New Zealand Journal of Marine and Freshwater Research abstracts

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Short communication Seasonal variation in the reproductive activity and biochemical composition of the Pacific oyster (Crassostrea gigas) from the Marlborough Sounds, New Zealand

Jeffrey S. Ren¹
Islay D. Marsden,*²
Alex H. Ross¹
David R. Schiel²

¹Centre of Excellence in Marine Ecology
and Aquaculture
National Institute of Water and Atmospheric
 Research Limited
P.O. Box 8602
Christchurch, New Zealand

²Department of Zoology
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
email: i.marsden@zool.canterbury.ac.nz
*Author for correspondence.

Abstract   Reproductive cycles of the Pacific oyster Crassostrea gigas (Thunberg) from the Marlborough Sounds, New Zealand, were followed between June 1998 and January 2000. Histological examination of the gonad confirms an annual cycle with a winter inactive period followed by rapid gonad development and a single short spawning period. The population gonad index correlated with seawater temperature and changes in tissue dry weight, condition index, and biochemical components. In winter, few individuals with early gametogenic stages were present and rapid development of primary oocytes (diam. 11 µm) occurred during spring (September-November). The developmental rate and the diameter of mature oocytes (37 µm) was similar for the 1998 and 1999 seasons. For a standard 110-mm-length oyster, maximal tissue body weight and condition index were recorded in December. Rapid weight loss in January was length dependent and was attributed to spawning. Temperature was the environmental variable which best correlated with the timing of gametogenesis. Food availability (phytoplankton biomass) may have been responsible for inter-annual variations. The biochemical composition (% glycogen, lipid, protein) of separated gonad and somatic tissues were variable seasonally and annually. Gametogenesis (oocyte diameter) was associated with increased gonad protein and glycogen and a decrease in lipid concentrations. These changes are similar to those in Pacific oyster populations from other parts of the world.

Keywords   oyster; Crassostrea gigas; gametogenesis; reproductive cycle; biochemical composition

M02018 Received 20 March 2002; accepted 1 October 2002; Published 20 March 2003
New Zealand Journal of Marine and Freshwater Research, 2003, Vol. 37: 171-182
0028-8330/03/3701-0171 $7.00 © The Royal Society of New Zealand 2003

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