The importance of broodstock nutrition on the viability of larvae and spat in the Chilean oyster Ostrea chilensis

Broodstock of the Chilean oyster Ostrea chilensis were conditioned at 17 °C and fed with monospecific cultures of Chaetoceros gracilis, Isochrysis aff. galbana or Pseudoisochrysis sp. offered daily at a ration equivalent to 1.5% of dry tissue weight of the oysters. A group of starved oysters maintained in the hatchery and a second group held under natural conditions in the estuary of the Quempillén River were used as controls. Spawning began earlier in the broodstock fed Pseudoisochrysis (mean time 23 days after the initiation of conditioning) than in the other groups held in the hatchery (32–35 days). In the estuary, however, spawning occurred much later (91 days from the beginning of the experiment). The mean diameter of the eggs released ranged from 210 μm ( Pseudoisochrysis condition) to 268 μm (estuary condition). There was a positive correlation between egg diameter and the lipid, protein and carbohydrate contents, which were highest in eggs produced by females maintained in the estuary and lowest in eggs from females fed Pseudoisochrysis. Females held in the estuary released the largest pediveliger larvae (mean diameter 461 μm) at the end of the brooding period, whereas starved females released the smallest pediveligers (mean diameter 317 μm). The highest growth rates were recorded in the spat produced by females which ripened in the estuary, followed by spat from females fed I. aff. galbana. Instantaneous mortality rates were lowest in these two groups. Spat produced by starved females showed low rates of growth and survival.