Yellow perch

The yellow perch has an elongate, oval body with a relatively long but blunt snout which does not reach past the tip of the lower jaw. Like most perches it has two separate dorsal fins[5] The anterior, or first, dorsal fin contains 12-14 spines while the second has 2-3 spines in its anterior followed by 12-13 soft rays. The anal fin has 2 spines and 7-8 soft rays.[6] The upper part of the head and body varies in colour from bright green through to olive or golden brown.[5] although typically they are golden yellow.[6] The colour on the upper body extends onto the flanks where it creates a pattern of 6-8 vertical bars over a background colour of yellow or yellowish green.[5] They normally show a blackish blotch on the membrane of the first dorsal fin between the rearmost 3 or 4 spines.[6] The colour of the dorsal and caudal fins vary from yellow to green while the anal and pelvic fins may be yellow through to silvery white. The pectoral fins are transparent and amber in colour. The ventral part of the body is white. The juvenile fish are paler and can have an almost whitish background colour.[6] The maximum recorded total length is 50 centimetres (20 in). although they are more commonly around 19.1 centimetres (7.5 in), and the maximum published weight is 1.9 kilograms (4.2 lb).[3]

Yellow perch are only found in North America; they are native to the Arctic and Atlantic Oceans, and the Great Lakes-St. Lawrence River and Mississippi River basins. In Canada, its native range extends throughout Nova Scotia and Quebec north to the Mackenzie River. It also is common in the northwest to Great Slave Lake and west into Alberta. It is not native to any other areas of Canada. In the United States, the native range extends south into Ohio and Illinois, and throughout most of the northeastern United States. It is also considered native to the Atlantic Slope basin, extending south to the Savannah River. There is also a small native population in the Dead Lakes region of the Apalachicola River system in Florida.[7]

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. However, unauthorized introductions have likely occurred from illegal introductions, dispersal through connected waterways, and use as live bait. Isolated populations now occur in the northwest and southwest portions of the United States. Currently, the yellow perch has not been introduced outside of North America. Introductions in Canada have been less intense than in the United States. It has been extirpated in Arkansas.[8]

Yellow perch typically reach sexual maturity in 2–3 years for males and 3–4 years for females. They are iteroparous, spawning annually in the spring when water temperatures are between 2.0 and 18.6 °C (35.6 and 65.5 °F). 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.[9] 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 15 m (49 ft) or on the bottom.[10]

In the northern waters, perch tend to live longer and grow at a slower rate. Females in general are larger, grow faster, live longer, and mature in 3-4 years compared to males, which mature in 2-3 years at a smaller size. Most research has showed the maximum age to be about 9–10 years, with a few living past 11 years. The preferred temperature range for the yellow perch is 17 to 25 °C (63 to 77 °F), with an optimum range of 21 to 24 °C (70 to 75 °F) and a lethal limit in upwards of 33 °C (91 °F) and a stress limit over 26 °C (79 °F). 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. Spawning typically takes place at night or in the early morning. Females have the potential to spawn up to eight times in their lifetimes.[10]

A small aquaculture industry in the US Midwest contributes about 90,800 kg (200,200 lb) of yellow perch annually, but the aquaculture is not expanding rapidly.[10] The yellow perch is absolutely crucial to the survival of the walleye and largemouth bass in its range.[10] Cormorants feed heavily on yellow perch in early spring, but over the entire season, only 10% of their diets is perch.[11] Cormorants and anglers combined harvest 40% of 1- and 2-year-old yellow perch and 25% of the adult yellow perch population in Lake Michigan. Total annual mortality of adult yellow perch has not changed since cormorant colonization.[12]

Yellow perch is often recognized by its dark vertical stripes and gold or yellow body color. Perca is derived from early Greek for "perch" and flavescens is Latin for "becoming gold" or "yellow colored". Adult sizes typically range from 3.9–11.4 in (10–30 cm); though have been known to grow larger. The yellow perch has a laterally compressed body with an oval, oblong shape. The anal fins are a green or yellow-orange, the dorsal fin is an olive color, and the belly is cream-colored. The vertical bands fade as they near the belly. Spawning intensifies the bands in males, and they can be nonexistent in juveniles. The spiny anterior dorsal fin has 13 to 15 spines. The soft rear fins also have one or two spines, but which are mostly made up of rays that range from 12 to 15 in number. The pelvic fins are close together, and the homocercal caudal fin is forked. The operculum tip has one spine, and the anal fin has two spines. Seven or eight branchiostegal rays are seen. Yellow perch have many fine and sharp teeth. They are rough to the touch because of their ctenoid scales. Common names for the perch are yellow perch, American perch, and lake perch. Yellow perch are one of the smaller-sized members of the perch family (Percidae). Due to their ability to crossbreed and their similar morphology, yellow perch are sometimes classified as a subspecies of the European perch.[10] 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 of the US and Canada. It even makes up around 85% of the sport fish caught in Lake Michigan.

Yellow perch are native to North America in the northern region east of the Rocky Mountains, including tributaries of the Arctic and Atlantic Oceans and the Mississippi River. Native distribution was driven by postglacial melt from the Mississippi River. It has been widely dispersed from its native range. Its distribution to other areas of the eastern US and Canada are due to its popularity as a sport and commercial fish, as well as being a forage fish for other sport fish species, such as bass or walleye. The current native and introduced range in the United States is through northern Missouri to western Pennsylvania to South Carolina and north to Maine. Introduced areas currently have not expanded outside of North America. These introductions were predominantly performed by the US Fish Commission in the late 1800s and early 1900s. The non-native dispersal was not as intense in Canada. It was primarily limited to the lakes in the Peace River drainage of British Columbia, but has currently expanded to other bordering areas since.[10]

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.[10]

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.[10]

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, 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's 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.[13]

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. In Canada, yellow perch are effective at escaping predation seasonally 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 Flavobacterium columnare, red worm Eustrongylides tubifex, broad tapeworm Diphyllobothrium latum, and parasitic copepods Ergasilus spp.[14]

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 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.[10]

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. Yellow perch do not travel far during the year, but 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.[10]

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.[10]

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.[15] 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.[10]

In 2000, the parasite Heterosporis spp. was discovered in yellow perch on the Eagle River Chain of Lakes in Vilas County in Wisconsin, and has since been found in Minnesota, Michigan, and Ontario. The parasite does not infect people, but can infect many important sport and forage fish including the yellow perch. It does not kill the infected fish, but the flesh of a severely infected fish becomes inedible when the fish dies and the spores are then spread through the water to infect another fish. That concerns commercial fisherman in the Great Lakes regions that depend on these fish. The infected perch are not marketable. The current infection rates are 5% of harvest. Viral hemorrhagic septicemia is another serious disease in perch in the Great Lakes region. It has already killed thousands of drum in Lake Ontario and caused a large die-off of yellow perch in Lake Erie in 2006. Ontario is restricting commercial bait licenses as a precaution against this disease. Outside its native range, very few diseases or parasites have been found.[10]

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.[16] 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.[17][18] 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.[17][18][19]

The market demand for wild yellow perch has decreased due to overfishing in the 60’s -70’s but farmed perch has become more popular. Farmed yellow perch reduce the need for mass harvesting from bodies of water. The domestic and international market have seen that farm perch are often the same or similar quality to wild perch. The aquaculture industry for yellow perch has added over 50 Metric Tons of farmed fish into the market to offset the need for wild caught fish according to Bill Manci from Fisheries Technology.[17] Currently, the demand of yellow perch fish has been increasing and will continue to increase at a 2.3% climb over the next decade. Yellow perch are an international fish that has 6,000 species worldwide, which helps with the global fish trade. In 2017, the production of fish trade led to 150 billion dollars. If the 2.3% increase continues over the decade, then the fish trade will have a major impact on the economy and will cause an increase in the Perch market due to the import market of perch being a driving force. In order for the perch market to increase, the population of perch needs to continue to be abundant which means limiting the pollutants that can cause harm to them in the waters.[20]