns, locomotor activity, pulses in recruitment) of the European eel ( Anguilla anguilla ) are well documented. In this study, we hypothesized that the orientation of glass eels at sea is related to the lunar cycle. The European eel hatches in the Sargasso Sea and migrates across the Atlantic Ocean towards Europe. Upon reaching the continental shelf, the larvae metamorphose into glass eels and migrate up the estuaries, where some individuals colonize freshwater habitats. How glass eels navigate pelagic waters is still an open question. We tested the orientation of 203 glass eels in a transparent circular arena that was drifting in situ during the daytime, in the coastal Norwegian North Sea, during different lunar phases. The glass eels swimming at sea oriented towards the azimuth of the moon at new moon, when the moon rose above the horizon and was invisible but not during the other moon phases. These results suggest that glass eels could use the moon position for orientation at sea and that the detection mechanism involved is not visual. We hypothesize a possible detection mechanism based on global-scale lunar disturbances in electrical fields and discuss the implications of lunar-related orientation for the recruitment of glass eels to estuaries. This behaviour could help glass eels to reach the European coasts during their marine migration.
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Dutil, J. D., M. Michaud, and A. Giroux. "Seasonal and diel patterns of stream invasion by American eels (Anguilla rostrata) in the northern Gulf of St. Lawrence." Canadian Journal of Zoology 67, no. 1 (January 1, 1989): 182–88. http://dx.doi.org/10.1139/z89-024.
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Seasonal and diel patterns of stream invasion by American eels (Anguilla rostrata) were monitored in a small stream located on the north shore of the Gulf of St. Lawrence from 1981 to 1985. Glass eels and elvers migrated from the sea in late June and July. Glass eels made up only a small percentage of the migrants. Pigmentation progressed quickly in the estuary, but elvers grew very slowly. Migration from the estuary and through the lower reaches of the stream was slow; no glass eels or elvers occurred at a station located only 4 km from saltwater. Juvenile eels reached that station in their second summer of stream residence. Juvenile eels migrated in July and August. They ranged from 70 to 250 mm in length and included more than one age-class. Those less than 100 mm in length were most numerous. Relative abundance of glass eels and elvers decreased in the estuary from 1981 to 1985. This coincided with a decrease in the proportion of smaller sized eels in the stream migration over the same period. Juvenile eels migrated progressively later in summer as the proportion of smaller sized eels decreased. Stream migration was nocturnal. Movements mainly occurred between 21:00 and 23:00. The relationship between glass eel and elver abundance in the estuary and juvenile eel abundance in the stream 1 and 2 years later was not clear.
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Wibowo, Arif, Nicolas Hubert, Hadi Dahruddin, Dirk Steinke, Rezki Antoni Suhaimi, Samuel, Dwi Atminarso, et al. "Assessing Temporal Patterns and Species Composition of Glass Eel (Anguilla spp.) Cohorts in Sumatra and Java Using DNA Barcodes." Diversity 13, no. 5 (April 29, 2021): 193. http://dx.doi.org/10.3390/d13050193.
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Anguillid eels are widely acknowledged for their ecological and socio-economic value in many countries. Yet, knowledge regarding their biodiversity, distribution and abundance remains superficial—particularly in tropical countries such as Indonesia, where demand for anguillid eels is steadily increasing along with the threat imposed by river infrastructure developments. We investigated the diversity of anguillid eels on the western Indonesian islands of Sumatra and Java using automated molecular classification and genetic species delimitation methods to explore temporal patterns of glass eel cohorts entering inland waters. A total of 278 glass eels were collected from monthly samplings along the west coast of Sumatra and the south coast of Java between March 2017 and February 2018. An automated, DNA-based glass eel identification was performed using a DNA barcode reference library consisting of 64 newly generated DNA barcodes and 117 DNA barcodes retrieved from BOLD for all nine Anguilla species known to occur in Indonesia. Species delimitation methods converged in delineating eight Molecular Operational Taxonomic Units (MOTUs), with A. nebolusa and A. bengalensis being undistinguishable by DNA barcodes. A total of four MOTUs were detected within the glass eel samples, corresponding to Anguilla bicolor, A. interioris, A. marmorata, and A. nebulosa/A. bengalensis. Monthly captures indicated that glass eel recruitment peaks in June, during the onset of the dry season, and that A. bicolor is the most prevalent species. Comparing indices of mitochondrial genetic diversity between yellow/silver eels, originating from several sites across the species range distribution, and glass eels, collected in West Sumatra and Java, indicated a marked difference. Glass eels displayed a much lower diversity than yellow/silver eels. Implications for the management of glass eel fisheries and species conservation are discussed.
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Wilson, Jonathan Mark, José Carlos Antunes, Patricío Duro Bouça, and João Coimbra. "Osmoregulatory plasticity of the glass eel of Anguilla anguilla: freshwater entry and changes in branchial ion-transport protein expression." Canadian Journal of Fisheries and Aquatic Sciences 61, no. 3 (March 1, 2004): 432–42. http://dx.doi.org/10.1139/f04-010.
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The glass-eel stage of the life history of Anguillid eels (Anguilla spp.) makes the important physiological transition from seawater (SW) to freshwater (FW) osmoregulation. Central to successful adaptation to fresh water is the switch from active hypoosmoregulation (ion excretion) to active hyperosmoregulation (ion uptake) to counter passive fluxes imposed by concentration gradients. Anguilla anguilla (L.) glass eels, captured from the lower Minho River estuary and maintained in brackish water (BW; 24), were fully capable of adapting to FW following acute transfer. In a comparison between SW- (34) and FW-adapted glass eels, gill Na+/K+-ATPase and Na+:K+:2Cl cotransporter (NKCC) expression were both markedly reduced in the FW group. Branchial mitochondria-rich chloride cells (MRCs) were also significantly larger in SW-adapted glass eels. Apical CFTR Cl channel immunoreactivity associated with branchial MRCs was also only present in SW-adapted glass eels. The expression of these three ion-transport proteins is strongly associated with active ion excretion in SW teleost fishes. In FW-adapted glass eels, cortisol treatment increased branchial Na+/K+-ATPase expression but was without effect on NKCC expression. Glucocorticoid receptor blockade by RU-486 had no effect on Na+/K+-ATPase or NKCC expression.
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Sukardi, Purnama, Norman Ari Prayogo, Tjahyo Winanto, Asrul Sahri Siregar, and Taufan Harisam. "Nursery I: The effect of stocking density on the performance of glass eels, Anguilla bicolor in the biofloc system." E3S Web of Conferences 47 (2018): 02009. http://dx.doi.org/10.1051/e3sconf/20184702009.
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Glass eels of Anguilla bicolor is an expensive and still abundant commodity in Laguna Segara Anakan, Central Java, Indonesia. However, the growth of glass eels to elver is still a problem because of high mortality in nursery I and II. The objective of the study was to evaluate the result of stocking density on the performance of glass eels in the biofloc system during nursery I. Glass eels were stocked at densities of 54.95, 109.89 and 164.84 fish/m3, respectively, with three replicate ponds for each density. Eels were fed a formulated pasta-diet containing 40% crude protein and , 4% crude lipid, 5% crude fiber, 11.5% ash and 12% moisture, respectively. The water quality were maintained at levels of for fish culture througout the experiements: water temperature was 27.1°C (ranged from 26.3 to 28.2°C), pH (7.6, ranged from 6.8 to 7.8) and DO (7.2 mg.L-1, ranged 6.9 to 7.5 mg.L-1). The results showed that the stocking density did not significantly affect the final weight, weight gain, AGR, SGR, FCR and survival, however this had a significant effect on the yield. The biofloc system was suitable for raising glass eels.
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Hewavitharane, C. A., T. D. Pickering, R. Ciro, and N. Mochioka. "Species composition, abundance and seasonal recruitment patterns of freshwater eels (Anguilla spp.) to Viti Levu, Fiji Islands, in the western South Pacific." Marine and Freshwater Research 69, no. 11 (2018): 1704. http://dx.doi.org/10.1071/mf18105.
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To understand the inshore recruitment mechanisms of tropical eels (Anguilla spp.), we collected 1368 glass eels at the mouth of a small river at Namelimeli, ~2km east of Navua Town, Fiji Islands, between April 2015 and June 2016. Specimens were identified using both morphological characters and DNA barcoding to only three species: one short-finned Anguilla obscura and two long-finned eels A. marmorata and A. megastoma. Anguilla obscura was the most abundant species (55% of glass eels collected) with peak recruitment periods from February to April. Anguilla marmorata was the second most abundant species (41.4% of glass eels collected) with peak recruitment periods in April 2015 and September–October 2015. Anguilla megastoma only comprised 3.9% of glass eels collected, with peak recruitment periods in April 2015 and October 2015. Anguilla obscura and A. marmorata were present in samples almost throughout the year, suggesting that tropical eels recruit to some degree throughout the year. Results suggest that peak recruitment occurs during seasons of heavy rain, from September to October and from February to April commencing 1h after sunset on the day following a new moon.
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ANGELIDIS, P., I. POURNARA, and G. PHOTIS. "Glass eels (Anguilla anguilla) growth in a recirculating system." Mediterranean Marine Science 6, no. 1 (June 1, 2005): 99. http://dx.doi.org/10.12681/mms.196.
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On a commercial eel farm, which uses a recirculation system, 400,000 glass eels were farmed for a period of 328 days at 20o – 23o C. The physicochemical parameters of the farm water were kept at normal conditions during the experiment. The NO 2 was kept between 1.0 and 3.0 mg/l. By the end of the experiment, 4,582 kg of fish feed were consumed and 2,939 kg of eels were produced (177,523 eels with mean final individual body weight of 16.6g and mean food conversion ratio of 1.625). The glass eels showed a high variability in their capacity to grow.
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Krismono, Krismono, and Endi Setiadi Kartamihardja. "OPTIMASI PEMANFAATAN DAN KONSERVASI STOK IKAN SIDAT (Anguilla spp) DI DAS POSO, SULAWESI TENGAH." Jurnal Kebijakan Perikanan Indonesia 4, no. 1 (May 31, 2012): 9. http://dx.doi.org/10.15578/jkpi.4.1.2012.9-16.
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<p>Daerah Aliran Sungai (DAS) Poso yang terdiri atas sungai Poso dan anak sungainya yang mengalir dari Danau Poso sampai muaranya di Teluk Tomini dan sungai-sungai kecil di sekitar muara Poso merupakan kawasan ruaya ikan sidat. Penangkapan ikan sidat dewasa (induk) di Tentena dengan Wayamassapi (perangkap) dan penangkapan glass eel di muara Poso yang sangat intensif akan berpengaruh terhadap penurunan produksi dan potensi ikan sidat di DAS Poso. Pembangunan PLTA Sulewana yang membendung sungai Poso di Sulewana juga akan berpengaruh terhadap penurunan produksi dan potensi ikan sidat karena pembendungan akan memutus ruaya ikan sidat. Selama periode tahun 2010-2012 anakan ikan sidat (glass eel) yang berruaya ke sungai Poso turun sekitar 10 juta ekor per tahun yaitu dari 36 juta ekor per tahun menjadi 35 juta ekor per tahun. Potensi induk sidat turun sekitar 3.000 ekor per tahun, yaitu dari 9.000 ekor menjadi 6.000 ekor per tahun. Dalam rangka konservasi dan optimasi pemanfaatan sumberdaya ikan sidat, upaya yang perlu dilakukan adalah menetapkan sungai Pandiri dan Rawa Pandiri sebagai kawasan konservasi, melakukan restocking elver yang berukuran panjang lebih besar dari 15 cm di Danau Poso, membangun jalur ruaya sidat (eels ladder) di Sulewana, mengatur penangkapan sidat dewasa di Tentena dan menetapkan kuota penangkapan “glass eels” di Muara Sungai Poso.</p><p>Poso watershed composting of Poso River and its tributaries flowing the waters from Poso Lake to its mouth at Tomini Bay is one of migration habitat of tropical eels (<em>Anguilla</em> spp). Intensive exploitation of adult eels at outlet of the lake Poso at Tentena by using trap and glass eel at mouth of the Poso River has affected on the decreasing of the eels production. Damming of the Poso River at Sulewana has also affected the eels production sustainability due to barrier of the eels migration. During the period 2010-2012, the glass eels migration from the mouth of Poso River to the river decreased about 10 millions, from 36 millions to 35 millions individuals per year. The adult eels also decreased for about 3000 individuals, from 9000 individuals to 6000 individuals per year. In order to conserve and optimize the exploitation of the eels stock, some efforts, i.e., establishment of conservation area at Pandiri river and its swampy area, restocking of the elver with a total length more than 15 cm at Lake Poso, establishment of eels ladder at Sulewana, regulation of fishing for adult eels at Tentena and glass eels at mouth of the Poso River should be implemented.</p>
Dissertations / Theses on the topic "Glass eels"
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Larkin, Brendan, and mikewood@deakin edu au. "The weaning and growth of Anguilla australis glass eels and elvers." Deakin University. School of Ecology and Environment, 2000. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20060713.113837.
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Anguilla australis glass eels proved to be resilient and present strong aquaculture potential. General husbandry techniques, anaesthesia and prophylactic treatments were established for glass eels between 0.1 g and 2.0 g and elvers between 2.0 g and 8.0 g, caught in rivers and estuaries along the South East Coast of Victoria. The protozoan parasites Ichthyobodo and Trichodina were found to be present on arrival to the hatchery developed during different rearing treatments, and were successfully eradicated. A. australis glass eels accepted artificial food, but it was recommended first be fed a preweaning diet of minced fish flesh. A weaning regime from minced fish flesh to commercially available eel grower mash, over 15 days was established. Growth rate proved to be highly variable, both between and within groups. The highest growth rate of 2.71%/day was found when the natural diet of minced fish and Artemia was fed. The maximum growth rate when reared on an artificial diet of 1.63%/day was observed at 25°C. Growth was affected by the presence or absence of a preweaning diet, weaning diet, weaning period, temperature, but not by size or density. Once weaned, glass eels were found to perform better on commercially available grower mash than on the minced fish flesh, which was used to aid in weaning them to artificial diets. Of the water quality parameters measured stocking density was found to affect pH, Total Ammonia Nitrogen, Total Phosphorus, and Dissolved Oxygen, through not to an extent which affected growth.
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Birrell, Lynne M. "Osmoregulation in glass eels and elvers of the European eel, Anguilla anguilla." Thesis, University of St Andrews, 1999. http://hdl.handle.net/10023/14934.
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Glass eels of the European eel migrate from coastal waters inland to freshwater as part of the catadromous lifecycle. The osmotic challenge faced at this time is augmented by their large surface area to volume ratio, and by the fact that the migration may only be completed after several attempts, due to the effects of tide and river flow. Glass eels and elvers developed normally when maintained in waters of differing salinity over a six month period. Drinking rates increased with environmental acclimation salinity (from 0.072 +/- 0.023 mul/g/h to 0.698 +/- 0.099 mul/g/h in FW and SW respectively), and freshwater acclimated fish exhibited a rapid drinking response upon contact with seawater. These accounts of dipsogenic behaviour are similar to those previously reported for adult eels. Results obtained from determinations of branchial Na+K+ATPase activities were more equivocal. Only after nearly five months were activities higher in SW (508.52 +/- 99.76 nmoles/Spairs gills/h) as compared to FW fish (151.65 +/- 8.9 nmoles/5pairs gills/h). Following the transfer of FW acclimated fish to SW there was a trend towards increased Na+K+ATPase activity after seven days post-transfer, which reached a significant peak after two months post-transfer. A transient increase in whole body cortisol content was noted following the transfer of fish from freshwater (388.02 + 90.38 pg/g) to seawater (6268.44 +/- 773.14 pg/g). However, it was not possible to ascertain that this was due to a direct effect of environmental salinity change. There were no clear changes in interrenal cell morphology between salinity groups, although the cells did appear reduced in size with time, regardless of environmental salinity. Total body Na+ content increased with time, and was higher in SW (58.66 +/- 1.66 mumoles/g) as compared to FW reared fish (44.85 +/-1.01 mumoles/g).
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White, Edward Michael. "A study of the exploitation, migration and management of elvers and juvenile eels (Anguilla anguilla L.) in the rivers Severn and Avon, England." Thesis, University of Westminster, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296121.
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Kullmann, Björn [Verfasser], and Ralf [Akademischer Betreuer] Thiel. "Growth and condition of stocked glass and farmed eels in a brackish water system / Björn Kullmann ; Betreuer: Ralf Thiel." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2018. http://d-nb.info/1169358314/34.
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Liu, Hengtong. "The relationship between migration behavior and energetic status in the European glass eel (Anguilla anguilla)." Thesis, Pau, 2020. http://www.theses.fr/2020PAUU3014.
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L'anguille européenne (Anguilla anguilla) présente un cycle de vie complexe avec un stade civelle qui remonte les estuaires pour atteindre les rivières et entamer une phase de croissance. Cependant, cette migration estuarienne est connue pour être facultative, certains individus s'installant en mer, en estuaire ou alternant les séjours en rivière et en estuaire. Les civelles ne se nourrissent pas ou peu pendant leur migration et leurs schémas migratoires pourraient donc être étroitement associés aux réserves énergétiques des individus. La migration facultative des civelles pourrait donc reposer sur une stratégie conditionnelle, les individus présentant d’importantes réserves d'énergie ayant une capacité migratoire élevée. Cependant, certaines études s’avèrent contradictoires et l’objectif de cette thèse était d'étudier la stratégie conditionnelle chez les civelles européennes en se basant non seulement sur les réserves d'énergie mais également sur la mobilisation de l'énergie (métabolisme et expression des gènes liés à l'énergie). L’essentiel des travaux a été mené à la fois sur des civelles d'automne et de printemps, car elles présentent d’importantes différences de réserves énergétiques. Nous avons tout d'abord caractérisé le statut énergétique individuel des civelles marines échantillonnées en automne et au printemps et l’avons relié à leur comportement migratoire évalué dans des installations expérimentales. Les civelles d'automne présentaient des réserves énergétiques plus élevées et une plus grande capacité à produire de l'énergie que les civelles de printemps. Ces résultats confirment que les civelles d'automne et de printemps présentent de fortes différences dans leur statut énergétique et qu'elles doivent être étudiées séparément. Nous émettons l'hypothèse qu'il pourrait exister un seuil énergétique en dessous duquel la migration pourrait être conditionnée par ce facteur. Afin de mieux comprendre les mécanismes de sédentarisation dans les estuaires, la relation entre le statut énergétique et le comportement migratoire des civelles marines et estuariennes a ensuite été étudié parallèlement en automne et au printemps. Nos résultats soutiennent l’hypothèse d’une stratégie conditionnelle basée sur l'énergie lorsque les réserves énergétiques deviennent un facteur limitant (civelles de printemps). La perte de poids, la mesure du métabolisme et l'expression de gènes liés au métabolisme suggèrent également que les civelles estuariennes étaient plus stressées et avaient une capacité de production d'énergie plus faible que les marines. Les civelles non synchronisées au courant (considérées comme ayant une faible probabilité de migration) présentaient une dépense énergétique plus élevée que les individus synchronisés, ce qui pourrait refléter un stress et/ou une vulnérabilité au stress plus élevés chez les premières. Afin de tester cette hypothèse, des civelles ont été exposées à un facteur de stress potentiel dans les estuaires, à savoir le méthylmercure (MeHg), et les effets de ce contaminant sur le comportement migratoire et le statut énergétique des individus a été étudié. Nos résultats mettent en évidence une diminution de l’activité de nage chez les civelles non synchronisées mais pas chez les synchronisés, suggérant que les premières pourraient être plus sensibles au MeHg. Puis, les civelles non synchronisées présentaient un niveau d'expression des gènes du métabolisme inférieur à celui de leurs homologues synchronisées dans la tête et pas dans le muscle ni dans les viscères. Les travaux réalisés dans le cadre de cette thèse suggèrent que le statut énergétique et la sensibilité au stress pourraient conditionner la migration estuarienne des civelles mais les mécanismes sous-jacents et les relations entre ces facteurs ainsi qu’avec les horloges endogènes qui contrôlent la migration restent à éluciderRésumé en anglais : The European eel (Anguilla anguilla) present a complex life cycle with a glass eel stage migrating up estuary to reach river for growth. However, this estuarine migration is known to be facultative, with some individuals settling at sea, in estuaries or alternating stays in rivers and estuaries. As glass eels feed little or not at all during their migration, their divergent migration patterns may be closely associated with individual’s body condition. To date, one major theory of conditional strategy proposed that the facultative migration in European glass eels is based on energy stores, the individuals with a high migratory capacity presenting high energy stores. However, this theory has been proved controversial and the aim of this thesis was to investigate the conditional strategy in European glass eels based on more comprehensive measures of energetic status, including not only energy stores but also energy mobilization (metabolism and energy-related genes expression). We also focused on both autumn and spring glass eels, which present dramatic difference in energy stores. We first characterized the individual energetic status of marine glass eels sampled in autumn and spring and related this status to their migration behavior assessed in experimental facilities. Autumn glass eels presented higher energy stores and a higher ability to produce energy than spring ones. This confirmed that autumn and spring glass eels present strong differences in their energetic status and that they have to be studied separately. We hypothesized that a potential threshold in energetic status may exist below which migration could be conditioned by energetics. Then, to unveil the underlying mechanisms of settlement processes in estuaries in relation to energy-based conditional strategy, we investigated the relationship between energetic status and migration behavior in both marine and estuarine glass eels. Estuarine individuals displayed lower weight than marine ones in autumn but not in spring supporting the idea that a conditional strategy based on energy may explain facultative migration when energy reserves become a limiting factor. Weight loss, standard metabolism and the expression of metabolism-related genes suggested that estuarine glass eels were more stressed and had a lower capacity of energy production than marine fish. The non-synchronized glass eels also presented a higher energy expenditure than synchronized individuals possibly reflecting a higher stress and/or vulnerability to stress in the former. We further exposed glass eels to a potential stressor in estuaries - methylmercury (MeHg) in order to investigate the effects of this contaminant on glass eels’ migratory behavior and energetic status. Our results first suggested that non-synchronized glass eels were more vulnerable to MeHg reflected by a decrease in swimming activity. MeHg also affected the relation between individual metabolism-related genes expression level and swimming activity, supporting our hypothesis that stress factors may influence the settlement processes in glass eels. Finally, it is noteworthy that non-synchronized glass eels displayed lower expression level of metabolism genes than their synchronized counterpart in the head but not in muscle nor in viscera. Altogether, these results provided evidences that the energetic status and sensitivity to stress may condition estuarine migration in glass eels but the underlying mechanisms and relationships between these factors but also with the endogenous clocks driving migration remain to be elucidated
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Julie, Célia Claveau. "Impact du méthylmercure sur le potentiel de migration, le statut énergétique et les mécanismes de détoxication chez la civelle d’anguille européenne (Anguilla anguilla) : Etudes in situ et expérimentale." Thesis, Pau, 2014. http://www.theses.fr/2014PAUU3040/document.
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Européenne, (Anguilla anguilla) a conduit à une diminution du nombre d’anguille jaune dans les bassins versants. En 2007, le règlement (CE) instaure que 60% des civelles pêchées (<12 cm de long) doivent être dédiés à des opérations de repeuplement. Cependant, pour migrer et coloniser un nouvel environnement, les civelles doivent avoir une bonne condition énergétique. Or, les civelles ne s’alimentent pas ou peu durant leur migration estuarienne et la vitesse d’utilisation de leurs réserves dépend de divers facteurs (température, contaminants etc.). Dans l’estuaire de l’Adour, différents travaux ont mis en évidence de fortes concentrations en methylmercure (MeHg) dans les sédiments et une bioaccumulation de ce composé chez l’anguille jaune. L’exposition au MeHg entraîne la mise en place de processus de détoxication qui pourraient être couteux en énergie ce qui, chez des organismes jeûnant comme les civelles, conduirait à une perte de poids pouvant affecter leurs capacités de migration. Pour étudier l’impact du méthylmercure sur le potentiel de migration des civelles, nous avons tout d’abord (1) effectuer un état des lieux des concentrations en MeHg des civelles de l’estuaire de l’Adour, (2) évaluer l’effet du MeHg sur deux synchroniseurs de la migration estuarienne: le signal crépusculaire et l’alternance des marées chez les civelles grâce à l’utilisation de traceurs isotopiques et (3) étudier dans le milieu naturel (Adour) le comportement de migration, les taux de contamination au mercure et les mécanismes de détoxication des civelles. Nos résultats montrent des fluctuations temporelles et saisonnières de la concentration en MeHg des civelles prélevées en entrée et en milieu de l’estuaire. Par ailleurs, l’exposition au MeHg, en milieu contrôlé, a augmenté l'activité des civelles mais pas leur comportement de migration. Cependant, suite à la contamination, la structure mitochondriale et le métabolisme ont été modifiés suggérant un plus fort stress oxydant et une activation des défenses antioxydantes notamment des civelles ayant un faible potentiel de migration (non migrantes).En complément, l’étude en milieu naturel a mis en évidence une plus forte demande énergétique pour les civelles non migrantes entrainant une augmentation du fonctionnement des mitochondries et pouvant conduire à un plus fort stress oxydantOver the last three decades, the arrival of Anguilla anguilla glass eels has markedly declined which has lead to a decrease in the number of yellow eels in the watersheds. In 2007, the Regulation (EC) indicated that 60% of glass eels (<12cm long) caught by fisheries should be used for restocking. To migrate and colonize a new environment, glass eels must have a good energetic condition. However, during their estuarine migration, glass eels either feed very little or more likely not at all. The speed at which they expend their energy stores depends on various factors (temperature, contaminants etc.). In the Adour estuary, many studies have reported relatively high methylmercury (MeHg) concentrations in the sediments, and bioaccumulation in yellow eels. Exposure to MeHg requires energy for detoxification which, in starving organisms such as glass eels, might lead to weight loss, decreasing their ability to migrate up the estuary. To study the impact of MeHg on migratory behaviour in glass eels, we first conducted an inventory of MeHg concentrations of glass eels in the estuary of the Adour, (2) evaluate the effect of MeHg on two synchronizers of estuarine migration: dusk and tide on glass eels through the use of isotopic tracers and (3) to study the natural environment (Adour) migratory behavior, mercury contamination levels and detoxification mechanisms of glass eels. Our results show temporal and seasonal fluctuations in the concentration of MeHg glass eels collected input and middle of the estuary. Moreover, MeHg exposure, in a controlled environment, increased the activity of glass eels but not in response to migratory behavior. However, due to contamination, mitochondrial structure and metabolism have been modified suggesting a stronger oxidative stress and activation of antioxidant defences of glass eels, particularly those with low migration potential (non-migrant). In addition, the wild study showed a higher energy demand for non-migrating glass eels causing an increase in mitochondrial function which may lead to higher oxidative stress
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Helme, Herehia. "Biodiversité anguillicole en milieu tropical insulaire (Tahiti) face aux aménagements hydroélectriques." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEP045/document.
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Cette thèse en recherches fondamentale et appliquée a pour modèle biologique l’anguille d’eau douce qui a toujours fasciné le monde de la recherche par son cycle de vie unique et tous ses mystères non encore résolus pour certains. Dans le monde, 19 espèces d’anguilles existent dont certaines en déclins dans les zones tempérées ce qui peut justifier l’amplification des recherches sous les tropiques. En Polynésie française, cet animal mystérieux est sacré ; les légendes polynésiennes associent les anguilles à la création de la vie. Trois espèces y sont présentes : l’anguille marbrée « Anguilla marmorata », l’anguille de montagne « Anguilla megastoma » et l’anguille de vase « Anguilla obscura ». Elles n’ont pas la même distribution spatiale où la première s’adapte à n’importe quel milieu, la deuxième remonte les rivières jusqu’en haute vallée à plusieurs centaines de mètres d’altitude, tandis que la dernière reste en basse vallée préférant les eaux stagnantes. Grâce aux nombreuses rivières présentes sur Tahiti, cette île principale de Polynésie est en pleine transition énergétique et privilégie maintenant les énergies renouvelables ; particulièrement l’hydroélectricité. Cependant, les aménagements hydroélectriques connus pour provoquer des problèmes de continuité écologique de la biodiversité dulçaquicole, notamment pour les anguilles, vont nous intéresser dans ce travail de thèse en bourse Cifre. C’est dans ce contexte que s’inscrit cette thèse, dans la plus grande vallée de Tahiti, la Papenoo. Deux problématiques y sont étudiées : le recrutement des civelles et l’étude de la population adulte. Nos résultats sur les trois années de suivi de l’arrivée des juvéniles d’anguilles dans l’embouchure de la Papenoo révèlent un recrutement saisonnier des civelles de Novembre à Mars avec deux pics en Décembre et Janvier. Plus de 80% des civelles sont des Anguilla marmorata. Concernant les populations adultes, nous observons : 1/ plus de 90% de la population sont également de l’espèce Anguilla marmorata, 2/ les anguilles adultes présentent un gradient de densité de l’aval vers l’amont et 3/ le problème de continuité biologique ne vient pas des barrages ou captages en eux-mêmes, mais proviendrait des canaux de fuite en sortie de centrale où nous observons une sur-attractivité pour les anguiles. Cette étude s’est révélée très importante dans l’avancement théorique de nos connaissances biologiques et écologique sur l’anguille, dans l’appropriation par l’industriel de bonnes pratiques et par une solide communication sur la coexistence possible entre gestion et développementThis thesis in fundamental and applied research has for biological model the freshwater eel which has always fascinated the world of the research by its unique cycle of life and all its mysteries not solved for some. Worldwide, 19 species of eels exist, some of which are declining in temperate zones, which may justify the increase in research in the tropics. In French Polynesia, this mysterious animal is sacred; the Polynesian legends associate the eels with the creation of life. Three species are present: the marbled eel "Anguilla marmorata", the mountain eel "Anguilla megastoma" and the eel "Anguilla obscura". They do not have the same spatial distribution where the former adapts to any medium, the second goes up the rivers to the upper valley at several hundred meters of altitude, while the latter remains in the lower valley preferring the stagnant waters. Thanks to the numerous rivers on Tahiti, this main island of Polynesia is in the midst of an energy transition and now favors renewable energies; particularly hydroelectricity. However, hydroelectric developments known to cause problems of ecological continuity of freshwater biodiversity, especially for eels, will interest us in this thesis work on the Cifre grant. It is in this context that this thesis, in the largest valley of Tahiti, is the Papenoo. Two problems are studied: the recruitment of glass eel and the study of the adult population. Our results over the three years following the arrival of juvenile eels in the mouth of the Papenoo reveal a seasonal recruitment of elvers from November to March with two peaks in December and January. More than 80% of elvers are Anguilla marmorata. For adult populations, we observe: 1/ more than 90% of the population is also Anguilla marmorata, 2/ adult eels have a density gradient from downstream to upstream, and 3/ biological continuity does not come from dams or water removal in themselves, but comes from the tailrace leaving the hydropower plant where we observe an over-attractiveness for the eels. This study proved to be very important in the theoretical advancement of our biological and ecological knowledge about the eel, in the appropriation by industry of good practices and in a solid communication on the possible coexistence between management and development
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Chiou, Jung-Hau, and 邱俊豪. "Studies on the disease control of glass eels and development of oral bacterial vaccines for juveniles of marbled eels (Anguilla marmorata)." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/75300691911584962906.
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碩士國立臺灣海洋大學
水產養殖學系
104
This study intended to control disease problems of glass eels and improve survival rate of juveniles of marbled eels (Anguilla marmorata), including the optimal salinity test, the disinfection of parasites, and the development of oral bacterial vaccines of Aeromonas hydrophila and Edwardsiella tarda. The optimal salinity in glass eel stage (12000/kg) to elver stage (2000/kg) was between 3 - 5 ‰, and after elver stage (500/kg), the optimal salinity was 0‰. The disinfection of blood worms by using 4 ppm ClO2 was most effective, while treated with 10 ppm formalin exhibited best palatability. Both of the treatments could help glass eels digest blood worms. In glass eel stage, the use of blood worms as food was found to be the best. When the parasite Dactylogyrus sp. hooked on the gills of eels, soaking with 10 ppm levamisole and 0.3 ppm copper sulfate were found to be effective for removing parasites and eggs by 7 days. The formalinized bacterial cells were sonicated for 1.5 hours and encapsulated with 5% of sodium alginate or 9% CAP exhibited the best amount of antigen-releasing in vaccines. Eels were i.p. challenged with A. hydrophila and E. tarda after oral vaccination. The results showed that the highest relative percent survival was obtained at the 12th week, with highest RPS reaching 100%, but the antibody titer decreased after the highest, it maintained steadily at high level. The results showed that oral administration with encapsulated vaccine could protect bacterial antigens against stomach acid, and might therefore help the antigens to induce immune responses in eel intestine. The sonicated bacterial antigens encapsulated with biomaterials, had a higher antibody titer and maintained longer time. Eels boosted with the same oral vaccine, could obviously exhibited higher antibody titer and maintain much longer time. Eels orally administrated with sodium alginate or formalin killed cells vaccine, could also improve its SOD responses. The present results revealed that some factors including fluctuation of water salinity, bacterial and parasitic infection, and drug resistance etc. were major problems leading to mass mortality during the culture of marbled eels at glass eel stage. To improve survival rate of glass eels and juveniles, adjustment of suitable salinity disinfection of live foods control of parasites and use of encapsulated oral vaccines and boosting were suggested for the farmers.
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"Recruitment and age dynamics of Anguilla australis and A. reinhardtii glass eels in the estuaries of New South Wales." University of Technology, Sydney. Department of Environmental Sciences, 2005. http://hdl.handle.net/2100/323.
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Shortfin eels (Anguilla australis) and longfin eels (A. reinhardtii) are true freshwater eels of the genus Anguilla. There are many mysteries still unsolved for the freshwater eel lifecycle, such as location of the spawning grounds, conditions that promote metamorphosis from the leptocephalid to glass eel phase, and the mechanisms that affect glass eel recruitment. In Australia, little is also known about the estuarine habitats of glass eels as they migrate towards freshwater, and the age at which these eels enter estuaries. Both species are of commercial importance in the estuary fishery where they are caught in eel traps for export. There is also a small, but potentially lucrative, aquaculture industry for ongrowing glass eels to market demand size. This thesis investigates the spatial and temporal recruitment of both species of glass eels to estuaries within NSW, the habitats that may be of importance to them as they continue their upstream migration, and the age at which these eels entered the estuaries. Firstly, a new sampling device needed to be developed since conventional methods to catch glass eels often required constant observation of gear, multiple operators, specific physical site characteristics, and/or were expensive. The artificial habitat collectors that were developed were then used to sample six estuaries in NSW monthly within one week of the new moon. Shortfins showed a more consistent and defined recruitment across all sites than longfins, where the peak shortfin recruitment season was from April - August. Longfins recruited primarily from January - May but often recruited outside of this period. Five year collections at one of these sites provided important recruitment information. It appeared that longfins failed to recruit to this site during 2000/01, which could affect commercial catches of this species when they enter the fishery. The East Australian Current (EAC) probably transports glass eels from spawning sites in the Coral Sea southward to the east coast of Australia but there was no predicted lag time in the recruitment of eels from northern to southern estuaries. Therefore, it was not possible to predict the timing of recruitment of glass eels in one estuary based on the timing of recruitment in another more northern estuary. When glass eels enter estuaries their upstream migration is assisted by the night flood tide. During the ebb tide, glass eels burrow into the substrate and resurface at the next night flood tide. The eels do not select particular habitats at this time, rather, their location is dictated by the tide. However, once glass eels reach the estuarine/freshwater interface, they may prefer more complex habitats such as seagrass/macrophytes or rocks/cobbles in which to hide during the day. At this interface, glass eels undergo a physiological change to adapt to a freshwater existence and this change may take up to a few weeks. During this time, glass eels commonly enter the water column during the night flood tide and may be able to locate more suitable habitats in which to hide during the day. The ages of shortfin and longfin glass eels caught in estuaries were examined both spatially and temporally. As the EAC travels north to south, glass eels recruiting to the southern sites were expected to be older. However, shortfins that recruited to the northern-most site in this thesis were older than at all other sites while there was no difference in the ages of longfins. Also, when the ages of longfins that recruited during the main recruitment period were compared to the ages of longfins that recruited outside of this period, there was no difference in ages. Therefore, the hypothesis that these later recruiting eels may have been caught in an eddy prior to their estuarine arrival has been disproved. The ages of shortfins that recruited in two separate years were significantly different from each other and may be due to shortfins' ability to detrain more easily from the weaker currents that exist at these recruitment periods. Conversely, there was no difference in the ages of longfins that recruited in the same month during three separate years. The estimated hatch dates for shortfins was estimated at October to January, while for longfins, estimated hatch time was July to September for eels that recruited during the peak recruitment period. For longfins that recruited outside of the main recruitment period, estimated hatch times were from December to February. It is unknown, however, whether longfins have an extended spawning period, or whether silver eels arrived at the spawning grounds later and thus produced later arriving longfins. Continuous monitoring of glass eel recruitment to estuaries is necessary to determine whether there are long term declines in the recruitment of Australian eels similar to the declines recently observed for eels in Europe and Asia.
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Ma, Chi, and 馬霽. "Variability of total length of Japanese glass eels in relation to the environmental factors during migration route." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/bxvf42.
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碩士國立臺灣大學
漁業科學研究所
107
Japanese eel (Anguilla japonica) is an important commercial freshwater fish in East Asia. However, eel aquaculture is a typical capture‐based aquaculture. Recruitment of Japanese eel has declined since 1980s, and large interannual fluctuations were also observed. The causes of decline or extremely poor recruitment events remain unclear. By using numerical modelling method to reproduce larval migration routes, previous studies showed that the inter-annual variability of ocean circulation may influence the migration success of Japanese eel. However, the effect of environmental factor on wild larvae is less discussed by biological points of view. In this study, a recent 8–yr total length data of Japanese glass eel was used as representative of eel larval condition to evaluate the effect of environment by generalized additive model. And the environment experienced by eel larvae was based on a coupled biological physical model which were the used to estimate the migration routes. The result of generalized additive model showed larger total length of Japanese glass eel were observed at 21-24.5°C for spawning area temperature, higher than 24°C for migration routes temperature, 0.03-0.07 mg/m3 for spawning area chlorophyll concentration, higher than 13 mg/m3 for accumulated migration routes chlorophyll concentration with increasing trend, 35.1-35.3 psu for spawning area salinity, and during El Niño year. The environment of spawning area has greater effect on glass eel total length. The results correspond to previous studies in laboratory experiment, except the effect of spawning area temperature. The synchronized spawning behavior in Japanese eel may cause the density-dependent effect which potentially influence the result of this study. This study provided a different perspective of environmental effect on Japanese larvae, and may help to understand the cause of recruitment fluctuation.
Books on the topic "Glass eels"
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Glass eels. London: Oberon Books, 2007.
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Willem, Dekker, Commission of the European Communities. Directorate-General for Fisheries., and Rijksinstituut voor Vissenjonderzoek, eds. Monitoring of glass eel recruitment. Ijmuiden: RIVO-Netherlands Institute for Fisheries Research, 2002.
Find full textBook chapters on the topic "Glass eels"
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Tabeta, Osame, and Noritaka Mochioka. "The Glass Eel." In Eel Biology, 75–87. Tokyo: Springer Japan, 2003. http://dx.doi.org/10.1007/978-4-431-65907-5_6.
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"European glass eels." In World Wildlife Crime Report, 93–106. United Nations, 2021. http://dx.doi.org/10.18356/9789210052252c012.
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"Eels at the Edge: Science, Status, and Conservation Concerns." In Eels at the Edge: Science, Status, and Conservation Concerns, edited by Laurent Beaulaton and Gérard Castelnaud. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781888569964.ch18.
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<em>Abstract.</em>—The glass eel is fished in the Gironde Basin, France, with large push nets, scoop nets, and the recently introduced small push net. This study uses fishery data to generate fisheries and abundance indicators for glass eels. Total catch, total effort, and catch per unit effort (CPUE) were calculated for the period 1978–1999 by classical statistical methods and by general linear models (GLM). Use of GLM enabled the correction of sampling variation and offered better trend estimation than classical CPUE. During the study period, the principal source of glass eel landings shifted from the scoop net fishery in the tidal river to the large push net fishery in the estuary. General linear model-based CPUEs for large push nets and for scoop nets showed that glass eel abundance declined by a factor of two to three at the beginning of the 1980s. Since 1985, abundance has stabilized at a low level and shows no sign of recovering. The abundance trend of glass eels in the Gironde Basin confirms the decline in glass eel populations observed elsewhere in Europe.
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"Eels at the Edge: Science, Status, and Conservation Concerns." In Eels at the Edge: Science, Status, and Conservation Concerns, edited by Katsumi Tsukamoto, Jun Aoyama, and Michael J. Miller. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781888569964.ch2.
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Abstract.—The Japanese eel, Anguilla japonica, is an important food fish in East Asia, and catches of glass eels and of eels in freshwater appear to have declined dramatically in recent decades, causing increasing concern for the health of wild stocks. During that time, research efforts to understand its biology have progressed considerably. The spawning area was successfully outlined to the west of the Mariana Islands in 1991, and other research suggests that their recruitment success may be related to El Niño events, which appear to affect the transfer of leptocephali from the north equatorial current into the Kuroshio Current. Otolith microstructure and microchemistry studies have revealed various aspects of their early life history that relate to their oceanic larval migration. The discovery of sea eels that live in marine habitats without entering freshwater may change the common understanding of freshwater eel ecology and affect management plans. Most genetic studies suggest that the Japanese eel is composed of a single panmictic population throughout East Asia. Therefore, international management is needed among the countries of China, Taiwan, Korea, and Japan, where glass eels recruit from a common stock and are used extensively for aquaculture.
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"Eels at the Edge: Science, Status, and Conservation Concerns." In Eels at the Edge: Science, Status, and Conservation Concerns, edited by Don J. Jellyman. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781888569964.ch3.
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<em>Abstract.—</em>The two main species of freshwater eels in New Zealand, the shortfin <em>Anguilla australis </em>and the endemic longfinned eel <em>A. dieffenbachii</em>, are extensively commercially exploited and also support important customary fisheries. Since there are no commercial glass eel fisheries in New Zealand, other indices must be used to indicate changes in recruitment over time. While there is some anecdotal evidence of reductions in glass eel recruitment, there is evidence of poorly represented cohorts of longfins within some populations, and modeling of these data indicate a substantial reduction in recruitment over the past two decades. Growth of both species is typically slow at 2–3 cm per year, meaning that both species are susceptible to commercial capture for many years until spawning escapement. Extensive commercial fishing has resulted in more substantial changes in length-frequency distributions of longfins than in shortfins; likewise, regional reductions in catch per unit effort are more significant for longfins. Theoretical models of silver eel escapement indicate that longfin females are especially susceptible to overexploitation. Shortfins would have been more impacted than longfins by loss of wetlands, but the impact of hydro stations on upstream access for juvenile eels and downstream access for silver eels would have been more severe for longfins. Overall, there is no clear evidence that the status of shortfin eel stocks has been seriously compromised by the extensive commercial eel fishery, but there is increasing evidence that longfins are unable to sustain present levels of exploitation.
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"Eels at the Edge: Science, Status, and Conservation Concerns." In Eels at the Edge: Science, Status, and Conservation Concerns, edited by Anthony Bark, Beth Williams, and Brian Knights. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781888569964.ch17.
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<em>Abstract.—</em>Long-term changes in eel stock status are examined in two catchments in England. The River Severn supports the UK’s major glass eel fishery. The Rivers Piddle and Frome and Poole Harbour form a linked river/tidal lagoon system supporting yellow and silver eel fisheries. Eel population density and structure in lower Severn tributaries appear unchanged since the early 1980s, as does eel distribution in the upper catchment. It is concluded that, despite a decline in glass eel numbers and increased fishing pressure in the 1990s, recruitment continues to be sufficient to fill local carrying capacity. In contrast, in the Piddle and Frome, population density has declined sharply since the 1970s, and there has been a major change in sex ratios from male to female domination. Although currently high, female silver eel escapement is likely to decline sharply over the next few years from the Piddle and possibly the Frome. It is postulated that the productive tidal lagoon acts as a sink for declining glass eel recruits so that fewer elvers and yellow eels are entering the rivers. Fishing pressure on harbor stocks is unquantified but potentially high. Management options and priorities for the two catchments are discussed.
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"Challenges for Diadromous Fishes in a Dynamic Global Environment." In Challenges for Diadromous Fishes in a Dynamic Global Environment, edited by Donald J. Jellyman and Melissa M. Bowen. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781934874080.ch17.
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<em>Abstract</em>.-The location of the spawning grounds of the three species of <em>Anguilla </em>that occur in New Zealand and Australia, shortfin eel <em>A. australis</em>, Australian longfin eel <em>A. dieffenbachii</em>, and Australian longfin eel (also known as speckled longfin eel) <em>A. reinhardtii</em>, are unknown. No larvae of New Zealand longfin eels have been collected, and too few shortfin eel and speckled longfin eel larvae have been collected to use conventional back-tracking of progressively smaller larvae to determine likely spawning areas. The limited larval material together with results from satellite tracking pop-up tags from New Zealand longfin eels indicate that spawning of all three species will be in the tropics, and possible areas were further demarcated by developing a Lagrangian trajectory model based on surface currents derived from hydrography, satellite altimetry, and wind stress. The initial model assumed passive drift of larvae, a third of the total time spent in near-surface layers, and arrival within the larval lifetimes indicated by ages of metamorphosing glass eels. The proportion of successful trajectories enabling arrival offshore of New Zealand or Australia was substantially improved by addition to the model of directed swimming of the larvae towards a destination. The model indicated that possible spawning areas for all three species would be in the northeast of New Caledonia, perhaps within the North Fiji basin between Vanuatu and Fiji. Spawning within this region is consistent with the locations of known larvae, probable migration routes, and the distribution of adult eels in both countries.
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"Eels at the Edge: Science, Status, and Conservation Concerns." In Eels at the Edge: Science, Status, and Conservation Concerns, edited by Michael J. Miller, Jun Aoyama, and Katsumi Tsukamoto. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781888569964.ch5.
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<em>Abstract.</em>—Recent studies on leptocephali and glass eels of anguillid species in the western North Pacific and Indonesian Seas suggest that tropical eels have very different life history characteristics than temperate species, which may have important implications for their conservation and management. Some species in the Indonesian Seas region, such as the Indonesian mottled eel <em>Anguilla celebesensis </em>and the Indonesian longfinned eel <em>A. borneensis</em>, appear to have short spawning migrations and larval durations compared with temperate species. Species such as the Indonesian mottled eel <em>A. celebesensis </em>likely have multiple populations that spawn locally and recruit back to the same area. However, the giant mottled eel <em>A. marmorata </em>appears to have several separate populations in various regions of the Indian Ocean and western North and South Pacific oceans. The northern population of this species probably spawns in the North Equatorial Current region of the western North Pacific and has a long spawning migration more characteristic of temperate species. These findings suggest that the population structures of various tropical and temperate eel species may be quite different. Therefore some tropical anguillid species may require management at regional levels rather than as single panmictic species, as generally has been the case for temperate species.
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"Eels at the Edge: Science, Status, and Conservation Concerns." In Eels at the Edge: Science, Status, and Conservation Concerns, edited by Michael I. Pedersen. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781888569964.ch11.
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<em>Abstract.</em>—To counteract low elver recruitment to the Danish coast, a stocking program has been under development since the late 1980s. Glass eels imported from southern Europe are cultured to 2–5 g and stocked throughout the country in fresh and brackish water. To assess the value of these stockings, selected streams were stocked with eels weighing 3 and 9 g. Poststock evaluations by electrofishing were done 3–63 d after stocking in one system and up to four years later in another system. Instantaneous daily disappearance rate, including emigration and natural mortality, was high (<EM>D </EM>= 0.006–0.153) in both river systems. The reasons may include low water temperatures combined with a habitat offering too little shelter for the stocked eels.
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"The Development of Form and Function in Fishes and the Question of Larval Adaptation." In The Development of Form and Function in Fishes and the Question of Larval Adaptation, edited by Bernd Pelster. American Fisheries Society, 2004. http://dx.doi.org/10.47886/9781888569582.ch3.
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<em>Abstract.</em>—The swim bladder originates as an unpaired dorsal outgrowth of the posterior foregut. While in physostome fish the embryonic connection to the pharynx persists, in physoclist fishes, it is lost during early development. In most fish larvae, the swim bladder is inflated shortly after hatching, just prior to the time of first feeding. At this time, many larvae swim up and start surfacing. In this case, initial inflation of the swim bladder is achieved by gulping air, and a lack of swim bladder inflation often is accompanied by a significant reduction of viability. While this appears to be the way most physostome fish inflate their swim bladder, some species obviously are able to inflate the swim bladder without surfacing. In adult fish, gas secretion into the swim bladder requires the activity of gas gland cells, which acidify the blood and thus induce a decrease in its gascarrying capacity. In consequence, gas partial pressures increase, providing a pressure head for the diffusive transport of gas from the blood into the swim bladder. Recent studies on the European glass eel <em>Anguilla anguilla </em>suggest that, at the time of first inflation, gas gland cells may not yet be functional. Nevertheless, glass eels can inflate their swim bladder without surfacing. Although various mechanisms have been proposed to explain the inflation of the swim bladder without gulping air, a decisive answer cannot yet be presented.
Conference papers on the topic "Glass eels"
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Jegadeesan, P., S. Amirthapandian, Kitheri Joseph, D. K. Shukla, Mukul Gupta, and B. K. Panigrahi. "XAS and EELS analysis on ion irradiated iron phosphate glass." In DAE SOLID STATE PHYSICS SYMPOSIUM 2019. AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0025337.
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Durza, O. "Magnetic mapping of soil pollution around a glass factory of Bratislava, Slovak Republic." In 4th EEGS Meeting. European Association of Geoscientists & Engineers, 1998. http://dx.doi.org/10.3997/2214-4609.201407030.
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Hananya, Ariel, and Bambang Retnoaji. "Vertebral column study on glass and elver eel of Anguilla bicolor (McClelland, 1844)." In THE 6TH INTERNATIONAL CONFERENCE ON BIOLOGICAL SCIENCE ICBS 2019: “Biodiversity as a Cornerstone for Embracing Future Humanity”. AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0015703.
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Griffioen, A. B., P. de Vries, R. H. Twijnstra, and M. de Graaf. Glass eel monitoring in the Netherlands. IJmuiden: Wageningen Marine Research, 2017. http://dx.doi.org/10.18174/408032.
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