The sides are covered with vertical bars that are a faint green or blue, which are typically more prevalent in female pumpkinseeds.

[12] Pumpkinseeds typically live in warm, calm lakes, ponds, and pools of creeks and small rivers with plenty of vegetation.

Pumpkinseeds are active throughout the day, but they rest at night near the bottom or in shelter areas in rocks or near submerged logs.

[citation needed] Pumpkinseeds are carnivorous and feed on a variety of small prey both at the water surface and at the bottom.

They are effective at destroying mosquito larvae and even occasionally consume small pieces of aquatic vegetation and detritus.

Many fishermen consider the pumpkinseed to be a nuisance fish, as it bites so easily and frequently when the fisherman is attempting to catch something else.

The pumpkinseeds are very popular with young fishermen due to their willingness to bite, their abundance and close locations to the shore.

Although many people consider the meat of a pumpkinseed to be good-tasting, it is typically not a popular sport fish due to its small size.

The fish do put up an aggressive fight on line, and they have an excellent flavor and are low in fat and high in protein.

[11] The IGFA world record for the species stands at 0.68 kg (1 lb 8 oz), caught near Honeoye, New York, in 2016.

[13] Once water temperatures reach 55–63 °F (13–17 °C) in the late spring or early summer, the male pumpkinseeds will begin to build nests.

The males will use their caudal fins to sweep out shallow, oval-shaped nesting holes that stretch about twice the length of the pumpkinseed itself.

The pumpkinseed has the ability to anticipate approaching predators (or prey) via a lateral line system, allowing it to detect changes or movements in the water using different mechanical receptors.

[citation needed] The brightly colored gill plates of the pumpkinseed sunfish also serve as a method of protection and dominance.

When a pumpkinseed feels threatened by a predator, it flares its gills to make it seem larger in size, and shows off the flashy red coloration.

[citation needed] In the southernmost regions of its distribution, the pumpkinseed has developed a larger mouth opening and abnormally large jaw muscles to aid in feeding; its forage is small crustaceans and mollusks.

The larger bite radius and enhanced jaw muscles allow the pumpkinseed to crack the shells of their prey to attain the soft flesh within, thus providing one common name of 'shellcracker'.