Because of the breadth of this four-family group, behavior varies widely. Some species school; some exist alone. Some are broadcast spawners; others build nests and mate one-on-one. Numerous species provide no parental care; others build nests and guard eggs and/or young.
The centrarchids are particularly known for their nestbuilding and parental care. Nest-building typically involves the male setting up a small territory, fanning its tail to create a depression in the substrate, then enticing a receptive female to his nest to lay her eggs, which he fertilizes. In many cen-trarchids, as well as darter perches, more than one female may be attracted to a male's territory. This often results in the male mating with different females in a single breeding season. Male centrarchids defend the nest at least until the eggs hatch, and the males of a few species continue to watch over the young for several weeks.
One unusual behavior has gained some attention. Large-mouth bass in the family Centrarchidae will frequently eat whirligig beetles (Dineutes hornii), which are flat, round insects that move along calm water surfaces in looping, swirling patterns. These beetles secrete a noxious slime that repels most predators. The bass, however, have developed a way to get around the goo. According to researchers, they rinse off the beetle by repeatedly taking the insect into the mouth, gargling it, and spitting it out until the unpleasant taste is gone, or until the bass gives up. If the bass is persistent enough to rinse off the slime (which can take more than a minute) it eats the beetle. If not, the beetle escapes.
The darters comprise a huge group within the perch family, and the 146 species live in waters of North America. Members are characterized by their wary nature: Whenever the slightest threat arises, they quickly "dart" for cover. They also exhibit other interesting behaviors. The johnny darter (Etheostoma nigrum), for instance, has atypical spawning habits. The male prepares a spot under some cover, perhaps a rock overhang. When a mate arrives, the male and female both swim to the site and turn upside down to spawn. The female's eggs stick to the overhead cover. The male's job is to tend and guard the eggs for the next several weeks until they hatch. Other fishes in the Percidae may mate in pairs like the johnny darter, spawn in small assemblages of one female and several males, or engage in mass spawning.
The breeding season for moronids begins with male courtship displays, usually involving one female and several males. The routine typically includes the males closely following a female and nudging her vent area, and in some species, stereotypically swimming in circles. When appropriately stimulated, the female rises to the surface with the males in tow, and spawning occurs. Occasionally, some Morone species will hybridize with each other.
Perhaps the most interesting behavior among the elasso-matids occurs during territorial and courtship displays. The territorial display takes place when a male approaches another's territory. The territorial male displays toward the intruder by expanding and/or rapidly flitting his fins, turning sideways as to present his largest view, bending his head and tail toward the intruder, and as a last resort, striking with his head. During courtship, a male elassomatid displays toward a female by bobbing up and down and waving his fins, while swimming toward the spawning site. When a female approaches, the male develops a bright spawning coloration and begins to tremble, while bumping and nipping at the female. Courtship continues for several minutes before the release of eggs and milt.
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