The reproductive cycle of the scallop Argopecten circularis (Sowerby, 1835) in relation to temperature and photoperiod, in Bahia Concepcion, B.C.S., Mexico

Abstract

The reproductive cycle of the scallop Argopecten circularis, an important resource of the fisheries in Baja California Sur, was studied in relation to exogenous factors such as temperature and photoperiod in Bahía Concepción. Monthly samples of adult specimens were used, and biometric data for the shell and soft body parts were recorded. The gonads were analysed histologically and five phases of gonadal maturation were described. This species was confirmed to be functionally hermaphroditic, with a reproductive pattern characterized by a period of maximum activity from December to March, when the dominant phases are maturity and spawning. The prevailing conditions during the main spawning peak were: water temperature between 16 and 22ºC, and photoperiod between 630 and 760 minutes of daily average illumination per month. The first maturation of the gonads, determined histologically, occurred when the organisms had an anteroposterior length of 35 mm. Spawning can occur at 47 mm. The minimum size for maturity and spawning in the general population was 58 mm. We determined that maximum reproductive potential starts at this size, and coincides with the lowest water temperature in the annual cycle. The annual variations in the spawning periods of this species, in different parts of Baja California Sur, suggest flexibility in the influence of exogenous factors and endogenous controls on the reproductive event.