Acoustic meso- and bathypelagic studies are scarce in the Bay of Biscay but increasing over the last years. This study provides a description of seasonal and bathymetric variation in the distribution of the main scattering layers. We combine acoustics and hydrographic information from four surveys carried out in 2015 in the southern Bay of Biscay. Water mass properties as well as mixing processes studied through optimum multiparameter (OMP) analysis provided information on the physical seascape. This study reports for the first time a bathypelagic deep scattering layer that was detected in autumn (1300–1500 m) and winter (800–1200 m) and did not present a daily migration pattern. Migrant deep scattering layers and non-migrant layers, stronger at 18 and 38 kHz respectively, are two separate entities with distinct spatial and seasonal dynamics. Migrant layers vary in number and intensity with primary production while the main non-migrant layer (400–800 m depth) is constant in intensity throughout the year. Non-migrant layers seem to locate at horizontal water mass boundaries with increased stratification.

比斯开湾的声学中和深海研究很少，但在过去几年中有所增加。这项研究描述了主要散射层分布的季节性和水深变化。我们结合了 2015 年在比斯开湾南部进行的四项调查的声学和水文信息。通过最佳多参数 (OMP) 分析研究的水团特性以及混合过程提供了有关物理海景的信息。该研究首次报告了在秋季（1300-1500 m）和冬季（800-1200 m）检测到的深海深散射层，并且没有呈现每日迁移模式。迁移深散射层和非迁移层分别在 18 kHz 和 38 kHz 处更强，是两个独立的实体，具有不同的空间和季节性动态。迁移层的数量和强度随初级生产而变化，而主要的非迁移层（400-800 m 深）全年强度恒定。非迁移层似乎位于水平水团边界，分层增加。