4/0 gamagatsu or Honer "j" hook, the problem with eels and circles are several,and sooner or latter it will happen.
1) when a fish takes the eel the hook will set into the eel insted of the fish,it happens with "j" hooks but nearly twice as often with circles..
2) you will miss alot more fish with the circles,alot of the fish just dont stick...
3) the third and most comon problem comes from hooking the bait itself,circles are hard to ge into the eels and tend to enlarge the hole in the bait causing alot of lost baits..
The above is based on 4 years of experiments with circle hooks and 30 years of "j" hook eel fishing, and an average of 20 hours a week on the water trolling and plugging eels and IMHO this is the one and only bait where "j" hooks are superior to circles when using bait for bass....