What algal blooms are and why they matter to anglers
An algal bloom is a rapid growth of algae in water, usually triggered by warm temperatures, excess nutrients, or stagnant conditions. Some blooms are harmless, but others produce toxins that can sicken people and animals. If you fish in water with a visible bloom—thick green, blue-green, or reddish scum on the surface, or murky water with an unusual smell—you need to take precautions before you fish, clean your catch, or let anyone eat what you catch.
Not every algal bloom is toxic, and not every toxic bloom affects fish the same way. But because you cannot tell by looking whether a bloom is dangerous, the safest approach is to treat all visible blooms as a potential health risk. The water itself may be unsafe to touch, and fish from that water may carry toxins in their flesh or organs.
State fish and wildlife agencies post bloom warnings when they detect toxins in specific bodies of water. Check your state's website before you go, and ask at the boat launch or local bait shop if you are unsure whether a water body has an active warning.
Key Takeaways
- Avoid fishing in water with visible algal blooms, or fish only if your state has confirmed the bloom is non-toxic.
- If you do fish in bloom-affected water, do not let the water touch your skin or mouth, and wash your hands and gear thoroughly afterward.
- Fish from bloom-affected water may contain toxins in their organs and flesh, and cooking does not destroy these toxins.
- Check your state fish and wildlife agency's website for current bloom warnings before you fish.
- If you or anyone who ate your catch develops nausea, vomiting, diarrhea, or neurological symptoms within hours or days, seek medical attention and mention the bloom.
When it is safe to fish in bloom-affected water
Your state's fish and wildlife agency monitors water bodies for toxic algal blooms and posts warnings when toxins are detected. If your state has tested the water and confirmed that the bloom is non-toxic, fishing is generally safe—though you should still avoid direct contact with the water and rinse off afterward.
Some states distinguish between blooms that are toxic to humans and blooms that are toxic to pets or livestock. A bloom may be safe for you to fish in but unsafe for your dog to swim in, or vice versa. Read the specific warning for the water body you plan to visit, not just the general bloom alert.
If no warning has been posted but you see a visible bloom, contact your local fish and wildlife office or the water body's management agency before you fish. They can tell you whether the bloom has been tested and what precautions to take.
Protecting yourself while fishing
If you fish in water with a visible bloom, keep the water off your skin and out of your mouth. Wear long sleeves and pants if possible, especially if you wade. Do not splash water on your face, and do not let children play in the water.
Rinse your hands, arms, and any exposed skin with fresh water as soon as you leave the water. Wash your clothes and any gear that touched the water—rod handles, tackle boxes, nets—with soap and water. If you wore waders or a wetsuit, rinse them inside and out before you take them off.
If you inhale mist or spray from the water, move to fresh air immediately. If you develop a cough, wheezing, or throat irritation within hours, seek medical attention and mention the bloom.
Handling and preparing fish from bloom-affected water
Fish from bloom-affected water may contain toxins in their organs, gills, and flesh. Cooking, freezing, and cleaning do not destroy these toxins. If you keep fish from a water body with a bloom warning, you need to know which parts are safe to eat.
Most state fish and wildlife agencies issue specific guidance for each bloom: some say not to eat fish at all, others say to remove the organs and gills and eat only the muscle tissue, and still others say the fish are safe if prepared a certain way. Check your state's website for the exact guidance for the water body where you fished.
If no specific guidance exists, the safest choice is not to eat the fish. If you do keep and prepare fish from bloom-affected water, wear gloves while cleaning them, and wash your hands, utensils, and cutting surfaces thoroughly with soap and water afterward. Do not let children handle raw fish from bloom-affected water.
Recognizing bloom warnings and where to find them
Your state fish and wildlife agency, your state health department, or both maintain lists of water bodies with active algal bloom warnings. Most states post these on their websites and update them weekly or more often during bloom season.
Some states use the term "harmful algal bloom" or "HAB." Others call them "blue-green algae" or "cyanobacteria blooms." The name varies, but the warning means the same thing: toxins have been detected in that water.
Warnings are usually organized by county or by water body name. Search for your state's name plus "algal bloom" or "harmful algal bloom" to find the current list. If you fish in a different state, check that state's website before you go.
What to do if you or someone else gets sick
Algal bloom toxins can cause nausea, vomiting, diarrhea, abdominal pain, headache, muscle aches, and in severe cases, neurological symptoms like tingling, numbness, or confusion. Symptoms usually appear within hours to a few days of exposure or eating contaminated fish.
If you or anyone who ate your catch develops these symptoms, seek medical attention. Tell the doctor or emergency room staff that you were exposed to or ate fish from water with an algal bloom, and describe which water body and when. This information helps the medical team treat you correctly.
You can also report the bloom to your state health department or fish and wildlife agency. They use these reports to track blooms and issue warnings for other anglers.
Frequently Asked Questions
Can I eat fish from water with an algal bloom if I cook it thoroughly?
No. Algal bloom toxins are not destroyed by heat, freezing, or any cooking method. The only safe approach is to follow your state's specific guidance for that water body, which may mean removing organs and gills, eating only muscle tissue, or not eating the fish at all.
What does an algal bloom look like?
Blooms often appear as thick green, blue-green, or reddish scum on the water surface, sometimes with a paint-like or oily appearance. Some blooms make the water murky or cloudy. Many have a strong, unpleasant smell—musty, earthy, or like rotting plants. If you see or smell this, assume the bloom may be toxic.
Is it safe to swim or wade in water with an algal bloom?
No, unless your state has confirmed the bloom is non-toxic. Even then, minimize skin contact and rinse off immediately afterward. Do not let children or pets swim in bloom-affected water without checking your state's specific warning first.
How do I learn about a specific lake or river has an algal bloom warning?
Search your state's fish and wildlife or health department website for "algal bloom" or "harmful algal bloom." Most states post current warnings by county or water body name and update them regularly during warm months.
What if I already ate fish from water with a bloom and did not know about it?
Most people who eat fish from bloom-affected water do not get sick. If you develop nausea, vomiting, diarrhea, or other symptoms within a few days, seek medical attention and mention the bloom and the water body. The doctor can advise you based on your symptoms.