Reproductive biology

Percid reproduction varies. Some scatter their eggs and milt into the water or over vegetation, while others spawn over gravel nests. Some species deposit individual eggs; others, such as the yellow perch and the European perch (Perca fluviatilis), lay their eggs in masses. Some species, such as the yellow perch and sauger (Stizostedion canadense), leave the area almost immediately after spawning; others, such as the johnny darter and tessellated darter (Etheostoma olmstedi), remain with their eggs until hatching. Among centrarchids, the bluegill and longear sunfishes prefer to spawn in still waters, others, including many darters, opt for the running water of a stream.

During mating season, males generally develop brighter coloration, which apparently assists in attracting females and announcing their territories to other males. Sunfishes spawn in one of three ways. A male may make a nest and attract females for mating there. Females may spawn with smaller males known as satellite and sneaker males. During breeding season, satellite males take on coloration of a female and trick the nesting male into allowing them to approach, giving them access to females coming to the nest. Sneaker males hide among vegetation near a nesting male's site, watch the females arrive, then dash through the nest site ejecting milt as they reach the females. Non-nesting males mature earlier than nesting males, commonly going through the sneaker stage when they reach the age of two years, then becoming satellite males in later years. Nesting males are usually older individuals that top the seven-year mark. Some controversy exists over whether elassomatids are nest builders. Scientists have reported spawning with and without nests in some species, leading to the hypothesis that substrate conditions determine whether nesting occurs.

Of the moronids, perhaps most is known about the behavior of the striped sea bass, probably because of its popularity as a sport fish. These fishes inhabit coastal waters along both the Atlantic (its native distribution) and Pacific coasts. The Pacific introduction can be traced to 1879 and 1882, when the fishes were translocated to the San Francisco shore. Striped sea basses are migratory, moving to cooler northern waters in summer and warmer southern waters in the fall. As breeding season approaches, they return to their home stream to spawn, apparently via olfactory cues. Feeding ceases prior to the annual breeding season, during which the fishes engage in broadcast spawning. One study of the European sea bass (Dicentrarchus labrax) indicated that its gender can be influenced by temperature. Experiments showed that temperature differences during the development of eggs could affect the ultimate sex ratio.

Bluegills (Lepomis macrochirus) occur in all three drainage basins in Wisconsin (Lake Michigan, Mississippi River, and Lake Superior). (Photo by Animals Animals ©E. R. Degginger. Rerpoduced by permission.
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