During both World Wars trawlers from Leith were requisitioned by the Admiralty. As at Granton these vessels were stripped of their fishing gear and converted to minesweepers and patrol vessels. The North Sea was to be closed to fishing during the Second World War. The remainder of the Leith fleet were transferred to the West Coast working out of ports such as Oban, Ardrossan and Ayr.

The Leith trawlers fished the same grounds and did similar trips to those at Granton.

Rules, regulations  and pay schemes followed the same format.

The Owners forming their own association:- Newhaven and Granton Trawler Owners Association

The steam trawlers at Leith usually berthed at the West Pier, bunker coal was loaded direct from rail wagons via a chute,  at a later date  they had to enter the dock system and berthed in Albert or Edinburgh docks. Here they still continued to use wagons, not the coal hoists, coal heavers and trimmers were employed to load the coal on board. This entailed using the restrictive lock gate system. These vessels would then have to be moved into the Albert basin fairway (The most favoured berth for trawlers in Leith) ready to go on a Sailing day. This was obviously expensive in time and labour.

Steam trawlers continued to operate from Leith until the early 1950's.

With the introduction of diesel powered trawlers and having a more efficient coaling berth and its own ice factory, the remaining trawlers transferred to Granton. 

Christian Salvesen operated a large whaling fleet out of Leith . In 1907 they opened a whaling station on South Georgia in the Antarctic, appropriately named Leith Harbour. By 1911 this was the largest whaling company in the world.   The company withdrew from whaling in 1963.