Esox Lucius - Northern pike

Esox lucius is found in freshwater 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

The northern pike gets its name from its resemblance to the pole-weapon known as the pike (from the Middle English for pointed). The genus name, Esox, comes from the Greek and Celtic for "big fish" and "salmon". Various other unofficial trivial names are: American pike, common pike, great northern pike, Great Lakes pike, grass pike, slough shark, snake, slough snake, northern, gators (due a head similar in shape to that of an alligator), jack, jackfish, and Mr. Toothy. 

Description

Northern pike are most often olive green, shading into yellow to white along the belly. The flank is marked with short, light bar-like spots and there are 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 they have large sensory pores on their head and on the underside of the 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 depending on the sex of each of the contributing species). 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.

Length and Weight

Pike grow to a relatively large size; lengths of 150 centimetres (59 in) and weights of 25 kilograms (55 lb) are not unheard of. The heaviest specimen known so far was caught in an abandoned stone quarry, in Germany, in 1983. She (the majority of all pikes over 8 kg or 18 lb are females) was 147 cm (58 in) long and weighed 31 kg (67 lb). The longest pike ever recorded was 152 cm (60 in) long and weighed 28 kg (61 lb). Historic reports of giant pike, caught in nets in Ireland in the late 1800s, of 41 to 42 kg (89 to 92 lb), were researched by Fred Buller and published in "The Domesday Book of Mammoth Pike". The British Isles have not managed to produce much in the way of giant pike in the last 50 years and as a result there is substantial doubt surrounding those earlier claims. Currently, the IGFA recognizes a 25 kg (55 lb) pike caught by Lothar Louis in Lake of Grefeern, Germany, on 16 October 1986 as the all-tackle world record northern pike. Northern pike in North America seldom reach the size of their European counterparts; one of the largest specimens known was a 21 kg (46 lb 2 oz) specimen from New York state. It was caught in Great Sacandaga Lake on 15 September 1940 by Peter Dubuc. There are reports of far larger pike, 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.

Habitat

Pike take big prey and are not very particular. Pike are found in sluggish streams and shallow, weedy places in lakes, as well as in cold, clear, rocky waters. Pike are typical ambush predators; they lie in wait for prey, holding perfectly still for long periods and then exhibit remarkable acceleration as they strike. In short, they will inhabit any water body that contains fish, but suitable places for spawning are essential for their numbers. Because of their cannibalistic nature, young pike need places where they can take shelter between plants so they are not eaten. In both cases it comes down to a rich submersible vegetation nearby. Pikes are seldom found in brackish water, except for the Baltic Sea area. Pike is known to prefer water with less turbidity but that is probably related to their dependence on the presence of submersible vegetation and not to their being a sight hunter.

Reproduction

Pike are known to spawn in spring when the water temperature first reaches 9°C (48.2°F). The males are first at the spawning grounds preceding the females for a few weeks. The larger females tend to be earlier than the smaller ones. Mostly a female is followed by several smaller males. When a pair starts slowing down the male will put his tail under the female's body and release his spawn that is mixed with the eggs due to the tail movement. The spawning consists of a great number of these moves several times a minute and going on for a few hours a day. Every move between 5 and 60 eggs are laid. A female can continue the mating for three days in a row. After the mating the males tend to stay in the area for a few extra weeks.

The color of the sticky eggs is yellow to orange, the diameter is 2.5 to 3 mm. The embryos are 7.5 to 10 mm in length and able to swim after hatching but stay on the bottom for some time. The embryonic stage is 5 to 16 days, dependent on water temperature (at 19°C and 10°C, respectively). Under natural circumstances the survival from free swimming larva to 75 mm pike is around 5 percent. Pike can reach the reproductive stage in a year, females being 30 cm, males 19 cm. Pike normally live 5 to 15 years, but can be as old as 30. Life expectancy and growth are dependent on circumstances. Some Canadian populations have many old slender pikes, Baltic pike grow to great lengths in a short time while eating nutrient rich herring.

Feeding

The young free swimming pike feed on small invertebrates starting with daphnia, and quicky moving on to bigger prey like isopods like asellus or gammarus. When the body length is 4 to 8 cm they start feeding on small fish.

The pike have a very typical hunting behavior, they are able to remain stationary in the water, by just moving the last fin rays of the dorsal fins and the breast fins. Before striking they bend their body and dash out to the prey using the large surface of tail fin, dorsal fin and anal fin to propel themselves. The fish has a distinctive habit of catching its prey sideways in the mouth, immobilising it with its sharp backward pointing teeth, and then turning the prey headfirst to swallow it. It eats mainly fish, but on occasion water voles and ducklings have also been known to fall prey to pike. Young pike have been found dead from choking on a pike of a similar size, an observation referred to by the renowned English poet Ted Hughes in his poem 'Pike'. Northern pike also feed on frogs, insects and leeches. It has often been suggested that pike optimally forage on prey that are from 25 to 35% of their body length. They are not very particular and eat spiny fish like perch and will even take sticklebacks if that is the only available prey.

The northern pike is a largely solitary predator. It migrates during a spawning season, and it follows the prey fish like roach to their deeper winter quarters. Sometimes divers observe groups of similar sized pike that might have some coorporation and it is known to anglers pike tend to start hunting at the same time, so there are some "wolfpack" theories about that. Large pike can be caught on dead immobile fish so it is thought that these pike move about in a rather large territory to find the food to sustain them. Large pike are also known to cruise large water bodies at a few metres depth, probably pursuing schools of prey fish. Smaller pike are more of an ambush predator, probably because of their vulnerability to cannibalism. Pikes are often found near the exit of culverts, which can be attributed to the presence of schools of prey fish and the opportunity for ambush. Being potamodromous, all esocids tend to display limited migration, although some local movement may be of key significance for population dynamics. In the Baltic they are known to hunt for shoals herring and therefore have some seasonal migration.

Source: Wikipedia, the free encyclopedia