You might think this is a funny question, but I get asked this a lot!
OK, for those who really want to know the answer, it is a YES… in most cases.
If they ARE animals, then are they covered under the Animal Welfare Legislation?
Every year, I give a 1 hour lecture to the veterinary students at Murdoch University on this topic. But here’s a good summary –
http://kb.rspca.org.au/Are-fish-protected-by-animal-welfare-legislation_448.html
