About Perca flavescens (Mitchill, 1814)
This is the yellow perch, with the scientific name Perca flavescens (Mitchill, 1814). Yellow perch have an elongate, laterally compressed body, a subterminal mouth, and a relatively long but blunt snout that is shorter than the lower jaw. They have 800 fine teeth, and their rough skin comes from their ctenoid scales. Like most perches, yellow perch have two separate dorsal fins: the first (anterior) dorsal fin holds 12–14 spines, while the second has 2–3 spines at its anterior followed by 12–13 soft rays. The anal fin has 2 spines and 7–8 soft rays. The tips of the opercula are spined, the pelvic fins sit close together, the homocercal caudal fin is forked, and individuals have 7 or 8 branchiostegal rays. The upper head and body ranges in color from bright green to olive or golden brown. This upper body color extends onto the flanks to form 6–8 vertical bars over a yellow or yellowish green background. There is normally a blackish blotch on the membrane of the first dorsal fin, between the rearmost 3 or 4 spines. The dorsal and caudal fins range in color from yellow to green, while the anal and pelvic fins can be yellow through silvery white; during spawning season, males develop prominent red or yellow coloring on their lower fins. The pectoral fins are transparent and amber, and the ventral part of the body is white or yellow. Juvenile yellow perch are paler, and can have an almost whitish background color. The maximum recorded total length of yellow perch is 50 centimetres (20 in), though most individuals reach around 19.1 centimetres (7.5 in), and the maximum published weight is 1.9 kilograms (4.2 lb). Yellow perch are native to North American tributaries of the Atlantic Ocean and Hudson Bay, particularly the Great Lakes–St. Lawrence River and Mississippi River basins. In Canada, its native range covers all the Great Lakes, extends from Nova Scotia to the Prairie provinces, and reaches north to the Mackenzie River; it is also common in Great Slave Lake. In the United States, its native range extends south into Ohio and Illinois, covers most of the northeastern United States, and includes the Atlantic Slope basin extending south to the Savannah River; its native distribution was shaped by postglacial melt from the Mississippi River. There is also a small, likely native population in the Dead Lakes region of Florida's Apalachicola River system. Yellow perch have been widely introduced for sport and commercial fishing, and to create a forage base for bass and walleye. Most introductions were carried out by the U.S. Fish Commission in the late 19th and early 20th centuries, but unauthorized introductions have also likely happened via illegal releases, dispersal through connected waterways, and use as live bait. Currently in the United States, the combined native and introduced range extends from northern Missouri to western Pennsylvania to South Carolina and north to Maine, with introduced populations in the northwest and southwest parts of the country; the species has been extirpated in Arkansas. Introductions in Canada have been less intense than in the United States. It was originally limited to lakes in the Peace River drainage of British Columbia, but has since expanded to other nearby border areas; a population in Swan Lake of the Peace River drainage may be indigenous. Yellow perch have also been introduced to China and Japan. Yellow perch are most commonly found in the littoral zones of both large and small lakes, but they also live in slow-moving rivers and streams, brackish waters, and ponds. Due to human activity, they are now found in many man-made lakes, reservoirs, and river impoundments. They are most abundant in both warm and cool lakes, and thrive in smaller lakes where they can become the dominant species unless controlled by predation. The diet of yellow perch is primarily determined by age and body size. Young and larval yellow perch feed mainly on zooplankton. By one year of age, they switch to feeding on macroinvertebrates such as midges and mosquitoes. Large adult yellow perch eat invertebrates, fish eggs, crayfish, mysid shrimp, and juvenile fish. In some cases, they are predominantly piscivorous and even cannibalistic. Around 20% of the diet of yellow perch weighing over 32 g (1.1 oz) is made up of small fish. Yellow perch feed most heavily just before dark, and their average daily consumption equals 1.4% of their body weight. Their microhabitat is typically along shorelines among reeds, aquatic weeds, docks, and other structures. They reach their highest densities in aquatic vegetation, as they naturally form schools, and they also prefer small, weed-filled water bodies with muck, gravel, or sand bottoms. They are less abundant in deep, clear open water or unproductive lakes. Within rivers, they only occur in pools, slack water, and moderately vegetated habitat. They inhabit inshore surface waters during the summer. Almost all cool- to warm-water predatory fish species, including northern pike, muskellunge, bass, sunfish, crappie, walleye, trout, and even other yellow perch, prey on yellow perch. They are the primary prey of walleye (Sander vitreus), and walleye consume 58% of age zero and 47% of age one yellow perch in northern lakes. In shallow natural lakes, however, largemouth bass (Micropterus salmoides) may be the most influential species in shaping the quality of yellow perch populations. In Nebraska's Sandhill lakes, the mean weight and quality of yellow perch is not linked to invertebrate abundance, but is linked to the abundance of largemouth bass. The three main factors that influence the quality of panfish populations like yellow perch are predators, prey, and the environment. In eastern North America, yellow perch are an extremely important food source for birds, particularly double-crested cormorants, which specifically target them as primary prey. Other birds that prey on yellow perch include eagles, herring gulls, hawks, diving ducks, kingfishers, herons, mergansers, loons, and white pelicans. High estimates show that cormorants can consume up to 29% of the age-three yellow perch population. Yellow perch can effectively escape predation from lake trout and other native fishes during the summer, likely due to their high thermal tolerance. Yellow perch are normally active during the day and inactive at night, except during spawning when they are active both day and night. They most often form schools. Their vision is required for schooling: schools break up at dusk and reform at dawn. Schools typically hold 50 to 200 fish, arranged by age and size into a spindle shape. Younger yellow perch school more often than older, larger fish, which occasionally travel alone. Males and females often form separate schools. Some yellow perch migrate, but only over short local distances. They have also been observed to live a semianadromous life. Yellow perch cannot accelerate quickly, and are relatively poor swimmers. The fastest recorded speed for a school of yellow perch is 54 cm/s (12.08 mph), and individual fish swim at less than half that speed. Parasites and diseases that affect yellow perch include the epizootic bacterium Flavobacterium columnare, the red worm Eustrongylides tubifex, myxozoan cnidarians including the brain parasite Myxobolus neurophilus, the broad tapeworm Diphyllobothrium latum, and parasitic copepods of the genus Ergasilus.
