A pike (Esox Lucius) is the only representative of its kin in Europe. In East Asia there is one additional relative to the pike and in North America there are three pike kin represented.
A pike's characteristics are very individual, and they cannot be mixed with any other fish in Europe.The body is long with an oval cross-section and the head is big with long powerful jaws which have an under bite. The dorsal fin is placed far back and the eyes are big. The pike has relatively small shells and the numbers of shells found on the side of its body are little over hundred.
The side-line, which is a sense organ, is well developed. In addition to the side-line the pike has more sense organs which belong to the same system. The side-line's extension channels in the head are also well developed.
The pike has a grey green color with dark cross stripes and yellow, oval spots. The cross stripes are most visible on smaller pike, but otherwise the color tones can vary from one fish to another and there can be significant variations in the appearance of pike even within the same body of water.
A pike's age is based on the number of year rings in the shell but it can be harder to determine when it comes to large pike. A better gauge of determining age can be obtained by cutting through and studying some bones (ear bones) in the fish's head.
It been found that some pike, based on shell analysis, have been found over 30 years of age but because shell analysis is not entirely accurate, experts do not agree with those impressive numbers. In the US, by using a more proven method, one study found that pike did not live more 24 years , but in Sweden one study has not, with certainty, been able to prove pike live longer than 16 years.
In any case, one can determine that a pike older than 15 years is rare, and even more so after 20 years. In South Finland one discovered that a pike of 16.5 lbs (7-8 kg) are usually 12-14 years old, but this does not mean that the really big pike which can weigh about 44 lbs (20 kilos) are really old. Instead, those pikes which achieve exceptional size, are fish with special growth abilities, and have grown quicker than other pike right from the beginning.
Harald Hoel, expert of pike fishing