Northern pike
The northern pike, also known as pickerel, jack, northern or simply pike, is a species of carnivorous fish of the genus Esox. It is commonly found in fresh waters of the Northern Hemisphere.
Pike can grow to a relatively large size. Their average length is about, with maximum recorded lengths of up to and maximum weights of. The IGFA currently recognises a pike caught by Lothar Louis on Greffern Lake, Germany, on 16 October 1986, as the all-tackle world-record holding northern pike. Northern pike grow to larger sizes in Eurasia than in North America, and in coastal Eurasian regions than inland ones.
Etymology
The northern pike gets its common name from its resemblance to the pole-weapon known as the pike. Names such as pike, pickerel, Lakes pike, great northern pike, jackfish, jack, slough shark snake, slimer, slough snake, gator, and hammer handle are used around the globe. Other names incorporating things such as "pointy nose" and "long head" are common as well. The name "Northern" is very popular in the Midwest or luce when fully grown, was used to form its taxonomic name and is used in heraldry.Description
Northern pike are most often olive green, shading from yellow to white along the belly. The flank is marked with short, light bar-like spots and a few to many dark spots on the fins. Sometimes, the fins are reddish. Younger pike have yellow stripes along a green body; later, the stripes divide into light spots and the body turns from green to olive green. The lower half of the gill cover lacks scales, and it has large sensory pores on its head and on the underside of its lower jaw which are part of the lateral line system. Unlike the similar-looking and closely related muskellunge, the northern pike has light markings on a dark body background and fewer than six sensory pores on the underside of each side of the lower jaw.A hybrid between northern pike and muskellunge is known as a tiger muskellunge. In the hybrids, the males are invariably sterile, while females are often fertile, and may back-cross with the parent species. Another form of northern pike, the silver pike, is not a subspecies but rather a mutation that occurs in scattered populations. Silver pike, sometimes called silver muskellunge, lack the rows of spots and appear silver, white, or silvery-blue in color. When ill, silver pike have been known to display a somewhat purplish hue; long illness is also the most common cause of male sterility.
In Italy, the newly identified species Esox cisalpinus was long thought to be a color variation of the northern pike, but was in 2011 announced to be a species of its own.
Length and weight
Northern pike in North America seldom reach the size of their European counterparts; one of the largest specimens known was a specimen from New York. It was caught in Great Sacandaga Lake on 15 September 1940 by Peter Dubuc. Reports of far larger pike have been made, but these are either misidentifications of the pike's larger relative, the muskellunge, or simply have not been properly documented and belong in the realm of legend.As northern pike grow longer, they increase in weight, and the relationship between length and weight is not linear. The relationship between total length and total weight for nearly all species of fish can be expressed by an equation of the form
Invariably, b is close to 3.0 for all species, and c is a constant that varies among species. For northern pike, b = 3.096 and c = 0.000180. The relationship described in this section suggests a northern pike will weigh about, while a northern pike will weigh about.
Age
Northern Pike typically live to 10–15 years, but sometimes up to 25 years.Habitat
Pike are found in sluggish streams and shallow, weedy places in lakes and reservoirs, as well as in cold, clear, rocky waters. They are typical ambush predators; they lie in wait for prey, holding perfectly still for long periods, and then exhibit remarkable acceleration as they strike. They inhabit any water body that contains fish, but suitable places for spawning are also essential. Because of their cannibalistic nature, young pike need places where they can take shelter between plants so they are not eaten. In both cases, rich submerged vegetation is needed. Pike are seldom found in brackish water, except for the Baltic Sea area, here they can be found spending time both in the mouths of rivers and in the open brackish waters of the Baltic Sea. It is normal for pike to return to fresh water after a period in these brackish waters. They seem to prefer water with less turbidity, but that is likely related to their dependence on the presence of vegetation.Geographic distribution
Esox lucius is found in fresh water throughout the Northern Hemisphere, including Russia, Europe, and North America. It has also been introduced to lakes in Morocco, and is even found in brackish water of the Baltic Sea, but they are confined to the low-salinity water at the surface of the sea, and are seldom seen in brackish water elsewhere.Within North America, northern pike populations are found in Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Pennsylvania, Maryland, West Virginia, Ohio, Michigan, Indiana, Illinois, Wisconsin, Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, Kansas, Montana, Idaho, Utah, Colorado, Oklahoma, northern Texas, northern New Mexico, northern Arizona, Alaska, the Yukon, the Northwest Territories, Alberta, Saskatchewan, Manitoba, Ontario, and Québec. Watersheds in which pike are found include the Ohio Valley, the upper Mississippi River and its tributaries, and the Great Lakes Basin. They are also stocked in, or have been introduced to, some western lakes and reservoirs for sport fishing, although some fisheries managers believe this practice often threatens other species of fish such as bass, trout, and salmon, causing government agencies to attempt to exterminate the pike by poisoning lakes, such as Stormy Lake, Alaska. E. lucius is a severe invasive predator in Box Canyon Reservoir on the Pend Oreille River in northeastern Washington.
Behaviour
Aggression
The northern pike is a relatively aggressive species, especially with regard to feeding. For example, when food sources are scarce, cannibalism develops, starting around five weeks in a small percentage of populations. This cannibalism occurs when the ratio of predator to prey is two to one. One can expect this because when food is scarce, Northern pike fight for survival, such as turning on smaller pike to feed; this is seen in other species such as tiger salamanders. Usually, pike tend to feed on smaller fish, such as the banded killifish. However, when pike exceed long, they feed on larger fish.Because of cannibalism when food is short, pike suffer a fairly high young mortality rate. Cannibalism is more prevalent in cool summers, as the upcoming pike have slow growth rates in that season and might not be able to reach a size to deter the larger pike. Cannibalism is likely to arise in low growth and low food conditions. Pike do not discriminate siblings well, so cannibalism between siblings is likely.
Aggression also arises from a need for space. Young pike tend to have their food stolen by larger pike. Pike are aggressive if not given enough space because they are territorial. They use a form of foraging known as ambush foraging. Unlike species such as perch, pike undergo bursts of energy instead of actively chasing down prey. As such, a fair amount of inactive time occurs until they find prey. Hunting efficiency decreases with competition; the larger the pike, the larger the area controlled by that particular pike. An inverse relation to vegetation density and pike size exists, which is due to the possibility of cannibalism from the largest pike. This makes sense, as the smaller pike need more vegetation to avoid being eaten. Large pike do not have this worry and can afford the advantage of a large line of sight. They prefer a tree structure habitat.
There has been at least one instance of a pike attacking a dog.
Pike are occasionally preyed upon by otters.
Physical behavioural traits
Pike are capable of "fast start" movements, which are sudden high-energy bursts of unsteady swimming. Many other fish exhibit this movement as well. Most fish use this mechanism to avoid life-threatening situations. For the pike, however, it is a tool used to capture prey from their sedentary positions. They flash out in such bursts and capture their prey. These fast starts terminate when the pike has reached maximum velocity. During such motions, pike make "S" conformations while swimming at high rates. To decelerate, they, simply make a "C" conformation, exponentially slowing down their speed so that they can "stop". An interesting behavioural trait that pike have is that they have short digestion times and long feeding periods. They can undergo many of these fast bursts to collect as much prey as they can. Pike are least active during the night.Reproduction
Pike have a strong homing behaviour; they inhabit certain areas by nature. During the summer, they tend to group closer to vegetation than during the winter. The exact reason is not clear, but likely is a result of foraging or possibly reproductive needs to safeguard young. Pike diel rhythm changes significantly over the year. On sunny days, pike stay closer to the shallow shore. On windy days, they are further from shore. When close to the shore, pike have a preference for shallow, vegetated areas. Pike are more stationary in reservoirs than lakes. A possibility is that lakes have more prey to feed upon, or possibly in reservoirs prey will ultimately cross paths with the pike. As such, this could be a form of energy conservation. Pike breed in the spring.Pike are physically capable of breeding at an age of about two years, spawning in spring when the water temperature first reaches about. They have a tendency to lay a large number of eggs. A likely explanation for such actions is to produce as many surviving offspring as possible, as many most likely die early in life. In females, the gonads enlarge when it is time to shed her eggs. However, after they are shed, these eggs will not hatch if the water is below. Male pike arrive at the breeding grounds before females do, preceding them by a few weeks. In addition, the males stay after the spawning is finished. Parental stock is vital for pike success. Egg survival has been shown to be positively correlated with number of eggs laid. For breeding, the more stable the water, the greater the fitness of the pike. Mortality results from toxic concentrations of iron or rapid temperature changes, and adult abundance and the strength of the resulting year classes are not related. It is based upon two points of development: one during embryo stage between fertilization and closure of the blastopore, and the second between hatching and the termination of the alevin stage.
The colour of the sticky eggs is yellow to orange; the diameter is. The embryos are in length and able to swim after hatching, but stay on the bottom for some time. The embryonic stage is five to 16 days, dependent on water temperature. Under natural circumstances, the survival from free-swimming larva to 75-mm pike is around 5%.