Improving scallop (Pecten maximus and Placopecten magellanicus) spat production by initial larvae size and hydrodynamic cues used in nursery system

Abstract

A B S T R A C TThere are several factors affecting scallops during the metamorphosis process that could explain the relatively low post-larvae yield observed in hatcheries. Competent bivalve larvae respond to different settlement cues to undergo metamorphosis and without adequate cues, larvae delay their metamorphosis. The objective of this study is to improve the settlement ratio of the two scallop species, Placopecten magellanicus and Pecten maximus by physical cues associated with hydrodynamic conditions, stocking density in settlement units and larval size at time of transfer to settling units. For each treatment, physiological condition was determined by fatty acid analysis to determine the energetic reserves and structural lipids. We observed similar results for the two important commercial pectinid species and validate the hypothesis on the positive effect of increased flow rate and larval size after transfer to settlement systems on settlement success. Increasing flow rate also affects positively the physiological condition of settled post-larvae by a higher accumulation of total fatty acids in neutral lipid fractions. Furthermore, no effect of larval stocking density until 90 larvae cm −2 in the downwelling sieves was observed. To our knowledge this study is the first to characterize the effect of seawater flow rate on settlement success of different pectinid species cultured under similar conditions. The experiments were performed in a close to commercial scale and thus are relevant to industry situations.

Physiological condition of the warty venus (Venus verrucosa L. 1758) larvae modulates response to pile driving and drilling underwater sounds

“…However, antibiotics also prevented the development of a biofilm, which constitutes a positive settlement cue for bivalve larvae (Leyton and Riquelme, 2008), inducing a negative effect on their settlement (Pernet et al, 2006). Furthermore, in the absence of air injection and water agitation in experimental tanks to avoid sound perturbation for anthropogenic noise emission, no positive settlement cue was related to hydrodynamics/turbulence (Tremblay et al, 2020). Finally, with the absence of artificial collectors in the tanks, larvae could only settle on the smooth walls of the cylinders, which is less suitable than filamentous or rough surfaces (Le Tourneux and Bourget, 1988;Harvey et al, 1993).…”

Marine invertebrates and sound

“…However, antibiotics also prevented the development of a biofilm, which constitutes a positive settlement cue for bivalve larvae , inducing a negative effect on their settlement (Pernet et al, 2006). Furthermore, in the absence of air injection and water agitation in experimental tanks to avoid sound perturbation for anthropogenic noise emission, no positive settlement cue was related to hydrodynamics/turbulence (Tremblay et al, 2020). Finally, with the absence of artificial collectors in the tanks, larvae could only settle on the smooth walls of the cylinders, which is less suitable than filamentous or rough surfaces (Le Tourneux and Bourget, 1988;Harvey et al, 1993).…”