Temporal variation of secondary migrations potential: concept of temporal windows in four commercial bivalve species

Abstract

Post-settlement dispersal potential of four commercial bivalve species (Mytilus edulis, Pecten maximus, Venus verrucosa and Ruditapes philippinarum) were studied through the assessment of recruits' sinking velocities by using a sinking velocity tube of five meters height. In parallel, dynamics of shear stress were monitored for five months on a tidal habitat characterized by the presence and the dispersal of the four species. By coupling both datasets we propose first theoretical estimates of temporal windows of secondary migrations. These experiments revealed interspecific differences in migration potential relate to shell shapes and behaviour, especially to secretion of byssal threads. The sensitivity to passive and active post-settlement migrations seems to rely on the synchronisation between the arrival on the sediment, the tidal regime (spring tide, neap tide), but also the rate of growth of the recruits. The present study confirms that patterns of secondary migrations of bivalve recruits result from a close physical-biological coupling involving benthic boundary layer (BBL) hydrodynamics and shell morphology as well as eco-ethological responses to environmental conditions but clearly modulated by the growth dynamics until a threshold size when drifting is no longer possible.

The loss of seed mussels in longline aquaculture

“…One of the most problematic factors to manage in the aquaculture of mussels is their ability to migrate entirely away from their location at seeding via byssus or passive drifting, [91][92][93][94] a process known as secondary settlement. 95 Secondary settlement is a common behaviour of mytilid mussels and many other bivalves 19,20,96,97 and is a considered to be a major cause of losses of seed mussels (P. canaliculus) in New Zealand. 9,11,56 Paradoxically, small-scale secondary settlement migrations, which are achieved by the seed crawling via their pedal organ (or foot), are essential to mussel aquaculture because the mussels must migrate from their substrate at seeding to the grow-out ropes, if they are to be retained.…”

Pull the trigger: interplay between benthic and pelagic cues driving the early recruitment of a natural bivalve assemblage

“…Mussels are intense drifters, using byssal threads to re-enter the water column and perform new dispersal (Sigurdsson 1976). Other species that lack such adaptations could resuspended through active swimming (Williams and Porter 1971) or because of a particular shell morphology, such as a flat shell that has slower sinking speeds (Forêt et al 2018b, Leal et al 2019. The strategy of a secondary migration, using active drifting, allows organisms to reach a more suitable habitat.…”

“…This trade-off between delayed metamorphosis and selection of a suitable habitat is known as the desperate larva hypothesis (Knight-Jones 1953, Toonen and Pawlik 2001, Marshall and Keough 2003, Tremblay et al 2007) and can impact the performance of postmetamorphic stages (Pechenik 2006). In addition, after contact with the substratum, post-larvae can perform secondary migrations to reach more suitable habitats by using active resuspension mechanisms (Olivier et al 1996, de Montaudouin 1997, Olivier and Reti ere 1998, Forêt et al 2018b). Such mechanisms are energetically expensive (Forêt et al 2020) and are therefore closely linked with the trophic ecology and energy storage dynamics of bivalve larvae.…”

Artificial habitat and biofouling species distributions in an aquaculture seascape

“…28 to 50 d (Gibbs et al 1991, Broekhuizen et al 2015. It is possible that these bays act as larval traps, where entrained larvae initially settle on the suspended farm structures and subsequently migrate to benthic habitats at more localised scales (Forêt et al 2018). For organisms with limited natural dispersal capacity, aquaculture related activities (e.g.…”