Estimating historical trawling effort in the German Bight from 1924 to 1938

Based on historical landings and landings-per-unit-effort data, fishing effort was estimated in the period of 1924-1938 in a study area representing the German exclusive economic zone (EEZ) in the North Sea. Three main trawling fisheries were identified, i.e. the international flatfish fisheries comprising the effort of steam trawlers and motor cutters, the German shrimp fisheries and the industrial inshore fisheries. Except for shrimp trawling, which was performed by beam trawling with one beam per vessel, all historical trawling effort was identified as otter board trawling. The trawling effort increased from 1,131,000 to 1,232,000 h in 1924 to 3,170,000 to 3,836,000 h in 1937 and declined in 1938. The main fishery effort was contributed by the German shrimp fisheries, accounting for a maximum of 2,140,000 h in 1937. In comparison, in 2006, approximately 540,000 h were spent fishing in the trawl fisheries of the study area, comprising effort from small (≤221 kW) to large beam trawlers (>221 kW), shrimp fisheries and otter board trawling. The bulk of the historical effort was concentrated at water depths of 5-20 m. With the implementation of combustion engines and new gear technology, the period of 1924-1938 marked a new era for marine fishing when virtually all space became accessible and, in particular, the trawling of inshore areas increased.