Man, not having this problem. Try using a clean version of DF? (never been modded or edited, even if it has been returned to normal)
The river, eh. A moat wouldn't be bad.
This map is a huge disappointment, no offense. It's just a huge smorgishborg of resources! Wonderful, great for fortress building; the only problem is that we were trying to have a survival game and we got plunked in a misnamed "Terrifying" paradise! Sure, if you blindly open the pool or pit wide open you'll be done for, and yes any dogs you bring with you tend to go off and attack the harpies and beak dogs (oops). Also, the map is not without danger. Granted, my dwarves beat the shiz out of some beak dogs and harpies, but dwarves don't swim and apparently harpies know this! Losing your miners and lumberjack along with their tools is the biggest handicap you can have. But in the end, there was never any real danger. I send my gatherers out unguarded daily with no casualties, and hunt to my heart's content.
There is still competition for what we can try to accomplish in 5 years! Clearing HFS would be a huge accomplishment, especially if you did it without drowning/trapping/atomsmashing them. Going to put a note up about NOT atomsmashing, though it should be obvious.
I finally get a replacement Mechanic (one of my miner's jobs) and he decides to get Possessed the first day, instead of ANY OTHER mood. Damnit! 1 mood per year, both possessed! Even if I get a couple of legendaries in year 3, there won't be enough time to do much with them!