BB is a 32/12/0.5 player after 350 hands. So he is quite passive and has a WTSD of 44%.

How should I think and play against this opponent on the river?

I guess a nine or a monster is somewhat discounted from his range. And AK (AQ I´m not sure about) probably caps pre flop.

On the one hand I could check and hope he checks behind with a pair. I feel akward trying to induce a passive player but I guess I have to call if I check since the pot is quite large and I dont know my opponent that well.

Or I could bet and hope to get called by another Ace high. I guess a thinking opponent would not call the river bet lightly recognizing my strong pre flop range. But this passive opponent might not think that far and make that A high call down or even with KQ just because he doesn´t know better. But I don´t know...

10/20 Limit Holdem
5 players

Pre-flop: (1.5 SB, 5 players) Hero is SB J A
UTG raises, 2 folds, Hero 3-bets, BB calls, UTG calls

Flop: 2 9 6 (9.0 SB, 3 players)
Hero bets, BB calls, UTG folds

Turn: 8 (5.5 BB, 2 players)
Hero bets, BB calls

River: 9 (7.5 BB, 2 players)
Hero ?

I doubt he is checking behind a pair because when you check the river your hand is a-high A WHOLE LOT. By the same token, its fairly rare that he tries a bluff in this nonscary board. For me, your best option by far is to value bet i think.

Its very possible for villain to get to the river with A-high + straight draw / gutshot on this board and those hands will often talk themselves into a river call.

right.

also, betting the river doesn't have to be for value, it just has to be better than your other options.

Thank you both!

I did bet and valuetowned myself vs his AQ.

I do however think that he can check low pairs behind. Do you feel that makes the play check/call instead?

If he was a thinking player he would bet any pair when checked too but he would also find it tough to call with Ax (because of the pre flop action). And if he is not thinking (and this guy isn´t) he could call with Ax but also check behind some pairs not knowing better. His AF is 0.5.