Even with gusty winds pushing around and mixing up the water at the San Luis Reservoir in Merced County, it was still easy to make out the tint of blue-green algae on the water's surface Thursday. State water officials say the algae has become toxic, urging everyone not to touch it or eat fish caught there. It was a warning that came just in time for a Modesto couple who caught a fish at the reservoir Wednesday. They were planning to cook it Thursday night. "If the fish is no good, I would advise people not to eat it," said fisherman Asuncion Olviedo. The Department of Water Resources says algae is always present at San Luis Reservoir but for reasons scientists have yet to figure out, it has turned toxic. Contact with the water can cause flu-like symptoms, including rashes, vomiting and diarrhea. "And for unknown reasons, under certain conditions, they start to free toxins," said Tanya Veldhuizen with the DWR's Environmental Assessment Branch. Olviedo said Wednesday, when it was not as windy, the algae buildup at the reservoir was the worst he has ever seen. "We've been going to that lake for 30 years and I've never seen that much in the water," he explained. Water at the reservoir is static, allowing the algae to collect. State water officials believe the water at the reservoir could remain toxic for the next few months. They said they're going to be testing it weekly until it's safe again.