FRV Scotia 0814S
|Ship name (ship code)||FRV Scotia (748S)|
|Cruise period||2014-06-28 — 2014-07-17|
|Port of departure||Aberdeen, United Kingdom|
|Port of return||Aberdeen, United Kingdom|
1. To conduct an acoustic survey to estimate the abundance and distribution of herring in the north western North Sea and north of Scotland between 58 30'-62N and from the shelf edge to 2E, excluding Faroese waters.
2. To obtain biological samples for echosounder trace identification using a pelagic trawl.
3. To obtain samples of herring for biological analysis, including age, length, weight, sex, maturity and ichthyophonus infection.
4. To obtain hydrographic data for comparison with the horizontal and vertical distribution of herring.
5. 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.
The survey will commence after calibration and follow a pattern of parallel transects running east/west, at normal steaming speed (10.5 knots), progressing northwards, along the east side of Orkney/Shetland, and southwards along the west side. The survey area is bounded by 58 30'-62N and 02E to the 250 m contour. Transect spacing is 15 nm for the entirety of the survey area. A pelagic vessel will be chartered to conduct an acoustic survey simultaneously with Scotia by interlacing between these transects giving an effective transect spacing for the combined surveys of 7.5 miles. The charter vessel will not collect herring biological samples other than those obtained during its commercial tow(s).
A mid survey break will take place on approximately 7 July in Lerwick to allow for the transfer of staff and to comply with the WTD policy. A calibration will be conducted either East of Shetland at the mid cruise break or in Orkney at the end of the survey if time permits.
Acoustic data will be collected at four frequencies (18, 38, 120 and 200 kHz) between 03:00 and 23:00 hours. Fish shoals seen on the echosounder will be identified using a pelagic trawl (PT160). Survey trawling operations will be carried out between two and four times per day at anytime between 03:00 and 23:00. 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 to partition the echo integral amongst species and size classes for target strength functions. Fish will also be weighed to establish a length-weight relationship. Otoliths will be collected from a sub-sample of the herring according to the following length stratified scheme to determine age; two per 0.5 cm class below 22 cm, five per 0.5 cm class from 22.5-27.5 cm and ten per 0.5 cm class for 28.0 cm and above. For each herring in the subsample the state of maturity, gonad weight, liver weight, whole and gutted weight, presence of food in the stomach as well as the presence of Icthyophonus infection will be recorded. The maturity scale used throughout the survey will be the Scottish 8 stage scale.
In the area west of 4W, in addition to the above described sampling, random sampling of 120 fish above 24 cm length will be carried out for each haul with photographs taken for morphometric stock identification analysis.
Where required, a vertical combined hydro and plankton dip will be carried out immediately following a pelagic trawl; this will require the vessel to use its DP system to remain on station. The decision to carry out vertical dips will be based on the requirement to achieve at least one station in each ICES rectangle. In addition to the vertical plankton hauls carried out at CTD stations, a small number of hauls may be conducted in the period between 23:00 and 03:00 hours to measure sampling variability.
|Chief scientist||Philip J Copland (Marine Scotland Aberdeen Marine Laboratory)|
North East Atlantic Ocean (limit 40W)
|Specific||Orkney & Shetland|
|Track charts||(00 MB)|