Occurrence of juvenile puffers Takifugu rubripes in estuaries of the Yoshii and Takahashi rivers, Seto Inland Sea

Abstract

To clarify the early life history of the tiger puffer Takifugu rubripes in the Seto Inland Sea, trawls using a small-mesh seine net were conducted in the littoral zone of the estuaries of the Yoshii and Takahashi rivers, from June to August in 2010-2012. A total of 206 juvenile Takifugu (9.8-67.9 mm total length: TL) were collected and subsequently identified as T. xanthopterus (60.2%), T. rubripes (36.4%), T. alboplumbeus (1.9%), and T. poecilonotus (1.5%) by mitochondrial DNA analysis. The juvenile T. rubripes with 10 mm TL occurred in mid-June and grew to 60 mm TL in early August. Most of the T. rubripes individuals (90%) were collected in habitats with low salinity (sample range 5.1-22.9), high turbidity (range 33.3-73.4 formazin turbidity unit), and muddy bottoms (range 20.5-47.4% mud content), suggesting that the muddy tidal flats of estuaries are a suitable nursery ground during the early life stage of T. rubripes. In contrast, several large-sized individuals over 35 mm TL were collected in areas with high salinity and sandy bottoms. The findings suggest that T. rubripes juveniles may begin to move away from the nursery ground in the river mouth at sizes of > 35 mm TL, as they expand the area they inhabit in the region.