Modelling growth variability in longline mussel farms as a function of stocking density and farm design

Abstract

The simulations demonstrate spatial growth patterns at longlines under environmental settings and farm configurations where flow reduction and seston depletion have significant impacts on individual mussel growth. Longline spacing has a strong impact on the spatial distribution of individual growth, and the spacing is characterised by a threshold value. Below the threshold growth reduction and spatial growth variability increase rapidly as a consequence of reduced water flow and seston supply rate, but increased filtration due to higher mussel densities also contributes to the growth reduction. The spacing threshold is moderated by other farm configuration factors and environmental conditions. Comparisons with seston depletion reported from other farm sites show that the model simulations are within observed ranges. A demonstration is provided on how the model can guide farm configuration with the aim of optimising total farm biomass and individual mussel quality (shell length, flesh mass, spatial flesh mass variability) under different environmental settings. The model has a potential as a decision support tool in mussel farm management and will be incorporated into a GIS-based toolbox for spatial aquaculture planning and management. Research highlights ► New model for flow reduction, seston depletion and mussel growth in longline farms. ► Integration of processes at the level of individual mussels and at the farm level. ► Mussel size and condition depend on farm configuration and environment. ► Spacing between longlines is the most influential farm parameter on mussel growth. ► The effects of farm configuration are moderated by environmental conditions.

Open water integrated multi-trophic aquaculture: constraints on the effectiveness of mussels as an organic extractive component

“…1). High levels of flow reduction and feedback effects on food depletion (increased) and mussel growth (decreased) have been observed and predicted for mussel longline and raft farms (reviewed by Rosland et al 2011). Persistent farm-induced flow reduction may also have undesirable effects in an IMTA situation if the presence of intensive culture structures reduced current flow to adjacent fish netpens to levels below the threshold (2 cm s −1 for more than 40 min) needed to maintain adequate oxygen in net-pens (> 6 mg O 2 l −1 ; Page et al 2005).…”

Numerical modelling of spatio-temporal variability of growth of Mytilus edulis (L.) and influence of its cultivation on ecosystem functioning

“…DEB models have been successfully applied to several shellfish species including Mytilus edulis (e.g. Handå et al, 2011;Filgueira et al, 2011;Maar et al, 2009;Rosland et al, 2009Rosland et al, , 2011Saraiva et al, 2011a;Thomas et al, 2011;van der Veer et al, 2006), Crassostrea gigas (e.g. Alunno-Bruscia et al, 2011;Barillé et al, 2011;Bernard et al, 2011;Bourlès et al, 2009;Emmery et al, 2011), and other species.…”

An ecosystem-based approach and management framework for the integrated evaluation of bivalve aquaculture impacts

“…In this respect, particle depletion and bivalve performance measurements are highly complementary. The former indicator provides information on changes in pelagic food supplies that likely control the latter (see Rosland et al 2011). Monitoring bivalve condition is a way to assess how the physiological status of the bivalve is affected by food limitation.…”