New Zealand Journal of Marine and Freshwater Research abstracts

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Measuring reproductive condition in the Greenshell(TM) mussel Perna canaliculus

S. BUCHANAN

Cawthron Institute
98 Halifax St East
Nelson
New Zealand
email: buchanansam@hotmail.com

Abstract  The annual reproductive cycle of Perna canaliculus (Gmelin) was investigated for 1 year by collecting monthly gonad samples from an intertidal population. Gonads of 50 animals were dissected and photographically recorded on video before being fixed for histological sectioning. The histological gonad sections were examined both qualitatively, using a classification and scoring system (S) and quantitatively, using image analysis technology. The quantitative measures used were the proportion of: (1) sections comprising follicles (FC); (2) sections comprising gametes (GC); and (3) the proportion of follicles comprising gametes (G/F). Significant consecutive monthly changes in the qualitative and quantitative measures indicated major spawning events. Gametogenesis occurred during winter with a spawning in August-September. Gonad condition remained low during the spring and early summer until a development period between January and March. A second major spawning event occurred between March and April. There was a high degree of synchrony in reproductive status observed between the sexes. When comparing the four measurement methods using the f statistic as an index of power the GC measure was found to be the most reliable. A gonad visual grading system was developed for rapid assessment of gonad reproductive status and tested. Visual grades of pre-recorded gonad samples were compared to the histological measures. Increasing visual grade correlated strongly with increases in all of the histological measurements. The visual grading was a good predictor of the spawning activity of female P. canaliculus.

Keywords  Perna canaliculus; Greenshell(TM) mussel; reproduction; image analysis

New Zealand Journal of Marine and Freshwater Research, 2001, Vol. 35 M00007
Received 9 February 2000; accepted 1 March 2001

PDF file of entire paper: medium quality (939K); (scanned from paper original: notes about this process)

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