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Bait fish hold key to monitoring gulf oil spill effects, conference concludes

SARASOTA — One way to keep tabs on the real impact of the Deepwater Horizon disaster on the Gulf of Mexico, a scientific conference decided Tuesday, is to watch what happens to the lowly bait fish: the menhaden, the mullet, the sardines.

The deaths of dolphins and sea turtles due to the oil spill have garnered a lot of headlines. And there are concerns the spill may push sharks and bluefin tuna to the brink of extinction.

But they're not the basis of the gulf's food chain.

On the other hand, "the bait fish are so important to the whole ecosystem that if something happens there, it will have a cascading effect right up to the top predators," said William Hogarth, dean of the college of marine sciences at the University of South Florida.

The two-day conference at Mote Marine Laboratory in Sarasota bore an unwieldy name: "Oil-Induced Trophic Cascades in the Gulf: Exploring Impacts, Research Needs and Management Responses." But it had a straightforward and urgent mission: crafting a long-term strategy for catching and managing any major ecological shifts likely to result from the Deepwater Horizon disaster.

Although the well has been killed and the story has faded from the national consciousness, oil is still present in the gulf and some of its impacts are just now showing up.

Last week, for instance, scientists found dying corals on the bottom, several miles from the site of the spill, surrounded by a brown substance that they believe is oil mingled with mucus from the corals. Corals are essential habitat for fish, snails, crabs and other species.

The fact is, when the spill occurred "we got caught with our pants down," said Mote fisheries scientist Aaron Adams. Now, everyone's scrambling to figure out what the impact is without having a lot of data on what the gulf was like prior to the spill, he said.

The group gathered for the Mote conference, co-sponsored by USF and the National Wildlife Federation, hopes to learn from the example set by the 1989 Exxon Valdez disaster in Alaska. Four years after the tanker spilled oil that contaminated Prince William Sound, the sound's herring fishery collapsed.

There were signs in scientific data that the collapse might occur but no one picked up on it in time, explained Mote vice president Michael Crosby. So 40 experts on life in the gulf —- fisheries biologists, state and federal officials, even commercial fishermen — sat down Monday and Tuesday to hash out what everyone should be watching in the gulf.

The group endorsed the idea of creating a center to coordinate and analyze all the data coming out of the Gulf of Mexico, Crosby said.

Next year's fishing will give an inkling of what happened, said Mitchell Roffer, a fisheries expert who runs a popular fish-forecasting service, but "you'll have to wait a couple more years to see if the population suffers more consequences."

Although the spill stayed in the northern gulf, the impacts could be far more widespread. Adams pointed out that crabs tagged south of Sarasota in oil-free Charlotte Harbor were found to migrate to the Florida Panhandle, where oil did wash ashore.

Both Hogarth and John Hammond, regional executive director of the National Wildlife Federation, mentioned that some of the data that's been gathered about the spill's impact has yet to be made public.

USF's first research trip after the spill gathered samples that were turned over to the federal government for use as evidence in the case against the companies blamed for the rig's April 20 explosion. So far, he said, the government has not shared the results.

"There's been a lot of data that's gone into the system that we have not seen," Hogarth said.

One of the questions the group tackled was whether reports of sharks swimming away from the oil slick and feeding instead in near-shore areas would affect the population of fish in those areas. However, Crosby said, shark experts said that the gulf's shark population is in such terrible shape already that it probably didn't hurt anything.

On the other hand, he said, the spill could be the tipping point for some of those already-stressed shark species to push them sliding down to the oblivion of extinction. Another species that could face a similar fate: Atlantic bluefin tuna.

"It's one of the most magnificent and economically important species in the world, and it is in bad shape," Hogarth said.

The conference organizers will produce a formal report on their findings in January, Crosby said.

Craig Pittman can be reached at craig@sptimes.com.

Bait fish hold key to monitoring gulf oil spill effects, conference concludes 11/09/10 [Last modified: Tuesday, November 9, 2010 8:21pm]
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