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Maeda T, Hagihara S, Wakiya R, Kimura S. Can displaced Anguilla marmorata return to their original habitat? Daily tracking study of their homing behavior. JOURNAL OF FISH BIOLOGY 2024. [PMID: 38811345 DOI: 10.1111/jfb.15824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 05/12/2024] [Accepted: 05/15/2024] [Indexed: 05/31/2024]
Abstract
Anguilla marmorata collected in the Odana River lower reaches were passive integrated transponder-tagged displaced and released into the upper river reaches (54 up-transported eels), and eels collected in the upper reaches were tagged and released downstream (52 down-transported eels). Their movements were detected once per day for 10 days using a portable radio-frequency identification (RFID) system. The homing rate of the down-transported eels was 38.9%, compared to 3.7% for the up-transported eels, suggesting that eels inhabiting upstream areas have relatively high fidelity to their habitats and downstream eels have less fidelity.
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Affiliation(s)
- Tatsuhiko Maeda
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
| | - Seishi Hagihara
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
- Nanae Freshwater Station, Field Science Center for Northern Biosphere, Hokkaido University, Hokkaido, Japan
| | - Ryoshiro Wakiya
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
| | - Shingo Kimura
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
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Williamson MJ, Pike C, Gollock M, Jacoby DMP, Piper AT. Anguillid eels. Curr Biol 2023; 33:R888-R893. [PMID: 37699341 DOI: 10.1016/j.cub.2023.07.044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/14/2023]
Abstract
Anguillid eels have fascinated humans for centuries, but our knowledge of these mysterious fish is still scant. There are 19 species or subspecies in the genus Anguilla, which are found globally, except in the eastern Pacific and southern Atlantic. Their common label 'freshwater eels' is a misnomer - all anguillids are facultatively catadromous, born in marine environments, developing in continental waters, with a proportion never entering freshwater at all. Anguillid eels have several life history traits that have allowed them to exploit a broad range of habitats. As such, anguillid eels play an important ecological role in both marine and freshwater environments as well as being commercially valuable. Because of this, anguillid eels are under threat from multiple stressors, such as barriers to migration, pollution, parasites, disease, climate change and unsustainable exploitation. Six species are listed as Threatened in the Red List of Threatened Species, and four are listed as Data Deficient. Strengthening conservation and management of these species is essential, and further research provides an exciting opportunity to develop a greater understanding of this mysterious clade of fish.
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Affiliation(s)
- Michael J Williamson
- Institute of Zoology, Zoological Society of London, Outer Circle, Regent's Park, London NW1 4RY, UK; Department of Genetics, Evolution and Environment, University College London, Darwin Building, 99-105 Gower Street, London WC1E 6BT, UK.
| | - Charlotte Pike
- Conservation and Policy, Zoological Society of London, Outer Circle, Regent's Park, London NW1 4RY, UK
| | - Matthew Gollock
- Conservation and Policy, Zoological Society of London, Outer Circle, Regent's Park, London NW1 4RY, UK
| | - David M P Jacoby
- Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK
| | - Adam T Piper
- Institute of Zoology, Zoological Society of London, Outer Circle, Regent's Park, London NW1 4RY, UK; Department of Genetics, Evolution and Environment, University College London, Darwin Building, 99-105 Gower Street, London WC1E 6BT, UK
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Wakiya R, Itakura H, Hirae T, Igari T, Manabe M, Matsuya N, Miyata K, Sakata MK, Minamoto T, Yada T, Kaifu K. Slower growth of farmed eels stocked into rivers with higher wild eel density. JOURNAL OF FISH BIOLOGY 2022; 101:613-627. [PMID: 35678211 DOI: 10.1111/jfb.15131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 06/01/2022] [Indexed: 06/15/2023]
Abstract
Farmed anguillid eels are frequently stocked into natural fresh waters to enhance eel resources, but little is known about what happens to these eels or their interactions with wild eels after stocking. A recent study observed a depressed survival and growth rate of farmed Japanese eels when they were reared with wild eels, which indicated that wild eels might interfere with the survival and growth of farmed-and-stocked eels through intraspecific competition. To contribute to improving eel stocking efficiency, the growth of farmed-and-stocked Japanese eels was compared among four rivers with different wild eel densities using mark-and-recapture studies. Based on the 2-year recapture survey after stocking, it was found that the density of the farmed-and-stocked eels was not significantly different among rivers. The daily growth rates of farmed-and-stocked eels in the rivers with lower wild eel density were significantly higher than those of the eels stocked into the rivers with higher wild eel density. The farmed-and-stocked eels moved significantly greater distances downstream than wild eels that showed sedentary behaviour. This and previous studies indicate that significant questions remain about the effectiveness of stocking farmed eels into water bodies where naturally recruited wild eels are present.
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Affiliation(s)
- Ryoshiro Wakiya
- Research and Development Initiative, Chuo University, Tokyo, Japan
| | - Hikaru Itakura
- Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, Maryland, USA
| | - Tatsumu Hirae
- Fisheries Technology and Development Center, Kagoshima, Japan
| | - Tadamitsu Igari
- Fisheries Technology and Development Center, Kagoshima, Japan
| | - Miyuki Manabe
- Fisheries Technology and Development Center, Kagoshima, Japan
| | - Noriaki Matsuya
- Inland Water Fisheries Institute, Aomori Prefectural Industrial Technology Research Center, Aomori, Japan
| | | | - Masayuki K Sakata
- Graduate School of Human Development and Environment, Kobe University, Kobe, Japan
| | - Toshifumi Minamoto
- Graduate School of Human Development and Environment, Kobe University, Kobe, Japan
| | - Takashi Yada
- Nikko Field Station, Fisheries Technology Institute, Japan Fisheries Research and Education Agency, Nikko, Japan
| | - Kenzo Kaifu
- Faculty of Law, Chuo University, Hachioji-shi, Japan
- The Zoological Society of London, London, UK
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Hagihara S, Wakiya R, Maeda T, Kimura S. Morphological and gonadal histological characteristics of the silver-phase male Indo-Pacific eel Anguilla marmorata. JOURNAL OF FISH BIOLOGY 2022; 101:749-752. [PMID: 35722834 DOI: 10.1111/jfb.15139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 06/15/2022] [Indexed: 06/15/2023]
Abstract
Eight silver-phase male Indo-Pacific eels (giant mottled eels) Anguilla marmorata were collected from three small rivers on subtropical Amami-Oshima Island, Japan, and their morphological and gonadal-histological characteristics were examined. The total length, body mass and age of the silver eels were 543.8 ± 49.3 (496-659) mm, 376.0 ± 116.0 (282-660) g and 14.6 ± 2.3 (11-19) years old, respectively. The silvering-related characteristics (eye index, pectoral-fin index, gut-somatic index) and reproductive characteristics (gonadosomatic index, histological stage) of the silver eels were significantly advanced compared to those of yellow eels, which is similar to other anguillid species.
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Affiliation(s)
- Seishi Hagihara
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
| | - Ryoshiro Wakiya
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
| | - Tatsuhiko Maeda
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
| | - Shingo Kimura
- Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
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Yokouchi K, Itakura H, Wakiya R, Yoshinaga T, Mochioka N, Kimura S, Kaifu K. Cumulative effects of low‐height barriers on distributions of catadromous Japanese eels in Japan. Anim Conserv 2021. [DOI: 10.1111/acv.12725] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- K. Yokouchi
- National Research Institute of Fisheries Science Japan Fisheries Research and Education Agency Yokohama Japan
- Center for International Collaborative Research Nagasaki University Nagasaki Japan
| | - H. Itakura
- Chesapeake Biological Laboratory University of Maryland Center for Environmental Science Solomons MD USA
- Atmosphere and Ocean Research Institute The University of Tokyo Kashiwa Japan
| | - R. Wakiya
- Atmosphere and Ocean Research Institute The University of Tokyo Kashiwa Japan
- Research and Development Initiative Chuo University Hachioji Japan
| | - T. Yoshinaga
- School of Marine Biosciences Kitasato University Sagamihara Japan
| | - N. Mochioka
- Faculty of Agriculture Kyushu University Fukuoka Japan
| | - S. Kimura
- Atmosphere and Ocean Research Institute The University of Tokyo Kashiwa Japan
| | - K. Kaifu
- Faculty of Law Chuo University Hachioji Japan
- The Zoological Society of London London UK
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Itakura H, Wakiya R. Habitat preference, movements and growth of giant mottled eels, Anguilla marmorata, in a small subtropical Amami-Oshima Island river. PeerJ 2020; 8:e10187. [PMID: 33194404 PMCID: PMC7646302 DOI: 10.7717/peerj.10187] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 09/24/2020] [Indexed: 02/02/2023] Open
Abstract
Although anguillid eel populations have decreased remarkably in recent decades, few detailed ecological studies have been conducted on tropical eels such as the giant mottled eel whose range extends across the whole Indo-Pacific. This species was studied throughout the entire 0.5 km mainstem reaches of Oganeku River on the subtropical Amami-Oshima Island of Japan over a two-year period using four sampling periods to understand its habitat preference, early life-stage dispersal process, movements, and annual growth using a mark-recapture experiment conducted with quantitative electrofishing. A total of 396 juvenile growth-phase A. marmorata eels were caught and tagged, with 48 individuals being recaptured at least once. Their density irrespective of size of eels was most strongly determined by distance from the river mouth, followed by riverbank type according to random forest models. Eel density decreased with increasing distance from the freshwater tidal limit located about 100-150 m from the river mouth. Eels preferred vegetated riverbanks, while they avoided those of concrete and sand. The density of small eels (total length: TL < 240 mm) was also associated with depth and velocity, with small eels tending to prefer riffle or run habitats. In contrast, large eels (TL ≥ 240 mm) were found in habitats of any depth and velocity. The TL of eels had a minimum peak at around the tidal limit, and it increased with increasing distance from the tidal limit. The observed density and size gradients of eels in relation to the distance from the river mouth suggested that A. marmorata initially recruited to freshwater tidal limit areas and then dispersed in both downstream and upstream directions. The growth rate of eels varied greatly among individuals that were at large for various periods of time and ranged from 0 to 163.2 mm/year (mean ± SD of 31.8 ± 31.0 mm/year). Of the recaptured eels, 52.1% were recaptured in a section that was different from the original capture section, and their mean ± SD distance travelled was 46.5 ± 72.5 m (median = 20 m). 47.9% of the eels were recaptured from the original section of capture (i.e., <10 m distances travelled), suggesting that they had strong fidelity to specific habitats with limited movements. The distance travelled of eels that had moved was greater for small eels (range = 10-380 m; mean ± SD = 84.4 ± 121.9 m) than large individuals (range = 10-120 m; mean ± SD = 30.9 ± 31.0 m), which indicates that the mobility of the eels declines as they grow. This is the first clear detailed documentation of the spatial distribution, growth, and movements of tropical eels in a small river system in relation to environmental conditions that provides an example of how future studies can be conducted in other areas to understand how conservation efforts can be most efficiently targeted for maximum success.
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Affiliation(s)
- Hikaru Itakura
- Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD, United States of America
- Graduate School of Science, Kobe University, Kobe, Hyogo, Japan
| | - Ryoshiro Wakiya
- Research and Development Initiative, Chuo University, Bunkyo-ku, Tokyo, Japan
- Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Chiba, Japan
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