SURVIVAL AND GROWTH OF LARVAE OF THE EUROPEAN OYSTER, O. EDULIS, AT LOWERED SALINITIES

Abstract

The effects of lowered salinities on several phases of reproduction of European oyster, O. edulis. Larvae released at normal salinity (26-27 ppt) were capable of growing to metamorphosis in salinities as low as 20 ppt, although individuals kept at this salinity grew more slowly and metamorphosed later than those kept at 22.5, 25 and 26-27 ppt. Some larvae kept at 17.5 ppt lived for more than 16 days, but growth was slow and all died before reaching metamorphosis. At 15 ppt all died within 16 days. Larvae kept at 12.5 and 10 ppt showed little growth and soon died. Some larvae that were reared almost to metamorphosis at 26-27 ppt, and then transferred to lower salinities, metamorphosed in salinities as low as 15 ppt. None of those transferred to 12.5, 10 and 7.5 ppt were able to complete metamorphosis. At 12.5 ppt some larvae lived for 6 or more days, but at the 2 lowest salinities all larvae died within 4 days after the transfer. Attempts to induce normal gonad development, spawning and incubation of O. edulis in 20 and 17.5 ppt were unsuccessful; no normal living larvae were obtained at either salinity.