Interspecific and sexual differences in riverine distribution of tropical eels <i>Anguilla</i> spp.

Hagihara, Seishi; Aoyama, Jun; Limbong, Daniel; Tsukamoto, Katsumi

doi:10.1111/jfb.13666

“…In our study river, only 7 Japanese eels were caught during the 4 sampling periods, so they are clearly not abundant compared to A. marmorata , or most do not survive very long. The dispersal process of A. marmorata shown in this study may change depending on whether sympatries of multiple eel species occur within same watersheds ( Marquet & Galzin, 1991 ; Shiao et al, 2003 ; Arai & Abdul Kadir, 2017 ; Hagihara et al, 2018a ; Hsu, Chen & Han, 2019 ). Therefore, future research conducted in regions with sympatries of multiple eel species will help to further understand how these sympatric eel species disperse to each habitat in river systems.…”

Section: Discussionmentioning

confidence: 86%

“…Several studies have found that although A. marmorata tends to live in freshwater areas rather than in brackish and marine habitats ( Shiao et al, 2003 ; Nguyen, Tsukamoto & Lokman, 2018 ; Hsu, Chen & Han, 2019 ), the species can occupy a broad range of habitats from brackish estuaries to upland headwaters ( Arai & Chino, 2018 ; Hagihara et al, 2018a ; Wakiya, Itakura & Kaifu, 2019 ; Kumai, Tsukamoto & Kuroki, 2020 ). There are often sympatries of multiple eel species in tropical rivers that appear to affect the patterns of habitat use among the species presumably to reduce interspecific competition ( Marquet & Galzin, 1991 ; Arai & Abdul Kadir, 2017 ; Hagihara et al, 2018a ), and sympatries of temperate and tropical eels also occur in subtropical regions of their distribution ranges ( Shiao et al, 2003 ; Hsu, Chen & Han, 2019 ; Itakura et al, 2020b ). In rivers where a single eel species such as A. marmorata is highly dominant among anguillid species, it is found throughout the river network ( Robinet et al, 2007 ; Itakura et al, 2019 ; Wakiya, Itakura & Kaifu, 2019 ).…”

Section: Introductionmentioning

confidence: 99%

Habitat preference, movements and growth of giant mottled eels, Anguilla marmorata, in a small subtropical Amami-Oshima Island river

Itakura

¹

,

Wakiya

²

2020

PeerJ

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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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“…In temperate regions, there are no plural anguillid eel species distributed in the continental habitats of each region except in New Zealand where Anguilla dieffenbachii and A. australis schmidtii are distributed sympatrically ( Glova, 1988 ; Glova et al., 1998 ). However, several species are distributed sympatrically in tropical areas and the habitat preferences also rely on the occurrence of multiple species within a habitat or a single species ( Robinet et al., 2007 ; Arai and Chino, 2012 , 2018 ; Arai et al., 2013 ; Arai and Abdul Kadir, 2017b ; Hagihara et al., 2018 ; Nguyen et al., 2018 ; Hsu et al., 2019 ; Arai et al., 2020 ). In rivers in the Réunion and Mauritius islands of the western Indian Ocean, A. marmorata showed a strong altitudinal distribution from the lower to upper areas, while A. mossambica was only found in the upper areas and A. bicolor bicolor occurred only in the lower areas ( Robinet et al., 2007 ).…”

Section: Plasticity Of Continental Migrationmentioning

confidence: 99%

“…Interspecific differences in the riverine distribution among sympatric species have also been found in various tropical areas, and it was suggested that environmental factors and interactive habitat segregation would affect the riverine distribution of sympatric anguillids ( Cumaranatunga et al., 1997 ; Robinet et al., 2007 ; Arai and Abdul Kadir, 2017b ; Hagihara et al., 2018 ; Arai et al., 2020 ). In Taiwan, A. japonica mainly inhabited the lower and middle reaches of rivers, while A. marmorata was distributed over the middle to upper reaches ( Shiao et al., 2003 ; Hsu et al., 2019 ).…”

Section: Plasticity Of Continental Migrationmentioning

confidence: 99%

Ecology and evolution of migration in the freshwater eels of the genus Anguilla Schrank, 1798

Arai

¹

2020

Heliyon

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Scientists have long sought to uncover the secrets of the migration of anguillid eels, genus Anguilla . As catadromous fishes, anguillid eels spend most of their lives in freshwater until they return to their spawning grounds in the tropics, although part of the population never enters freshwater and instead resides in brackish and marine areas close to coastlines. Molecular phylogenetic research suggests that anguillid eels originated from deep-ocean midwater marine anguilliform species and that tropical eels originating from the Indo-Pacific region are the most basal species of anguillid eels. Anguillid eels left the tropical ocean to colonize temperate areas. The yearly spawning of tropical species and constant larval growth throughout the year extend to periods of recruitment in continental habitats to last all year for tropical eels. Tropical eels such as A. celebesensis and A. borneensis have relatively short migrations periods of less than 100 km to their spawning grounds. Conversely, the temperate European eel A. anguilla travels the longest distances and migrates more than 5000 km across the Atlantic Ocean to spawn in the Sargasso Sea. The ancestral state of migration in the genus Anguilla may have been local, short-scale and nonseasonal spawning migration throughout the year as defined in tropical eels. With the expansion of dispersion of global oceanic migration across the world, migration scales can gradually change. Temperate anguillid eels migrate thousands of kilometres from spawning areas to coastal and inland water habitats while retaining spawning areas in tropical areas, accompanied by seasonal downstream and spawning migrations with consequences for seasonal recruitment. Recent advances and the availability of electronic tags such as pop-up satellite archival tag could reconstruct the entire spawning migration from continental growth habitats to spawning sites with detailed migration behaviours and routes. Migration ecology and mechanisms throughout the life of anguillid eels have gradually been revealed in recent decades.

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“…Several studies have found that although A. marmorata tends to live in freshwater areas rather than in brackish and marine habitats (Shiao et al, 2003;Nguyen, Tsukamoto & Lokman, 2018;Hsu, Chen & Han, 2019), the species can occupy a broad range of habitats from brackish estuaries to upland headwaters (Arai & Chino, 2018;Hagihara et al, 2018a;Kumai, Tsukamoto & Kuroki, 2020). There are often sympatries of multiple eel species in tropical rivers that appear to affect the patterns of habitat use among the species presumably to reduce interspecific competition (Marquet & Galzin, 1991;Arai & Abdul Kadir, 2017;Hagihara et al, 2018a), and sympatries of temperate and tropical eels also occur in subtropical regions of their distribution ranges (Shiao et al, 2003;Hsu, Chen & Han, 2019;Itakura et al, 2020b). In rivers where a single eel species such as A. marmorata is highly dominant among anguillid species, it is found throughout the river network (Robinet et al, 2007;Itakura et al, 2019;.…”

Section: Introductionmentioning

confidence: 99%

Peer Review #1 of "Habitat preference, movements and growth of giant mottled eels, Anguilla marmorata, in a small subtropical Amami-Oshima Island river (v0.1)"

2020

0

View full text Add to dashboard Cite

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 4 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,

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Interspecific and sexual differences in riverine distribution of tropical eels Anguilla spp.

Cited by 13 publications

References 54 publications

Habitat preference, movements and growth of giant mottled eels, Anguilla marmorata, in a small subtropical Amami-Oshima Island river

Habitat preference, movements and growth of giant mottled eels, Anguilla marmorata, in a small subtropical Amami-Oshima Island river

Ecology and evolution of migration in the freshwater eels of the genus Anguilla Schrank, 1798

Peer Review #1 of "Habitat preference, movements and growth of giant mottled eels, Anguilla marmorata, in a small subtropical Amami-Oshima Island river (v0.1)"

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