A thermocline develops in most lakes, ponds and reservoirs in the West. However, most of the time it doesn’t form until early to mid-summer as warmer water floats on top of the cold water. By mid-summer, that middle layer -- the thermocline -- becomes more visible and stands out as a greater fish-holding zone. Algae and other zooplankton hide out in this zone, while pond smelt, shad, minnows and other baitfish stay near the upper and lower layers of the thermocline. Baitfish and game fish are commonly found in the thermocline throughout the warmer months, partially because of ideal water temperatures and also because their food is here.

In summer, you’ll increase catch rates by trolling spoons, stickbaits, spinners and night crawlers through the thermocline. It’s also effective to drift salmon eggs, dough baits, worms, crickets and grasshoppers.

Locating the thermocline isn’t as challenging as it might seem. Most reservoirs take daily or weekly readings to keep track of it, and the officials often make their findings public. High-end fish finders can also indicate where the zone is. Your best bet may be to call local marinas, tackle shops and lake offices to ask how deep the thermocline is. Most can give you up-to-date information, which will help you catch more trout.

If you are a troller, you’ll probably need downriggers or lead-core line to fish the thermocline, which wanders from 30 to 150 feet or deeper, depending on water temperature, elevation, recent wind and weather patterns, the size of the lake or reservoir and its depth.

The thermocline can vary by week. From July through September, this will likely be the zone you’ll want to target for the best trout-fishing action.

When working the thermocline, experiment. Try running some lures near the top of it, others in the middle and a few towards the bottom. Once you discover where the fish are most active, then it’s safe to concentrate your efforts close to that depth.

3) TARGET TOP AREAS
During the summer, knowing where to fish is imperative. Regardless of what water you fish, there are certain locations that draw trout. These spots can differ from lowland reservoirs to high mountain lakes, but knowing where to target can mean success over failure.

Whether you’re fishing in an urban area, lowland reservoir, mountain lake or natural pond, two spots you’ll want to focus on during the heat of summer are inlets and outlets.

These areas serve to transport oxygen, food, cool water and nutrients into the lakes. Trout are naturally drawn to these sections.

“We don’t get a lot of summer rains in the West. But when we do, it brings a lot of nutrients in,” said Buzz Ramsey, a former Luhr Jensen designer who’s now in charge of freshwater fishing for Berkeley in the West.

“If you get a shower or a thunderstorm, you are going to want to fish the inlets.”

Oxygenated water almost always comes in with inlet water, but if you get a little extra push of water, the fish know, Ramsey said.

“They are often there anyway. But if you get that extra push of water, it’s going to bring more bugs and insects in.”

Whenever you fish in the summer months, target inlets. This can be achieved by tossing salmon eggs, night crawlers, spoons or spinners from the bank, or the same lures from a boat anchored offshore.

Springs are the most overlooked spot in all waters that harbor trout, but especially in high mountain lakes and natural ponds.

Most of these waters have springs. They can be small and hard to locate or they can be strong and highly visible. Often the easiest way to find a spring or upwelling is to look for bubbles. Lake operators should also know where these areas are.