Spatial Distribution Patterns of Japanese Eels <i>Anguilla japonica</i> in a Large Subtropical River (Pearl River), China

Shuai, Fangmin; Liu, Qianfu; Liu, Yaqiu; Wu, Zijun; Lek, Sovan; Chen, Yushun

doi:10.1002/nafm.10420

Cited by 4 publications

(3 citation statements)

References 46 publications

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“…The decline of eel stocks is a global phenomenon affecting not only Japanese eels but also European and American eels [51][52][53][54]. Many causes have been put forward to explain the declining trend in eel populations, mostly anthropogenic, including habitat destruction, construction of dams, fishing, and human-introduced parasites and viruses [55][56][57][58]. One of the plausible causes of the decline of Japanese eels might be the construction of dams along the Pearl River.…”

Section: Stable But Low Recruitment Of Japanese Eel In the Pearl Rive...mentioning

confidence: 99%

Temporal Pattern of the Occurrence of Japanese Glass Eels (Anguilla japonica) in the Pearl River Estuary

Shuai

et al. 2023

Fishes

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Japanese eels (Anguilla japonica) are a typical migratory fish species with high commercial importance. The Pearl River estuary in southern China is an important natural growing ground for Japanese glass eels, but limited information on Japanese glass eel population characteristics is available, despite their ecological importance. In this paper, we examined the annual patterns of the occurrence of Japanese glass eels in the Pearl River estuary from 2011 to 2022. The most frequently occurring Japanese glass eel’s total length is 5.3 cm. The collecting period extended from December to February, and the collection catch-per-unit-effort (CPUE) decreased significantly from 2011 to 2022. The generalized linear model (GLM) indicated that daily changes in Japanese glass eel collection were significantly affected by tidal range, water temperature, and lunar distance. The catch peak appeared when the tidal range rose to 1.7 m, and the water temperature dropped below 8 °C on the full moon days. Overall CPUE analysis showed no significant periodic and inter-annual variability in the period 2011–2022, with the ARIMA model suggesting that the CPUE is expected to remain stable but low in the coming years (2023–2026), although recruitment ultimately depends on the overall spawning stock.

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Section: Stable But Low Recruitment Of Japanese Eel In the Pearl Rive...mentioning

confidence: 99%

Temporal Pattern of the Occurrence of Japanese Glass Eels (Anguilla japonica) in the Pearl River Estuary

Shuai

et al. 2023

Fishes

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“…Most sampled individuals were quite small, with about half of those collected (45.75%) being juveniles, with total length ≤255 mm, indicating that this population is now extremely scarce in south China. In history, lots of eel seedlings move into the Pearl River system to grow (Shuai et al ., 2020). However, the current population of this species is very worrying.…”

Section: Discussionmentioning

confidence: 99%

Unravelling the life‐history patterns and habitat preferences of the Japanese eel (Anguilla japonica) in the Pearl River, China

Shuai

et al. 2023

Journal of Fish Biology

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Eels have fascinated biologists for centuries due to their amazing long‐distance migrations between freshwater habitats and very distant ocean spawning areas. The migratory life histories of the Japanese eel, Anguilla japonica, in the waters of south China are not very clear despite its ecological importance, and the need for fishery regulation and management. In this study, strontium (Sr) and calcium (Ca) microchemical profiles of the otoliths of silver eels were measured by X‐ray electron probe microanalysis based on data collected from different habitats (including freshwater and brackish habitats), in the large subtropical Pearl River. The corresponding habitat preference characteristics were further analysed using redundancy analysis (RDA). A total of 195 Japanese eels were collected over 6 years. The collected individuals ranged from 180 to 771 mm in total length and from 8 to 612 g in body weight. Two‐dimensional pictures of the Sr:Ca concentrations in otoliths revealed that the A. japonica in the Pearl River are almost entirely river eels, spending the majority of their lives in fresh water without exposure to salt water, while the catadromous migration time has delayed about 1 month in the Pearl River estuary in the past 20 years. RDA analysis further indicated that juveniles and adults preferred water with high salinity and high tide levels. Youth preferred habitats with high river fractals. Our findings contribute to a growing body of evidence showing that the eels are extremely scarce currently and conservation measures against them are imminent, including the protection of brackish and freshwater areas where they live in south China.

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“…However, these gradual shifts have not been sufficiently considered when evaluating their habitat use. Many previous studies have examined differences in habitat use only between two or more size classes (Itakura & Wakiya, 2020; Matsushige, Yasutake & Mochioka, 2020) or between two or more life stages (Degerman et al, 2019; Kume et al, 2020; Shuai et al, 2021b; Harwood et al, 2022). These classifications make it difficult to capture gradual changes in habitat use and may lead to inaccurate evaluation of habitat use.…”

Section: Discussionmentioning

confidence: 99%

Ontogenetic habitat shift of Anguilla marmorata and A. japonica in the rivers of southern Japan: Implications for habitat use evaluation and conservation

Kumai,

Kuroki,

Goto

et al. 2023

Aquatic Conservation

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Understanding the habitat requirements of fishes throughout their life cycle is essential for effective conservation. Despite the growing need to conserve anguillid eels, the current understanding of the ontogenetic habitat shifts during their riverine stages remains limited, particularly for the Japanese eel Anguilla japonica and the Indo‐Pacific eel Anguilla marmorata. Here, changes in habitat use during the riverine stages of these two eel species were investigated in the southern Japan rivers, where they coexist. Eels were classified into total length (TL) classes at 10 cm intervals, and generalized additive models were constructed using these classes as an ordinal, quasi‐continuous explanatory variable. The models showed that the habitat use of the two species changed with growth; both species shifted to deeper and more lentic habitats as they grew larger. Small‐ and mid‐sized (<25 and 25–55 cm in TL, respectively) A. japonica used more lentic habitats with smaller substrates, ranging from sand/silt to cobbles, than small‐ and mid‐sized A. marmorata, which mainly used lotic habitats with cobble and boulder substrates. However, compared with small‐sized conspecifics, mid‐sized A. japonica mainly used habitats with larger substrates, such as pebbles and cobbles, suggesting that the interspecific overlap in habitat use is relatively high for mid‐sized individuals of both species. Large A. marmorata (85 cm) mainly used habitats with smaller substrates as they grew larger. The results suggest that using a fine body size classification and including these classes as a quasi‐continuous explanatory variable in habitat models capture gradual changes in habitat use, improving habitat use evaluation of anguillid eels. Preserving the environmental heterogeneity of river habitats in terms of water depth, current velocity and substrate size would facilitate habitat segregation of both conspecifics and allospecifics in the same rivers, thereby promoting the conservation of anguillid eels.

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Spatial Distribution Patterns of Japanese Eels Anguilla japonica in a Large Subtropical River (Pearl River), China

Cited by 4 publications

References 46 publications

Temporal Pattern of the Occurrence of Japanese Glass Eels (Anguilla japonica) in the Pearl River Estuary

Temporal Pattern of the Occurrence of Japanese Glass Eels (Anguilla japonica) in the Pearl River Estuary

Unravelling the life‐history patterns and habitat preferences of the Japanese eel (Anguilla japonica) in the Pearl River, China

Ontogenetic habitat shift of Anguilla marmorata and A. japonica in the rivers of southern Japan: Implications for habitat use evaluation and conservation

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