Since I live in a city of veggie havens like Millenium, Greens and Joubert's, keeping kosher isn't terribly constraining for me. It can be a pain, though. No kitties, no badgers, no pigs, no weasels, no puppies, no snakes. Of the flying creatures, no eagles, no vultures, no owls, no bats. Insects are out, except for grasshoppers, locusts, crickets and katydids, reasons unclear.
Fish are fine as long as they have scales and fins.
This eliminates all shellfish, eels and catfish. In short, no one knows. They ARE giant bugs. But Torah be darned, there seems to be a mystical connection between Jews and shellfish. After all, everyone knows Jews are huge foodies.