UPPER KEYS -- It's too soon to tell whether the large fish kill caused by this month's heavy cold snap will have a long-term impact on the Florida Bay fisheries, according to the chief biologist for Everglades National Park.

But a local Audubon biologist, who is also a licensed captain, says several days of taking stock of carcasses on the water has left him plenty concerned.

"I think this will have an effect on the fishery for many years," said Pete Frezza of Audubon. "That's just the extent of it from the amount of dead fish we're seeing in the water."

Two weeks of subnormal temperatures killed off fish in both the freshwater and saltwater environments of South Florida.

"The bottom line is we have observed widespread fish kills," said Dave Hallac, the chief Everglades biologist. "Everywhere we look we are seeing them."

Between Jan. 8 and Jan. 12 the Florida Fish and Wildlife Commission's fish kill hotline received 13 calls from the Keys. Callers reported dead species big and small.

One caller alone reported dead pilchard, red grouper, pinfish, shad, yellow grunt, sardines, herring, greenback, puffer fish, silver mullet, shovelnose shark and snapper off Tavernier on Jan. 11.

Some of Florida Bay's most popular gamefish weren't spared either.

On Jan. 15, the FWC issued an executive order eliminating this year's spring snook season. It also closed the tarpon and bonefish fisheries to harvesting until April. However, catch-and-release fishing for those species will be permitted.

"Extending the snook closed season and temporarily closing bonefish and tarpon fishing will protect surviving snook that spawn in the spring and will give our research team time to evaluate the extent of damage," FWC Chairman Rodney Barreto said in a prepared statement.

Mike Larkin, a doctoral candidate at the University of Miami's Rosentiel School of Marine and Atmospheric Science, said that with the assistance of South Florida fishing guides he collected 163 dead juvenile bonefish last week. That amounts to less than 1 percent of the region's estimated 300,000-strong bonefish population, but Larkin said the die-off was likely more widespread than he has been able to document.

"I guess the concern is the unknown part," he said. "We're finding them in the flats. But we don't know how many are in the mangroves or drifted out to sea.

Meanwhile, local kayaking guide Garl Harrold said even the live fish he saw last week in the waters of Everglades National Park were rendered defenseless by the cold.

"I could reach down and pluck live fish out with my bare hand," he said.

Still, there is good news despite the die-offs. For one thing, the cold likely didn't have any impact on South Florida's wading bird populations, according to Karen Dyer, the Audubon field worker responsible for monitoring roseate spoonbill nesting.

Also, exotic species like the Mayan cichlid and the African jewel fish, which have thrived in Glades waters, were hit especially hard by the cold weather.

"That's actually not so bad," Hallac said.

The Everglades National Park biologist emphasized that this month's cold weather was a natural event, and that the fish die-off it caused, while unpleasant to people, is natural to the Everglades ecosystem. He added that he doesn't have enough information to know what impact, if any, the events will have on the fisheries in the coming months and years.

"I wish I had an X-ray machine that could tell me how many live fish there are in the bay compared to dead fish," Hallac said.

Frezza, though, said that while the fish kill was a natural event, it was one the occurred in an environment that has been heavily degraded by human activity over many decades.

"We should use this as a signal or a sign to be real good about conservation," he said.

rsilk@keysnews.com