fishing as well as lines and drift nets. These were large boats, usually in length with a beam of around . They weighed 40–50 tons and travelled at . The earliest purpose-built fishing vessels were designed and made by David Allan in Leith, Scotland in March 1875, when he converted a drifter to steam power. In 1877, he built the first screw propelled steam trawler in the world. Steam trawlers were introduced at Grimsby and Hull in the 1880s. In 1890 it was estimated that there were 20,000 men on the North Sea. The steam drifter was not used in the herring fishery until 1897. The last sailing fishing trawler was built in 1925 in Grimsby. Trawler designs adapted as the way they were powered changed from sail to coal-fired steam by World War I to diesel and turbines by the end of World War II. In 1931, the first powered drum was created by Laurie Jarelainen. The drum was a circular device that was set to the side of the boat and would draw in the nets. Since World War II, radio navigation aids and fish finders have been widely used. The first trawlers fished over the side, rather than over the stern. The first purpose-built stern trawler was Fairtry built-in 1953 at Aberdeen, Scotland. The ship was much larger than any other trawlers then in operation and inaugurated the era of the 'super trawler'. As the ship pulled its nets over the stern, it could lift out a much greater haul of up to 60 tons. The ship served as a basis for the expansion of 'super trawlers' around the world in the following decades. Recreational fishing The early evolution of fishing as recreation is not clear. For example, there is anecdotal evidence for fly fishing in Japan, however, fly fishing was likely to have been a means of survival, rather than recreation. The earliest English essay on recreational fishing was published in 1496, by Dame Juliana Berners, the prioress of the Benedictine Sopwell Nunnery. The essay was titled Treatyse of Fysshynge wyth an Angle, and included detailed information on fishing waters, the construction of rods and lines, and the use of natural baits and artificial flies. Recreational fishing took a great leap forward after the English Civil War, where a newly found interest in the activity left its mark on the many books and treatises that were