Bulletin of the SFI 1 (161) 2004 - Estimates of the fishing power of bottom trawls applied in Baltic fish surveys

Estimates of the fishing power of bottom trawls applied in Baltic fish surveys
Bulletin of the Sea Fisheries Institute 1 (161) 2004, pp. 29-41

Rainer Oeberst¹, WŁODZIMIERZ Grygiel²
¹Institut f�r Ostseefischerei, An der J�gerb�k 2, 18069 Rostock, Germany
²Sea Fisheries Institute, Kołłątaja 1, 81-332 Gdynia, Poland

Key words: bottom-fishing gear, inter-calibration experiments, fishing power, cod CPUE, southern Baltic.

Abstract.
Since autumn 1999, inter-calibration experiments have been carried out to compare historical catch per unit effort values (CPUE) of national and new standard bottom trawls (types TV3#520 and TV3#930) applied in Baltic fish surveys. Estimates of the fishing power of the former Polish standard P20/25 and the Latvian LBT trawls differed significantly with regard to cod. In contrast, both independent estimates of the Granton (Denmark), GOV (Sweden), Hake 4M (Russia) and HG20/25 (Germany) trawls were comparable. The relationship between the two estimates of the fishing power of Polish gears is 1 to 2. The comparison of the Baltic cod CPUE-values of paired stations (in ICES Sub-division 25) between P20/25 and HG20/25 trawls show that the fishing power of the Polish gear characterize catchability well in relation to the former, standard GOV gear. The impact of the revised estimate of the fishing power of the Polish gear regarding stock abundance indices of Baltic cod are described and discussed.