Hey welcome to Crappie.Com from NW AR. We lived in Jonesboro twenty two years ago and yes we fished Cow Bayou but not Shell or Blackfish. It is my understanding, that they have cut the little stream in half with a culvert which denies access to the full length of the Bayou. Years ago we caught some quality fish there. Like all oxbows you had to catch the river at a favorable level - if you have a small boat it would be worth checking out the north end. I think the only access now is down a couple of field rows and really not for sure if it is private land or not. Also, my guess is if there is a bait shop around Marianne they could give you more details.