Biologists and anglers have theorized what causes catfish to suspend off the bottom at different times, with feeding, water quality, oxygen, and thermoclines being the most-common answers.
In areas where other fish — including black or striped bass — are feeding on the surface, catfish are known to leave the bottom and shadow surface-feeding fish to take advantage of missed, wounded, or pieces of baitfish left over. Striped bass, in particular, are known for slashing into schools of baitfish to stun the bait, and then circling back to eat the prey. In some cases, the wounded fish sink to where suspended catfish are the next-level feeders without exerting the effort.
At other times, without current to keep them pinned to the bottom, baitfish are freer to move about in a large river and its tributaries. When catfish are feeding, it’s a common scenario to see them leave the bottom and move into schools of baitfish.
During the fall turnover in reservoirs, water quality turns sour near the bottom, with low levels of dissolved oxygen. That could explain why catfish leave the bottom, but turnover is not a scenario to be found in moving water rivers.
“I suspect is has a lot to do with oxygen levels in the water and, of course, catfish are going to go where the food is, but I couldn’t tell you exactly why they at times will suspend up off the bottom,” according to angler David Shipman of Corinth.