Importance of the upper estuary as a nursery ground for fishes in Ariake Bay, Japan

Abstract

To examine the importance of the upper estuarine areas of Ariake Bay as a nursery ground for fish, assemblages of larvae and juveniles were compared among various aquatic habitats. The upper estuaries of the bay (the Rokkaku and Hayatsue estuaries) are brackish, highly turbid waters with high tidal velocities, and differ substantially from the Isahaya area, which has been separated from the bay by a man-made dike, to the middle estuary (the Kikuchi estuary). Abundances of larvae and juveniles were higher in the estuaries than in the open bay and Isahaya areas. Abundant species in the upper estuaries were similar to each other, but differed from those of the middle estuary. This was primarily due to larvae and juveniles of fishes that occurred almost entirely in the upper estuaries, such as Acanthogobius hasta, Boleophthalmus pectinirostris, Coilia nasus, Cynoglossus abbreviatus, Nibea albiflora, Odontamblyopus lacepedii, Trachidermus fasciatus and Tridentiger barbatus. These results suggest that the upper estuaries play an important role as nursery grounds for fishes.

New records of the Japanese seahorse Hippocampus mohnikei in Southeast Asia lead to updates in range, habitat and threats

“…New records support what is known about the habitat preferences of H. mohnikei , that it lives in shallow waters, predominantly in seagrass (Lourie et al ., ) with other syngnathid species (Yagi et al ., ; Choi et al ., ; Lipton & Thangaraj, ; Zhang et al ., ), while expanding its habitat range to include mangroves, oyster beds and mussel farms. Such preferences should raise concern, as H. mohnikei lives in the same habitats as other seahorse species ( H. kuda, H. spinosissimus and H. trimaculatus ) considered Vulnerable by the IUCN Red List (IUCN, ).…”

“…Additionally mangrove, oyster and mussel farms were reported as habitat for this seahorse species. The new records support previous reports (Yagi et al ., ; Laksanawimol et al ., ; Lipton & Thangaraj, ; Zhang et al, ) that H. mohnikei co‐occur with congener species including Hippocampus kuda Bleeker 1852 and Hippocampus trimaculatus Leach 1814 and the pipefish genus Trachyrhamphus . The new sightings are the first reports of H. mohnikei inhabiting the same areas as Hippocampus spinosissimus Weber 1913 and two additional genera of pipefishes Acentronura and Halicampus .…”

Year-round accumulation of particulate organic matter in the estuarine turbidity maximum: comparative observations in three macrotidal estuaries (Chikugo, Midori, and Kuma Rivers), southwestern Japan

“…Given the well-developed ETM incidental to large tidal ranges and long tidal intrusions, estuaries similar to the Chikugo River estuary could occur only in the innermost part of the Ariake Sea within Japan (e.g., Rokkaku River estuary, Yagi et al 2011).…”

Microdistribution and feeding dynamics of Coilia nasus (Engraulidae) larvae and juveniles in relation to the estuarine turbidity maximum of the macrotidal Chikugo River estuary, Ariake Sea, Japan

“…Coilia nasus is one of seven continental relict fishes occurring only in the Ariake Sea within Japan (Sato and Takita, 2000). Macrotidal estuaries characteristic of the innermost part of the Ariake Sea are thought to be primarily responsible for the survival of the relict fish populations after the isolation of the Japanese Archipelago from the Eurasian Continent caused by marine transgressions (Sato and Takita, 2000;Hibino et al, 2002;Yagi et al, 2011). Reproduction of the relict C. nasus population depends greatly on the Chikugo River estuary (Takita, 1967b;Matsui et al, 1986b), although sporadic reproduction has been observed in other estuaries of the Ariake Sea (Igita, 1986;Yagi et al, 2011).…”

“…Macrotidal estuaries characteristic of the innermost part of the Ariake Sea are thought to be primarily responsible for the survival of the relict fish populations after the isolation of the Japanese Archipelago from the Eurasian Continent caused by marine transgressions (Sato and Takita, 2000;Hibino et al, 2002;Yagi et al, 2011). Reproduction of the relict C. nasus population depends greatly on the Chikugo River estuary (Takita, 1967b;Matsui et al, 1986b), although sporadic reproduction has been observed in other estuaries of the Ariake Sea (Igita, 1986;Yagi et al, 2011). Given high fishing pressure on migrating adults during the spawning season (Takita, 1967b;Yoshimoto and Kitajima, 1993), effective fishing regulations are necessary to preserve the relict C. nasus population.…”