So long as active perch are grouped and holding in shallow water, it’s preferable to fish for them, because it’s more efficient to fish shallow than to fish deep. First-ice often produces good fishing for perch in shallow water, but for most of the winter, most perch hold deeper than the first drop-off. It’s not just a matter of fishing where most of the perch hold most of the winter. Perch in deep water usually receive less fishing pressure than those in shallow water. Especially after the first few weeks of ice cover, deeper-lying fish often are easier to encourage to bite.

When water mixes during fall turnover, lakes and reservoirs destratify, returning oxygen to the depths. Later, during winter, another phenomenon makes the deep zone appealing. Water is most dense (sinks) at about 39°F. Water chilled below that temperature rises.

Certainly by midwinter, colder temperature bands get bigger from the surface down, pushing the heavier 39°F water off flats into deeper areas. The heavier water rolls down into the basin, carrying along dead weeds, other debris, and food. Minnows, perch, and other fish roll right along with this punch.

There’s lots of food besides minnows in basin waters. Segmented worms called oligochates, averaging close to an inch long, are sometimes concentrated as thickly as 8,000 per square inch on deep flats. Other invertebrates like the aquatic stages of various chronomidae (midges and gnats) are found deep too.

Deep Patterns

Basin depth varies by lake type. In fertile (eutrophic) lakes, basins may run 20 to 30 feet deep. In slightly less fertile (late mesotrophic) lakes, basins may be 30 to 45 feet deep, while in mesotrophic lakes, deep flats might lie 50 to 80 feet down. The fish just roam, particularly in shallower basins, until they find spots where nymphs and larvae are abundant. They may also move, constantly herding packs of minnows, then begin foraging on worms and larvae when minnow schools are reduced.

In this search for deep perch, remember that basin areas aren’t necessarily the deepest water in the lake, but they are the beginning of the deepest water in a particular section of the lake. Perch eventually slide down the drop-off, hit the base of the drop-off, and roam in the general area at the base of the drop-off, particularly in the area where the transition from harder to softer bottom begins. This transition usually occurs within 50 yards or so of the base of the drop-off, so it pays to begin targeting the 100-yard zone beginning at the base of the drop-off into the basin.

Basins often begin at different depths in different portions of the same lake. Say a major shallow bay (big enough to be a small lake) is connected to the main lake. Say the shallow flats around the bay run 10 to 12 feet deep, then drop off into 25 feet, at which point softer bottom begins in the 25- to 28-foot range. Say the deepest water in the bay runs 34 feet. The basin in this bay begins at 25 feet.

In the main lake, by comparison, flats run 12 to 15 feet deep, then in one main-lake section they drop off into 25 to 30 feet, at which point mid-depth flats offering softer bottom begin—followed by another drop-off into 45 feet of water, at which point soft bottom begins in the 45- to 50-foot range. Say depth in this main-lake section eventually slides to 90 feet. Some perch roam those mid-depth flats, but most of the fish are at the beginning of the basin in 45 feet of water. In still other main-lake areas, the basin may begin in 35 feet of water. And so on.