system
Given the following post, respond as if you're commenting on Reddit:
human
[General fantasy] Do you think the top part of a mermaid also tastes like fish or that it would actually be red meat? Would there be a solid line where the meat changes in their body or would it kind of blend? Could you make a surf and turf platter with one carcass?
gpt
Fish (and reptiles for that matter) developed to move through lateral undulations, and therefore their tails are arranged to move side to side.

Mammals on the other hand, developed a vertical gait, and mammals that adapted to a marine environment developed tails that follow this movement, i.e. moving up and down. This has happened separately several times in evolutionary history.

Mermaids have developed a tail that utilizes vertical undulations rather than a lateral one. 

Therefore Merfolk are mammals. Their entire flesh would be the same, mammals flesh. As they are a subspecies of humanity (perhaps Homo Maritimus is a good taxonomic designation) they would probably taste similar to us, and some have said that human flesh tastes like pork.