I trapped the park heavily years ago. I once got 51 rats on opening day there. Would always get 150+ rats a year there. That was then, last year, I looked over my old spots.... No sign of any rats. You can water trap about anywhere, except in safety zone areas, marinas, and the south shore day use areas are closed. The 528 bridge areas and back inlets used to be a muskrat battleground years ago, I avoided that mess altogether. The north shore woods always held fair numbers of coon, pressure wasn't too bad. Same with the south shores bordering 422, fair trapping, a little pressure.
Dog walkers, hikers, joggers are common in the park, be prepared for some human interactions.