Evolution

World-wide Evolution. It is now known that species of the family Esocidae have been present for at least 80 million years and that they probably evolved from the herring-salmon order of fishes during the mid-to-late Cretaceous period between 80 and 90 million years ago.

Until recently, it had been believed that the genus Esox had evolved in Eurasia from Palaeoesox fritschei (c. 60 million years ago) through Esox papyraceus (c. 30 million years ago) and Esox lepidotus (c. 10 to 25 million years ago) until relatively late in time (less than 2 million years ago) when Esox lucius evolved and spread across the upper latitudes of the northern hemisphere to North America by means of the Bering Strait land bridge. This had been under the ocean since the drifting apart of the continents began around 60-70 million years ago, but the ice age of the Pleistocene epoch caused a lowering of sea levels making the land bridge possible again.

This comfortable and widely accepted view was well and truly ‘kicked into touch’ in 1980 when a fossilised skeleton of Esox tiemani was discovered in Canada, which dated from at least 62 million years ago. Further discoveries have since been made which puts E. tiemani, or similar, on earth approximately 80 million years ago, i.e. millions of years before Palaeoesox, which until that time had been considered to be its ancestor. This also puts the genus Esox in North America between 32 and 50 million years before it first appeared in Europe.

The latest hypothesis now has Esox tiemani (North America) and Palaeoesox fritschei (Eurasia) evolving from the herring-salmon order during the Cretaceous period as before but then following separate parallel evolutionary paths until the glacial period of the Pleistocene epoch. In the Americas, E. tiemani had evolved into Esox masquinongy (the Muskellunge) by about 25 million years ago. Then as the North American continent gradually drifted closer to the North Pole, another species evolved which was more tolerant of the colder conditions, and this eventually became the Northern pike, Esox lucius. This ties in well with the situation, which is to be found in North America today where the Muskellunge has a more southerly distribution within the continent than the Northern pike does.

In Europe and Asia, P.fritschei evolved entirely separately, through E. papyraceus, E. waltschanus to E. lepidotus (10 to 25 million years ago). Esox lepidotus was another warmer water loving species like Esox masquinongy but unlike the American species it had less sure north-south land connections, which appears to have prevented any evolution of a parallel cold-water species and led to the temporary demise of the family Esocidae in Eurasia. As in the earlier scenario, Esox lucius had to wait until the Ice Age before it could spread out and become truly circumpolar in distribution, but from a North American source not a Eurasian one!

Evolution – Scotland

The earliest pike fossils found in Britain, were discovered in the Cromer Forest beds at West Runton in Norfolk, and were found to be approximately half a million years old. These have been identified as Esox lucius, the same species that is to be found in Britain today. This would tend to refute the oft-quoted, popular legend that pike were introduced into the British mainland by the monks at some point in time after the Romans came. However, the discovery of these fossils alone does not in itself prove an unbroken line of pike existence in Britain since Pleistocene times.

This proof came with the discovery of pike (Esox lucius) fin rays and bones at a peat site near Skipsea on the Yorkshire coast, which dated from the post-Pleistocene and pre-Roman period. As these items were found together with harpoon heads we can only deduce that our ancestors hunted pike because they were indeed an indigenous species. These pike (Esox lucius) are believed to have originally found their way into Britain via the ‘North Sea’ land-river bridge, when the River Thames was a tributary of the River Rhine. Once again this land bridge was made possible by the much lower sea-levels caused by the vast amounts of water being held in the glaciers which covered great tracts of the northern hemisphere.

In Ireland, however, the story is very different with much of the evidence pointing to the fact that pike were introduced by the monks around the fourteenth century.

Distribution

Esox lucius is circumpolar and entirely of northern hemisphere occurrence. In North America, the pike is found to the north of a line from Pennsylvania to Nebraska and east of the Rockies north to the Canadian border. It is also found in Alaska and all over Canada except in the polar reaches to the north of Hudson Bay and the Maritime Provinces. In the northeastern United States it also overlaps with the northern half of the Muskellunge, E. masquinongy range. In Europe the pike distribution reaches southwards to the Mediterranean regions, including northern Spain and Italy (roughly 40°N) and to just north of Turkey.

In the north it extends into Sweden, Norway and Finland, although not to the northern and western mountain areas of Norway, where it is absent. It is in northern Europe that we find, perhaps the strangest habitat of all, with the pike having adapted to live in the low salinity of the northern Baltic Sea and the Stockholm archipelago. East of Turkey, in Asia, the southern limit swings up to well north of 50°, because the species cannot survive in areas such as the arid Ust Urt plateau or the Kyzyl Kum desert of Kazakhstan and Uzbekistan, the Tien Shan Mountains in north western China and the Gobi Desert in Mongolia.

The northern limit, however, reaches almost to the polar shores of Siberia. Here again though, as in North America, it does not fare so well in these coastal regions of the continent. In the region of the Bering Straits, the pike occurs well to the north of its normal range in both the former Soviet Union and the United States. In the U.K., the pike occurs almost everywhere but begins to thin out in the very far north of Scotland, as much due to the small, acidic lochs as anything else.