Effect of stocking density on larval performance and post-larvae settlement of clam Ruditapes decussatus (Linnaeus, 1758) in bivalve hatchery production

¹ Research team of Agriculture and Aquaculture Engineering G2A, Polydisciplinary Faculty of Larache FPL, Abdelmalek Essaadi University, Tetouan, Morocco
² Amsa Shellfish Station, National Institute of Fisheries Research (INRH), Amsa, Tetouan, 93022, Morocco

^* Corresponding author: Rania.azirar@etu.uae.ac.ma

Abstract

Larval rearing is a critical phase in bivalve hatchery production and plays a crucial role in the success of spat production. Therefore, understanding the effect of density on larval performance and post-larvae settlement is crucial for optimizing and improving the success of bivalve hatchery production. This study aimed to evaluate the effect of different stocking density on larval performances and settlement rate of clams Ruditapes decussatus. Three different larval rearing densities (10, 20, and 40 larvae/mL) and four settlement densities (35, 70, 100, and 140 larvae/cm²) were studied. The results regarding larval performance showed that high density resulted in low larval survival (18% for D40) compared to low and moderate densities (23% for D10 and 26% for D20, respectively). In terms of post-larvae settlement, a density of 35 larvae/cm² exhibited the highest fixation rate (36%) compared to 33%, 18%, and 9% at 70, 100, and 140 larvae/cm², respectively. Statistical analysis revealed a significant effect of larval density on both survival and growth (F = 11.79, p < 0.05; F = 18.63, p < 0.05, respectively), as well as a highly significant effect on settlement (F = 14.88, p < 0.001). Overall, it is advisable to maintain moderate densities during both larval performance and post-larvae settlement for seed production of R. decussatus in the hatchery.