The Battle of the Atlantic was effectively over by the summer of 43 and the Battle of the Ruhr in Mar-Jul 43 was directed at German industry, a large part of which was supplying UBoat production. This battle alone took up 5% of Bomber Commands total sorties for WW2. Along with other raids that were specifically on yards and the devastating Operation Gomorrah in July 43, I would argue that in Bomber Commands early war, a substantial part of it was targeted at UBoat production. - Rolling20
The turning point in the Battle of the Atlantic is generally regarded as being 23 May 1943, the date on which Admiral Dönitz is believed to have realised that he was obliged to alter his U-boat strategy, coinciding as it did with the arrival in the Mersey of Convoy HX238 from New York and Halifax NS the same week, having incurred fewer losses than almost any other in the previous year.
The anniversary is celebrated in great style in Liverpool every year - as I know to my cost!
Jack