Comparative reproductive biology of Yezo scallop, Patinopecten yessoensis, under two different culture systems on the east coast of Korea

The annual gametogenesis of Yezo scallop, Patinopecten yessoensis, raised in suspended-hanging (SHCS) and bottom-sowing culture systems (BSCS) on the east coast of Korea was investigated over 2 years. Gametogenesis was initiated in October, when the surface water temperature reached 18 °C. The gametes matured fully and were ready for spawning in March and early April. Spawning occurred from late March to late May, when the water temperature rose from 7 °C to 11 °C. The gonado-somatic index (GSI), a ratio of gonad weight to total tissue weight, ranged from 3.05 (September) to 23.11 (April) for SHCS scallops and from 3.02 (August) to 20.30 (April) for BSCS scallops. The GSI of SHCS scallops was significantly higher (P < 0.05) than that of BSCS scallops during the first reproductive season, but not the next spawning season. SHCS scallops also maintained a significantly higher condition factor (CF) than that of BSCS scallops (P > 0.05) throughout most of the period, indicating that the SHCS may provide better growth and reproductive conditions. The higher GSI of SHCS scallops in the first spawning season may have resulted from different levels of food availability and the stocking size of the spats.