ROCHESTER, N.Y. — Officials say the large numbers of dead fish seen in some upstate New York waterways doesn’t indicate a problem — it’s a common occurrence in late winter and early spring.

The Department of Environmental Conservation says fish die-offs have been reported in areas such as Irondequoit Bay near Rochester and the Erie Canal in Wayne County. Inspections by biologists found nearly all the fish were gizzard shad, a type of herring.

Gizzard shad commonly have high mortality at this time of year because they’re very sensitive to cold water temperatures. Another factor may be a viral infection that was detected in a sample of the fish tested at Cornell University.