Are you feeding with a feeder and if so and you dont see any come May they are gone for the most part. SHocking is inefficient for shocking catfish unless setup for that goal. We shock lots of poor water (low conductivity) and if there are a bunch and 400 in 3 acres is bunch a few will show in the survey. I suspected either a high percntage were 8 inches and fell victim to bass, they were stressed on hauling truck and died later or you have an otter.

Greg Grimes
www.lakework.com