Behavioural responses of juvenile green-lipped mussels to suspended sediment

Despite extensive restoration efforts, green-lipped mussel (Perna canaliculus) recruitment in Aotearoa New Zealand remains limited. Suspended sediment (SS) is frequently proposed as a contributing factor, despite limited direct evidence. To investigate this, laboratory experiments quantified juvenile mussel (shell length 0.5–12.0 mm) behaviours in response to SS. Experiment 1 assessed siphon extension, pseudofaeces (PF) production, pedal locomotion, mucus drifting, and foot extension in 400 or 0 mg L−1 SS, with or without turbulence. Experiment 2 identified SS thresholds for PF production and pedal locomotion. Overall, SS exerted limited influence, only increasing PF production frequency and decreasing latency. In contrast, water turbulence delayed siphon and foot extensions. Shell length was the strongest predictor: smaller juveniles (<6 mm) exhibited faster relocation, while larger individuals (>6 mm) demonstrated more effective particle filtration. These findings reveal ontogenetic differences in particle handling and environmental sensitivity and provide evidence against SS as a behavioural mechanism limiting juvenile mussel recruitment.