The mechanism depends on volume change. When the bass drops its lower jaw, flares the hyoid apparatus and abducts the gill covers in a coordinated sequence, the buccal cavity expands faster than water can flow in from behind, creating a pressure drop at the mouth. Water rushes in from the front, carrying the prey with it, and is then expelled through the gills while the prey is retained.
High-speed video of centrarchid feeding shows the whole event lasting on the order of twenty to forty milliseconds. The unusually large gape, which gives the fish its name, matters because suction force falls off very sharply with distance; a wider mouth placed closer to the prey captures more of the flow. The bass's inward-slanting teeth grip rather than cut, since nothing needs to be sliced.
The habit of holding and rejecting a lure before swallowing is consistent with this: an item drawn in by suction can be assessed and expelled with the same machinery.