Blue Whiting Acoustic Survey Cruise Report March-April 2004

Abstract

Acoustic surveys on northern blue whiting (Micromesistius poutassou) stocks have been carried out since the early 1970s by the Institute of Marine Research (IMR), Bergen. In the early 1980s a coordinated acoustic survey approach was adopted, with both Russia and Norway participating to estimate the size of the stock. The acoustic survey programme is carried out for fishery management purposes, results are presented annually at the ICES led Northern Pelagic and Blue Whiting Fisheries Working Group and from this catch advice is determined for the following year.

The highly migratory nature of this stock and its components require a large geographical area to be surveyed during a relatively short spawning window. Acoustic surveys are routinely carried out on specific spawning and pre-spawning aggregations of blue whiting. This can allow for high concentrations of fish to be surveyed in a relatively small geographical and often well defined area, if the timing is synchronised.

This survey was conducted as part of a collaborative survey coordinated by the Institute of Marine Research, Bergen, Norway, using the vessel the MRV “Johan Hjort”. Also participating were the MRV “Fridtjof Nansen” (PINRO, Russia) and the MRV “Tridens” (RIVO, Netherlands).

The total combined area surveyed in 2004 covered from the Faroe Islands in the north (62º of longitude) to the southern coast of Ireland (50.5º N), area coverage to the west extended from 2º -18º of latitude. The Irish component of the survey was made up of transects covering some 2,080 nautical miles. In addition to the collection of acoustic data fishing hauls were carried out to determine the make up of fish marks recorded by the equipment and to assess the length, weight, age, sex and maturity of the stock. Oceanographic data was collected using a number of spaced hydrograhic stations where salinity and temperature of the water column was recorded at depths of up to 1200 m.