Report 2 of the Study Group on Red-fish Stocks (SGRS)

A trawl-acoustic survey on pelagic redfish (Sebastes mentella) in the Irminger Sea and adjacent waters was carried out by Germany, Iceland and Russia in June/July 2005. Nearly 400 000 nm2 were covered. A total biomass of 551 000 t was estimated at depths shallower than the “deep scattering layer” (DSL) by hydroacoustic measurements, and about 674 000 t within and deeper than the DSL by an experimental “trawl method”. In both depth layers, the highest concentrations of redfish were found in the western and southwestern part of the survey

area. The estimated biomass and abundance of redfish within and deeper than the DSL derived from the trawl data is considered highly uncertain due to the short time series and the large error involved in the estimation.

Although the estimates divided by depth layers are not comparable between years due to changes in the depth range covered in the deeper layer in the 2005 survey, the total estimates of the shallower and deeper layer combined can be compared between years. The total biomass estimate of 1.2 million t, encompassing the shallower and the deeper layer, represents a value within the range of the 1999 and 2001 estimates. The group recommends that the survey should be continued, that it should be carried out every second year, that as many vessels as possible should participate to improve the quality of the derived estimates, and that the timing of the survey should be kept in June/July.