Population dynamics of mantis shrimp Oratosquilla oratoria in Ise Bay, central Japan

The present study deals with seasonal and interannual variations in abundance, biomass and spatio-temporal distributions of the mantis shrimp Oratosquilla oratoria in Ise Bay, central Japan. The abundance and biomass of the mantis shrimp decreased in summer when oxygen-poor water developed in the central to inner parts of the bay, and then increased due to new recruits from autumn to spring of the following year when the oxygen-poor water disappeared. Planktonic larvae appeared from June to November, whereas two cohorts were detected for new recruits: one in summer ("summer" cohort) and the other in autumn ("autumn" cohort), respectively. Usually the "summer" cohort grew to 50 mm BL by autumn and became a target for fisheries. This "summer" cohort largely contributed to establishing and maintaining benthic populations of the mantis shrimp in the bay.