Settlement and ovigerous season of sand shrimp Crangon uritai in the central Inland Sea, Japan

Abstract

Sand shrimp Crangon uritai is distributed in shallow waters including the intertidal zone in eastern Asia and is known to be a prey item and a predator of juveniles of commercially important fishes. Specimens were collected on the Kawaradzu tidal flat, using a rake sledge net (mesh size 2.0 mm) from June to December 2016 and 2017, and in the adjacent shallow bottom (3–4 m depth at high tide) using a sledge net (mesh size 0.76 mm) from January to August 2018 and 2019. Seasonal changes in the density index and carapace length distribution were studied in both sites. The frequency of ovigerous females were indicated for the tidal flat. Settlement mainly occurred from May to July although low intensity settlement seemed to occur throughout the year except for September and October. Ovigerous season in the tidal flat finished in August or September by disappearance of the cohort including ovigerous females and resumed in October with the oviposition of 0-year individuals. Ovigerous females might occur throughout the year except for August or September, although their occurrence was not checked in the shallow bottom. Research on the offshore area is needed to detail the whole life history.