Green sea turtle nests have long been a rare sight along Florida's Gulf Coast, their numbers so few that state experts request photos of each one to ensure that volunteers identify them properly. Two years ago just 19 of the endangered green turtles nested on the beaches from Manasota Key to Anna Maria Island. This year that number jumped to 104, an increase sea turtle experts describe as remarkable. And it's just a fraction of a much larger population explosion statewide. Once considered a prized delicacy and hunted to the point of population collapse, green sea turtles may be one of Florida's greatest conservation success stories in recent years. Greens are having a historic nesting year across the state, and Sarasota County is the main hotspot for the turtles on the Gulf Coast. Experts say the number of nests statewide is on track to more than double this year, on a scale that is rare among endangered creatures. The phenomenon is more pronounced on Florida's east coast, which has a much higher concentration of green turtles. The most important nesting grounds in North America for the turtles — the Archie Carr National Wildlife Refuge south of Melbourne — already has more than 13,000 green turtle nests this year, more than double the record from two years ago and an extraordinary jump from the 50 nests found at the refuge 30 years ago. “It's astounding,” said Blair Witherington, a sea turtle expert with the Florida Fish and Wildlife Research Institute. Scientists often are careful about interpreting fluctuations in wildlife populations, but Witherington said in this case there is little doubt the turtles are experiencing a dramatic comeback.