I have 87 people in a game,all puzzles solved.Now every time I close the game I have at least 5 dead people.They shouldn't starve there is loads of food and they can fish.Why do I loose someone everytime IO close the game?

they died of old age

Abbey has stated one cause of villager death: old age. Your villagers will not live forever. They could also have died from uncured illness if you don't have an assigned doctor. You can determine exactly why your villagers died if you check the game log. You can see information about the game log in this post.

Once I got up to 90 population I would have dead bodies every morning when I checked on my villagers, then I would check the gravestone to see how old they were, all elderly.
Then when your Graveyard gets full.....the only way you can tell who died is by clicking on thier remains.

And it's annoying when I see "burying the dead" and I run over to see who's dead, but the bones have been picked up already. I can check the log, of course, but it's still annoying.