Question for the BioShock experts

I have just killed a Big Daddy and saved the (?) girl. The rosie has re-appeared with another girl in the same location. There are supposedly a total of 3 girls on the level and I aim to get them all. Do I have to kill the big daddy here 3 times, or will I see another two later in the level?

Depends on the location, the Little Sisters typically hang-out inside those things in the wall with a hole in the middle, as to which Big Daddies bang on to see if there's a Sister in there or not. Splicers and Daddies respawn abouts as you explore the areas also, so you can't accidently screw yourself out of a Sister by killing them all.

They're sporadic throughout the level. Occasionally, I've tooked out a Big Daddy, left the area to explore, then came back and another Big Daddy/Little Sister would respawn. I could be wrong but I think the game is set to only allow one Big Daddy/Little Sister to appear at a time. It'll be kinda tough to take on more than one of them at a time...unless you set them on each other lol...

Ok, thanks guys. I think I'll take a look around and come back if I need to.

If you're down by the docks, that Big Daddy and Little Sister respawned twice for me, giving me a total of five Big Daddies on a level which only had three in theory. Oddly, when I completed the level, having killed all five, it warned me that I hadn't killed all the Big Daddies. I ignored it and when it came to the crunch later in the game, it emerged that I had, in fact, saved every single Little Sister, so I guess it's just bit buggy.

Ahhh.... I am by the docks. So if I kill five, do I get a decent ADAM payout from the extra ones?

Yes, you get a full payout of ADAM for each little sister you kill and you get the full "bonus" if you're choosing to rescue them.

Thanks, Gabe... that's all I need to know!