Observation and photo by @niceislife
Something killed several in this pond, as well as more in several other ponds and waterways in the area. Mass Fish & Wildlife is investigating. Other fish are unaffected, so it is not just low oxygen levels as happens sometimes when the weather gets warm and water levels fall.
Fontanile via s.Maria, some individuals with orange-red habitus
The Cypriniformes are an order of ray-finned fish, including the carps, minnows, loaches and relatives. This order contains five to six families, over 320 genera, and more than 3,250 species, with new species being described every few months or so, and new genera being recognized frequently. They are most diverse in southeastern Asia, but are entirely absent from Australia and South America.