Contrasting diets of the Japanese eel, Anguilla japonica, in the upper and lower areas of Tsuchikawa-gawa River, Kagoshima, Japan

Wakiya, Ryoshiro; Mochioka, Noritaka

doi:10.1007/s10228-020-00755-5

Cited by 14 publications

(8 citation statements)

References 30 publications

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“…The nocturnal behavior was associated with foraging and predation avoidance. Eels feed on a variety of prey such as crayfish, crab, shrimp, bivalves, insects, and fish [ 20 , 21 , 47 ]. There is a difference in the preferred prey because prey distribution differs by habitat (freshwater vs. brackish water).…”

Section: Discussionmentioning

confidence: 99%

“…Joint research by multiple countries has revealed the spawning ecology [ 2 , 15 , 16 ] and migration of A. japonica [ 17 , 18 ] and environmental factors affecting its migration [ 19 ]. Most of the studies have been associated with spawning migration in the ocean; ecological studies in the freshwater ecosystem where the eels grow into yellow eels have been conducted on a limited basis in terms of their diet (e.g., Kaifu et al [ 20 ], Wakiya and Mochioka [ 21 ]) and morphological changes [ 22 ].…”

Section: Introductionmentioning

confidence: 99%

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Movement Patterns and Diel Activity of Anguilla japonica in the Middle Part of a Large River in South Korea

Kim¹,

Baek²,

Jang

et al. 2020

Animals

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To investigate movement patterns and diel activities of Anguilla japonica in the freshwater ecosystem, we applied acoustic telemetry on A. japonica in the Geum River, a large river in South Korea. The acoustic tags were attached on 19 individuals of A. japonica (12 with a depth sensor) in May and October 2015 and tracked at approximately 100-km sections from an estuary barrage by 20 automatic listening stations. Only four individuals showed longitudinal movement (mean, 5.2 km), and others were detected by the receivers at release sites; therefore, A. japonica showed high site fidelity. We did not identify seaward migration during the study period (May to November). Conversely, A. japonica showed active diel movement. The number of detections (p = 0.002) and movement distance (p = 0.004) were higher at night-time (18:00–06:00). As most individuals were actively moving at nighttime, we confirmed that A. japonica is nocturnal, although few individuals also showed daytime movement. Although the population and habitats of A. japonica have been decreasing simultaneously, the East-Asian countries are still severely exploiting rivers and streams to use water resources, and result in habitat simplification generated. Therefore, these results contribute to effective A. japonica management regarding habitat and population conservation and restoration.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Movement Patterns and Diel Activity of Anguilla japonica in the Middle Part of a Large River in South Korea

Kim¹,

Baek²,

Jang

et al. 2020

Animals

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show abstract

Section: Introductionmentioning

confidence: 99%

“…Various aspects of Japanese eel ecology have been studied intensively, such as their marine life history (spawning grounds and oceanic migration; Tsukamoto, Aoyama & Miller, 2009, and references therein), and recruitment, dispersal, demographic characteristics, and diet during estuarine and freshwater stages (Kotake et al, 2007; Yokouchi et al, 2008; Kaifu et al, 2010; Yokouchi et al, 2012; Kaifu et al, 2013; Itakura et al, 2015; Wakiya & Mochioka, 2021). However, until recently, few studies have focused on habitat effects on the distribution and abundance of Japanese eel in freshwater systems (Itakura et al, 2015; Kume et al, 2020; Matsushige, Yasutake & Mochioka, 2020; Yokouchi et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Riverine distribution and abundance of Japanese eel in Shikoku, south‐western Japan: Varying importance of regional and local factors

Yamamoto

Uemura

Mimachi

et al. 2023

Aquatic Conservation

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Regional and local habitat factors affecting the distribution and abundance of Japanese eel (Anguilla japonica) were systematically analysed in 123 reaches of 21 stream systems in south‐western Japan, with particular attention paid to human habitat modification, such as artificial barriers and concrete revetment. The density of Japanese eel decreased upstream, and they were absent from the upper reaches of each stream system. The upper limits of their distribution were explained by the distance from the sea and the channel gradient, rather than barriers. However, the number of barriers had the highest explanatory capacity for the upstream decline in abundance of small eels (<40 cm in total length). Analyses of the relative importance of regional and local habitat factors showed that the number of barriers (regional factor) was more important than local habitat factors in determining small eel abundance, whereas regional and local habitat factors (e.g. concrete revetment or cover habitat) were similarly important for large eel abundance. These results suggest that: (i) barriers are not a major factor limiting the distribution (presence/absence) of the Japanese eel in the streams studied; (ii) barriers can substantially decrease the abundance of young eels; and (iii) as eels grow older and larger, local habitat factors, such as bank conditions and cover, become more important in determining their abundance. The results for the relative importance of regional and local habitat factors suggest that in habitat restoration for the Japanese eel, priority should be given to mitigating barrier effects. The improvement of longitudinal connectivity to facilitate colonization by young eels is primarily needed for a more efficient use of the existing carrying capacity of streams. The improvement of local habitat conditions to increase the carrying capacity should be conducted in stream reaches free from barrier effects.

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“…Jellyman (1989) found that earthworms constituted more than 50% by weight of the food of the Anguilla australis and A. dieffenbachii in a lake during the flood season. Earthworms are also a common food item for Japanese eels (A. japonica) in temperate rivers (Itakura et al 2015;Wakiya and Mochioka 2020). However, since the results of these previous studies were based solely on stomach content analysis of eels obtained from samplings over one to few months, the seasonality (i.e., frequency) and the importance of earthworm inputs as an energy subsidy on eels are still unclear.…”

Section: Introductionmentioning

confidence: 99%

Large contribution of pulsed subsidies to a predatory fish inhabiting large stream channels

Itakura

Miyake

Kitagawa

et al. 2021

Can. J. Fish. Aquat. Sci.

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Resource subsidies exert critical influences on recipient habitats with relatively higher perimeter-to-area ratios, such as headwaters in watersheds. However, little is known about how those subsidies contribute to the energy sources in recipient habitats where the perimeter-to-area ratio is low, such as large stream channels. Here, we show that the diet of small Japanese eels <500 mm in total length inhabiting natural shoreline areas in large stream channels, consists largely of terrestrial earthworms. Stable isotopic analyses showed that the earthworms were the prey animal that contributed most to the eels’ diet (45–47%). Earthworms constituted the largest portion of the eels’ stomach contents (7–93%). Eels ingested earthworms within 2 days after rainfall during spring, summer, and autumn, and their consumption increased as the precipitation increased. These findings indicate that the pulsed earthworm subsidy that is driven by rainfall could temporarily bias the eels’ diet toward this allochthonous resource, which may explain the large contribution of the subsidy for consumers inhabiting large stream channels. Furthermore, diverse earthworm species could drive multiple pulsed subsidies across seasons and provide the predators with a prolonged subsidy, enhancing the long-term contribution of the subsidy to the predators’ diet.

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Contrasting diets of the Japanese eel, Anguilla japonica, in the upper and lower areas of Tsuchikawa-gawa River, Kagoshima, Japan

Cited by 14 publications

References 30 publications

Movement Patterns and Diel Activity of Anguilla japonica in the Middle Part of a Large River in South Korea

Movement Patterns and Diel Activity of Anguilla japonica in the Middle Part of a Large River in South Korea

Riverine distribution and abundance of Japanese eel in Shikoku, south‐western Japan: Varying importance of regional and local factors

Large contribution of pulsed subsidies to a predatory fish inhabiting large stream channels

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