If you ever owned a goldfish, you probably remember dropping pinches of flake food into the bowl to feed it. But we all know that there are no flake dispensers in the wild. So, what do fish really eat?
What a fish eats varies by the species, habitat, and size of the fish. Baitfish like the many varieties of the minnow family, feast on algae, insects and insect larvae, fish eggs, and zooplankton, among other things. Larger fish like trout or pike can feed on this smaller fare also, however, most of them prefer to eat other smaller fish or aquatic wildlife like frogs, crayfish, leeches, or large insects.
Some fish are filter feeders who pass water through their gills and catch small organisms in internal screens called gill rakers as they swim. The Whale Shark, the world’s largest fish, feeds in this way. It swims with its large mouth open collecting plankton, squid, and small fish, but it does not eat large prey.
There are reports though of several divers who were partially ingested accidentally by whale sharks but promptly spat out. Another fun anecdote on this is the dubious story of James Bartley, who was reportedly swallowed by a sperm whale and rescued 36 hours later when the whale was harpooned and gutted.
Other fish are pure herbivores who eat algae or other aquatic plants. One of these is the parrotfish who cleans algae from coral reefs, giving space to slow-growing corals and keeping reef healthy.
Predator fish, such as pike, walleye, and sharks, are carnivores. This means they like meat and feed on smaller fish and other aquatic life.
The last type of feeder is the omnivore. These opportunistic feeders will eat anything that comes along, protein or plant. An example of this is the durable common carp.
Methods of hunting
Predator fish have developed specialized ways of hunting, and this shows in their body types and behavior.
Long, thin fish like the pike or the barracuda are designed for fast, straight-line strikes in open water. Speed comes at the expense of maneuverability for these fish. Pike will lie in wait on the bottom or in a weed-bed, watching above and ahead of them. When prey is sighted, the water wolf strikes with the speed of a rattlesnake. The pike slams the baitfish with its toothy jaws and then finds a spot to let go of the prey and re-orient to swallow it headfirst.
Bass, both smallmouth and largemouth, are stocky creatures built for maneuverability at speed. They are nimble and quick but cannot pursue prey over a long distance, instead preferring hunting grounds like weed beds where prey is encountered at short range.
Trout lie somewhere in between pike and bass for maneuverability and speed. They have perfect straight-ahead vision and the stamina to pursue their food in the open. They can hold a position in the current while waiting for dinner and then strike fast, swallowing their prey whole.
Sailfish are known to work in groups against a school of baitfish. The sailfish will circle the prey to push the group into a ball before taking turns charging through the ball, stunning several baitfish in the process. The sailfish will then turn around and grabs the stunned prey, swallowing it whole.
The name of the game for predator fish is to expend the least amount of energy possible to catch its dinner.
Fish eat a wide variety of food and acquire it in many ways depending on the species and type of water where the fish resides. An understanding of the diet of a desired fish and its method of hunting or foraging can mean the difference between a successful outing and going home empty-handed. Know your quarry.