Goddard and Mathis (1997b) found that female longear sunfish prefer male longears with longer opercular flaps, and they found that opercular flaps grew significantly faster than pelvic fins in males, both of which they argue indicate flap length serves as sexual ornamentation.
Goddard and Mathis (2000) also performed experiments where they artificially manipulated the lengths of male flaps. If a male with long flaps had his artificially shortened, he still archived dominance over males with naturally short flaps. If opercular flaps were artificially lengthened, the abnormally long-flapped males were dominant significantly more often than the ‘normal’ males. They argue that these results indicate that opercular flap length of male longear sunfish may serve as an honest indicator of male quality and may be used to assess the resource holding power of rival males without risking injury from combat.
When a breeding female enters a nesting colony, a male longear sunfish will attempt to lead her to its nest. Leading involves behavior where the male spreads its fins, swims directly toward the female and then returns directly to his nest. If a female follows the male to his nest, they begin a circular spiral of the nest with the female always toward the center. Direction of movement is dependant on which direction the male is going when he reenters the nest after chasing out an intruder. Both will circle the nest in an upright position, every 50 to 60 seconds the female will turn over on her side at a 20° to 30° angle and bring her vent close to his and both fish will shudder, releasing his sperm and her eggs. Several spawning events will occur and then the female is chased from the nest. In one study, the total number of eggs deposited in a nest varied from about 137 to 2,836 eggs.
Immediately after the female leaves, the male begins to fan the nest with his paired and caudal fins. He then assumes a near vertical position over the nest and fans with his tail. The fanning is vigorous enough to dislodge small pebbles. He will fan the nest up to an hour after the spawning event. This behavior may aid in the mixing of eggs and sperm and help drive the eggs deep into the gravel. The female, after being chased from the nest, will enter the nests of other males for additional spawning events.
Mating System: polyandrous
Like most other members of Lepomis, longear sunfish are colonial nesters, although in low-density populations individuals will build solitary nests. Colony size and proximity of the nests vary. In crowded conditions the colonies can be quite large with the nests so close together their rims almost touch. In dense conditions the male fish only defends the nest itself. In less dense conditions, the nests are further apart and the male will guard a territory slightly larger than the nest.
Male longear sunfish, like other members of Lepomis build the nest without aid from the female. In late spring or early summer, males move into relatively shallow water (20 to 60 cm deep) and establish territories in which they build nests. Preferred substrate is gravel if available; otherwise, they will build in sand or hard mud. The nest is a mostly circular excavation created by the vigorous sweeping of the male’s tail (called tail-wags) across the substrate while the fish is oriented at a 45° angle to the bottom. This action excavates a circular depression that is about 35 to 45 cm in diameter, 3 to 7 cm deep, with rims 7 to 9 cm wide. During the construction of one nest, a male was observed making 145 tail-wags in the center of the nest, 128 tail-wags along the edge, and 22 tail-wags across the nest. In addition, the male circled the nest 14 times, circled back to deep waters 39 times, chased off other longear sunfish 36 times, and chased off other species 3 times. Water temperatures in the nest area are relatively warm and vary from approximately from 23° to 31° C. They will reoccupy nests abandoned by other sunfish.
Male longear sunfish also exhibit an interesting alternative reproductive strategy to nest building. Some males are sneakers. The sneaker male is generally younger and less colorful than a nest building (dominant) male. The sneaker male mimics the appearance of a female longear sunfish. The sneaker will hide near an active nest and dash into the nest and release sperm while the dominant male is spawning with a female. The satellite male is similar in age and appearance to the sneaker male, but instead of dashing into the nest, he will hover over a nest, acting the part of a non-threatening female, and slowly descend into the nest containing a courting pair of sunfish and, like the sneaker, release sperm during the spawning event. Male longear sunfish that build solitary nests have better success defending their nests from sneaker and satellite males than males with nests in colonies. Colonial nesting is believed to favor the existence of sneaker and satellite males because it allows these males access to breeding females.
Breeding season: Late May to late August
Range number of offspring: 137 to 2800.
Range time to hatching: 2 to 7 days.
Average time to hatching: 5 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous
A male longear sunfish guards the nest territory during all phases of reproduction. He will continuously chase both his own and other species out of his nesting territory. He seems most territorially responsive to potential predators of himself or his young and to potential intruding spawners like the sneaker and satellite males discussed above. The males are less responsive to non-threatening fish like topminnows (family Fundulidae). During one 20 minute spawning event, a male was observed to leave the nest 15 times to chase after other longear sunfish. When the defending male leaves the nest while eggs are present, young longear sunfish, 5 to 10 cm in length, will invade the unguarded nest and eat the eggs. Aggressiveness of the nesting male has been shown to be highest when eggs and young are present and lowest before and after. The male will continue to guard the nest even after all the young have left.
Parental Investment: pre-fertilization (Protecting: Male, Female); pre-hatching/birth (Protecting: Male)