Utilization patterns of estuarine and marine habitats by the halfbeak Zenarchopterus dunckeri at Iriomote Island, southern Japan, evaluated from otolith microchemistry

Abstract

Estuarine and marine habitat use patterns in the halfbeak Zenarchopterus dunckeri were examined at Iriomote Island, southern Japan, by analyzing otolith Li/Ca and Sr/Ca ratios. The ranges of both Li/Ca and Sr/Ca ratios in juvenile Z. dunckeri from the maximum (30 psu) to minimum (0.5 psu) salinity levels of brackish water estimated from rearing experiments, were compared with those of wild individuals collected from upstream and downstream stations in the Urauchi River estuary. The majority of wildcaught individuals had invariable Li/Ca and Sr/Ca ratios along an otolith transect from the core to the posterior edge, which fell within the otolith Li/Ca and Sr/Ca ranges estimated for estuarine individuals in the rearing experiments, suggesting that such individuals developed within the estuary without migrating to a marine environment at any time, although some downstream-dwelling fish had higher otolith elemental ratios than the predetermined estuarine ranges in the mid transect section. The latter fish may have been accidentally flushed from the estuary into the sea by heavy flood events, subsequently returning to the estuary. The overall results suggested that Z. dunckeri is essentially an estuarine resident, completing its life cycle within an estuarine system.Keywords Estuary Á Habitat use pattern Á Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) Á Lithium/calcium ratio Á Movement Á Otolith microchemistry Á Strontium/calcium ratio Á Zenarchopterus dunckeri

Random PCR‐based genotyping by sequencing technology GRAS‐Di (genotyping by random amplicon sequencing, direct) reveals genetic structure of mangrove fishes

“…Gene flow analysis suggested that the differentiations are due to limited contemporary gene flow (Figure ). This is supported by otolith microchemistry/stable isotopic analyses, which suggested that these species are estuarine residents but not active marine migrants (Kanai et al, ; Shirai et al, ). Although the two species are sympatric mangrove residents, they had different population structure; population differentiations in F. amboinensis were observed between Okinawa Island and the other sites, whereas each population was genetically differentiated in Z. dunckeri (Figure ).…”

“…However, genomic information has not been fully exploited in the conservation of mangrove fishes, as most are nonmodel organisms with ensuing difficulty of applying molecular tools. We focused on three fish species from mangrove estuaries on the Ryukyu Islands, southern Japan (Figure 1 (Kanai et al, 2014;Shirai et al, 2018). Lutjanus fulvus, however, is a marine migrant, utilizing mangrove estuaries as nurseries and then migrating to coral reefs as they age , as commonly seen in snappers (Aburto-Oropeza, Dominguez-Guerrero, Cota-Nieto, & Plomozo-Lugo, 2009;Beck et al, 2001).…”

“…We focused on three fish species from mangrove estuaries on the Ryukyu Islands, southern Japan (Figure ), namely the Amboina cardinalfish ( Fibramia amboinensis , Bleeker, 1853), the Duncker's river garfish ( Zenarchopterus dunckeri , Mohr, 1926) and the blacktail snapper ( Lutjanus fulvus , Foster, 1801), and tested genetic connection/isolation among local populations using GRAS‐Di. Previous otolith microchemistry and stable isotope analyses suggested that F. amboinensis and Z. dunckeri are estuarine residents, completing their life cycles within the estuary but occasionally being found at sea (Kanai et al, ; Shirai et al, ). Lutjanus fulvus , however, is a marine migrant, utilizing mangrove estuaries as nurseries and then migrating to coral reefs as they age (Nakamura et al, ; Shibuno, Nakamura, Horinouchi, & Sano, ), as commonly seen in snappers (Aburto‐Oropeza, Dominguez‐Guerrero, Cota‐Nieto, & Plomozo‐Lugo, ; Beck et al, ).…”

Migration and brackish environment use of Prochilodus lineatus (Characiformes: Prochilodontidae) inferred by Sr:Ca ratio transects of otolith

“…For example, Bradbury et al (2008) has reported values ~2.3 mmol/mol for Osmerus mordax (Mitchill, 1814) while Smith, Kwak (2014) reported values of ~3 mmol/mol for Gobiomorus dormitor Lacepède, 1800. However, euryhaline species were associated with significantly higher values of reference, as Mugil cephalus Linnaeus, 1758 (Sr:Ca=3.3 mmol/mol) (Fowler et al, 2016), Genidens barbus (Lacepède, 1803) (Sr:Ca=3.75 mmol/mol) (Avigliano et al, 2017b) and Zenarchopterus dunckeri Mohr, 1926 (Sr:Ca=4.2 mmol/ mol for freshwater-brackish) (Kanai et al, 2014).…”

Silversides ( Odontesthes bonariensis ) reside within freshwater and estuarine habitats, not marine environments

“…There are few studies that related salinity with the levels of Sr:Ca of otolith (Avigliano, and Volpedo, 2013a;Kanai et al, 2014;Secor et al, 1995;Shrimpton et al, 2014). For example, Kanai et al (2014) experimentally estimated the relationship between Sr:Ca of otolith and salinity for Zenarchopterus dunckeri and have subsequently used this function to study displacements of wild individuals. Secor et al (1995) performed similar approximations on the striped bass, Morone suxntilis, through laboratory tests and later making inferences about wild specimens.…”