Bait fish are small fish caught for use as bait to attract large predatory fish, particularly game fish. Species used are typically those that are common and breed rapidly, making them easy to catch and in regular supply. Examples of marine bait fish are anchovies, halfbeaks, and scad. Freshwater bait fish include any fish of the minnow or carp family (Cyprinidae), sucker family (Catostomidae), top minnows or killifish family (Cyprinodontidae), shad family (Clupeidae), sculpin of the order Osteichthyes or sunfish family (Centrarchidae), excluding black basses and crappie.
Bait fish are consumed by larger, aquatic predators. Swimming in ocean water occupied with bait fish is dangerous, as these fish are known to attract sharks. Bait fish will sometimes use whale sharks as a shield from their other predators such as tuna, as tuna are usually wary of approaching the shark. The shark cannot attack the bait fish easily, as they constantly swim above its back and are too fast for the shark to maneuver its mouth into position. However, the shark eventually dives deep, where the bait fish cannot follow, and as the other predators finally dare attack the stranded bait fish, the shark comes back to eat numerous bait fish who are already preoccupied with the attacking tuna.
Although bait fish typically have populations that fluctuate rapidly anyway, and so can potentially sustain significant recreational and commercial fisheries, regulations may exist to prevent overexploitation, as in Arkansas and Massachusetts Studies by fisheries and conservation agencies monitor the health of bait fish populations, allowing regional governments to set quotas .