We troll over peaks of between 15 and 45 ft depth. Ideal spots are where there is deeper water, say 50 or 60 feet, then a steep incline or wall up to say 25ft, and back down. The pollack seem to use these to ambush fish. The key bit of gear is the diver, I've tried a few and most are ok down to 25ft at 3 knots but the the best one by a mile is a luhr jensen double deep six. These are used on the great lakes in america for salmon, I had to get mine from cabela's in usa - not cheap but I've only lost one in 3 years. If you've got hot spots for pollack in your area this is the way to do it. It pays to run over your chosen patch first with the sounder to check depth of peaks. Hope you have a try (and catch).