Spawning, settlement, and growth of the New Zealand venerid Ruditapes largillierti (Philippi 1849) in culture

Spawning, larval rearing, and growout of Ruditapes largillierti (Philippi 1849) were investigated in a series of trials conducted at the University of Tasmania (UTAS), Launceston and Georges Bay, St Helens, Tasmania, Australia. Intramuscular injection of serotonin (3 x 10-7 to 1.5 x 10-6 moles) failed to induce spawning in female Ruditapes largillierti, although some males did spawn. Fecundity of R. largillierti induced to spawn by thermal stimulus ranged from 0.5 to 0.9 x 106 eggs female-1. Fertilised eggs developed into trochophore larvae by 24 h at 20°C and D veligers with a mean shell length of 85.3 ± 4.7 μm within 48 h. Early larvae were frequently deformed and their mortality rates were very high. Development to pediveliger stage (mean shell length 200.3 ± 7.3 μm) took between 11 and 16 days at 20°C, and metamorphosis to spat (mean shell length 240 μm) occurred between Days 16 and 19. There was no significant difference in efficacy of epinephrine, norepinephrine, or untreated groups for inducing larval settlement. Average growth of juveniles held subtidally within trays or baskets (mesh size 1.7-12.0 mm) was 1.3 mm month-1. The aquaculture potential of this subtidal venerid clam warrants further investigation.