I'm not sure about your's but, my two on either side of the flip up are pin mounted and lift out. They can be tough to pull out and, must be pulled straight up. Some penetrating oil or lithium grease on them will help.
I have a Nitro 175 Sport f&s 2001. I suspect your's are the same to be used as front and rear pedestal seats.
If you have room to remove the bolts holding the seat to the pedestal, doing this will make it much easier to spin the pedestals which helps in pulling the seats out. I had this same problem with my 2008 189 Sport when I purchased it last year. Someone here also mentioned lightly filing the holes once the pedestals are out. I did this, as well as adding grease, and have not had any problems since.
This is my 2001 Nitro, Im needing to pull the back bench seats out, needs to be reupholstered, I don't have a good picture of them separately, but is that the same idea? they are mounted on a post? My boat came with 2 separate seats for the fishing decks. Thanks.