FFS Walther Herwig III 404
Cruise summary report
| Cruise Info. | |
| Ship name (ship code) | FFS Walther Herwig III (06NI) |
| Cruise identifier | 404 |
| Cruise period | 2017-03-03 — 2017-04-24 |
| Status | Completed |
| Port of departure | Bremerhaven, Germany |
| Port of return | Bremerhaven, Germany |
| Purpose | Research |
| Objectives | The 404th cruise of the Walther Herwig took the vessel for the third time since 2011 to the central Sargasso Sea to carry out studies on the distribution and abundance of the early life stages of the European eel (Anguilla anguilla). The core study area ranged from 30° - 22°N and 64° - 58°W with stations being sampled along three north-south transects. The primary objectives of this cruise were the documentation of leptocephalus distributions and abundances with a special focus on European eel larvae and a further delineation of the total spawning area of the species. The study also aimed at gathering more detailed information on the influence of abiotic factors for the eel's choice of potential spawning sites. Together with the results of the 342nd and the 373rd voyage of the FRV "Walther Herwig III" in 2011 and 2014, respectively, as well as the 41st voyage of RV Maria S. Merian (2015), the results of this cruise shall deliver insights into possible changes in leptocephalus assemblages in the Sargasso Sea and to shed light on the influence of varying hydrographic conditions on the presence of early life stages. For this purpose, as in the previous years, all caught leptocephalus larvae were sorted out of the catch, identified, measured and preserved. In order to study the accompanying fauna in the spawning area of the European eel, a pelagic fishery trawl was deployed. The net was equipped with a multi-closing system that allowed a stratified sampling of the water column, whereby the changes of the nekton community by depth strata was documented. During the entire cruise, hydroacoustic data were recorded. A combination analysis of the hydroacoustic data and pelagic trawl catches shall provide information on nekton abundance, distribution and composition in the study area. As a special aspect, the genetic basis of sensory adaptation of mesopelagic fish will be studied. A 55 micron Apstein net was deployed to sample micro- and mesoplankton from the upper water layers. A later analysis of the samples in cooperation with the University of Hamburg will provide information on phytoplankton and POM particles. |
| Chief scientist | Reinhold Hanel (Thünen Institute of Sea Fisheries, Hamburg) |
| Cruise report |  (2.22 MB) |
| Ocean/sea areas | |
| General | North West Atlantic Ocean (limit 40W) |
| Specific | Sargasso Sea |
