Abstract:
The potential exists for New Zealand to
exploit already established markets for razor clams
through development of fisheries or aquaculture
industries for the New Zealand razor clam, Zenatia
acinaces. However, fishery or aquaculture development
for Z. acinaces requires an understanding of
the reproductive cycle including the timing of gametogenic
development and spawning. The reproductive
cycle of Z. acinaces was studied over an
11-month period from May 2000 to March 2001 at
Kennedy Bay, Coromandel Peninsula, using qualitative
standard histological analysis and quantitative
measures of oocytes. Histological analysis indicated
that Z. acinaces is dioecious and gametogenic development
was synchronous between the sexes.
Gametogenesis began in June with gametes maturing
quickly and by August/September (late winter/
early spring) most razor clams were ripe. Spawning
began as early as September (spring) although
spawning mainly occurred during October. By
December (summer), nearly all clams were completely
spent. From January 2001 most clams could
not be sexed as all residual gametes were resorbed.
Razor clams remained in this stage during March
2001. Spawning began when the water temperature
was around its lowest, c. 15°C. Monthly mean
number of eggs/follicle was sensitive to changes in
reproductive development, closely following patterns
observed in the qualitative stagings. Patterns
of monthly mean oocyte diameters did not adequately
describe the spawning events observed in
qualitative analyses. Sex ratios were equal over the
size range (69–99 mm shell length) of clams that could be sexed. The data presented in this study
provide valuable information on the timing of
spawning events for Z. acinaces, necessary for developing
sustainable management strategies and
selecting broodstock for aquaculture.
