AGGREGATION IMPACT ON THE FILTRATION AND GROWTH RATES OF MUSSELS MYTILUS GALLOPROVINCIALIS LAM.
This study presents the results of field and laboratory-based experiments performed to determine the mussel density effect on an individual mollusk’s growth and clearance rates. We measured the weight and length growth rates of single and aggregated mussels exposed into the sea for three monthly periods in summer and autumn 2015. The sample group contained 140 mollusks from natural populations within the length range of 15-20 mm. The average growth rate of aggregated mussels was almost the same as the growth rate of single ones. Clearance rate of single and aggregated mussels was measured in the laboratory using indirect method. There were selected 5 groups of mussels within the length ranges: 12-16 mm, 17-18 mm, 18-25 mm, 22-23 mm, and 35-38 mm. The clearance rate was measured for each mussel from the group and then for the whole group aggregated in a clump. Water temperature and seston concentration were the same for single and clumped mollusks. The volume of water in chambers was proportional to the weight of mussels put in water. The ratio of aggregated and single mussels’ clearance rates varied from 0.48 to 0.85 at the same density of aggregation and without regard to the animal size. Significant individual variability was recorded in all field and laboratory-based experiments.