Research into the attacks, which took place in the Baltic Sea over three months in 2016, is still ongoing.
The video was filmed by Newport Coastal Adventure on May 16 during an afternoon trip off Laguna Beach.
"I've seen it all...but this excited me," said the fisherman who shot the video.
"With four out of eight dolphins dying inside of 16 months, the situation has reached critical mass," said a campaigner.
The study "highlights the magnitude of plastic pollution," a professor of conservation told Newsweek.
An animal rescue organization is offering a $5,000 reward for information.
A pod of dolphins helped protect a humpback whale calf in Australia.
"Sharkie," an Atlantic bottlenose dolphin, suffered severe shark bites to her body and right flipper.
Researchers say the fossil underscores how little we know about these mysterious ancient beasts.
"Hat's off to him, he collected me really well."
The dolphin is still in critical condition.
If Katrina is anything to go by, 2019 will be a good year for baby dolphins.
The eight-foot screen is complete with dolphin friendly apps and a keyboard.
The dolphin may have suffered from pneumonia.
The men were fined more than $7,000 and cannot hunt or fish during a year's probation.
The trainer and his family received death threats, according to his employer.