wow, you weren't kidding when you said you had a lot of duplicates.
Unfortunately, there is no way to release more then one pet at one, so you will have to release any wild duplicates one by one. However, the majority of the pets you have duplicates of seem to be cageable pets, so with empty bags you should be able to cage a bunch of them instead of releasing them, and possibly sell them on. As far as I know, there is no addon for this either, as most people will not have more then two duplicates of a given pet.
When looking at which pet to keep, though, you most likely will have to look at their breeds, as there is often no other distinction between them. There should be a petaddon displaying breeds, or you could look at your collection on warcraftpets. Some of your duplicates only come in one breed, so it does not matter which one you keep. For others, such as for example your brown rabbit, you have multiple breeds. Warcraftpets has a few great posts on which breeds are best. As a quick rule, B/B isn't what you want. Incase of the rabbit, you have S/B, B/B and S/S rabbits. S/S would be the best choice to keep here. Which of the three is best is different per type of pet, but removing all the B/B and same breed duplicates first should probebly get you quite far already.
Last edited by Nagini
on November 6th, 2014, 9:14 am, edited 1 time in total.