Arizona Game and Fish Investigates Mass Fish Deaths at Two Yuma Lakes

Dead fish have turned up at both Martinez Lake and Ferguson Lake, and Arizona Game and Fish Department investigators have yet to identify a cause, after ruling out the two most common explanations: disease and golden algae.

The department confirmed it is actively investigating the mass die-offs at the two lakes, which sit along the Lower Colorado River roughly 60 miles north of Yuma within and adjacent to the Imperial National Wildlife Refuge. Ferguson Lake, reachable only by boat at mile 57.5 of the Colorado, lies just upstream from Martinez Lake. Together, the pair rank among Yuma County's most productive freshwater fishing destinations, drawing anglers year-round after largemouth bass, striped bass, catfish, crappie, and walleye.

The golden algae ruling is notable. The microscopic toxin has repeatedly devastated fish populations at other Arizona lakes, including Saguaro, Canyon, and Apache lakes in the Salt River chain, where mass die-offs in 2022 and 2024 killed tens of thousands of fish. Golden algae produces toxins lethal to gill-breathing animals but has no known adverse effects on humans. Water quality samples taken at the Yuma-area lakes have not confirmed its presence, nor has any identifiable pathogen emerged from testing so far.

With conventional causes eliminated, the department is appealing to the public. Anyone who observed unusual activity near either lake, including signs of chemical runoff, discolored water, or other disturbances, is encouraged to contact Arizona Game and Fish with tips as the investigation continues.

The simultaneous die-offs at two connected water bodies adds urgency to the inquiry. Martinez and Ferguson lakes share the same Colorado River corridor, meaning a common upstream or systemic trigger cannot yet be discounted. The investigation remains open.