A Famous Arizona Fishing Lake Has Been Closed Indefinitely After Almost Every Fish Died

San Carlos Lake’s collapse shows how fast stressed reservoirs can turn lethal.

There is a lake in eastern Arizona where the fish once drew anglers from across the state. Now the shoreline of San Carlos Lake is covered with their bodies, and it seems they all died in a single wave.

Along the receding shoreline of the eastern Arizona reservoir, dead largemouth bass, black crappie, bluegill, and catfish now rot in the desert heat. Officials closed the lake indefinitely on June 5 after what they described as a near-total collapse of its fish population.

A Reservoir’s Limit

The San Carlos Recreation and Wildlife Department said the lake would remain closed “until further notice” because decomposing fish may pose health risks to visitors.

“Recent drought conditions, combined with water releases from the dam, have resulted in a major fish kill affecting approximately 100% of the fish population within the lake,” the department wrote on Facebook.

The agency banned fishing, harvesting, or possessing fish from the lake, along with shoreline recreation in affected areas.

San Carlos Lake sits on San Carlos Apache tribal land and was created by the Coolidge Dam on the Gila River in 1930. It has long been marketed as a fishing destination, with 254 kilometers (158 miles) of shoreline and a history of record-size warmwater fish.

But the lake was built first for irrigation. During dry years, water releases for downstream agriculture can pull the reservoir down to dangerous levels.

Severe drought and required releases from Coolidge Dam left fish packed into shallow, warming pools. Warm water carries less oxygen than cold water, and crowded fish consume it quickly. Algae and rotting organic matter can drain away what little oxygen remains.

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When oxygen in the water crashes, fish suffocate.

How a Mass Fish Die-off Unfolds

A fish kill sounds sudden, but the ingredients often build for weeks or months.

As a lake shrinks, its water warms faster. Stagnant water allows algae to spread. During the day, algae can add oxygen through photosynthesis. At night, algae consume oxygen. When algae die, bacteria break them down and use even more oxygen.

Usually, fish are last in line and their population can collapse fast during the last stage of reservoir degradation.

In San Carlos Lake, the die-off appears to have hit nearly every species in the reservoir. Local images published by the Gila Herald and Phoenix-area television showed carcasses scattered across exposed mud and shallow water.

The Arizona Game and Fish Commission has warned in past reports that fertilizer runoff can feed algal blooms, which can lower dissolved oxygen and stress or kill aquatic life. Some algae can also produce toxins, although officials have not said toxins played a role here.

Officials have not yet released a full scientific analysis of the latest San Carlos event. The public explanation so far points to drought and dam releases as the main trigger.

Not the First Rodeo

The collapse shocked anglers, but San Carlos Lake has faced this danger before.

The reservoir has filled only a few times in its nearly 100-year history. It has dropped to near-empty or “dead pool” levels roughly 20 times since 1930. The Gila Herald called the latest die-off “a recurring scar for San Carlos Lake.”

A major fish kill occurred in 2018, when the reservoir dropped below 1% capacity. During the 1976–77 drought, an estimated 5 million fish died, and the ecosystem took years to recover.

The same cycle has played out for decades: drought reduces the lake, water releases lower it further, and fish become trapped in warm, oxygen-starved pools.

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Warning Signs

San Carlos Lake is a local disaster, but its causes reach far beyond one reservoir.

Across the US, drought, heat and water withdrawals increasingly strain lakes and rivers. Low water can raise temperatures, concentrate pollutants, and make oxygen crashes more likely. In other regions, nutrient pollution can drive algal blooms even when water levels appear stable.

The warning signs look different from place to place. Lake Mead and Lake Powell face shrinking water supplies. The Great Salt Lake is growing saltier as it contracts. Lake Erie continues to struggle with toxic algal blooms, while Lake Tahoe is under pressure from drought and warming. Each system is different, but they point to the same broader problem: lakes can change quickly when climate pressure collides with heavy human use.

At San Carlos Lake, the immediate concern is public safety. Rotting fish can foul the shoreline and water, and officials have urged visitors to stay away.

For now, the lake once promoted as a fisherman’s paradise is covered with dead fish.