The impact of the adult blue mussel (Mytilus edulis) population on settling of conspecific larvae

Abstract

The choice of a mussel bed as a settling locality by conspecific mussel larvae is a trade-off between reduced fitness due to an increased risk of larval predation and post-settling food competition with the filtering adults and the benefit from a reduced post-settling mortality. This reduced post-settling mortality may be due to a reduced benthic predation in habitats with high complexity. In a field experiment, the larval settling of blue mussels, Mytilus edulis, was recorded on an artificial substrate 0.25, 1 and 2 m above the bottom during six periods in spring 1999. The experiment was conducted at four stations with dense mussel beds located at two of these stations. Two of the four stations, one with mussel beds and one without, were located in a wind-exposed area and the two other stations in a sheltered area. It was demonstrated that the larval settling was reduced up to 1 m above the mussel beds. A size analysis of the settled mussels indicated that the reduction in settling intensity close to mussel beds was due to a pre-settling process: the larvae were predated by the filtering adult mussels. Settling was significantly affected by wind stress. During periods with a high mean wind velocity and a turbulent water column, the larvae showed a reduced settlement 1 m above a mussel bed relative to 2 m above, whereas the same patterns not could be observed outside a mussel bed. The importance of the filtration activity of the adult mussels and the behaviour of the larvae is discussed. The recruitment of blue mussels into a mussel bed was investigated. Here, significant positive correlations were observed between the density of recruits and density of adult mussels and weights of empty shells. This indicates that the filtering mussels not only increase the mortality of larvae, but also serve as an important substrate reducing post-settling predation from benthic predators.

Differential effects of adult mussels on the retention and fine-scale distribution of juvenile seed mussels and biofouling organisms in long-line aquaculture

“…Similar positive effects of adults on settlement have been reported in other studies of mytilid mussels (Nielsen & Franz 1995, Dobretsov & Wahl 2001, Sardiña et al 2009, Dolmer & Stenalt 2010. Adding mussel shells in high density also had a positive, albeit a smaller, effect on the number of M. galloprovincialis, indicating that this species may be bene fitting from the structural properties of P. canaliculus shells (Dolmer & Stenalt 2010). Given the small size (0.25−1.5 mm) of M. galloprovincialis settlers at 1 mo, it is likely that these arrived as primary settlers, although this experiment was not structured to test this.…”

“…The number of M. galloprovincialis was more than double in the high live adult density treatment after 1 mo compared to the controls, clearly showing that experimental ropes bearing live mussels promote settlement or survival of M. galloprovincialis. Similar positive effects of adults on settlement have been reported in other studies of mytilid mussels (Nielsen & Franz 1995, Dobretsov & Wahl 2001, Sardiña et al 2009, Dolmer & Stenalt 2010. Adding mussel shells in high density also had a positive, albeit a smaller, effect on the number of M. galloprovincialis, indicating that this species may be bene fitting from the structural properties of P. canaliculus shells (Dolmer & Stenalt 2010).…”

Body size, population density and factors regulating suspension-cultured blue mussel (Mytilusspp.) populations

“…Spat abundance has been found to increase with adult density because spat settle in the byssus threads of adults and because post-settlement survivorship increases with adult density (McGrorty et al 1990;McGrorty and Goss-Custard 1993). Adult mussels and shell debris in mussel beds increase structural complexity of the bottom and this also has been related to increased postsettlement survivorship in mussel beds (Frandsen and Dolmer 2002;Dolmer and Stenalt 2010). Therefore, we may speculate that the situation with cohort 1 was analogous to that of raw samples and that cohort 1 was made of 1 year old animals (hereafter cohort 1 + ) and spat of the year (hereafter cohort 0 + ), both growing without density-dependence.…”

Spatial patterns of larval settlement and early post-settlement survivorship of Mytilus galloprovincialis in a Galician Ría (NW Spain). Effect on recruitment success

“…Recruitment of marine benthic invertebrates is determined by the interaction between settlement abundance and post-settlement processes, such as migration and mortality. Post-settlement mortality has been mainly attributed to the physiological stress associated with metamorphosis, a greater vulnerability to physical stress in smaller individuals, predation and intra and/or interspecific competition for food and/or space (Bownes and McQuaid, 2009;Capelle et al, 2014;Dolmer and Stenalt, 2010;Gosselin and Qian, 1997;Peteiro et al, 2010;Peteiro et al, 2007a).…”