Yellow perch

Yellow perch are native to the tributaries of the Atlantic Oceans and Hudson Bay in North America, particularly the Great Lakes–St. Lawrence River and Mississippi River basins. In Canada, its native range includes all the Great Lakes, and from Nova Scotia to the Prairie provinces north to the Mackenzie River. It also is common in the Great Slave Lake. The yellow perch has also been widely introduced for sport and commercial fishing purposes. It has also been introduced to establish a forage base for bass and walleye. These introductions were predominantly performed by the U.S. Fish Commission in the late 19th and early 20th centuries. It has been extirpated in Arkansas. ==Description==

The yellow perch has an elongate, laterally compressed body and a relatively long but blunt snout which is surpassed in length by the lower jaw. Yellow perch have 800 fine teeth. The juvenile fish are paler and can have an almost whitish background colour. The maximum recorded total length is —although they are more commonly around —and the maximum published weight is . ==Habitat==

Yellow perch are commonly found in the littoral zones of both large and small lakes, but also inhabit slow-moving rivers and streams, brackish waters, and ponds. Due to human intervention, they are currently found in many man-made lakes, reservoirs, and river impoundments. The perch are most abundant in lakes that may be warm or cool and are extremely productive in smaller lakes where they can dominate unless controlled by predation. ==Biology==

Yellow perch typically reach sexual maturity in two to three years for males and three to four years for females. They are iteroparous, spawning annually in the spring when water temperatures are between . Spawning is communal and typically occurs at night. Yellow perch are oviparous, as eggs are fertilized externally. Eggs are laid in a gelatinous strand (commonly 10,000–40,000), a characteristic unique among North American freshwater fishes. Egg strands are commonly draped over weeds, the branches of submerged trees or shrubs, or some other structure. Eggs hatch in 11–27 days, depending on temperature and other abiotic factors. They are commonly found in the littoral zones of both large and small lakes, but they also inhabit slow-moving rivers and streams, brackish waters, and ponds. Yellow perch commonly reside in shallow water, but are occasionally found deeper than or on the bottom. According to VanDeValk et al. (2002), "Cormorant consumption of adult yellow perch was similar to angler harvest, but cormorants consumed almost 10 times more age‐2 yellow perch and only cormorants harvested age‐1 yellow perch. Cormorants and anglers combined harvested 40% of age‐1 and age‐2 yellow perch and 25% of the adult yellow perch population. Total annual mortality of adult percids has not changed since cormorant colonization. Although cormorant consumption of adult percids has little effect on harvest by anglers, consumption of subadults will reduce future angler harvest of yellow perch and, to a lesser extent, walleyes." ==Life history==

Yellow perch spawn once a year in spring using large schools and shallow areas of a lake or low-current tributary streams. They do not build a redd or nest. Females have the potential to spawn up to eight times in their lifetimes. Two to five males go to the spawning grounds first and are with the female throughout the spawning process. The female deposits her egg mass, and then at least two males release their milt over the eggs, with the total process taking about five seconds. The males stay with the eggs for a short time, but the females leave immediately. No parental care is provided for the eggs or fry. The average clutch size is 23,000 eggs, but can range from 2,000 to 90,000. The egg mass is jelly-like, semibuoyant, and can reach up to 2 m long. The egg mass attaches to some vegetation, while the rest flows with the water current. Other substrate includes sand, gravel, rubble, and submerged trees and brush in wetland habitat. Yellow perch eggs are thought to contain a chemical in the jelly-like sheath that protects the eggs and makes them undesirable since they are rarely ever eaten by other fish. The eggs usually hatch in 8–10 days, but can take up to 21 days depending on temperature and proper spawning habitat. Sedentary populations in small freshwater lakes move into deeper water during winter and return to shallow water in spring to spawn. Spawning occurs in the spring when water temperatures are between 6.7 and 12.8 °C. Growth of fry is initiated at 6–10 °C, but is inactive below 5.3 °C. Larval yellow perch survival is based on a variety of factors, such as wind speed, turbidity, food availability, and food composition. Immediately after hatching, yellow perch head for the pelagic shores to school and are typically 5 mm long at this point. This pelagic phase is usually 30–40 days long. Sexual dimorphism is known to occur in the northern waters where females are often larger, grow faster, live longer, and mature in 3–4 years. Males mature in 2–3 years at a smaller size. Perch do not grow as large in the northern waters, but tend to live longer. Maximum age estimates vary widely. The age of the perch is highly based on the condition of the lake. Most research has shown the maximum age to be approximately 9–10 years, with a few living past 11 years. Yellow perch have been proven to grow the best in lakes where they are piscivorous due to the lack of predators. Perch do not perform well in cold, deep, oligotrophic lakes. Seasonal movements tend to follow the 20 °C isotherm and water temperature is the most important factor influencing fish distribution. Yellow perch commonly reside in shallow water, but are occasionally found deeper than 15 m or on the bottom. Their optimum temperature range is 21–24 °C, but have been known to adapt to warmer or cooler habitats. The common lethal limit is 26.5 °C, but some research has shown it to be upwards of 33 °C with a stress limit at anything over 26 °C. To grow properly, yellow perch prefer a pH of 7 to 8. The tolerable pH ranges have been found to be about 3.9 to 9.5. They also may survive in brackish and saline waters, as well as water with low dissolved oxygen levels. ==Ecology==

Primarily, age and body size determine the diets 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 g (1.1 oz) in weight consists of small fish. Maximum feeding occurs just before dark, with typical consumption averaging 1.4% of their body weight. 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 are effective at escaping predation seasonally by lake trout and other native fishes during summer, perhaps due to the high thermal tolerance of yellow perch. red worm Eustrongylides tubifex, including brain parasite Myxobolus neurophilus, broad tapeworm Diphyllobothrium latum, and parasitic copepods Ergasilus spp. ==Current management==

Managers employed management techniques at Drummond Island, Michigan, such as harassing the cormorants and killing them as needed. Overall, the harassment deterred 90% of cormorant foraging attempts, while killing less than 6% on average at each site; yellow perch abundance increased significantly due to their being the predominant prey of cormorants by total number and weight at that lake. Lakes in South Dakota without suitable spawning substrate have had conifers introduced, such as short-needle spruce, to increase both spawning habitat and hatching success. Managers have identified seven key unauthorized pathways for the introduction of the yellow perch to non-native regions: shipping, recreational and commercial boating, construction of new canals and water diversions, releases from live food fish markets, releases from the aquarium and water garden trade, use of live bait, and illegal introductions to create new fisheries. The most likely unofficial pathways are illegal introductions, dispersal through connected waterways, and live bait. Many authorized introductions by natural resources agencies have taken place, as well, due to the sport-fishing demand. The stocking project was completed using broodstock from other water bodies. It is hypothesized that egg and sperm viability was decreased by hypoxic conditions in the Severn River affecting juveniles and adults in late summer or through exposure to endocrine-disrupting chemicals. Rates of helminth infections affecting the gonads were low in a histological study conducted during perch spawning runs between 2007 and 2009, suggesting that parasitic castration by those species is not a major contributor to the pathology. Female yellow perch undergo synchronous development of oocytes in their single ovary and allocate energy in late summer and fall to developing the eggs they will lay en masse the following spring. Fishing Yellow perch are a popular sport fish, prized by both recreational anglers and commercial fishermen for their delicious, mild flavor. Because yellow perch are among the finest flavored pan fish, they are occasionally misrepresented on menus within the restaurant industry. White perch, rock bass, and many species of sunfish (genus Lepomis) are sometimes referred to as "perch" on menus. The voracious feeding habits of yellow perch make them fairly easy to catch when schools are located, and they are frequently caught by recreational anglers targeting other species. Perch at times attack lures normally used for bass such a 3" tubes, Rapala minnows, and larger curl tail grubs on jigheads, and small, brightly colored casting spoons, but the simplest way to catch them is to use light line, 4 to 8# test and light, unpainted jig heads, 1/32–1/16 oz. Too many small soft plastic lure designs to mention can catch all panfish, but minnow-shaped lures with a quivering tail work much of the time, so long as the retrieval speed is slow and the lure is fished at the depth the perch are swimming. Thin, straight-tail grubs require the slowest speed of retrieval and are preferred when the bite is slow, which is much of the time. Some good baits for perch include worms, live and dead minnows, small freshwater clams, crickets, and any small lure resembling any of these. Larger perch are often caught on large live minnow on a jighead, especially when fished over weed beds. Bobbers, if used, should be spindle type for the least resistance when the bait is struck, but small, round bobbers work well, too, yet indicate any slight pull of the bait. Raising the rod tip is usually more than enough force to set the hook. Some yellow perch fisheries have been affected by intense harvesting, and commercial and recreational harvest rates often are regulated by management agencies. In most aquatic systems, yellow perch are an important prey source for larger, piscivorous species, and many fishing lures are designed to resemble yellow perch. ==Aquaculture ==

Yellow perch is a viable species for aquaculture. This species has shown a net weight gain between 37 and 78 grams over a three-year period in a study that raised yellow perch in outdoor ponds. Yellow perch meet several characteristics that make a species fit for aquaculture. Some such characteristics are as follows: they are low on the food chain, needing an optimal protein content of 21–27%, are accepting of pelleted fish feed, grow well in high densities due to their schooling nature, and the fish do not turn cannibalistic at high densities. When grown in ponds or tanks, yellow perch do not exhibit off flavors compared to wild caught yellow perch. These fish become sexually mature before they reach market size under natural conditions. Yellow perch rely on environmental cues, such as cooler temperatures, to mature. Controlling the temperature of the system allows yellow perch to be grown to market size before they mature. ==Market==

For over 100 years, Canada and the United States have been commercially harvesting yellow perch in the Great Lakes with trapnets, gillnets, and poundnets. In Canada, the estimated catch in 2002 was 3,622 tons with a value of $16.7 million, second only to walleye at $28.2 million. The greatest demand in the United States is in the north-central region, where nearly 70% of all yellow perch sales in the US occur within 80 km (49.7 mi) of the Great Lakes. Yellow perch is one of the easiest fish to catch, and can be taken in all seasons, and tastes great. Therefore, it is a desirable sport fish in some locations within the US and Canada. It even makes up around 85% of the sport fish caught in Lake Michigan. The market demand for wild yellow perch has decreased due to overfishing in the 1960s and 1970s but farmed perch has become more popular. Farmed yellow perch reduce the need for mass harvesting from bodies of water. In 2000 farmed perch on the domestic and international markets were often the same or similar quality to wild perch. ==Etymology==

According to Brown, Runciman, Bradford and Pollard (2009), the genus name, Perca, is derived from ancient Greek for "perch" and the specific epithet, flavescens, is Latin for "becoming gold" or "yellow colored". ==References==