GALVESTON, Texas _ It's graduation day Tuesday for some 1,100 Kemp's Ridley sea turtles, the most endangered sea turtle. Marine biologists hope the turtles, released into the Gulf of Mexico after being raised in captivity, will someday return to the Gulf's beaches to nest. Survival of the species is the goal. Tuesday's freedom for members of the species known as Lepidochelys kempi is the 10th annual turtle release, and experts still are waiting to see if the experiment to bolster the animal's population is a success. None of the 12,422 turtles raised and released by the National Marine Fisheries Service in Galveston since the so-called ``head start'' program began in 1977 has returned to the western Gulf of Mexico beaches to nest. ``You have to be patient to be a sea turtle scientist,'' Charles W. Caillouet, chief of the Life Studies Division at the service's Galveston laboratory, said Monday. This latest senior class spent its entire lifetime circumnavigating small circular tubs, one turtle to each container, stored in climate-controlled greenhouses. Early Tuesday, three truckloads of cardboard boxes carrying the 1-and 2-year-old turtles head to Port Aransas about 200 miles away, where they will be loaded on a boat and taken several miles into the Gulf off Padre Island. ``When that last turtle hits the water, it's like a lead weight has been lifted off our backs,'' said Tim Fontaine, a research fishery biologist. ``We've done our job.'' Fontaine has overseen the growth of the turtles since they were 3 to 5 days old, about the size of silver dollars and weighing less than an ounce. Today the year-old turtles weigh about 2{ pounds each. And for the first time this year, 98 2-year-old turtles weighing about 25 pounds each will be released. Biologists hope the more mature animals will stand a better chance of surviving. Scientists are looking for the answer to attract the turtle back to the western Gulf of Mexico beaches, its only known nesting area. Turtle eggs were taken a year ago to the North Padre Island beach and the hatchlings scurried across the beach into the water before they were captured and moved to Galveston. It's hoped when they reach sexual maturity, the turtles will return instinctively to the beach. ``That's the critical objective,'' Caillouet said. ``It's documented very clearly our turtles survive for a long time and mix themselves in with the natural stocks.'' Galveston-grown turtles marked with metal tags or special skin grafts or electronic and magnetic devices have been found as far away as Morocco, France and Newfoundland. The mystery, however, is what triggers the animal's nesting and a return to the Gulf. ``We don't know how long it takes for them to mature in the wild,'' Caillouet said. ``We would guess we are looking for 8 to 10 years for early maturity in the wild, but we really don't know.'' In the late 1940s, as many as 40,000 turtles nested in a single day near Rancho Nuevo, Mexico, about 200 miles south of Brownsville, Texas. Today, less than 600 turtles nest in the entire season from April through July or August, Caillouet said. There may be as many as 100 eggs incubating over 60 days in each nest. Upon hatching, the tiny turtles flee into the Gulf. The decline in population came as the beaches and turtles and eggs were exploited from the 1940s until the 1960s. ``That problem has been resolved, but we yet don't see any of the increase in the number of nesters,'' Caillouet said. ``So something's happening to the turtle at sea.'' Once they reach adult growth, the turtles only known natural predator is shark. ``They are the bulldogs of the sea,'' says Fontaine. ``They are a highly agressive animal.''