I have a friend (who I don't think reads this blog...if she does, CLAIRE, STOP NOW! DON'T LOOK AT THE PICTURE! (I'M SHOUTING SO SHE'LL HEAR IT BEFORE SHE SEES THE PICTURE.) She is not a cat person but she is spending a long time (I thought it was 5 months but it turns out to be more like 10 months) caring for the cat of a friend while that friend is in another province for college. I decided poor Kittums (the cat, I kid you not that's the name her human slave gave her) needs lots of toys. Claire has made friends with the cat; they bonded over sushi. But she still needs toys.
I made this out of an unidentified furry type yarn. I am assuming it's bulky (5) weight because most such yarns are. This isn't the kind of project that requires a gauge swatch so I didn't even consider doing one. I used a size G crochet hook. If you want a large fishie, use a larger hook. Smaller, use a smaller hook. You can also adjust based on the type of yarn you use. I make no promises that your yarn will give the same results but no cat would criticize for that reason alone.