Gulf oil spill: Many sea turtles drowned since gusher began

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It has been an exhausting and depressing detective enterprise, trying to establish how hundreds of sea turtles died before washing up on the shores of the Gulf of Mexico since the Deepwater Horizon oil spill.

Now it appears that oil was not the direct cause for many of the turtles that died in the first days after the spill began. Rather, early necropsy findings show that 21 of 40 intact turtle carcasses examined showed signs of drowning, or aspiration of sediment from the seafloor, according to Barbara Schroeder, national sea turtle coordinator for the National Marine Fisheries Service.

That suggests the turtles could have become caught in shrimp nets during the special fishing season, which opened in the immediate aftermath of the spill. But investigators also will try to determine whether a toxic algae bloom could have paralyzed the turtles and caused them to drown -- a somewhat less likely prospect, since no toxic blooms known to be dangerous to turtles have been found in the area.

After the death of large numbers of sea turtles in shrimp nets in recent years, shrimpers have been required to open an escapement device in their nets to allow turtles to swim out safely. But turtle researchers fear that some fishermen may have closed their nets in the rush to catch as many shrimp as they could before fishing grounds were closed off with the rapidly spreading oil spill.

More will be known when researchers complete their toxicology tests. Necropsies are yet to be conducted on turtles that washed up more recently. Oil may have been a bigger factor there, researchers say. And the impact of oil in the water and in turtles’ food sources also is yet to be determined.

Full story: Gulf fishing nets, not oil, may be culprit in initial sea turtle deaths

--Kim Murphy