While driving on the Cedar Point Causeway last week, Josh Pribanic thought he smelled death. He assumed it was the mufflehead flies, whose mass deaths this time of year often give off an unappealing scent. But when Pribanic went running the next morning along the Chaussee beach, he found his answer. “There were thousands of them, all along the beach,” Pribanic said. “They stretched from one end all the way down to Cedar Point.” Since early last week, tens of thousands of tiny rainbow smelt have washed up along the Chaussee’s beach, blanketing the shoreline with tiny fish carcasses. For the most part, the decomposing brown bodies of the fish — only a couple inches long and slightly thicker than a pencil — blend in with the sand. Jeff Tyson, the head biologist with ODNR’s Sandusky Fisheries Research Unit, described the situation as a “mortality event.” He said the smelt died from excessive stress related to spawning season. “It happens frequently,” said Tyson, whose department began studying the deaths early last week. “But we haven’t seen it in the west end of Lake Erie recently, because smelt numbers have been down.” Tyson said rainbow smelt have significantly declined in population in Lake Erie since the 1970s, which led to fewer mortality events in the Sandusky area. But in the last two years, the population has boomed, so the mass deaths may become a seasonal event again. Tyson said communities along Lake Erie experienced similar mortality events as far away as Ontario, Canada. Scientists attributed the decades-long decline in the smelt population to zebra mussels, which filter plankton out of the Great Lakes. Smelt feed on plankton, so the reduction in plankton has led to a reduction in their population. Zebra mussels still reside in Lake Erie, however. So Tyson said his department can’t explain the sudden boom in smelt. “It’s a good question, one we haven’t figured out,” he said. The massive deaths shouldn’t affect the lake’s ecosystem, he added. Because of the boom in smelt population, the deaths won’t make a significant dent in their numbers. Tyson said his department conducted tests for bacterial infections and ruled out any viruses or other outside causes for the deaths. Since spawning season recently finished, the hypothesis makes sense, he said. The mortality event reminded some of the VHS epidemic that killed tens of thousands of freshwater drums, trout and other fish in Lake Erie last decade. VHS, which stands for the viral hemorrhagic septicemia virus, causes anemia and hemorrhaging in fish. At its peak, the epidemic led to a similar phenomenon of groups of fish washing ashore on local beaches from 2005-2007.