Trout Fishing Big Lakes, Part 1: Finding Fish

Written by: Jim Elias, Fish Mammoth Guide Service 

I’ve been guiding on Lake Crowley in the Mammoth Lakes region of California for more than a decade, and in that time, I’ve learned a lot about how to find trout in these large still waters and how to catch them on fly–even during the heat of summer. In this two-part series, I will first discuss strategies for finding fish, followed by a second chapter highlighting specific techniques for presenting flies once you’ve identified a likely spot.    

Keeping Cool

Fly-fishing summer still waters can be an intimidating prospect for most anglers, particularly if you’re used to fishing in rivers. Finding trout stacked up in a current seam is one thing, but finding fish on a 5,000-acre lake is a bit more complicated. 

During the heat of summer, bottom temperature is the single most important variable to consider when searching for trout in lakes. It’s not uncommon to see midday surface temperatures well into the upper 70s in July and August, forcing trout to actively seek out colder water once the sun rises. That often means moving down to greater depths throughout the day, but trout can also be found near coldwater inlets, or hovering around submerged coldwater springs, as the surrounding lake warms up. 

A regular stream thermometer won’t cut it when you’re trying to check the bottom temperature, since it will be showing the warmer reading near the surface by the time it’s fully retrieved. I suggest using a “min-max” style thermometer, which will record both the lowest and highest temperature throughout the water column.  

Keep in mind that the warm surface water will stress trout, so play them quickly, and get them in and out of the net as fast as you can, so they can return to the cooler depths.

Finding the Food

The next variable to consider when searching for stillwater trout is the availability of food, especially during summer months when feeding activity is usually highest. You’re looking for any signs of their favorite meals, including (but not limited to) insect species such as chironomids, Callibaetis, and damselflies.  

Chironomid hatches are usually strongest here in the mid-morning, and if these large midges are actively hatching, you will see empty shucks on the water on calm days. If it’s windy, however, the bugs on the bottom will know based on changes they can detect in the light shining down from the waves above, and they’ll wait to hatch until the wind calms down. 

Generally, Callibaetis will be flying high above you, so look up every now and then to see what’s hovering around, you might be surprised by how many you see.

Damsels are pretty easy to spot, given their distinctive, bright-blue bodies. They require some sort of structure to climb out of the water to hatch, including weeds, rocks, downed trees, anchor lines, or just about any floating debris.

For measuring water temps or looking for signs of life on still waters, it helps to have a motorboat equipped with a fish-finder capable of displaying depth, temperature, GPS position, bottom contours, and suspended fish all at the same time. But that doesn’t mean boatless anglers are out of luck. Some smaller lakes are more forgiving, and can be effectively fished from a float tube, stand-up paddle board, or kayak (particularly if you’re able to equip it with a fish-finder) without much risk. However, Lake Crowley–and many other large impoundments like it–can generate 4-foot waves surprisingly quickly when the wind kicks up, so be sure to choose your vessel accordingly. 

Jim Elias is owner and operator of Fish Mammoth guide service in Mammoth Lakes, California.