Yes, dolphins are mammals, not fish. And this one’s hunting pattern actually gives it better odds of catching its prey. Schooling fish such as herring generally hang out in huge roiling balls. This is a common defense technique serving to confuse predators. The predators which focus on one particular fish are more likely to catch it, vs. going from one to another in a constantly moving mass.
In this case, there could be some play involved, too. Dolphins seem to incorporate play into everything they do, which is another sign of their intelligence.
Interesting. Learned a bit thanks.