Yellow Perch - Ecology

Ecology

Primarily age and body size determine the diet of yellow perch. Zooplankton is the primary food source for young and larval perch. By age one, they shift to macroinvertebrates such as midges and mosquitos. Large adult perch feed on invertebrates, fish eggs, crayfish, mysid shrimp, and juvenile fish. They have been known to be predominantly piscivorous and even cannibalistic in some cases. About 20% of the diet of a yellow perch over 32 grams (1.1oz) in weight consists of small fish. Maximum feeding occurs just before dark, with typical consumption averaging 1.4% of their body weight.

Their microhabitat is usually along the shore among reeds and aquatic weeds, docks, and other structures. They are most dense within aquatic vegetation, since they naturally school, but also prefer small weed-filled water bodies with muck, gravel, or sand bottoms. They are less abundant in deep and clear open water or unproductive lakes. Within rivers, they only frequent pools, slack water, and moderately vegetated habitat. They frequent inshore surface waters during the summer. Almost every cool to warm water predatory fish species, such as northern pike, muskellunge, bass, sunfish, crappie, walleye, lake trout, and even other yellow perch, are predators of the yellow perch. They are the primary prey for walleye Sander vitreus, and they consume 58% of the age zero and 47% of the age one yellow perch in northern lakes. However, in shallow natural lakes, largemouth bass Micropterus salmoides may be most influential in structuring the quality of yellow perch populations. In Nebraska sandhill lakes, the mean weight and quality of yellow perch is not related to invertebrate abundance, but is related to the abundance of largemouth bass. The three primary factors influencing quality panfish populations are predators, prey, and the environment.

In eastern North America, yellow perch are an extremely important food source for birds such as double-crested cormorants. The cormorants specifically target yellow perch as primary prey. Other birds also prey on them, such as eagles, herring gulls, hawks, diving ducks, kingfishers, herons, mergansers, loons, and white pelicans. High estimates show that cormorants were capable of consuming 29% of the age three perch population. Yellow perch have such an extensive impact on trout species in the bodies of water in which they were introduced and established, they caused a drastic change in the food habits and reduced the growth rates of the trout by more than 50% in some locations. Trout in lakes where perch have been introduced typically cannot compete successfully for the available food, and once yellow perch get established in small lakes, even intervention by the use of trout hatcheries has been shown to be ineffective. In Canada, yellow perch are effective at escaping predation by lake trout and other native fishes during summer due to their high thermal tolerance. Parasites and diseases in yellow perch are often shared with salmonids in eastern North American lakes. A few examples are: brain parasite Flexibactor collumaris, red worm Eustrongylides tubifex, broad tapeworm Diphyllobothrium latum, and parasitic copepods Ergasilus spp.

Perch are commonly active during the day and inactive at night except during spawning, when they are active both day and night. Perch are most often found in schools. Their vision is necessary for schooling and the schools break up at dusk and reform at dawn. The schools typically contain 50 to 200 fish, and are arranged by age and size in a spindle shape. Younger perch tend to school more than older and larger fish, which occasionally like to travel alone, and males and females often form separate schools. Some perch are migratory, but only in a short and local form. They also have been observed leading a semianadromous life. Yellow perch do not accelerate quickly and are relatively poor swimmers. The fastest recorded speed for a school was 54 cm/s (12.08 mph), with individual fish swimming at less than half that speed.