There are hundreds of types of "blue green algae"
Actually there are thousands of types (species) of blue-green (BGrn) algae (aka Cyanobacteria)..
Testing positive for BGrn can be two ways" Identification and a toxicity test. The species of Cyanobacteria that can produce toxins do not always produce toxins. Water quality seems to determines when the toxin is produced.
Fish flesh (fillets) gathered from water that has dense Cyanobacteria bloom will likely have an off flavor - distasteful.
This from AI if you can believe it.
Eating fish from waters with cyanobacteria (blue-green algae) blooms carries unknown risks, though risks are reduced if precautions are taken. Toxins often accumulate in organs, not fillets. The safest practice is to avoid eating fish caught in, or near, scummy or discolored water to avoid potential liver or neurological damage, say the Centers for Disease Control and Prevention.
