Shipping noise may trigger valve closure responses in exploited scallop beds of the Gulf of St. Lawrence

Abstract

Shipping noise is a pervasive form of underwater noise pollution, yet its effects on benthic invertebrates remain poorly integrated into spatial risk assessments. The Atlantic sea scallop (Placopecten magellanicus), a benthic bivalve supporting the world's largest wild pectinid fishery, detects low-frequency sound (100-500 Hz), overlapping the dominant range of shipping noise. Previous experiments documented life-stage-dependent valve-closure responses, with juveniles showing higher response probabilities than young adults, particularly at 100-150 Hz. We combined commercially exploited scallop-bed distributions, life-cycle information, experimentally derived acoustic dose-response relationships, and probabilistic shipping-noise models to assess the probability that shipping noise may elicit valve closure across scallop habitats in the Gulf of St. Lawrence. Particle-acceleration dose-response relationships were converted into pressure-level response functions compatible with the modeled mean-square sound pressure spectral density level, Lp,f. Their integration generated seasonal response-probability maps at 125 Hz, the modeled frequency located between the experimental frequencies of strongest response. Response probability showed strong spatial and seasonal variability. The highest probabilities occurred near major shipping routes during winter and early spring. Juveniles showed higher response probabilities and broader affected areas than young adults, reaching >30% in some beds during winter months. Several peripheral beds displayed consistently low response probabilities and may function as acoustic refuges. Because these peaks coincide with periods of elevated energetic demand, shipping noise warrants consideration in cumulative-stressor assessments and marine spatial planning. To our knowledge, this is the first spatial mapping of shipping-noise-induced behavioral-response probability for a marine invertebrate. Maps are available through the Ocean Soundscape Atlas.