200NL - Is this river VB too thin?

[spivey]

Only played with villain about a dozen or two dozen hands. He seems loose/passive, and is definitely limping too much preflop.

Full Tilt Poker, $1/$2 NL Hold'em Cash Game, 6 Players
LegoPoker Hand History Converter

MP: $198.90
Hero (CO): $190
BTN: $213.55
SB: $139.35
BB: $280.70
UTG: $162.30

Pre-Flop: A[img]/images/graemlins/club.gif[/img] A[img]/images/graemlins/diamond.gif[/img] dealt to Hero (CO)
UTG folds, MP calls $2, <font color="red">Hero raises to $9</font>, 3 folds, MP calls $7

Flop: ($21) J[img]/images/graemlins/spade.gif[/img] Q[img]/images/graemlins/spade.gif[/img] 4[img]/images/graemlins/spade.gif[/img] (2 Players)
MP checks, <font color="red">Hero bets $16</font>, MP calls $16

Turn: ($53) 8[img]/images/graemlins/spade.gif[/img] (2 Players)
MP checks, Hero checks

River: ($53) 5[img]/images/graemlins/diamond.gif[/img] (2 Players)
MP checks, <font color="red">Hero bets $15</font>

I felt this bet was mandatory at the time. Was it?