Gonadal development and the reproductive cycle of the geoduck clam (Panopea japonica) in the Sea of Japan

Abstract China is currently one of the fastest-growing and largest markets for geoduck clams (Panopea japonica), which suggests substantial commercial potential. We investigated the dynamics of the P. japonica reproductive cycle from November 2016 to October 2017. Gametogenesis development and spawning of P. japonica were evaluated using the gonad index and histological analysis. Results showed that the gametogenesis of P. japonica is divided into five stages: resting, proliferating, growing, maturing, and spawning. P. japonica matured in batches with increasing temperature. Male gonads in the maturing stage were observed throughout the year, whereas female gonads developed asynchronously. The breeding season lasted from May to October, when the average seawater temperature was 7.00–17.37 °C, and there were two spawning periods in May and October. In conclusion, this work demonstrated the reproductive cycle of P. japonica, and our data may provide useful information for the artificial breeding of P. japonica.