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Esox americanus

By Sophia Schroeder

Geographic Range

There are two subspecies of pickerel, Esox americanus: grass pickerel (Esox americanus vermiculatus) and redfin pickerel (Esox americanus americanus). Grass pickerel and redfin pickerel are distributed from the St. Lawrence River drainage in southern Canada and the Finger Lakes southward to Lake Okeechobee, Florida. Grass pickerel mainly exist west of the Appalachian mountain chain, along the Mississippi River regions. Redfin pickerel exist mainly east along the Atlantic slope. Grass pickerel replace redfin pickerel in the drainages of the Gulf of Mexico, the Mississippi River, and in Ontario. Grass pickerel were introduced to Idaho, Colorado, Utah, Washington, western Pennsylvania, Maryland, western New York, and potentially even Wisconsin (COSEWIC, 2005). ("COSEWIC assessment and status report on the grass pickerel Esox americanus vermiculatus in Canada", 2005; Page and Burr, 1991; Page and Burr, 2011)

Habitat

Grass and redfin pickerel reside in aquatic areas where there are large spans of aquatic vegetation. They are mainly found in relatively shallow (less than 2 meters) and warm (24-27 degrees Celsius) swamps, lakes, backwaters, and slow-moving pool habitats within stream channels that are clear. Usually, they reside in bodies of water that have muddy bottoms, but they can also exist in rocky substrates. They are mainly a freshwater species, but have been reported to be found in the brackish waters of New York and New Jersey and occasionally in brackish water around the Chesapeake Bay. ("COSEWIC assessment and status report on the grass pickerel Esox americanus vermiculatus in Canada", 2005; Crossman, 1962; Hildebrand and Schroeder, 1972; Page and Burr, 1991; Page and Burr, 2011)

  • Range depth
    2 (high) m
    6.56 (high) ft

Physical Description

One of the most distinctive characteristics identifying young redfin pickerel is a silvery-green stripe spanning the region from the tip of the snout to the base of the caudal fin. Also, their fins are not fully red, only the tips of their fins contain any red pigmentation. Juvenile redfin pickerel are typically between 10-20mm in length at the time of hatching and grow rapidly. Scales do not appear on young redfin pickerel until they are at least 50mm.

Grass pickerel are distinguished from their pike relatives mainly by their small size. On average, they rarely grow to be more than 300mm in length and can obtain a mass of 28-170 grams, with the largest specimens weighing just under 400 grams. They have a long, cylindrical, yet flattened body shape, a forked caudal fin. Like most members of the pike family, their snout is often considered duck-like and filled with sharp teeth. Their dusty-brown dorsal and anal fins are located posteriorly on their body. They also have dark vertical, but rear slanted, suborbital and preorbital bars, which means a stripe that runs above and below the eye. Also on their heads, the majority of their cheeks and opercles are scaled. Grass pickerel vary in color but most are a greenish-brown with a brown stripe running the length of their spines. Along their sides, they have dark greenish-brown bars that run vertically and are fairly narrow. Grass pickerel have lateral lines consisting of fewer than 110 scales and 3-5 submandibular pores.

Redfin pickerel, compared to grass pickerel, have a shorter, broader snout. Also, their pelvic and pectoral fins are red. Redfin pickerel total lengths average between 150-200mm. Also, redfin pickerel grow faster than grass pickerel (Sternberg, 1987). Redfin pickerel have a complete lateral line with 94-117 scales, and 3-5, usually 4, submandibular pores.

Male and female grass and redfin pickerel are patterned alike, but females tend to be larger than males in specimens over 200mm. Ming (1968) examining grass pickerel in Oklahoma, found females weighed more and grew to longer lengths than males did over the 4 years this study was conducted. Specifically, females averaged 127g, 197g, 248g, and 306g in the 1st, 2nd, 3rd, and 4th years of the study respectively, whereas males were averaged 123g, 195g, and 235g (no 4th year) in the same time period. The total lengths of male and female grass pickerel follow the same trend; 3-year-old females had average lengths of 140mm, 203mm, and 245mm through years 1-3 respectively. Males were smaller than females through the same time period, with average lengths of 132mm, 194mm, 235mm (Ming, 1968). ("COSEWIC assessment and status report on the grass pickerel Esox americanus vermiculatus in Canada", 2005; Crossman, 1962; Ming, 1968; Parnell, et al., 1994; Sternberg, 1987; Trautman, 1986)

  • Sexual Dimorphism
  • female larger
  • Range mass
    28 to 400 g
    0.99 to 14.10 oz
  • Range length
    10 to 300 mm
    0.39 to 11.81 in

Development

According to Crossman (1962), the growth of newly hatched grass or redfin pickerel is relatively rapid. The fry hatch with no scales, an unsegmented spinal chord, and a notochord that spans to the tip of the rounded caudal fin. Once the fry reach approximately 30mm their vertebrae begin to segment and the urostyle begins to develop. By 20mm, their lateral lines have developed. The pickerels' scales appear when they are approximately 50mm and form behind the head and pelvic area. Once the pickerel have reached 65mm they become fully scaled and their caudal fin becomes completely formed and forked, and the urostyle is completely developed and spine completely segmented. Grass pickerel grow faster than redfin pickerel, which grow 25-35mm a year. Like most fish, pickerel exhibit indeterminate growth. (Crossman, 1962; Ross, 2001)

Reproduction

Grass and redfin pickerel spawn in the late winter to early spring months, with grass pickerels occasionally spawning a second time in the late summer to early winter months. Spawning occurs in heavily vegetated floodplains, swamps, and tributary streams that are sometimes so shallow (less than 30.5cm), that the male and female pickerel are out of the water.

Female grass and redfin pickerel are polyandrous, meaning that they have more than one male mate. A group of one female pickerel and 1-3 male pickerel swim along, scattering fertilized eggs. The eggs and milt, or semen, are ejected from the respective fishes and mixed together by lashing their caudal fins. The fertilized eggs are spread over areas that are dense with aquatic vegetation and are usually closer to the shore than other members of the family Esocidae, like the northern pike (Esox lucius). After the act of spawning is finished, the eggs are abandoned. ("COSEWIC assessment and status report on the grass pickerel Esox americanus vermiculatus in Canada", 2005; Crossman, 1962; Ming, 1968; Parnell, et al., 1994; Wallus, et al., 1990)

Grass and redfin pickerel reach sexual maturity between ages 1-3 years old. They are some of the first fish to spawn, with the process occurring in the late winter to early spring (February-April) when water temperatures are drawing near 4-10 °C. Grass pickerel occasionally spawn more than once a year with the second spawning season in the late summer-early winter (August-November). On occasion, grass pickerel have been known to migrate to streams from lakes to spawn.

As with most fish species, eggs are fertilized externally. The duration of spawning takes place in a 2-4 week time frame. The actual act takes place in the daytime and lasts about 5 minutes. Eggs that are ready to be dispersed are clear, golden-yellow or amber, and are 1.9mm in diameter, on average, and located in the ovary. According to Wallus et al. (1990), the pickerel eggs are scattered among or on the edges of aquatic vegetation like moss or grasses, and underwater debris like leaves and twigs. These eggs can be found in floodplains, tributary streams, and swamps. Once the eggs are dispersed they are abandoned and hatch within 12-14 days.

Grass pickerel have a higher egg count than redfin pickerel. According to Crossman (1962), of 10 3-4-year-old redfin pickerel females sampled, the average primary egg count was 269.4 with a range of 186-542, and the total egg count was estimated at 3716.2 with a range of 722-4364 (Crossman, 1962). A single redfin pickerel was compared to a grass pickerel of similar size and the egg count varied significantly. The redfin had 186 primary, or mature eggs, with a total egg count of 3,672 while the grass pickerel had 803 and 15,732 respectively (Crossman, 1962).

Grass and redfin pickerel reach sexual maturity as early as age one when the males are at least 188mm in total length and females are 109mm total length. The pickerel are usually able to spawn by age 2. (Clark, 1950; Crossman, 1962; Jenkins and Burkhead, 1994; Ross, 2001; Wallus, et al., 1990)

  • Breeding interval
    Spawn once in the late winter and early spring months for a period of 2-4 weeks. Grass pickerel occasionally spawn again in the late summer to early winter months.
  • Breeding season
    February-March and for grass pickerel, possibly again in August-November.
  • Range number of offspring
    186 to 803
  • Range time to hatching
    12 to 14 days
  • Average time to independence
    0 days
  • Range age at sexual or reproductive maturity (female)
    1 to 3 years
  • Range age at sexual or reproductive maturity (male)
    1 to 3 years

There is no parental care after spawning with grass and redfin pickerel young. After spawning, the adult pickerel abandon the eggs. (Parnell, et al., 1994)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

In the wild, the maximum life span of grass pickerel is 7 years. In North Carolina, the expected lifespan of redfin pickerel is 5-7 years. According to Sternberg (1987), grass and redfin pickerel can reach a maximum age of 8 years old in the wild. Female redfin pickerel live longer than males. Grass and redfin pickerel are not kept in captivity. (Crossman, 1962; Jenkins and Burkhead, 1994; Sternberg, 1987)

  • Range lifespan
    Status: wild
    8 (high) years
  • Typical lifespan
    Status: wild
    5 to 7 years

Behavior

Grass and redfin pickerel are diurnal, meaning they are most active and do most of their activities like feeding and spawning in the daytime. Grass and redfin pickerel are relatively solitary fish, and interact little with other species beyond acts of predation. Though pickerel are solitary, their larvae gather in nursery areas in weedy swamps. When not in spawning season, they are sedentary and do not travel very far daily, but they do migrate to other areas in order to spawn. They will travel out of their area to feed, or in response to water level changes, but this is not as frequent. This is how they become isolated or trapped in pools of water that are not part of the stream or channel. Grass pickerel usually orient themselves with their head toward the shore or edge of the water.

Grass pickerel grow at faster rates than redfin pickerel and both can hybridize with chain pickerel (Esox niger) and northern pike (Esox lucius) if they are found in the same geographic area. Grass and redfin pickerel have a lateral line system, which is a sensory canal system made up of pores and sensory organs. This is useful in detecting water pressure/movement changes. Grass and redfin pickerel use ram style ambush when capturing prey. This means that the pickerel move towards their prey by propelling themselves forward, at first slowly, then curving their bodies to help propel themselves at the fastest acceleration they can reach. ("COSEWIC assessment and status report on the grass pickerel Esox americanus vermiculatus in Canada", 2005; Pitcher, 1986; Ross, 2013; Wallus, et al., 1990)

Home Range

According to Wagner and Wahl (2011), muskelllunge (Esox masquinongy), move between 40m-75m per hour in the spring, 15m-40m in the summer, and 26m-55m in the fall. There has been no documentation of a home range for grass and redfin pickerel, but it is likely that they travel in a similar seasonal pattern. Grass and redfin pickerel are mostly sedentary when not in spawning season, when they will migrate to other areas, and only travel in response to water level changes or to feed. (Wagner and Wahl, 2011)

Communication and Perception

Grass pickerel are visual predators and rely on sight to catch their prey during the daylight hours. There is not much information found on the methods of communication and perception of pickerels, but it is likely that they are similar to that of the rest of the family Esocidae. Muskellunge (Esox masquinongy) primarily use their sight to locate prey, but the lateral line system helps them determine the distance and angle as to which they should strike prey (New and Fewkes, 2001). Also, fathead minnows (Pimephales promelas) excrete alarm pheromones and are able to detect those pheromones in the feces of northern pike (Esox lucius) that have recently consumed a minnow. Due to this, northern pike often times will excrete waste farther from their home area in order to not be identified as a predator to minnows (Brown et al., 1995).

The lateral line system is present in every fish species. It is a sensory canal system that detects the changes in water pressure and water movement through open pores and sensory organs, which is useful in detecting prey. Lateral lines are made up of pores that can span from the head to the caudal fin. Redfin pickerel have a complete lateral line, meaning it reaches from the head to the caudal fin, with 94-117 scales and grass pickerel have a lateral line with fewer than 110 scales. Both pickerel have 3-5 submandibular pores which, along with the lateral line, are connected to the cephalic lateralis canal system (sensory canals on the head). These pores are open, located under the jaw, and aid the lateral line in the detection of water pressure and movement changes. ("COSEWIC assessment and status report on the grass pickerel Esox americanus vermiculatus in Canada", 2005; Brown, et al., 1995; Jenkins and Burkhead, 1994; Page and Burr, 1991; Parnell, et al., 1994; Trautman, 1986)

  • Communication Channels
  • visual

Food Habits

Younger grass and redfin pickerel diets vary from the diet of adult pickerel. Until they are about 50 mm in size, juveniles primarily rely on small crustaceans, like cladocerans or amphipods, and aquatic insects for food.

Grass and redfin pickerel are piscivorous, meaning they eat other fish. The diet of grass pickerel 50-100mm consists mainly of small crustaceans and aquatic insects, such as members of the orders Trichoptera (caddisflies) and Odonata (dragonflies and damselflies). Their diet also includes crayfish and some fish, like sunfish (family Centrarchidae) and fish of the genus Etheostoma. Adult grass pickerel 100-199mm consume mostly sunfish and minnows (family Cyprinidae). Larger pickerel 200-340mm consume a diet mainly of fish, most of which are sunfish. Being daytime eaters, they hide in submerged aquatic vegetation to wait out the prey that they visually locate. ("COSEWIC assessment and status report on the grass pickerel Esox americanus vermiculatus in Canada", 2005; Crossman, 1962; Jenkins and Burkhead, 1994; Ming, 1968)

  • Animal Foods
  • fish
  • aquatic crustaceans

Predation

Species of the family Esocidae are usually the top predators in their environments. Grass and redfin pickerel are cannibalistic at times and can be predators to themselves. Though they are rarely caught for sport fishing purposes, humans (Homo sapiens) impose a predatory threat upon grass and redfin pickerel. (Crossman, 1962)

Ecosystem Roles

Grass and redfin pickerel are typically top predators in their habitats. The protozoan parasites of these pickerel include Trichodina renicola that exists in the urinary tract of pickerel. Trematode parasites of these pickerel are Azygia angusticauda, Crassiphiala bulboglossa in its larval form, and Macrodeiodes flavus. Cestode parasites are bass tapeworms Proteocephalus ambloplitis and Proteocephalus pinguis. Nematode parasites include an unidentified roundworm in the family Spiruridae in its larval form. (Hoffman, 1967)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Grass and redfin pickerel are not notable gamefish due to their small size, but are sometimes caught on accident by game fisherman. If pickerel are caught and not thrown back, they can be eaten as food. According to Sternberg (1987), their meat is described as white, flaky, and sweet-tasting but bony. (Sternberg, 1987)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

There are no negative economic impacts of grass or redfin pickerel on humans.

Conservation Status

Redfin pickerel are listed as a species of "Least Concern" on the IUCN Red List and have no special status on the federal endangered species list, through CITES list, or on the state of Michigan list. According to COSEWIC (2005), grass pickerel were designated a species of special concern in Canada in 2005. Major threats here include of loss of habitat from dredging and the deepening, or channelization, of wetland areas that the grass pickerel inhabit. ("COSEWIC assessment and status report on the grass pickerel Esox americanus vermiculatus in Canada", 2005)

Contributors

Sophia Schroeder (author), Radford University, Alex Atwood (editor), Radford University, Karen Powers (editor), Radford University, Joshua Turner (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

piscivore

an animal that mainly eats fish

polyandrous

Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

visual

uses sight to communicate

References

Committee on the Status of Endangered Wildlife in Canada. COSEWIC assessment and status report on the grass pickerel Esox americanus vermiculatus in Canada. None. Ottawa: Committee on the Status of Endangered Wildlife in Canada. 2005.

U.S. Army Corps of Engineers. Mitigated wetland restoration: Environmental effects at Green Bottom Wildlife Management Area, West Virginia. WRP-RE-10. Washington D.C.: U.S. Army Corps of Engineers. 1995.

Brown, G., D. Chivers, R. Smith. 1995. Localized defecation by a pike: A response to labeling by cyprinid alarm pheremone?. Behavioral Ecology and Sociobiology, 36: 105-110.

Clark, C. 1950. Observations on the spawning habits of the northern pike, Esox lucius, in northwestern Ohio. Copeia, 1950/4: 285-288.

Crossman, E. 1962. The redfin pickerel, Esox a. americanus in North Carolina. Copeia, 1962/1: 114-123.

Hildebrand, S., W. Schroeder. 1972. Fishes of Chesapeake Bay. Neptune, NJ: T.F.H Publications.

Hoffman, G. 1967. Parasites of North American Freshwater Fishes. Berkley and Los Angeles, CA: University of California Press.

Hoyle, J., H. Gill, A. Weatherley. 1986. Histochemical characterization of myotomal muscle in the grass pickerel, Esox americanus vermiculatus (LeSeuer), and the muskellunge, E. masquinongy (Mitchell). Journal of Fish Biology, 28/4: 393-401.

Jenkins, R., N. Burkhead. 1994. Freshwater Fishes of Virginia. Bethesda, MD: American Fisheries Society.

Ming, A. 1968. Life history of the grass pickerel, Esox americanus vermiculatus, in Oklahoma. Oklahoma Research Laboratory Bulletin, 8: 66.

Mueller, J. 1938. A new species of Trichodina (Ciliata) from the urinary tract of the muskellunge, with a repartition of the genus. The Journal of Parasitology, 24/3: 251-258.

New, J., L. Fewkes. 2001. Strike feeding behavior in the muskellunge, Esox masquinongy: contributions of the lateral line system and visual sensory systems. The Journal of Experimental Biology, 204: 1207-1221.

Page, L., B. Burr. 1991. A Field Guide to Freshwater Fishes: North America north of Mexico. Boston, MA: Houghton Mifflin.

Page, L., B. Burr. 2011. Peterson Field Guide to Freshwater Fishes. Boston, MA: Houghton Mifflin Harcourt.

Parnell, J., F. Rohde, D. Lindquist, R. Arndt. 1994. Freshwater Fishes of the Carolinas, Virginia, Maryland, and Delaware. Chapel Hill, NC: University of North Carolina Press.

Pitcher, T. 1986. The Behavior of Teleost Fishes. Kent, UK: Croom Helm Ltd.

Ross, S. 2013. Ecology of North American Freshwater Fishes. Berkeley and Los Angeles, CA: University of California Press.

Ross, S. 2001. Inland Fishes of the Mississippi. Jackson, MS: University Press of Mississippi.

Sternberg, D. 1987. Freshwater Gamefish of North America. New York, NY: Prentice Hall Press.

Trautman, M. 1986. The Fishes of Ohio. Columbus, OH: Ohio State University Press.

Wagner, C., D. Wahl. 2011. Movement, home range and habitat selection of stocked juvenile muskellunge, Esox masquinongy, in Forbes Lake, Illinois: Exploring the effects of latitudinal origin. Fisheries Management and Ecology, 18/6: 482-496.

Wallus, R., B. Yeager, T. Simon. 1990. Reproductive Biology and Early Life History of Fishes in the Ohio River Drainage. Chattanooga, TN: Tennessee Valley Authority.

Weinman, M., T. Lauer. 2007. Diet of grass pickerel (Esox americanus vermiculatus) in Indiana streams. Journal of Freshwater Ecology, 22/3: 451-460.

Willis, D., J. Jolley, D. Willis. 2008. Characteristics of a grass pickerel (Esox americanus vermiculatus) population in Pony Lake, Nebraska. Journal of Freshwater Ecology, 23/3: 497-499.

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