Thomas Schoene wrote:
Simply, the Super Hornet has no need of canards. They would just complicate
the design without offering any obvious advantage. They certianly woudl
have driven up development costs and complicated the RCS reduction effort
(more moving fins means more hard to conceal flat surfaces).

Finally found a good reference for this.

http://www.aerospaceweb.org/question/planes/q0176.shtml
The benefits of these vortices can be appreciated when one realizes that
nearly all current military aircraft designs incorporate leading edge
extensions and/or canards that perform much the same function.
....
Instead of fences, the F-18E/F makes use of vents located near the junction
of the LEX and main wing. These vents automatically open at high angle of
attack allowing air to flow over the inner wing. This additional air flow
interacts with the LEX vortex to delay vortex bursting in much the same
manner as the fence did.

So it has LEX vents instead of adjustable canards to deal with high AoAs.

-HJC