Temporal and spatial variation in food availability and meat ratio in a longline mussel farm (Mytilus edulis)

Abstract

The influence of temporal and spatial variation in food availability on mussel meat ratio and biomass was studied in a longline mussel farm (100 m wide and 250 m long, Mytilus edulis) during an eight-month period. Current velocity and phytoplankton concentration were measured and mean mussel biomass, density, wet weight and meat ratio were determined. The longline farm aligned the current direction lengthwise through the farm and reduced the current speed and flow to approximately one half to one third of reference station. The mean fluorescence depletion in the centre of the farm was 11% and the phytoplankton concentration (cells L¯¹) was 20 to 91% less in the centre of the farm compared to the reference station. The mean meat ratio increased 1.8 times through the spring phytoplankton bloom. The mean meat ratio (%) and biomass (kg) were spatially variable through the farm with low values in the centre and increasing values towards the edges of the farm. This variation in meat ratio and biomass was observed at all natural phytoplankton concentrations and attributed to spatial variation in food availability through the farm.