Sargasso Sea Environmental Assessment - European Eel Larval Studies (2016) - Cruise No. MSM41 - April 1 - April 29, 2015 - St. George's (Bermuda) - Dockyards (Bermuda) (English)

From April 1 to 29 2015 a research survey on board RV MARIA S. MERIAN was conducted to assess the hydrographic and ecological situation of the central Sargasso Sea pelagic community, its key components and major trophic pathways. Special focus was given to evaluate the relative abundance of anguillid leptocephali in the central Sargasso Sea in relation to previous findings and to better define the European eel spawning area. Abundance of leptocephali along 5 north-south transects across the spawning area from 58°W to 70°W and from 22.5°N to 31°N were assessed using 49 tows of an Isaacs-Kidd midwater trawl (IKMT) accompanied by Conductivity, Temperature, Depth (CTD) profiles at each station. Meso- and macrozooplankton as well as micronekton and neuston were collected by various nets, whereas phytoplankton was obtained from the rosette water sampler attached to the CTD. Stations were positioned at 1 degree latitude intervals and transects spaced every 3 degrees of longitude. More than 360 anguillid leptocephali and almost 2000 marine eel leptocephali were collected and identified onboard. Extensive samples and data sets were also obtained from all the other gears, and ecophysiological measurements were made on the freshly collected Sargassum. Many samples will be analyzed later, and methodologies such as nitrogen and carbon stable isotopic and fatty acid analyses will be conducted to evaluate the trophic structure of the marine food web and the possible interactions of the various components of the food web of the Sargasso Sea.