This New York Times piece isn’t so sure. An excerpt:

Despite an obvious suspect, oil, the answer is far from clear. The vast majority of the dead animals that have been found — 1,866 birds, 463 turtles, 59 dolphins and one sperm whale — show no visible signs of oil contamination. Much of the evidence in the turtle cases points, in fact, to shrimping or other commercial fishing, but other suspects include oil fumes, oiled food, the dispersants used to break up the oil or even disease.

And this on the shrimpers:

When Lt. Donald Armes of the Mississippi Marine Patrol heard about the rash of dead sea turtles littering the state’s shores, his first thought was not of oil but of shrimp boats.
“Right off the bat, you figure somebody’s gear was wrong,” he said recently, after patrolling for shrimpers in the Mississippi Sound, a few days before floating islands of oil forced officials to close it. By gear, Lieutenant Armes meant turtle excluder devices, which shrimp trawlers are supposed to have. Without them, trawls can be one of the biggest dangers for turtles, which can get trapped in the nets and drown. The devices provide an escape hatch. Another kind of shrimp net, called a skimmer, is not required to have an excluder device — instead, the length of time the skimmers can be dragged is limited by law to give trapped turtles a chance to come up for air.
When shrimp season began in Mississippi on June 3, the marine patrol inspected all the boats and found no violations involving the excluders, Lieutenant Armes said. But on June 6, 12 dead turtles were found in Mississippi in a single day. Similar spikes have occurred when parts of Louisiana waters were opened to shrimpers, and since most of the waters in the spill area have closed, the turtle deaths have subsided.
Shrimpers emerged as a prime suspect in the NOAA investigation when, after a round of turtle necropsies in early May, Dr. Stacy announced that more than half the carcasses had sediment in the airways or lungs — evidence of drowning. The only plausible explanation for such a high number of drowning deaths, he said, was, as he put it, “fisheries interaction.”
Environmentalists saw the findings as confirmation of their suspicions that shrimpers, taking advantage of the fact that the Coast Guard and other inspectors were busy with the oil spill, had disabled their turtle excluder devices.
The devices are so contentious that Louisiana law has long forbidden its wildlife and fisheries agents to enforce federal regulations on the devices. Last month, Gov. Bobby Jindal vetoed legislation that would have finally lifted the ban, citing the “challenges and issues currently facing our fishermen.” By contrast, Mississippi officials strengthened turtle protections by decreasing the allowable tow time for skimmers, posting observers on boats, and sending out pamphlets on turtle resuscitation.
Officials in both states say that turtles die in shrimp season even when shrimpers follow the law, from boat strikes and other accidents. They also say there have been far fewer shrimpers working since the spill, in part because many have hired out their boats to BP. That should mean fewer, not more, turtle deaths.
But there has also been illegal activity. In Louisiana, agents have seized more than 20,000 pounds of shrimp and issued more than 350 citations to commercial fishermen working in waters closed because of the oil spill. In Mississippi in June, three skimmer boats were caught exceeding legal tow times — one just hours after the shrimper had been given a handout explaining that the maximum time had been reduced, Lieutenant Armes said.
As for the piece of shrimp that Dr. Stacy found lodged in the turtle’s throat during the necropsy, it, too, pointed to shrimpers. A turtle is normally not quick enough to catch shrimp, Dr. Stacy said. Unless, of course, it is caught in a net with them.

More on this to come I’m sure.