Broodstock conditioning of New Zealand geoduck (Panopea zelandica) within different temperature and feeding ration regimes

Abstract

Two-year-old New Zealand geoducks (Panopea zelandica) were conditioned within combinations of three water temperatures (7-8, 11-12 and 16-17 °C) and three feeding rations (10,000, 50,000 and 100,000 cells mL-1of Chaetoceros mulleri and Isochrysis galbana) for 73 days. Similar percent matured and dry condition index values were observed among temperatures. However, significantly higher dry gonadosomatic indices (GSIdw) were recorded at 8 and 12 °C. Although no difference was detected in percentage of spawned individuals and connective tissue occupation indices, a higher percent matured were recorded when fed 10,000 and 50,000 cells mL-1. A reference group conditioned in pond water became matured 2 months later than the other nine experimental groups, but GSIdwwere similar. To maximise reproductive output, we suggest that 2-year-old P. zelandica may be conditioned in pond water for a month and then in 8 or 12 °C seawater with 50,000 cells mL-1.