The Maryland Department of the Environment now estimates that 100,000 dead menhaden have washed up on Maryland and Delaware beaches.
Department spokeswoman Dawn Stoltzfus said many of the fish found Sunday were missing their heads and appeared to have been dead for about a week. Stoltzfus said water quality doesn't seem to be a factor because other species of fish don't appear to have been affected.
The small fish that travel in large schools and are harvested for bait, fishmeal and fish oil started washing ashore in Delaware on Saturday afternoon.
The spokeswoman said the department is working with officials in Delaware and the Maryland Department of Natural Resources. Rehoboth Beach Patrol Captain Kent Buckson says the fish were likely dumped or spilled from a commercial vessel.