why does semen smell the way it does?

i have noticed semen has two scents.

the first scent is the ocean breeze scent that you smell when you first ejaculate. sometimes it smells like bleach too

the second is when its been sitting around for a while.. when it begins to smell like squid or rotting seafood.

i have no problem with the first kind, but the second one is truly annoying.
why does semen start to smell like that, and how can i prevent it or reduce the stench?

My girlfriend says my semen is the best shes tasted and she enjoys having a mouthfull lol :D, i do sports for at least 4-5 hours a day around 5-6 days a week and i only drink water and squash and fruit juice, and mainly eat chicken if i eat meat, i would say that drinking a lot of water and fruit juice and eating less dark meats is the answer to your girlfriend enjoying your cum i suppose .