Duration:  October 9 – November 1, 2019

Area:  Baltic Sea; Ore Sound

Purpose:  Hydroacoustic investigations in the Sound

Main aim of the cruise is hydroacoustic monitoring of clupeid distribution in the Sound and adjacent areas: Estimation of distribution and stock size parameters of small pelagics (herring and sprat) contributing to concurrent investigations (FRV “Solea”) in the framework of an international, ICES-coordinated hydroacoustic survey. Additionally, other tasks will be conducted in German waters.

Tasks:

• Hydroacoustic investigation
  Reference fishing on selected fishery stations, length and weight measurements, fish sampling for age determination, hydrographic water sampling, pelagic trawling.
  Background: Within recent years a drastic decline in abundance and biomass of aggregations in that area was registered during the BIAS survey. Therefore, it is essential to reassess the presumptions for the standard acoustic-survey. This is mainly related to the questions, whether the survey-area in the Sound does cover representative parts and whether the survey timing (acoustic transects during night) is still the best option.
• Calibration of Echosounder
• Biological sampling
  Fishery hauls are necessary to identify fish echoes, sampling species composition, length dsitributions and age distribution. The hauls will be conducted using the pelagic trawl PSN388. Additionally, biological samples of selected species and hauls will be taken.
• Hydrographic sampling
• Search and recovery of lost sampling device
  During a previous survey, a sampling device was lost North-East of Ruegen. It is the aim to search and (hopefully) to recover the sampling gear. For search operation, a side scan sonar will be used.
• Bottom Trawl Fishing
  In the waters off Rostock or off Ruegen, fishery hauls will be conducted using bottom trawl to obtain live fish (cod) for experiments and to conduct gear research experiments.

Cruise report (PDF)