title: Oceanic spawning ecology of freshwater eels in the western North Pacific.
abstract: The natural reproductive ecology of freshwater eels remained a mystery even after some of their offshore spawning areas were discovered approximately 100 years ago. In this study, we investigate the spawning ecology of freshwater eels for the first time using collections of eggs, larvae and spawning-condition adults of two species in their shared spawning area in the Pacific. Ovaries of female Japanese eel and giant mottled eel adults were polycyclic, suggesting that freshwater eels can spawn more than once during a spawning season. The first collection of Japanese eel eggs near the West Mariana Ridge where adults and newly hatched larvae were also caught shows that spawning occurs during new moon periods throughout the spawning season. The depths where adults and newly hatched larvae were captured indicate that spawning occurs in shallower layers of 150-200 m and not at great depths. This type of spawning may reduce predation and facilitate reproductive success.
authors.affiliation: Department of Marine Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan. ktpc@aori.u-tokyo.ac.jp
authors.forename: Katsumi
authors.initials: K
authors.lastname: Tsukamoto
authors.forename: Seinen
authors.initials: S
authors.lastname: Chow
authors.forename: Tsuguo
authors.initials: T
authors.lastname: Otake
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kurogi
authors.forename: Noritaka
authors.initials: N
authors.lastname: Mochioka
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Miller
authors.forename: Jun
authors.initials: J
authors.lastname: Aoyama
authors.forename: Shingo
authors.initials: S
authors.lastname: Kimura
authors.forename: Shun
authors.initials: S
authors.lastname: Watanabe
authors.forename: Tatsuki
authors.initials: T
authors.lastname: Yoshinaga
authors.forename: Akira
authors.initials: A
authors.lastname: Shinoda
authors.forename: Mari
authors.initials: M
authors.lastname: Kuroki
authors.forename: Machiko
authors.initials: M
authors.lastname: Oya
authors.forename: Tomowo
authors.initials: T
authors.lastname: Watanabe
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Hata
authors.forename: Shigeho
authors.initials: S
authors.lastname: Ijiri
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Kazeto
authors.forename: Kazuharu
authors.initials: K
authors.lastname: Nomura
authors.forename: Hideki
authors.initials: H
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004524:Eels / Q000033:anatomy & histology / Q000235:genetics / Q000502:physiology*; D004553:Electric Conductivity; D005260:Female; D005838:Genotype; D007814:Larva / Q000502:physiology; D008969:Molecular Sequence Data; D010053:Ovary / Q000502:physiology; D010140:Pacific Ocean; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012098:Reproduction / Q000502:physiology*; D017422:Sequence Analysis, DNA; D012726:Sexual Behavior, Animal / Q000502:physiology*; D013045:Species Specificity; D013696:Temperature
chemical_list: D017931:DNA Primers; D012336:RNA, Ribosomal, 16S