Abundance data (individuals.100 m-3) of planktonic cnidarians collected during the Camadas Finas III oceanographic cruise along the North Brazilian continental shelf between the Amazon and Oyapok river mouths and equatorial Atlantic oceanic waters between 8°N, 51°W and 3.5°S, 37°W. Data was obtained during the oceanographic cruise Camadas Finas III, aboard the research vessel NHo. Cruzeiro do Sul - H38 (DHN/Brazilian Navy), performed in 9-31 October 2012. Planktonic cnidarians were sorted from zooplankton samples collected at at 44 stations in oblique hauls, using Bongo nets with 120 and 300 µm mesh and 0.3 and 0.6 m mouth diameter, respectively. The water column was sampled from near the bottom to the surface over the continental shelf and from 200 m to the surface in the offshore. The net was towed at approximately 2 knots, at various times of day and night. Important Note: This submission has been initially submitted to SEA scieNtific Open data Edition (SEANOE) publication service and received the recorded DOI. The metadata elements have been further processed (refined) in EMODnet Ingestion Service in order to conform with the Data Submission Service specifications.

Sound scattering layers (SSLs) are observed over a broad range of spatio-temporal scales and geographical areas. SSLs represent a large biomass, likely involved in the biological carbon pump and the structure of marine trophic webs. Yet, the taxonomic composition remains largely unknown for many SSLs. To investigate the challenges of SSL sampling, we performed a survey in a small study area in the Northern Bay of Biscay (France) by combining broadband and narrowband acoustics, net sampling, imagery and video recordings. In order to identify organisms contributing to the observed SSLs, we compared measured frequency spectra to forward predicted spectra derived from biological data. This dataset comprises the echo-integrated broadband acoustic data (in Sv(f)), the nets position and depth, and the abundance and the size of the catched organisms acquired during a specific operation of SSLs sampling during (Blanluet et al.)-[https://doi.org/10.1371/journal.pone.0223618]. Important Note: This submission has been initially submitted to SEA scieNtific Open data Edition (SEANOE) publication service and received the recorded DOI. The metadata elements have been further processed (refined) in EMODnet Ingestion Service in order to conform with the Data Submission Service specifications.