An estimated 1 million dead fish were discovered yesterday in the lower Pocomoke River and one of its creeks. State officials believe it is the largest fish kill in Chesapeake Bay tributaries in a decade.
Scientists said they suspect low oxygen is responsible rather than Pfiesteria piscicida, the toxic microorganism that afflicted fish, watermen and the state fishing industry in 1997.
"The immediate indication is this is not Pfiesteria," Gov. Parris N. Glendening said. "There are no lesions, and there are no fish in distress."
Nearly all of the fish appeared to have died in a small Virginia tributary of the river called Bullbegger Creek, according to the Maryland Department of Natural Resources.
"The fish were all crammed, crowded into a small creek," said David Goshorn, a biologist with the department. "With the warm temperatures, the algae increases and it's very easy for large numbers of fish to consume all the oxygen and essentially suffocate themselves."
Test results from samples of water and fish will not be available until next week, he said. Because Virginia and Maryland share the Pocomoke River, and the fish were found in waters in both states, each is conducting tests. Calls to the Virginia Department of Environmental Quality were not immediately returned yesterday.
Since late June, fish kills have been confirmed in more than a dozen Maryland waterways and Baltimore's Inner Harbor. Earlier this month, after an estimated 200,000 yellow perch, menhaden and other small fish died in tributaries of the Magothy and Patapsco Rivers, state officials predicted an extended drought would result in more fish kills.
Even so, the size of the kill and its proximity to the Pocomoke River spot where Pfiesteria first made its appearance two summers ago concerns at least one person.
Jack Howard, a Shelltown waterman who assisted the state throughout the 1997 Pfiesteria scare, vividly recalls how the toxic microbe forced the closing of three waterways back then -- the Pocomoke and Chicamacomico rivers, and Kings Creek.
Howard discovered the first of the dead fish Sunday. At that time, he said, they numbered only 50 to 100, and he did not report his find to the state until Wednesday. When he accompanied a state biologist to the site early yesterday morning, he said he saw thousands of dead menhaden, although he declined to estimate how many.
"They were in piles and piles," Howard said.
He said he saw only two fish with lesions, sores he said were similar to those associated with Pfiesteria. Howard said many of the dead fish were in the middle of the mouth of the Pocomoke in water 20 feet deep, which he considered an unlikely spot for a fish kill caused by oxygen depletion.
"I'm pretty sure these fish didn't die of an oxygen deficiency, but I don't know," Howard said.
From the river banks in Shelltown last night, the most visible feature on the water was the thick haze clinging to it. Not a single dead fish was visible, not one bird diving to guzzle down morsels of menhaden.
"I'm not worried about it at all," said a waterman who lives within view of the spot and who did not want to be named. "We haven't seen any dead fish all year."
Health officials said yesterday there had been no reports from residents or watermen suggesting symptoms of Pfiesteria in the area.
And Goshorn called it "highly premature" to suppose Pfiesteria is responsible for the fish kill.
But as a precaution, the department shifted into "rapid response" testing for Pfiesteria, collecting water samples at six sites along the creek and the river, and sending them to seven laboratories, including the major Pfiesteria testing sites in North Carolina and Florida.
Besides the presence of Pfiesteria, the tests should reveal bacteria or parasites that might have killed the fish. Officials will also perform an analysis of data from three "hydrolabs" that constantly measure oxygen levels in the water.
"The one we're most interested in is as close as we could get to the epicenter of the kills in '97," said Goshorn.
Tests for the presence of toxins in the water also might be done, but only if there is evidence of chemicals in the water.
State fisheries biologists were to return to the Pocomoke before sunrise today, to further evaluate the waters for sick or dead fish.
Chris Guy and Timothy B. Wheeler contributed to this story.