The California Department of Fish and Wildlife (CDFW) is urging anglers and other recreational water users to be vigilant about checking for harmful freshwater algal blooms (HABs) while out enjoying California’s lakes, reservoirs, rivers, streams and creeks this year.

Algae and cyanobacteria, the organisms that cause HABs, have existed for billions of years as essential components of freshwater ecosystems. But when certain conditions accelerate their growth – warm temperatures, stagnant water flows and excessive nutrients – they can multiply very rapidly creating “blooms.” These blooms can produce toxins and taste and odor compounds that pose health risks to humans and animals. When blooms pose a risk, they are referred to as harmful algal blooms or HABs.

These blooms pose risks to the health and safety of people and pets drinking the water and recreating in water bodies affected by blooms. Children and pets, especially dogs, are particularly susceptible to HABs because of their smaller body size, increased potential to swallow water while swimming and tendency to stay in the water longer. Dogs tend to lick their fur afterward, increasing their risk of exposure and illness.

Symptoms of HAB-related illness in people and animals are available at the California HABs portal human health and domestic animal pages, the Centers for Disease Control and Prevention (CDC), and by contacting the California Poison Control Center (1-800-222-1222). If you, your children, or your pet experience these symptoms after potential HAB exposure, contact your doctor or veterinarian.

These toxins also can accumulate in fish and shellfish to levels that pose threats to people and wildlife. Specifically, these chemicals accumulate in the guts of fish and in shellfish. For this reason, only cleaned fish fillets (no consumption of fish guts) and no shellfish consumption is recommended if a HAB is present and an advisory is posted at the “Caution” or “Warning” level. If a “Danger” advisory is posted, no water contact or fish consumption is recommended.

CDFW urges anglers and others to practice the following Healthy Water Habits when visiting California’s waterways:

Heed all instructions on posted advisories if present.

Avoid algae and scum in the water and on the shore.

Keep an eye on children and dogs.

If you think a HAB is present, do not let pets and other animals go into or drink the water, or eat scum/algal accumulations on the shore.

Don’t drink the water or use it for cooking.

Wash yourself, your family and your pets with clean water after water play.

If you catch fish, discard the guts and clean fillets with tap water or bottled water before cooking.

Avoid eating shellfish if you think a HAB is present.

Report any suspected or confirmed algal bloom and any related human, animal illness.