Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Tridens II	North Sea Herring Ac	28.06.2019 - 19.07.2019	NHAS	North Sea

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
Couperus Bram	IMARES, Wageningen UR, Institute for Marine Resources and Ecosystem Studies, Texel	Scheveningen	Scheveningen

Ziel der Reise / Objectives of Cruise:

The objective was to carry out an hydro acoustic survey defining the abundance of herring and sprat in the North Sea. The Dutch Institute Wageningen Marine Research (WMR, previously IMARES) has participated in the international North Sea acoustic survey for herring since 1991. The other participating countries in this survey are Scotland, Norway, Germany, Denmark and Ireland. The survey is part of the EU data collection framework (DCF) and is coordinated by the ICES Working Group for International Pelagic Surveys (WGIPS). The aim of this survey is to provide an abundance estimate of the whole North Sea herring population. This estimate is used as a tuning index by the ICES Herring Assessment Working Group (HAWG) in its assessment of the population size. In this report the results for the survey in the central North Sea, as carried out by the Dutch vessel R/V Tridens, are presented. The area covered is therefore limited to the biological strata covered by the Dutch research vessel Tridens. As a consequence, the presented size and composition of the herring and sprat stock is independent from the remainder of the North Sea. For the estimation of the total North Sea stocks, the acoustic and biological data of all participating countries will be uploaded to the ICES acoustic database and used by WGIPS to carry out an integrated analysis using the software StoX. As the biological strata in the integrated analysis will be based on biological samples in the whole North Sea, the results for the Tridens area will differ from the results presented in this report.

Messungen / Measurements