© 2001 by ICES/CIEM International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer
Time changes in fishing power in the Danish cod fisheries of the Baltic Sea
a Danish Institute for Fisheries Research Charlottenlund Castle, DK 2920, Charlottenlund, Denmark
b Danish Institute for Fisheries Research North Sea Center, Postboks 101, DK 9850, Hirtshals, Denmark
c ICES Palægade 2–4, DK 1261, Copenhagen K, Denmark
Correspondence to Paul Marchal: e-mail: pam{at}dfu.min.dk
Using nominal fishing effort to control fishing mortality and using cpue data from commercial fisheries as abundance indices require ability to correct fishing power for temporal development. It is often assumed in ICES stock assessments that fishing power is constant over time. However, experience has suggested that this assumption may be false. This study investigates the time dynamics of an Index of Fishing Power (IFP). This index is based on the fleet's cpue, relative to the cpue of a subset of vessels from the same fleet. The primary characteristic of the reference vessels is that their fishing power has not varied much over time. IFP is calculated for some of the Danish cod fisheries in the Baltic Sea. IFP appeared to be independent of the vessel composition of the reference sub-fleet and for the fleets fishing in the Eastern Baltic Sea, but less so for the Western Baltic Sea fleets. Variations in IFP are analysed by a GLM (General Linear Model). Results suggest that fishing power has developed in the Eastern Baltic Sea cod fishery at an annual rate of 2% and 6% for trawlers and gillnetters respectively. Mechanisms of fishing power creeping may include increased technical efficiency and also changes in vessel composition of the fleets over the period of analysis.
Keywords: variations in fishing power, catchability, effort regulation, fishing effort, fishing mortality, cpue, GLM, Danish commercial fisheries, Baltic Sea cod
Received 29 November 1999; accepted 26 October 2000.
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