Contaminazione: dopo mucca pazza, ora "squalo pazzo" (18 ottobre)

Shark deaths off Florida a mystery
Usual suspects don’t appear to be the cause

Oct. 18 — Several hundred dead sharks have been washing up on beaches along the Gulf of Mexico, and officials are baffled by what’s causing their deaths. With no hard evidence to guide them, scientists are testing the sharks’ tissue to see if it holds clues that will help solve the mystery.

‘Why would these sharks be dead and the fish be alive?’
— SKIP FRANCK - Helicopter pilot who flew over area

  “WE REALLY have no idea,” said Jack Mobley, a wildlife biologist at Tyndall Air Force Base, Fla., where about 50 sharks, mostly blacktips as well as some Atlantic sharpnose, had washed up. “There needs to be tests done before that can be determined.”

  The sharks, which ranged up to 5 feet long, started showing up Monday in waters off the Florida Panhandle. Officials estimate between 200 and 300 sharks have died.

  Traces of blood reported on nostrils and gills of some sharks suggest that an infection might be the culprit, said Mike Brim, an ecologist with the U.S. Fish and Wildlife Service.

  Other theories include the lack of oxygen in shallow waters and dumping of shark carcasses by fishermen who sell the prized fins for food. The practice is banned in state waters, but continues nonetheless.

  Red tide, an algae bloom toxic to fish, is also a suspect, and it was reported in the area last week. The Florida Marine Research Institute is testing shark tissue for red tide, which gets its name from the fact that the water turns reddish when the bloom shows up.

  But if it was red tide, other species would have been affected as well, and that doesn’t appear to have happened.  “Why would these sharks be dead and the fish be alive?” helicopter pilot Skip Franck said after flying over the bay. “When we flew over, it was bubbling with fish.”


  Another theory is that seas have become such a toxic mess that diseases are becoming more common, affecting species at different times and on different scales.   Bruce McKay, a senior researcher for the nonprofit group SeaWeb, acknowledges that fish die-offs might be natural events, but he feels the litany of incidents over the last two years suggests otherwise. Writing recently in the journal Sea Technology, McKay cited these examples:

- More than 70 dead bottlenose dolphins were found dead along Florida’s far west coast last year.

- 225 harbor porpoise carcasses were found along mid-Atlantic shores earlier last year.

- An estimated 300 gray whales died along Pacific shores.

- California sea otters and Pacific Northwest orcas continued their mysterious decline.

- A large-scale sea urchin die-off occurred in Maine waters.

- Disease plagued lobsters in Long Island Sound.

- Black abalone off southern California have been decimated by withering syndrome, and red abalone is now being affected.

- New diseases have been noticed in Alaskan fur seals, California sea otters, and Florida manatees.

- Green sea turtles in Hawaii and Florida are suffering from a disease characterized by grotesque external tumors. Virtually unheard of before 1985, it recently appeared in loggerhead and olive ridley sea turtles in the Caribbean.

- Coral diseases are substantially reducing reef cover and biodiversity in parts of the Florida Keys. Disease was found at 26 of 160 monitoring stations in 1996. By 1998, 131 stations had diseased coral while the number of species affected rose from 11 to 31. New coral diseases have emerged there as well.

- The first reported epidemic of mycobacterium-induced sores in wild striped bass has hit the Chesapeake Bay. This disease is usually found in fish farms, McKay noted.


  “Very little is typically known about the underlying environmental changes and conditions that may be at the heart of these events,” he wrote. The potential factors, he added, include “dead zones” caused by nutrient run-off, red tide, human development, climate change and invasive species that bring in new diseases. McKay argues that most studies of die-offs are piecemeal and that more should be done to study these as a global problem. He’d also like to see stronger coastal protections.

  “Changes in agricultural practices involving massive reductions in fertilizer and pesticide use are required,” he wrote. “Coastal wetlands as natural filtering bodies need to be protected and restored.”

  We should also move away from fossil fuels and to renewable energy, he added, and industries should phase out harsh chemicals.

  “It should now be the time to focus attention on what our marine wildlife is telling us,” he concluded, “and the important task of ocean protection.”’s Miguel Llanos and The Associated Press contributed to this report.