1) To conduct an acoustic survey to estimate the abundance and distribution of herring in the north western North Sea and west of Scotland (ICES area Via(N) as part of the ICES International North Sea Herring Acoustic Survey).
2) To obtain samples of herring for biological analysis, including age, length, weight, sex, maturity and ichthyophonus infection.
The vessel departed from Peterhead on 1 July at 13:00 and proceeded to Loch Eriboll where calibration of the three transducers was carried out. The survey commenced in the North Minch at 19:00 on 2 July. Zig-zag transects at a spacing of 15 n.mi. were adopted in the Minch. On reaching the southern limit of the Minch, transects progressed northwards along lines of latitude, at spacings of 15, 7.5 or 3.75 nautical miles (n.mi.). Transects extended as far as the shelf edge (250 m contour) to the west, and as far as safely possible to the east, on approaching the coast. A half landing took place on 12 July in Ullapool for the exchange of personnel. The 38 kHz transducer was calibrated in Loch Broom prior to landing. The vessel resumed surveying at 18:00 on 13 July. North of the Hebrides, transects extended from the shelf edge to longitude 2° West, progressing northwards as far as 60° 04' North. The survey was completed on 20 July at 20:15. A second calibration was carried out at 08:00 in Scapa Flow on 21 July. The vessel returned to Peterhead on the evening of 21 July.
Paul G Fernandes (Fisheries Research Services Aberdeen Marine Laboratory)
International North Sea Herring acoustic survey
North Sea Inner Seas off the West Coast of Scotland North East Atlantic Ocean (limit 40W)
north western North Sea; west of Scotland
North Sea, Inland Sea off the West of Scotland (Minch ?), NE Atlantic Ocean
Biology and fisheries
Quantity: number of hauls = 49 Description: Measurements of fish length, weight, sex, maturity, age and species composition from catches of a PT160 pelagic trawl with a 20 mm cod end.
Acoustic reflection on marine organisms.
Quantity: track kilometres = 4630 Description: Acoustic backscatter (MVBS and power) from 38, 120 and 200 kHz, and single echo target strength from 38 kHz, from almost entire water column (transducers mounted in towed body at depth of 5 m) using an EK500 scientific echosounder; continuous at rate of 1 transmission per second, over 19 hour daily period.