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

Two-year-old New Zealand geoducks (Panopea zelandica) were conditioned within combinations of three water temperatures (7-8, 11-12 and 16-17 degrees C) and three feeding rations (10,000, 50,000 and 100,000 cells mL(-1) of 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 (GSI(dw)) were recorded at 8 and 12 degrees 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 GSIdw were 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 degrees C seawater with 50,000 cells mL(-1).