"Diamond Lake may be the most productive lake in the state for trout food and quick-growing rainbows. Fish over five pounds are taken each year. People tend to think of Diamond as a trolling and bait-fishing lake, but you can also have great fly fishing action, depending on the chub activity. The Oregon Department of Fish & Wildlife poisoned unwanted fish in 1999. Healthy Williamson rainbow trout were reintroduced, which provided thousands of 18-to 20-inch brutes. Then, by the late summer of 2001, the illegally introduced tui chub population again grew out of control. This trash fish, up to four inches long, ate the microscopic zooplankton that normally keep the lake’s algae in check.
The uncontrolled bluegreen algae then dominated and released toxins that led to the lake’s closure. When this edition went to press, the lake was back to near normal with about 100,000 catchable fish planted each year, including chinook salmon, Eagle Lake rainbow trout, and about 15,000 two-pound rainbow trout. Types of Fish: Chinook salmon and rainbow trout, 10 to 24 inches, averaging one pound plus. This eTrail covers the "where, when, and how" to fish in this region. You'll get a full-page map and information on the known hatches, suggested equipment to bring, and the best flies to use."