Algae-Caused Fish Kills Confirmed At Saguro and Canyon Lakes

The Arizona Game and Fish Department (AZGFD) has confirmed golden algae toxin blooms as the cause of recent fish kills in both Saguaro and Canyon lakes.

When golden algae is the cause of a fish kill in one of the Salt River chain lakes (Saguaro, Canyon and Apache), varying degrees of fish kills are typically observed in all three of the lakes.  AZGFD staff recently collected water-quality samples at both Saguaro and Canyon, which confirmed golden algae as the cause of the fish kills.

At Saguaro Lake, AZGFD staff observed small numbers of dead and dying threadfin shad (less than 500), along with a handful of other species including largemouth bass, bluegill and catfish. At Canyon Lake, about 1,000 dead threadfin shad were observed; no other species were affected at that time.

Golden algae can produce toxins harmful to gill-breathing animals, such as fish. Similar golden algae-related fish kills have occurred in Saguaro, Canyon and Apache lakes since 2003. To date, no adverse health impacts have been noted for humans or non-gill-breathing wildlife that have come in contact with waters experiencing a golden algae toxin bloom.

In addition, select coves in Saguaro Lake appeared bright green in color, an indication of another type of algae present in high concentrations. Water samples confirmed a filamentous cyanobacteria Dolichospermum (formerly Anabaena) was also present in high concentrations. Dolichiospermum can release toxins that have been associated with health impacts on humans and pets. Click here to learn more information on human health impacts.

It is likely fish kills will continue in Saguaro, Canyon and Apache lakes over the next two months and range in severity. Occasionally, select coves in Roosevelt Lake are affected with minor fish kills, as well as the Salt River near the inflow to Roosevelt Lake. Salt River Project (SRP) will be doing its annual springtime swap to the Salt River, which is usually completed by late April.

With the influx of water, there is a chance the algae bloom will be flushed through the system and decrease the severity of the fish kill. Keep in mind several factors can determine the severity and duration of fish kills in all three lakes. AZGFD will continue to monitor the situation and provide updates as needed.