The girls, ages 9 and 4, collided with a semi-truck 10 miles into their joyride, but nobody was harmed, police said.
Freshwater diversion projects that have divided environmental advocates are intended to save the coast but may imperil dolphins.
A $20,000 reward is being offered to anyone who can help solve the case.
Someone stabbed an adult male dolphin in Florida, possibly while it was in a "begging posture" at a fishing boat.
The algal bloom has also killed fish, sea turtles and manatees along the Gulf Coast.
Experts say heavy winter rains may be contributing to more beached marine mammals.
Dolphinaris Arizona, which opened a little over 2 years ago, is temporarily closing amid an investigation.
“The mother is grieving and needs space and time to do this,” the New Zealand Department of Conservation said.
A marine animal rescue group is offering a reward of $5,000 for information leading to conviction of the perp.
Noise from ships and boats are causing dolphins to make their calls less complex, according to a new study.
Seeing this many dolphins move together is mesmerizing.
Honey the dolphin, along with dozens of penguins, were left at Japan's Inubosaki Marine Park Aquarium when the place closed.
But what they did discover was still really amazing.
There's a big reward for anyone who helps find the killer.
The key question is how NOAA will define standards that are "comparable in effectiveness" to U.S. requirements for monitoring
The current season of the bloody dolphin hunts, that take place every year in Taiji, Japan, is now two-thirds over. For four
They'll be deployed in Mexico this spring to help locate the world's rarest marine mammal.
I feel a deep responsibility for having led you down this path, believing that together we could make a difference in this