Attachment Mechanism and Control Efficacy of an Adhesive Nuisance Mussel, Limnoperna fortunei, for Coating and Materials

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The attachment strength of the freshwater mussel Limnoperna fortunei against water flow was studied. Newton's expression successfully described the hydrodynamic drag force acting on the mussel with a drag coefficient value of 1.03. The drag-resistant force (defined as hydrodynamic drag force at mussel detachment) was smaller than the detachment force measured using a tensile load test. A fairly good correlation was obtained between the drag-resistant force and the number of secreted threads. The drag-resistant force divided by the number of threads increased with shell size, suggesting that byssal thread strength increased with mussel growth. For the mussel specimens obtained from a water transmission pipe, thread width increased with shell size. However, thread width was not dependent on current velocity. There was no correlation between the number of secreted threads and shell length, which indicated that the number of secreted threads did not change with mussel size. Therefore, the … More water velocity needed to detach mussels increases with shell size of the mussel when the number of secreted threads is constant. The increases in the water velocity to detach mussels with larger shell suggested that the mussel becomes more resistant to water flow as it grows. It is estimated that a flow velocity around 1 m/s was critical for attachment/detachment of a juvenile mussel with a shell length of a few millimeters and one hundred byssal threads.Various anti-fouling substrates were tested for their effectiveness in inhibiting attachment of Limnoperna fortunei. Field experiments revealed that surface properties affected anti-fouling capabilities for nontoxic substrates. Anti-fouling capabilities were observed for 3 silicone-resin-based coatings with smooth surfaces of < 30 μm roughness and low surface free energy of the hydrogen-bonding force component. However, the remaining 3 silicone-resin-based coatings tested, as well as other types of nontoxic coatings, did not show any anti-fouling capabilities. The percentages of mussels that attached in laboratory experiments using juvenile mussels were correlated with the settling densities of mussels in the field experiments. This suggests that the laboratory experiments may be effective as short-term preliminary assays to select promising materials/coatings for longer-term field experiments. Mussel abundance surveys within a water transmission pipe and pipe current velocity simulation revealed that less mussel infestation was observed in the areas with wall-vicinity fluid velocity of > 1.3 m/s. Conversely, pipe surfaces with flows of < 1.2 m/s were heavily fouled by L. fortunei. Less