Potential striped bass die off - AGFC

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Update on Norfork Lake Striped Bass Die-Off

 

District Biologists monitored the recent Striped Bass die-off at Norfork Lake from August 11-25, 2025, and want to share their findings while reassuring anglers that the fishery remains healthy and there are plenty of fish to catch.

As many of you know, these die-offs have occurred in past years, particularly during periods of high water. Starting in July, large Striped Bass seek refuge in the deep water (80-110 feet) near the dam to find tolerable temperatures and oxygen levels, which protects them from the warmer surface water. In high-water years, a combination of biological oxygen demand and hydrological factors rapidly depletes oxygen within this deep-water refuge, leading to fish mortality.

The die-off this year occurred between August 8 and August 25, with peak mortality observed from August 18-20. On August 18, dissolved oxygen in the deep areas of the lake fell below 1.5 mg/L, leading to the peak of Striped Bass mortality.  In total, 555 Striped Bass, 5 Hybrid Striped Bass, and 20 Walleye were collected and measured. The event primarily impacted larger, older fish, with collected Striped Bass averaging 28 inches.

By the final collection day on August 25, biologists found only a single Striped Bass, indicating the die-off had concluded as fish utilizing the deep-water habitat had either perished or relocated. This year's mortality was relatively moderate compared to previous high-water years like 2017 and 2019, when biologists collected 663 and 843 Striped Bass, respectively. However, the 2025 event occurred earlier than typical die-offs, which usually occur after Labor Day.

Historical data confirms these natural events don't harm long-term population health. Norfork Lake maintains a robust Striped Bass fishery, and anglers should expect excellent fishing to continue. The newly stocked fish and survivors will benefit from abundant forage produced by high water conditions, often leading to improved growth rates and exceptional fishing in the years ahead. Biologists will continue to monitor the fishery and provide updates as necessary.