ok, so iv been doing experimenting and i think this should help.
The number of sharks is a glitch. Your survivors need to have no jobs cued to have a baby. The sharks and sea gulls? well, your screwed. i had to restart that save to get a bone, and then i happened all the time. seemed like the further out you built, the more sharks and the stronger they got, so build up. To get gulls back, your gonna have to restart the game and play on a new save.