Dolphins, which are another highly intelligent species, don't seem to have any qualms about eating octopus.
But there are many, many differences between humans and dolphins. We're smarter, for one. Debate philosophy. Are rarely seriously in danger of starving. Have much more culture. Etc., etc.
So, probably as intelligent as nomadic pre-historic humans. I wouldn't rate that as "highly" intelligent. Just somewhat intelligent.
These are still pre-historic dolphins, since they don't seem to record history for themselves yet. If they carry oral traditions, they seem to be limited to hunting techniques, and not specific events and personalities measured across time. There is no evidence of symbolism invented by dolphins.
Either way, the octopus is similarly prehistoric, despite readily prehensile appendages.
Nor does a lack of hands readily explain the level of elephant intelligence, given a prehensile trunk.
Hint: the animals are less intelligent for doing so.
Mahi-mahi is a fish
Killing and eating a pig when you need it to survive is not immoral. Killing a pig because you felt like having pork rinds, and then leaving the rest of the body to rot because you'd rather have steak is immoral.
While there are dolphins who won't eat octopuses because it's dangerous or difficult, I bet there are some who won't because they empathize with them. If the humans in this thread can empathize with an octopus why couldn't a dolphin?
But when does that happen? Wouldn't the butcher or supermarket usually sell most of the meat and the rest of the carcass is used for dog food or whatever?
I suppose there is probably some waste, but I find it hard to believe there are animals left to rot as you describe simply due to economics.
Personally, I think consumption of more than a few ounces of meat per week is unethical, by the same logic. It's not necessary for health. However, most people in my country don't have the food culture necessary to make adequate non-meat-based dishes. We weren't all born in a family where we were taught thrifty cooking techniques. So it's a strange gray area of "unnecessary". One doesn't need to eat more than a couple ounces of meat, but one needs food and if one doesn't know how to cook plants into something that could stand in for meat in a satisfactory way, then they "need" meat.
The internet is there, so anyone could do it though. I think whether it's ethical comes down to how much free time you have and how comfortable you are with cooking. But again, that's my personal view. I wouldn't expect someone else to live by my ethics. I would expect them to have some measure of "need" in their scheme though. If their habit is "I eat as much red meat as I want I don't even think about it", unless they're and abuse victim or something that's probably not an ethically defensible position.
The waste is almost entirely on the consumer side.
The dolphin life span varies between 20-50 years for the various species.
Cooperative hunting, altruism, care for the members of the group, and colective child care are normal.
Innate interest and sense of compassion for other marine mammals in distress, including humans, and a strong protection response in dangerous situations.
They have grandparents. This is particularly remarkable. Old specimens past their reproductive days are treated as expendable and die quickly in 99% of the animal species. Grandma's are instead VID (very important dolphins) in its societies, and live much longer than expected.
Mourning was also reported in some cases.