Posted under General
Yeah, they don't look like a typical fish, plus, 'In zoology, lampreys are sometimes not considered to be true fish because of their distinctive morphology and physiology.'
I'm really not sure what to think right now. People do tend to have a rather specific concept of what a fish is, which is usually anything that belongs to the group of bony fish or sharks. On the other hand, what actually falls under the term fish is quite broad. Eels are fish, manta rays are a fish (sharks are more closely related to them than most of the other stuff we'd label fish), sea horses are a fish.
Furthermore "fish" isn't really a visual grouping, because there do exist non-fish that have fish-like body shapes, like dolphins, whales, ichthyosaurs, etc. The body shape here is based very much on the environment they live in, given that several occurrences of convergent evolution has lead to these similar body shapes. Certainly there are real life visual differences, but many of these many not be significant enough to appear in visuals, let alone what an artist draws.
Really can't use actual relationship of lampreys with other fish, since your goal seems to be to exclude them from the fish tag, but in using such an argument you're turning around and saying that eels should receive the fish tag. This is because eels are bony fish, and thus closely related to most of the things you're tagging fish.
tl;dr: Visually there are a lot of things that fit a similar body plan as fish, and there are plenty of things that are fish that do not fit the stereotypic appearance, making using the tag with a visual rule a rather poor approach. Though this does not mean a non-visual approach is any better, as it starts lumping a lot of stuff under one tag.
