Habitat use patterns of fishes across the mangrove-seagrass-coral reef seascape at Ishigaki Island, southern Japan

Abstract

To clarify seascape-scale habitat use patterns of fishes in the Ryukyu Islands (southern Japan), visual censuses were conducted in the mangrove estuary, sand area, seagrass bed, coral rubble area, branching coral area on the reef flat, and tabular coral area on the outer reef slope at Ishigaki . During the study period a total of 319 species were observed. Species richness and abundance were highest in the branching and tabular coral areas, followed in order by the seagrass bed and mangrove estuary, and coral rubble and sand areas, in each month. Cluster analysis resulted in a clear grouping of assemblage structures by habitat type rather than by census month. SIMPER analysis showed that fish assemblages in the tabular coral area were mainly characterized by Acanthurus nigrofuscus, Pomacentrus lepidogenys, P. philippinus and P. vaiuli, the branching coral area by Chromis viridis and Pomacentrus moluccensis, the coral rubble area by Amblyeleotris steinitzi and Ctenogobiops pomastictus, the seagrass bed by Cheilio inermis, Lethrinus atkinsoni and Stethojulis strigiventer, the sand area by Valenciennea longipinnis, and the mangrove estuary by Gerres oyena, Lutjanus fulvus and Yongeichthys criniger. Moreover, fishes exhibited two habitat use strategies, inhabiting either a single or several specific habitats throughout their benthic life history stages, or having a possible ontogenetic habitat shift from the mangrove estuary or seagrass bed to coraldominated habitats (e.g., Lethrinus atkinsoni, Lethrinus obsoletus, Lutjanus fulviflamma, Lutjanus fulvus, Lutjanus gibbus, Lutjanus monostigma and Parupeneus barberinus), suggesting that the mangrove estuary and seagrass bed have a nursery function.

Evidence of ontogenetic migration from mangroves to coral reefs by black-tail snapper Lutjanus fulvus: stable isotope approach

“…(4) Do L. fulvus use mangroves as a nursery? The stomach contents and isotopic signatures of several sizes of 2 other species of snappers, humpback red snapper L. gibbus and mangrove red snapper L. argentimaculatus, were also investigated (as habitat control fishes), the former residing on coral reefs during the juvenile and adult life stages (control species for coral reef habitat), and the latter inhabiting mangroves until the body length reaches around 300 mm TL (control species for mangrove habitat; Shibuno et al 2008).…”

“…At Ishigaki Island, southern Japan, Shibuno et al (2008) found that juvenile L. fulvus (30 to 120 mm in total length, TL) predominantly occurred in mangrove estuaries but sometimes occurred over reef flats, while subadults and adults (>120 mm TL) inhabited coral reefs, based on a quantitative visual census across multiple habitats (mangrove estuary, sand area, seagrass bed, coral rubble area, branching coral area on the reef flat, and tabular coral area on the reef slope). During the daytime, L. fulvus swim actively within each habitat, while at night they are found around mangrove prop roots, rocks on river bottoms, or under corals.…”

Role of Demersal Zooplankton as a Food Source for Higher Trophic Levels at Fukido Estuary, Ishigaki Island, Okinawa, Japan

“…Rhizophora stylosa, Bruguiera gymnorrhiza, Kandelia candel, and Lumnitzera racemose dominate the mangrove forest. In the center of the river mouth, the water depth ranges from 0.5 to 1 m at low tide and 1 to 2 m at high tide, where mangrove prop roots are alternately inundated and exposed, during the tidal cycle Shibuno et al, 2008). The seagrass bed (water depth range of 0.5-1 m at low tide and 2-3 m at high tide) extends for about 2.5 km along the coast at a distance of 30 to 120 m offshore, and is dominated by Thalassia hemprichii .…”

“…Juvenile stage Lutjanus sp. are relatively small (around 30-125 cm) Shibuno et al, 2008), and they inhabit MG as a nursery. Juvenile Lutjanus sp.…”

Habitat selection by emperor fish larvae

“…Lethrinus spp. predominantly inhabit back-reef seagrass beds at the juvenile life stage (Wilson 1998, Nakamura & Tsuchiya 2008, Shibuno et al 2008, thereby utilizing the beds as a potential nursery habitat that produces relatively more adult recruits per unit area than other juvenile habitats (Beck et al 2001). Afterwards, juveniles move to coral reef habitats at maturity, and adults often form large aggregations for pelagic spawning at outer reefs.…”