This study investigated growth and mortality of mussels, Mytilus edulis, cultivated on the seabed in order to suggest new and improved management techniques that would optimise the limited natural resource of seed mussels and hence provide a more sustainable approach to mussel cultivation. In addition the environmental effects of intertidal mussel cultivation on invertebrate communities were considered.
The problems associated with an unpredictable and limited supply of seed mussels was addressed through a novel management technique in which excess seed mussels could be 'banked' at higher tidal levels in times of abundant seed fall, and subsequently moved downshore for on-growth in times of low seed fall.
Mussel growth in terms of shell length and flesh dry weight decreased with increasing tidal height and initial stocking density. Statistical models of seasonal growth and mortality as a function of shore height and initial seeding density were developed for use in the prediction, and hence management, of mussel production at a commercial scale. Additionally, intrinsic mussel mortality through density-dependent effects was addressed to obtain a better understanding of the seasonal relationship between mussed biomass and density.
Mussel cultivation had a significant effect on the invertebrate community of the
underlying sediment. This was demonstrated by a change in the composition of
species of the infaunal community and, at all but the areas of lowest mussel cover, a decrease in the number of individuals and number of species compared to the control areas. Within the mussel bed itself negative trends of species numbers and abundance of individuals with increased mussel shell area were also demonstrated.
Current and potential management of mussel cultivation through the use of
production models was reviewed and discussed. Finally, the implications of this study were discussed in relation to the management of mussel cultivation and the future sustainability of the mussel cultivation industry.l