Marine

MRV Scotia; Survey 0814S – Herring Acoustic Survey

July 16, 2014 by Marine Directorate Communications No Comments | Category Marine Directorate general, Marine Directorate Science, Research Vessel Surveys

Proposed Survey Track Scotia 0814S

Overview of survey:
The MRV Scotia and a chartered pelagic vessel will conduct the Herring Acoustic Survey covering the area shown below. The pelagic vessel will identify fish shoals using the echosounder and fishing operations will be carried out using the multisampler cod end unless large aggregations are seen in the area. Samples of all species caught will be measured for length and weighed to establish a length-weight relationship.

Otoliths will be collected from a sub-sample of the herring to determine age. For each herring in the sub-sample the state of maturity, gonad weight, liver weight, whole and gutted weight, presence of food in the stomach as well as any presence of infection. In addition, random sampling of fish above 24 cm length will be carried out and photographs taken for identification analysis. Otoliths from these fish will, subsequent to ageing, will be made available for analysis.

The ships thermosalinograph will be run continuously to obtain sea surface temperature and salinity throughout the survey area.

Duration: 28 June – 17 July 2014
Personnel: 8 (Part 1) 8 (Part 2)

Gear: Midwater trawl PT160 x 3; Multisampling pelagic cod-end with one fine mesh cod-end; Seabird 911 CTD; One metre vertical plankton sampling net 350µm mesh.

Objectives: To conduct an acoustic survey to estimate the abundance and distribution of herring in the north western North Sea and north of Scotland between 58º30’-62ºN and from the shelf edge to 2ºE, excluding Faroese waters and;

• To obtain biological samples for echosounder trace identification using a pelagic trawl.
• To obtain samples of herring for biological analysis, including age, length, weight, sex, maturity and ichthyophonus infection.
• To obtain hydrographic data for comparison with the horizontal and vertical distribution of herring.
• To obtain dry weight estimates of macro zooplankton biomass throughout the study area for comparison with acoustically derived plankton biomass estimates and observed herring distribution.

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