Environmental drivers’ threat for Acadian redfish revealed by growth chronology

Biological productivity and food webs on the Flemish Cap are influenced by the position of the boundary between the Labrador Current and the North Atlantic (Gulf Stream) current. Warm conditions in the study area occur when the Gulf Stream moves farther north and limit the advection of cold and fresh water from the Labrador Current into the Flemish Cap.Warm Gulf Stream water and high-pressure systems strengthens the anticyclonic gyre from northern Gulf Stream, leading to high productivity over the Flemish Cap. Yet, the potential effect of large-scale linked oceanographic conditions on fish growth remains poorly understood. Otolith growth increments provide an approach for evaluating long-term relationships between environmental variability and growth. Here, we apply crossdating to the commercially important Acadian redfish (Sebastes fasciatus Storer, 1854) collected over 42.000 km2 of the Flemish Cap bank in the northwestern Atlantic. We measured 1132 growth increments across 54 individuals and found that growth variability was synchronous among fish. Anomalies in otolith growth-increment widths were positively correlated with sea surface temperature in November and negatively correlated with sea level pressures in March and September. Positive correlations with temperature indicate that otolith growth is enhanced when these warm conditions occur late in the autumn, potentially extending redfish growing season. Negative correlations with high pressure indicate that such conditions favor Acadian redfish in their spawning season as opposed to growth. Our finding implies that stock assessment requires enhanced programs that track changes in physical and biological attributes, integrating into the assessment models.