Effects of stock origin and environment on growth and reproduction of the green-lipped mussel Perna canaliculus

The effect of stock origin and growing environment on growth and reproduction of the green-lipped mussel Perna canaliculus was investigated on the marine farms in the Marlborough Sounds, New Zealand. Following the normal commercial practice, mussel stocks from three widely separated origins in New Zealand were transplanted to six sites in Marlborough Sounds and grown on ropes hung from commercial longlines for eleven months. Stock origin had significant effects on growth rates as measured by shell length and flesh weight. Growing sites also showed a significant effect on flesh growth rate but only a small effect on shell length growth, with considerable variation among sites. Two sites (Beatrix Bay and Hallam Cove) had the fastest growth in flesh weight. One stock (Golden Bay) showed the fastest growth and lowest mid-winter reproductive rates, while the Kaitaia stock (the most commonly used one in industry) showed highest winter reproductive rate. Spawning was responsible for mid-winter declines in flesh weight among all stocks, but the Golden Bay stock recovered flesh weight more rapidly than other stocks after spawning. The stock differences in growth suggest that genetic traits of stock origin remained after mussels were grown in different environments (sites). In addition, we speculate that there would be a large variation of physiological rates between stocks including filtration, ingestion and respiration rates. The variation in growth and reproduction suggests that there would be a significant difference in energy allocation for reproduction, flesh and shell growth among stocks. The study has obvious application to the mussel industry for planning and selective seeding of stocks to maximise economic benefits. The use of fast-growing stocks and timing of harvesting in mid-winter can dramatically improve quality and quantity of production.