Through biological flume experiments, we studied the effect of shear velocity and attachment period on the percent detachment of Pecten maximus post-larvae of different sizes reared on two experimental diets. The first diet, (Pavlova lutheri, Isochrysis galbana, Chaetoceros calcitrans), which served as a reference diet (PTC), is commonly used in bivalve hatcheries; the second is the PTC diet with the addition of Rhodomonas salina (PTCR). Our results indicate that the detachment of post-larvae fed PTCR diet showed significant interactions between scallop length, attachment period and shear stress, while the post-larvae feed with the PTC diet showed only effect of shear stress factor. Furthermore, post-larvae exposed to various flume velocities showed different percentages of detachment according to diet (PTC=36% and PTCR=57%) for flow velocities between 1.42 to 2.45 cm s(-1) after 12 h attachment periods. This result could be related to differences in the biochemical composition of post-larvae as discussed. (C) 2012 Elsevier B. V. All rights reserved.