Abstract
The grooved carpet shell Ruditapes decussatus is one of the most abundant species in the coastal ecosystems of the gulf of Gabès (South-East Mediterranean Sea, Tunisia); however, natural population are overexploited or depleted, so production by culture is recommended and aquaculture represents an alternative for preserving this resource.
The aim of this work is to define methods to support successful larval, postlarval and spat culture of R. decussatus and provide a basis for large-scale propagation of this species.
Adult R. decussatus obtained from natural banks were used as broodstock. Conditioning, induction of spawning, cultivation of larvae, then settlement of pediveliger larvae and nursing of postlarvae were performed under laboratory conditions in the shellfish experimental hatchery (INSTM Monastir).
The larval development was completed in 18 days at 18°C and postlarvae reached 617.47±130.28µm at day 50 and growth rate was 0.36 mm month-1. Larvae, postlarvae and spat showed exponential growth.
Pediveligers (length 250µm) entered metamorphosis at days 18-24 after fertilization, and reached spat size (˃5 mm) after 126 days of culture.
Spats were seeded in their natural habitat (Oued Maltine, Sfax S4) to complete their culture over a period of 27 months. Samples of clams and tissues were collected each season to measure shell growth and weight increase and a Condition Index.
The survival rate during fattening phase of the first two groups seeded showed a decrease until the end of the experiment and was 36% after 12 months of growth (length 24.45± 2.95 mm) and 11% after 27 months of growth (length 52.65±4.07mm) with growth rate 1.93 mm month-1.
Our results show that spat of R. decussatus can be produced in the hatchery and were able to grow in the intertidal zone of South of Sfax until reaching the first sexual maturation and the commercial size.