Early life history of tropical freshwater eels (Anguilla spp.) recruiting to Viti Levu, Fiji Islands, in the western South Pacific

Abstract

Abstract. The oceanic early life histories of three species of tropical anguillid glass eels, namely Anguilla marmorata, Anguilla megastoma and Anguilla obscura, recruiting to Viti Levu, Fiji Islands, in the western South Pacific, were studied using otolith microstructures of 94 individuals. A. megastoma had the shortest leptocephalus duration, age at recruitment and metamorphosis stage (mean±s.d. 104.7±7.2, 141.3±8.7 and 36.6±8.5 days respectively), followed by A. marmorata (September–October recruitment peak: 113.0±11.9, 115.1±8.3 and 39.2±11.1 days respectively; April recruitment peak: 152.2±13.5, 154.0±12.5 and 38.9±10.1 days respectively) and A. obscura (118.0±10.2, 168.4±16.5 and 49.6±12.5 days respectively). A. obscura also had the shortest oceanic glass eel duration of (12.2±3.4 days), followed by both peaks of A. marmorata (23.3±3.2 and 20.2±3.3 days) and A. megastoma (20.7±6.7 days). Otolith increment rates during the leptocephalus stage did not differ significantly among the three species, but there were significant differences between the leptocephalus duration and metamorphosis stage of A. megastoma compared with A. marmorata and A. obscura, as well as in the oceanic glass eel duration of A. obscura compared with A. marmorata and A. megastoma. There were also significant differences in the age at recruitment among all three species. Back-calculated hatch dates suggest separate peak seasonal spawning periods for each of the three species.

Distribution of anguillid leptocephali and possible spawning areas in the South Pacific Ocean

“…The back calculated hatching data also provided useful information about when these eels may spawn. Combining the results of both present and previous studies estimated from leptocephali (Kuroki et al, 2008) and glass eels (Shiao et al, 2001(Shiao et al, , 2002Helme et al, 2018;Hewavitharane et al, 2018Hewavitharane et al, , 2019, the spawning of each species appears to occur over a wide range of months. Hatching date estimates of A. marmorata from the various studies occurred in almost all months of the year, and almost to the same extent for A. australis and A. reinhardtii (Fig.…”

“…The recruitment patterns of glass eels to tropical islands such as French Polynesia and Fiji have begun to be studied (Helme et al, 2018;Hewavitharane et al, 2019). Other efforts to find the spawning areas of tropical eel species in the South Pacific have been conducted using popup satellite archival tags (PSATs) on adult silver eels (e.g., Tsukamoto, 2002, 2010;Schabetsberger et al, 2013Schabetsberger et al, , 2019.…”

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

“…A variety of recent advancements made by means of molecular genetic and ecological studies have better elucidated the ecology and evolution of anguillid eels. Scales of spawning migration distinctly differ among tropical eel species ( Aoyama et al., 2003 , 2018 ; Robinet et al., 2008 ; Réveillac et al., 2008 , 2009 ; Schabetsberger et al., 2013 , 2015 ; 2019 ; Arai, 2014a ; Arai and Abdul Kadir, 2017a ; Han et al., 2019 ; Hewavitharane et al., 2020 ). Less than 100 km of small-scale migration and 1000–3000 km of mid-scale migration are suggested in A. clelebesensis and A. borneensis ( Aoyama et al., 2003 , 2018 ; Arai, 2014a ) and A. marmorata , A. bicolor bicolor , A. mossambica and A. bengalensis bengalensis ( Robinet et al., 2008 ; Réveillac et al., 2008 , 2009 ; Arai, 2014a ; Arai and Abdul Kadir, 2017a ; Aoyama et al., 2018 ; Han et al., 2019 ), respectively.…”

“…The multiple spawning sites in A. celebesensis and A. interioris were definitely in contrast to temperate species. It is assumed that western South Pacific eels such as A. marmorata , A. megastoma , A. obscura and A. reinhardtii spawn somewhere within the South Equatorial Current ( Jellyman, 2003 ; Schabetsberger et al., 2013 , 2015 ; 2019 ; Hewavitharane et al., 2020 ), and it has been suggested these western South Pacific eels may migrate a short distance between their continental habitats and spawning sites by means of recently developed pop-up satellite archival tag (PSAT) studies ( Schabetsberger et al., 2013 , 2015 , 2019 ). These findings suggest that certain tropical anguillids exhibit considerably short-scale migrations between spawning areas and continental habitats compared to temperate species that make large-scale migrations.…”

“…The lengthy duration of the larval stage might lead to global dispersion and their consequent speciation. The durations of leptocephalus stages span from several months to approximately two years (e.g., Tsukamoto, 1990 ; Lecomte-Finiger, 1992 ; Cheng and Tzeng, 1996 ; Arai et al., 1999a , 2001 ; 2003a ; Wang and Tzeng, 2000 ; Marui et al., 2001 ; Robinet et al., 2003a ; Robinet et al., 2008 ; Réveillac et al., 2008 , 2009 ; Bonhommeau et al., 2010 ; Han et al., 2016a , 2019 ; Hewavitharane et al., 2020 ). Many marine organisms have a planktonic larval stage during their early life and larvae are passively transported by oceanic currents.…”