Potter deaths along mid-Atlantic states at least 164 times higher than normal . Barco has recorded 78 dolphin deaths this year alone . Causes , including infections , biotoxins , human intervention and malnutrition , have been determined for the 29 of those cases . Scientists investigating respiratory infection . Dolphins send a message on health of environment , Unusual Mortality Event says .
Potter deaths along mid-Atlantic states at least 164 times higher than normal . Barco has recorded 78 dolphin deaths this year alone . Scientists investigating respiratory infection . Dolphins send a message on health of environment , Unusual Mortality Event says .