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Eric Feunteun - One of the best experts on this subject based on the ideXlab platform.
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Anguilla marmorata larval migration plasticity as revealed by otolith microstructural analysis
Canadian Journal of Fisheries and Aquatic Sciences, 2008Co-Authors: Elodie Réveillac, Eric Feunteun, Patrick Berrebi, Pierre-alexandre Gagnaire, Raymonde Lecomte-finiger, Pierre Bosc, Tony RobinetAbstract:The oceanic early-life history of Anguilla marmorata was examined in the southwestern Indian Ocean in Mayotte, Mauritius, and Reunion islands through otolith microstructural analysis. The study of the hatching dates, the first feeding check diameter (FFD), the Leptocephalus (LD) and metamorphosis (MD) durations, the age at recruitment (AR), and the Leptocephalus otolith growth rate (OGR) of glass eels revealed great variations in early-life traits and relationships between them. An agglomerative nesting analysis discriminated three early-life histories, differently represented according to the locality: (i) fast migrants with short LD, short MD, young AR, large FFD, and high OGR dominated in Reunion and Mayotte; (ii) midspeed migrants with intermediate LD, MD, AR, FFD, and OGR dominated in Mauritius; (iii) slow migrants with long LD, long MD, old AR, small FFD, and low OGR were recorded only in Mauritius. All possible strategies were not observed and therefore not successful at the sampling time. However, several were simultaneously expressed, which suggests larval migration plasticity at the population level. This evidence is crucial information regarding both the species dispersal capabilities and the evolution from short-migratory tropical species towards long-migratory temperate ones in the genus Anguilla.
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New clues for freshwater eels (Anguilla spp.) migration routes to eastern Madagascar and surrounding islands
Marine Biology, 2008Co-Authors: Tony Robinet, Elodie Réveillac, Patrick Berrebi, Pierre-alexandre Gagnaire, Katsumi Tsukamoto, Mari Kuroki, Jun Aoyama, M. W. Rabenevanana, Pierre Valade, Eric FeunteunAbstract:A total of 4,172 freshwater eels have been collected by electrofishing in upper estuaries from Madagascar (East coast), Mascarene (Reunion and Mauritius Is.), Comoros (Mayotte Is.) and Seychelles (Mahe and Praslin Is.) Archipelagos, between October 2003 and February 2006. Eel species composition in the sampling stations was contrasted between eastern Madagascar (Anguilla mossambica 96.0%, A. marmorata 3.9% and A. bicolor bicolor 0.2%), the Comoros (A. marmorata 56.1% and A. bicolor bicolor 43.9%), the Mascarene (A. marmorata 91.4%, A. bicolor bicolor 5.4% and A. mossambica 3.2%) and the Seychelles Archipelagos (A. bicolor bicolor 100.0%). This gradient in species composition, even concerning the short time-range of our sampling, argued for separate migration routes between species. A total of 168 eels were aged by reading their otolith microstructure, and otolith growth rates were calculated from pre-Leptocephalus stage (post-hatching) to metamorphosis, until freshwater check. For all species, mean otolith growth rate (OGR) was related to specific migration routes: A. bicolor bicolor is distributed in the lowest latitudes and showed the highest OGR during Leptocephalus stage, whereas A. mossambica, endemic of the Malagasy area, has the most southern distribution and showed the lowest OGR. OGR during Leptocephalus stage was negatively correlated to the Leptocephalus stage duration, showing a decrease of global metabolism with time, classical in leptocephali. This relationship was found significant for A. marmorata and A. mossambica, probably because all these larvae crossed successively the same environments, but not for A. bicolor bicolor, probably because their larvae crossed different pelagic environments, opening the hypothesis of larvae from different origins.
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New clues for freshwater eels (Anguilla spp.) migration routes to eastern Madagascar and surrounding islands
Marine Biology, 2008Co-Authors: Tony Robinet, Elodie Réveillac, Patrick Berrebi, Pierre-alexandre Gagnaire, K. Tsukamoto, Mari Kuroki, Jun Aoyama, M. W. Rabenevanana, Pierre Valade, Eric FeunteunAbstract:A total of 4,172 freshwater eels have been collected by electroWshing in upper estuaries from Madagascar (East coast), Mascarene (Réunion and Mauritius Is.), Comoros (Mayotte Is.) and Seychelles (Mahé and Praslin Is.) Archipelagos, between October 2003 and February 2006. Eel species composition in the sampling stations was contrasted between eastern Madagascar (Anguilla mossambica 96.0%, A. marmorata 3.9% and A. bicolor bicolor 0.2%), the Comoros (A. marmorata 56.1% and A. bicolor bicolor 43.9%), the Mascarene (A. marmorata 91.4%, A. bicolor bicolor 5.4% and A. mossambica 3.2%) and the Seychelles Archipelagos (A. bicolor bicolor 100.0%). This gradient in species composition, even concerning the short time-range of our sampling, argued for separate migration routes between species. A total of 168 eels were aged by reading their otolith microstructure, and otolith growth rates were calculated from pre-Leptocephalus stage (post-hatching) to metamorphosis, until freshwater check. For all species, mean otolith growth rate (OGR) was related to specific migration routes: A. bicolor bicolor is distributed in the lowest latitudes and showed the highest OGR during Leptocephalus stage, whereas A. mossambica, endemic of the Malagasy area, has the most southern distribution and showed the lowest OGR. OGR during Leptocephalus stage was negatively correlated to the Leptocephalus stage duration, showing a decrease of global metabolism with time, classical in leptocephali. This relationship was found significant for A. marmorata and A. mossambica, probably because all these larvae crossed successively the same environments, but not for A. bicolor bicolor, probably because their larvae crossed diVerent pelagic environments, opening the hypothesis of larvae from diVerent origins.
Katsumi Tsukamoto - One of the best experts on this subject based on the ideXlab platform.
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Larval abundance across the European eel spawning area: An analysis of recent and historic data
Fish and Fisheries, 2018Co-Authors: Håkan Westerberg, Michael J. Miller, Katsumi Tsukamoto, Lasse Marohn, Klaus Wysujack, Marko Freese, Jan-dag Pohlmann, Shun Watanabe, Reinhold HanelAbstract:The abundance and distribution of Leptocephalus larvae of the European eel (Anguilla anguilla, Anguillidae) were examined using ten historic and recent Sargasso Sea expeditions that were selected on the basis of having the largest number of sampling stations and highest catches. The surveys cover the period 1920–2014. Station data were recalculated to the same unit of larval density per unit area, and the irregular station positions were transformed to a regular spatial grid to allow calculation of comparable measures of abundance of the youngest (0+) Leptocephalus cohort. The result is that the mean and maximum densities of 0+ leptocephali after 2007 on average have decreased by 70%–80% from the densities during the period before the drastic decrease in glass eel recruitment, which started in the 1980s. This is of the same magnitude as the change in spawning stock, if the total continental commercial landings are used as a proxy. In the same period, the glass eel recruitment in Europe has decreased by more than 95%. The conclusion is that a major cause for the recruitment decrease may be an increased Leptocephalus mortality during the oceanic phase or a large geographic shift in glass eel arrival. Combining the survey data, the spatial distribution of 0+ leptocephali was concentrated south of the northernmost front in the Subtropical Convergence Zone, but high densities were also found far south of the front in the western part of the distribution area and leptocephali were present also north of the average frontal position.
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Resolving deep-sea pelagic saccopharyngiform eel mysteries: Identification of Neocyema and Monognathidae leptocephali and establishment of a new fish family "Neocyematidae" based on larvae, adults and mitogenomic gene orders - Fig 3
2018Co-Authors: Jan Y. Poulsen, Michael J. Miller, Tetsuya Sado, Reinhold Hanel, Katsumi Tsukamoto, Masaki MiyaAbstract:Leptocephalus larvae of saccopharyngiform fishes known until the present study (A–F). A, Eurypharynx (WH404_906) 25.3 mm. B, Saccopharynx (WH342_1580) 40.0 mm. C, Cyema (WH404_82) 26.2 mm. D, “Leptocephalus holti” Type I (KH-11-6_184) 15.4 mm. E, “Leptocephalus holti” Type II (WH342_418) 38.0 mm. F, “Leptocephalus holti” Type III (MSM41_1404) 27.1 mm. Scale bars 5 mm.
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Resolving deep-sea pelagic saccopharyngiform eel mysteries: Identification of Neocyema and Monognathidae leptocephali and establishment of a new fish family "Neocyematidae" based on larvae, adults and mitogenomic gene orders - Fig 2
2018Co-Authors: Jan Y. Poulsen, Michael J. Miller, Tetsuya Sado, Reinhold Hanel, Katsumi Tsukamoto, Masaki MiyaAbstract:Line-illustrations of Leptocephalus larvae of meso- and bathypelagic anguilliform families (A–K). A, Cyema (Cyematidae). B, “Leptocephalus holti”. C, Monognathidae (metamorphic stage). D, Unidentified saccopharyngiform. E, Saccopharynx (Saccopharyngidae). F, Eurypharynx (Eurypharyngidae). G, Serrivomer beani (Serrivomeridae). H, Nemichthys curvirostris (Nemichthyidae). I, Avocettina infans (Nemichthyidae). J, Derichthys serpentinus (Derichthyidae). K, Nessorhamphus ingolfianus (Derichthyidae). The dotted line separates the saccopharyngiform larvae from the larvae of other meso- and bathy-pelagic eel families. Illustrations A, C, D, F–K are reproduced or modified from Böhlke [1], B is modified from Smith and Miller [24], and E is modified from Castle [84] with permission under a CC BY license, from the Sears Foundation for Marine Research original copyright 1989, illustrator Mary H. Fuges, Yale University, and the American Society of Ichthyologists and Herpetologists, Lawrence, Kansas, respectively.
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Resolving deep-sea pelagic saccopharyngiform eel mysteries: Identification of Neocyema and Monognathidae leptocephali and establishment of a new fish family "Neocyematidae" based on larvae, adults and mitogenomic gene orders - Fig 4
2018Co-Authors: Jan Y. Poulsen, Michael J. Miller, Tetsuya Sado, Reinhold Hanel, Katsumi Tsukamoto, Masaki MiyaAbstract:A Leptocephalus larva (WH342_1248, 22.5 mm) of Neocyema erythrosoma from the Sargasso Sea that has unique orange pigment spots (A–D). A, Whole specimen, 22.5 mm TL. B, Head region. C, Esophagus, liver, stomach region. D, End of the gut region. Scale bar 5 mm.
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Parentage assignment of a hormonally induced mass spawning in Japanese eel (Anguillla japonica)
Aquaculture, 2018Co-Authors: Ryusuke Sudo, Katsumi Tsukamoto, Moeri Miyao, Tsubasa Uchino, Yoshiaki Yamada, Takashi SakamotoAbstract:Abstract Anguillid eels are a high value species for aquaculture in East Asian countries, but natural stocks of eels have been decreasing. Mass production of glass eels is one of the most effective ways to solve this problem. Genetic improvements will become important to establish mass production of glass eels in the near future. However, there is a lack of basic information, such as parentage assignments, for implementing an eel breeding program. In this study, we aimed to understand the parentage assignment of Japanese eel ( Anguilla japonica ) using a multiple breeding method and microsatellites from eight loci. Five female and 15 male eels were used for mass spawning, and the progeny were collected at the pre-Leptocephalus (2 days post-hatch [dph]) and the Leptocephalus stage (30 dph). Almost all progeny (297/301 = 98.7%) were assigned to a parental couple. Only two female eels (F86 and F88) contributed to the next generation, whereas 13 of 15 males contributed to the next generation. Although there were no statistical differences in the paternity ratio between stages, some males changed the ratio in both females. These data are not directly useful for a breeding program, but are useful to maintain pedigree information, which is essential for implementing a breeding program.
Tony Robinet - One of the best experts on this subject based on the ideXlab platform.
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Anguilla marmorata larval migration plasticity as revealed by otolith microstructural analysis
Canadian Journal of Fisheries and Aquatic Sciences, 2008Co-Authors: Elodie Réveillac, Eric Feunteun, Patrick Berrebi, Pierre-alexandre Gagnaire, Raymonde Lecomte-finiger, Pierre Bosc, Tony RobinetAbstract:The oceanic early-life history of Anguilla marmorata was examined in the southwestern Indian Ocean in Mayotte, Mauritius, and Reunion islands through otolith microstructural analysis. The study of the hatching dates, the first feeding check diameter (FFD), the Leptocephalus (LD) and metamorphosis (MD) durations, the age at recruitment (AR), and the Leptocephalus otolith growth rate (OGR) of glass eels revealed great variations in early-life traits and relationships between them. An agglomerative nesting analysis discriminated three early-life histories, differently represented according to the locality: (i) fast migrants with short LD, short MD, young AR, large FFD, and high OGR dominated in Reunion and Mayotte; (ii) midspeed migrants with intermediate LD, MD, AR, FFD, and OGR dominated in Mauritius; (iii) slow migrants with long LD, long MD, old AR, small FFD, and low OGR were recorded only in Mauritius. All possible strategies were not observed and therefore not successful at the sampling time. However, several were simultaneously expressed, which suggests larval migration plasticity at the population level. This evidence is crucial information regarding both the species dispersal capabilities and the evolution from short-migratory tropical species towards long-migratory temperate ones in the genus Anguilla.
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New clues for freshwater eels (Anguilla spp.) migration routes to eastern Madagascar and surrounding islands
Marine Biology, 2008Co-Authors: Tony Robinet, Elodie Réveillac, Patrick Berrebi, Pierre-alexandre Gagnaire, Katsumi Tsukamoto, Mari Kuroki, Jun Aoyama, M. W. Rabenevanana, Pierre Valade, Eric FeunteunAbstract:A total of 4,172 freshwater eels have been collected by electrofishing in upper estuaries from Madagascar (East coast), Mascarene (Reunion and Mauritius Is.), Comoros (Mayotte Is.) and Seychelles (Mahe and Praslin Is.) Archipelagos, between October 2003 and February 2006. Eel species composition in the sampling stations was contrasted between eastern Madagascar (Anguilla mossambica 96.0%, A. marmorata 3.9% and A. bicolor bicolor 0.2%), the Comoros (A. marmorata 56.1% and A. bicolor bicolor 43.9%), the Mascarene (A. marmorata 91.4%, A. bicolor bicolor 5.4% and A. mossambica 3.2%) and the Seychelles Archipelagos (A. bicolor bicolor 100.0%). This gradient in species composition, even concerning the short time-range of our sampling, argued for separate migration routes between species. A total of 168 eels were aged by reading their otolith microstructure, and otolith growth rates were calculated from pre-Leptocephalus stage (post-hatching) to metamorphosis, until freshwater check. For all species, mean otolith growth rate (OGR) was related to specific migration routes: A. bicolor bicolor is distributed in the lowest latitudes and showed the highest OGR during Leptocephalus stage, whereas A. mossambica, endemic of the Malagasy area, has the most southern distribution and showed the lowest OGR. OGR during Leptocephalus stage was negatively correlated to the Leptocephalus stage duration, showing a decrease of global metabolism with time, classical in leptocephali. This relationship was found significant for A. marmorata and A. mossambica, probably because all these larvae crossed successively the same environments, but not for A. bicolor bicolor, probably because their larvae crossed different pelagic environments, opening the hypothesis of larvae from different origins.
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New clues for freshwater eels (Anguilla spp.) migration routes to eastern Madagascar and surrounding islands
Marine Biology, 2008Co-Authors: Tony Robinet, Elodie Réveillac, Patrick Berrebi, Pierre-alexandre Gagnaire, K. Tsukamoto, Mari Kuroki, Jun Aoyama, M. W. Rabenevanana, Pierre Valade, Eric FeunteunAbstract:A total of 4,172 freshwater eels have been collected by electroWshing in upper estuaries from Madagascar (East coast), Mascarene (Réunion and Mauritius Is.), Comoros (Mayotte Is.) and Seychelles (Mahé and Praslin Is.) Archipelagos, between October 2003 and February 2006. Eel species composition in the sampling stations was contrasted between eastern Madagascar (Anguilla mossambica 96.0%, A. marmorata 3.9% and A. bicolor bicolor 0.2%), the Comoros (A. marmorata 56.1% and A. bicolor bicolor 43.9%), the Mascarene (A. marmorata 91.4%, A. bicolor bicolor 5.4% and A. mossambica 3.2%) and the Seychelles Archipelagos (A. bicolor bicolor 100.0%). This gradient in species composition, even concerning the short time-range of our sampling, argued for separate migration routes between species. A total of 168 eels were aged by reading their otolith microstructure, and otolith growth rates were calculated from pre-Leptocephalus stage (post-hatching) to metamorphosis, until freshwater check. For all species, mean otolith growth rate (OGR) was related to specific migration routes: A. bicolor bicolor is distributed in the lowest latitudes and showed the highest OGR during Leptocephalus stage, whereas A. mossambica, endemic of the Malagasy area, has the most southern distribution and showed the lowest OGR. OGR during Leptocephalus stage was negatively correlated to the Leptocephalus stage duration, showing a decrease of global metabolism with time, classical in leptocephali. This relationship was found significant for A. marmorata and A. mossambica, probably because all these larvae crossed successively the same environments, but not for A. bicolor bicolor, probably because their larvae crossed diVerent pelagic environments, opening the hypothesis of larvae from diVerent origins.
Elodie Réveillac - One of the best experts on this subject based on the ideXlab platform.
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Anguilla marmorata larval migration plasticity as revealed by otolith microstructural analysis
Canadian Journal of Fisheries and Aquatic Sciences, 2008Co-Authors: Elodie Réveillac, Eric Feunteun, Patrick Berrebi, Pierre-alexandre Gagnaire, Raymonde Lecomte-finiger, Pierre Bosc, Tony RobinetAbstract:The oceanic early-life history of Anguilla marmorata was examined in the southwestern Indian Ocean in Mayotte, Mauritius, and Reunion islands through otolith microstructural analysis. The study of the hatching dates, the first feeding check diameter (FFD), the Leptocephalus (LD) and metamorphosis (MD) durations, the age at recruitment (AR), and the Leptocephalus otolith growth rate (OGR) of glass eels revealed great variations in early-life traits and relationships between them. An agglomerative nesting analysis discriminated three early-life histories, differently represented according to the locality: (i) fast migrants with short LD, short MD, young AR, large FFD, and high OGR dominated in Reunion and Mayotte; (ii) midspeed migrants with intermediate LD, MD, AR, FFD, and OGR dominated in Mauritius; (iii) slow migrants with long LD, long MD, old AR, small FFD, and low OGR were recorded only in Mauritius. All possible strategies were not observed and therefore not successful at the sampling time. However, several were simultaneously expressed, which suggests larval migration plasticity at the population level. This evidence is crucial information regarding both the species dispersal capabilities and the evolution from short-migratory tropical species towards long-migratory temperate ones in the genus Anguilla.
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New clues for freshwater eels (Anguilla spp.) migration routes to eastern Madagascar and surrounding islands
Marine Biology, 2008Co-Authors: Tony Robinet, Elodie Réveillac, Patrick Berrebi, Pierre-alexandre Gagnaire, Katsumi Tsukamoto, Mari Kuroki, Jun Aoyama, M. W. Rabenevanana, Pierre Valade, Eric FeunteunAbstract:A total of 4,172 freshwater eels have been collected by electrofishing in upper estuaries from Madagascar (East coast), Mascarene (Reunion and Mauritius Is.), Comoros (Mayotte Is.) and Seychelles (Mahe and Praslin Is.) Archipelagos, between October 2003 and February 2006. Eel species composition in the sampling stations was contrasted between eastern Madagascar (Anguilla mossambica 96.0%, A. marmorata 3.9% and A. bicolor bicolor 0.2%), the Comoros (A. marmorata 56.1% and A. bicolor bicolor 43.9%), the Mascarene (A. marmorata 91.4%, A. bicolor bicolor 5.4% and A. mossambica 3.2%) and the Seychelles Archipelagos (A. bicolor bicolor 100.0%). This gradient in species composition, even concerning the short time-range of our sampling, argued for separate migration routes between species. A total of 168 eels were aged by reading their otolith microstructure, and otolith growth rates were calculated from pre-Leptocephalus stage (post-hatching) to metamorphosis, until freshwater check. For all species, mean otolith growth rate (OGR) was related to specific migration routes: A. bicolor bicolor is distributed in the lowest latitudes and showed the highest OGR during Leptocephalus stage, whereas A. mossambica, endemic of the Malagasy area, has the most southern distribution and showed the lowest OGR. OGR during Leptocephalus stage was negatively correlated to the Leptocephalus stage duration, showing a decrease of global metabolism with time, classical in leptocephali. This relationship was found significant for A. marmorata and A. mossambica, probably because all these larvae crossed successively the same environments, but not for A. bicolor bicolor, probably because their larvae crossed different pelagic environments, opening the hypothesis of larvae from different origins.
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New clues for freshwater eels (Anguilla spp.) migration routes to eastern Madagascar and surrounding islands
Marine Biology, 2008Co-Authors: Tony Robinet, Elodie Réveillac, Patrick Berrebi, Pierre-alexandre Gagnaire, K. Tsukamoto, Mari Kuroki, Jun Aoyama, M. W. Rabenevanana, Pierre Valade, Eric FeunteunAbstract:A total of 4,172 freshwater eels have been collected by electroWshing in upper estuaries from Madagascar (East coast), Mascarene (Réunion and Mauritius Is.), Comoros (Mayotte Is.) and Seychelles (Mahé and Praslin Is.) Archipelagos, between October 2003 and February 2006. Eel species composition in the sampling stations was contrasted between eastern Madagascar (Anguilla mossambica 96.0%, A. marmorata 3.9% and A. bicolor bicolor 0.2%), the Comoros (A. marmorata 56.1% and A. bicolor bicolor 43.9%), the Mascarene (A. marmorata 91.4%, A. bicolor bicolor 5.4% and A. mossambica 3.2%) and the Seychelles Archipelagos (A. bicolor bicolor 100.0%). This gradient in species composition, even concerning the short time-range of our sampling, argued for separate migration routes between species. A total of 168 eels were aged by reading their otolith microstructure, and otolith growth rates were calculated from pre-Leptocephalus stage (post-hatching) to metamorphosis, until freshwater check. For all species, mean otolith growth rate (OGR) was related to specific migration routes: A. bicolor bicolor is distributed in the lowest latitudes and showed the highest OGR during Leptocephalus stage, whereas A. mossambica, endemic of the Malagasy area, has the most southern distribution and showed the lowest OGR. OGR during Leptocephalus stage was negatively correlated to the Leptocephalus stage duration, showing a decrease of global metabolism with time, classical in leptocephali. This relationship was found significant for A. marmorata and A. mossambica, probably because all these larvae crossed successively the same environments, but not for A. bicolor bicolor, probably because their larvae crossed diVerent pelagic environments, opening the hypothesis of larvae from diVerent origins.
Mari Kuroki - One of the best experts on this subject based on the ideXlab platform.
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Changes in the role of the thyroid axis during metamorphosis of the Japanese eel, Anguilla japonica.
Journal of experimental zoology. Part A Ecological genetics and physiology, 2014Co-Authors: Ryusuke Sudo, Akihiro Okamura, Mari Kuroki, Katsumi TsukamotoAbstract:To clarify the role of thyroid function during metamorphosis from Leptocephalus to glass eel in the Japanese eel, we examined the histology of the thyroid gland and measured whole-body concentrations of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), and thyroid stimulating hormone β-subunit TSH (TSHβ) mRNA expression levels in five stages of artificially hatched eels (Leptocephalus, early-metamorphosis, late-metamorphosis, glass eel, and elver). During metamorphosis, the inner colloid of thyroid follicles showed positive immunoreactivity for T4, and both T4 and T3 levels were significantly increased, whereas a small peak of TSHβ mRNA level was observed at the early-metamorphosis stage. Similarly, TSHβ mRNA levels were highest in the glass eel stage, and then decreased markedly in the elver stage. In contrast to TSHβ mRNA expression, thyroid hormones (both T4 and T3) increased further from the glass eel to elver stages. These results indicated that thyroid function in the Japanese eel was active both during and after metamorphosis. Therefore, the thyrotropic axis may play important roles not only in metamorphosis but also in subsequent inshore or upstream migrations. J. Exp. Zool. 321A: 357–364, 2014. © 2014 Wiley Periodicals, Inc.
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New clues for freshwater eels (Anguilla spp.) migration routes to eastern Madagascar and surrounding islands
Marine Biology, 2008Co-Authors: Tony Robinet, Elodie Réveillac, Patrick Berrebi, Pierre-alexandre Gagnaire, Katsumi Tsukamoto, Mari Kuroki, Jun Aoyama, M. W. Rabenevanana, Pierre Valade, Eric FeunteunAbstract:A total of 4,172 freshwater eels have been collected by electrofishing in upper estuaries from Madagascar (East coast), Mascarene (Reunion and Mauritius Is.), Comoros (Mayotte Is.) and Seychelles (Mahe and Praslin Is.) Archipelagos, between October 2003 and February 2006. Eel species composition in the sampling stations was contrasted between eastern Madagascar (Anguilla mossambica 96.0%, A. marmorata 3.9% and A. bicolor bicolor 0.2%), the Comoros (A. marmorata 56.1% and A. bicolor bicolor 43.9%), the Mascarene (A. marmorata 91.4%, A. bicolor bicolor 5.4% and A. mossambica 3.2%) and the Seychelles Archipelagos (A. bicolor bicolor 100.0%). This gradient in species composition, even concerning the short time-range of our sampling, argued for separate migration routes between species. A total of 168 eels were aged by reading their otolith microstructure, and otolith growth rates were calculated from pre-Leptocephalus stage (post-hatching) to metamorphosis, until freshwater check. For all species, mean otolith growth rate (OGR) was related to specific migration routes: A. bicolor bicolor is distributed in the lowest latitudes and showed the highest OGR during Leptocephalus stage, whereas A. mossambica, endemic of the Malagasy area, has the most southern distribution and showed the lowest OGR. OGR during Leptocephalus stage was negatively correlated to the Leptocephalus stage duration, showing a decrease of global metabolism with time, classical in leptocephali. This relationship was found significant for A. marmorata and A. mossambica, probably because all these larvae crossed successively the same environments, but not for A. bicolor bicolor, probably because their larvae crossed different pelagic environments, opening the hypothesis of larvae from different origins.
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New clues for freshwater eels (Anguilla spp.) migration routes to eastern Madagascar and surrounding islands
Marine Biology, 2008Co-Authors: Tony Robinet, Elodie Réveillac, Patrick Berrebi, Pierre-alexandre Gagnaire, K. Tsukamoto, Mari Kuroki, Jun Aoyama, M. W. Rabenevanana, Pierre Valade, Eric FeunteunAbstract:A total of 4,172 freshwater eels have been collected by electroWshing in upper estuaries from Madagascar (East coast), Mascarene (Réunion and Mauritius Is.), Comoros (Mayotte Is.) and Seychelles (Mahé and Praslin Is.) Archipelagos, between October 2003 and February 2006. Eel species composition in the sampling stations was contrasted between eastern Madagascar (Anguilla mossambica 96.0%, A. marmorata 3.9% and A. bicolor bicolor 0.2%), the Comoros (A. marmorata 56.1% and A. bicolor bicolor 43.9%), the Mascarene (A. marmorata 91.4%, A. bicolor bicolor 5.4% and A. mossambica 3.2%) and the Seychelles Archipelagos (A. bicolor bicolor 100.0%). This gradient in species composition, even concerning the short time-range of our sampling, argued for separate migration routes between species. A total of 168 eels were aged by reading their otolith microstructure, and otolith growth rates were calculated from pre-Leptocephalus stage (post-hatching) to metamorphosis, until freshwater check. For all species, mean otolith growth rate (OGR) was related to specific migration routes: A. bicolor bicolor is distributed in the lowest latitudes and showed the highest OGR during Leptocephalus stage, whereas A. mossambica, endemic of the Malagasy area, has the most southern distribution and showed the lowest OGR. OGR during Leptocephalus stage was negatively correlated to the Leptocephalus stage duration, showing a decrease of global metabolism with time, classical in leptocephali. This relationship was found significant for A. marmorata and A. mossambica, probably because all these larvae crossed successively the same environments, but not for A. bicolor bicolor, probably because their larvae crossed diVerent pelagic environments, opening the hypothesis of larvae from diVerent origins.