For 13 to be unlucky would require there to be some kind of cosmic intelligence that counts things that humans count and that also makes certain things happen on certain dates or in certain places according to whether the number 13 'is involved' or not (whatever 'is involved' might mean).
If a mosquito has a soul, it is mostly evil. So I don't have too many qualms about putting a mosquito out of its misery. I'm a little more respectful of ants.
You make decisions, take actions, affect the world, receive feedback from the world, incorporate it into yourself, then the updated 'you' makes more decisions, and so forth, 'round and 'round.
We all have heard it claimed that 13 is an 'unlucky number.' Indeed, there are many hotels in America that for this very reason claim not to have a 13th floor, in the sense that there is no button bearing the label '13' in their elevators (I recently stayed in one in New York, in fact).
I don't feel I have the right to snuff the lives of chicken and fish.