They are not considered parasitic. There are some copepod parasites of whales. References are limited. Note also that there are some insect parasites on seals including demodectic mange. Chelonibia, Platylepas, and Balanus may occur on sirenians.
Whales also have Lepas.
Thanks in advance. If anyone is interested, I have the authors for each of the barnacle species. 1.0 Good morning, all, I have listed some names in response to the messages regarding crustacean parasites on marine mammals. The lists of cirripede and copepod names were compiled from information gleaned only from the literature, and I would certainly be interested in comments on those names. The list of cyamid taxa comes from my M.S. thesis research.