Scallops caught in the headlights: swimming escape behaviour of the Atlantic sea scallop (Placopecten magellanicus) reduced by artificial light

Quantifying the distribution and abundance of the Atlantic sea scallop (Placopecten magellanicus) is a fishery management priority, and stock assessments increasingly rely on video surveys. Interpreting the results of these surveys requires understanding the inherent biases introduced as a result of target animal behaviour. Our study investigated the effect of artificial lights on the behaviour of Atlantic sea scallops during a video survey using a towed benthic sled. Swimming and stationary scallops were counted in survey videos using event logging software. In addition, the locations, orientations, and swimming directions of the scallops were noted in a subset of the videos. The proportion of scallops that swam when an artificial light was turned on was significantly smaller than the proportion that swam when the light was off. Further analysis using a logistic model showed that only light state (off or on) predicted the likelihood of scallop swimming responses. Possible reasons for this unexpected behaviour are discussed, with a focus on the scallop visual system.