Grimsby is strongly linked with the sea fishing industry, which once generated wealth for the town. At its peak in the 1950s, it was the largest and busiest fishing port in the world. As a result of the Cod Wars with Iceland, this industry has been in decline for many years. In 1970 around 400 trawlers were based in the port, by 2013 only 5 trawlers remain based there. By comparison, 15 vessels are used to maintain offshore wind farms in the North Sea. The town still has the largest fish market in the UK, but most of what is sold
Cod Wars would generally protect the British trawling fleet. Over the course of this Cod War, a total of 32 British frigates had entered the contested waters. On 19 July 1974, more than nine months after the signing of the agreement, one of the largest wet fish stern trawlers in the British fleet, "C.S. Forester", which had been fishing inside the limit, was shelled and captured by the Icelandic gunboat V/s "Þór" after a pursuit. "C. S. Forester" was shelled with non-explosive ammunition after repeated warnings. The trawler was hit by at least two rounds, which damaged the engine room and a