You can call it speciesism if you want, but fish are just not quite as cuddly as cats. So if you like a pet thats cuddly, you will prefer cats over fish and admitting that is in no way problematic.
Equating speciesism with racism also doesn't make a lot of sense to me. Species do exist in nature, they are hard boundaries which animals can breed. Races on the other hand are a made-up concept with no biological basis, used to distinguish between similar-looking groups within a species.
A fish and a cat cannot breed, as they are different species. A british shorthair and a sphynx on the other hand can, as the distinction is entirely artificial.
Racism is the wrong belief that races, like species are a biological concept that can be found in nature.
Speciesism differs from that, because different species do exist. For any two individual animals you can always determine if they belong to the same species, which isn't true for races. Animals of the same species do share traits, while there are differences between animals of different species.
In my opinion, pretending that every living being is the same would be way more problematic than what you call speciesism.