During the 40 years Don Walker has fished at Blue Mesa Reservoir he's caught plenty of big lake trout, but none measured up to the one he caught on May 23.Walker, 61, now holds the record for the biggest lake trout caught in Colorado: The fish weighed 50 pounds, 5 ounces, and measured 44 1/4 inches long.The record lake trout, also known as a Mackinaw, weighed nearly 4 pounds more than the previous record lake trout caught in 2003 that weighed 46 pounds 14 ounces and measured 42 1/2 inches long."I've been fishing over there for a long time, so when it hit I knew I had a big fish on," Walker said from his home in Florence, Colo.Walker and his wife, Paula, were fishing from a boat near Soap Creek in about 40 feet of water. He used a tube jig and was bouncing the lure on the bottom. The technique is known as "jigging."The temperature of the water at the surface was 53 degrees. Walker explained that lake trout fishing seems to be the best when the surface water temperature is between 50 degrees and 55 degrees.With his graphite rod rigged with 12-pound test line, Walker fought the fish for 25 minutes before bringing it up to the boat."You have to play a fish like that just right or you'll break the line. The rod was bent double," Walker said.His wife netted the fish when it got near the boat."You need a lot of help with a fish like that, you need a good netter. Paula did a good job," Walker said.Ironically, the man who held the record previously was fishing from another boat a short distance away. Larry Cornell, of Pueblo, who is also Walker's brother-in-law, watched as the new record Mackinaw was brought to the surface.Walker took his fish it to the Gunnison office of the Colorado Division of Wildlife for an official weigh-in and measurement. A DOW wildlife officer verified that the fish set the new record.Walker plans to have his big fish mounted.His tip for catching big Mackinaws: "We've sat out there many days and haven't caught any fish. You've got to have a lot of patience and be at the right place at the right time."Blue Mesa Reservoir is one of Colorado's most productive fisheries. The water warms up more than other higher-elevation reservoirs and that encourages abundant growth of microorganisms that provide a food source for fish. Kokanee salmon, brown trout and rainbow trout thrive in the lake. In turn those fish provide a food source for lake trout, which are a predator species.Blue Mesa Reservoir is located about 10 miles west of Gunnison in south central Colorado.