From: San Antonio, TX
By 43 you're going to lose some ships, period. You can try to help stem the tide and hit the subs by using several tactics.
1. Big convoys (15 ships) with AV/AMC/CVE air search embedded, with a LOT of escorts. Usually 50% of the ships is what I use. These are my big TK convoys. Always make sure the commander of the convoy has good naval and decent aggression, and hopefully some of your escort captains will have these as well, to help find and attack subs that come in contact with it. If they're going open ocean use escorts with type 2 DCs ideally. By 43 the PBs are either relegated to the shallows or just work as targets in the big convoys to take a shot instead of the TKs.
2. Good coastal routing with air search ASW on the way. The more the better.
3. Sometimes I have a convoy follow an ASW TF. This has worked pretty well too. I just had one run over a sub and drop a bunch of hits on it in deep water.
4. Change things up. Move your routes periodically so he can't concentrate on one or two locations. Also, occasionally if you can afford them, send in your best DDs in ASW TFs near air search where a lot of subs are operating. Over a few weeks several TFs working the same ocean will both make the subs ineffective and get to a few with the DCs.
Helpful comments here. Also agree with other posters about the role of aerial ASW training and deployment. These combined efforts, along with advancement of escort-type ships, should pay dividends.