Steelhead, Coho and Chinook: Why They Stack at Different Depths

A Great Lakes trolling spread can produce three salmonid species from three different parts of the water column.

A high spoon takes a steelhead.

A middle rod takes a Coho.

A deeper presentation fires on a Chinook.

That pattern is common enough to be useful, but it should not be turned into a rigid rule.

Steelhead, Coho and Chinook overlap extensively. What changes is how strongly each species tends to use different portions of the pelagic water column.

Why species separate at all

These fish share many of the same forage species.

If they all used exactly the same depth, temperature and feeding strategy, competition would be intense.

Instead, differences in physiology and behavior allow them to use overlapping but somewhat different habitats.

Depth can be one part of that separation.

Steelhead often give you the high opportunity

Lake Ontario research has repeatedly found steelhead or rainbow trout higher in the water column than some other salmonids.

A spring thermal-front study found Chinook and lake trout were caught deeper than Coho and steelhead.

Another long-term Lake Ontario study found rainbow trout and Chinook both moved offshore and deeper through early summer, but rainbow trout often occupied different offshore locations and were sometimes caught in cooler water despite their different vertical position.

That last point is important.

"Steelhead are high because they like warm water" is too simple.

Depth and temperature are related, but they are not interchangeable.

Coho often relate well to the break

Coho are frequently associated with thermocline or frontal water.

In the Lake Ontario thermal-front study, Coho catch per unit effort was higher in the spring thermocline than outside frontal water.

For an angler building a mixed-species spread, the thermocline is therefore a logical place to begin searching for Coho.

But keep some coverage above and below it.

Coho can move, and the bait may not sit exactly in the temperature break.

Chinook often provide the wider vertical target

Chinook are exceptionally mobile.

Lake Ontario telemetry found summer Chinook used a broader vertical and thermal niche than lake trout and accumulated much larger vertical movements through the day.

That gives Chinook the ability to exploit forage at several levels.

You might catch one below your main Coho program and another considerably higher shortly afterward.

This is why a Chinook spread usually benefits from covering water rather than concentrating immediately at one exact depth.

A generalized summer stack

A useful starting picture looks something like this:

Upper water: steelhead opportunity.

Upper to middle temperature break: steelhead and Coho.

Around and across the thermocline: Coho and Chinook.

Below the break: Chinook, with lake trout increasingly likely as you move colder and deeper.

These zones overlap heavily.

They are not species boundaries.

Bait can rearrange the stack

The biggest reason the pattern changes is forage.

Alewife distribution can change with temperature, plankton and time of day. Lake Ontario research observed many alewife moving upward near dusk.

When bait moves, predators can follow.

A high Chinook is not violating a rule.

It may simply be feeding.

The same applies to a steelhead encountered deeper than expected.

How to set a mixed-species trolling spread

Start broad.

If your thermocline is around 60 feet, you might want presentations well above it, around it and below it rather than stacking everything within a five-foot band.

The exact setup depends on how many rods you can legally and safely run.

The principle is what matters.

High lines test the steelhead and Coho zone.

Middle lines test the break.

Deeper lines test Chinook and colder water.

Then use bites to compress the spread.

What repeated bites tell you

One fish can be random.

Three bites from the same 15-foot band are information.

If high rods repeatedly fire, move another presentation up.

If the only action comes from deep Chinook gear, stop wasting half the spread in empty water.

Species tendencies help you start.

The day's fish tell you how to finish.

Use species behavior to interpret sonar cautiously

A large deep mark is not automatically a lake trout.

A mark above the thermocline is not automatically steelhead.

Chinook can make extensive vertical movements, and species overlap is substantial.

Use sonar to choose fishing depths, not to identify every individual fish.

Sources

• Lake Ontario spring thermal-front study.
• Lake Ontario Chinook and rainbow trout catch-distribution study.
• Chinook and lake trout telemetry research.