Biochemical composition of New Zealand geoduck clam broodstock (Panopea zelandica ) conditioned under different temperature and feeding regimes

Abstract

Geoduck clams are amongst the most valuable cultured shellfish available on the world market, driving interest in the establishment of the native New Zealand species, Panopea zelandica (Quoy & Gaimard, 1835), as a candidate for aquaculture. A critical element of domestication is the effective management of breeding stock to optimize gamete and offspring quality. To develop a reliable broodstock conditioning protocol for P. zelandica, we investigated the biochemical composition of geoducks exposed to nine factorial treatment combinations of temperature (7.5, 11.5 and 16.5°C) and feeding ration [10 000, 50 000 and 100 000 cells mL−1 of a (1:1 cell count) mixture of Tisochrysis lutea and Chaetoceros muelleri]. In addition, a reference group of geoducks was conditioned in an aquaculture pond-nursery system, providing a dilute, mixed phytoplankton culture at ambient temperature. Glycogen, protein, lipid and fatty acid contents of flesh and viscera were measured at days 0, 36 and 73 of conditioning. Glycogen, protein and lipid analyses indicated that geoducks within all treatments achieved a positive energy balance, except for those in the treatment combining the highest temperature and lowest feeding ration. Comparisons of fatty acid profiles of animals among treatments and with the reference group revealed that eicosapentaenoic (EPA, C20:5n-3), docosahexaenoic (DHA, C22:6n-3) and arachidonic (ARA, C20:4n-6) fatty acids were important contributors to gametogenic development for geoduck conditioning.