The abundant life of northern seas. 



After the months of the long polar night, when all life seems to be held in abeyance, the sun 

 creeps back over the horizon and for several hours its slanting rays bring out clear blue and green 

 shades in the icebergs. Then more and more it becomes the master of the sky. Towards the 

 time of the summer solstice, twilight has vanished, and the glaring sun prevails over the northern 

 landscape, never for one hour leaving the sky. At midnight its orange gleams light up a greenish 

 sky and cast long purple shadows from the ice onto the slaty sea. And the broken pa<k-ice 

 gleams a dazzling white in the dark mass of open waters. 



At the ice-edge the polar bears, swaying their triangular heads in an uncertain rhythm, are 

 well aware that this is their mating season. Seals lie solemnly on isolated floes or suddenly 

 dive to overtake some prey seen in the transparent sea. In the ocean there is a prodigious 

 development of living beings, both in the sunlit surface waters and in the depths. The rays of 

 the sun bring forth swarms of microscopic algae and the endless division of the diatoms gives 

 rise to dark green patches in the sea. This abundance of plant life, the well-known floating 

 pastures, is an eiuUess source of food to countless small crustaceans and these, while they eat, 

 become the fodder of more powerful animals. Small shrimps ( Mcfjanydiphanes and Tliysa- 

 nui'ssa) mass together in such dense swarms that the sea surface grows crimson as they pass. 

 Scandinavian fishermen call these swarms of restless shrimps " krill "'. Voracious fishes dart 

 into these teeming masses. Cireat whales with mouths agape plunge through the krill, engulfing 

 countless numbers, which are screened by their whale-bone filters when the jaws are closed. 

 Suddenly depressing their great, tongues the whales swallow the krill at one gulp. 



The drifting i)elagic life of the northern .seas is also revealed in the form of numerous trans- 

 |)arent and hyaline jelly-fishes, some of which can be very large. The bluish umbrella of the 

 great brown-tentacled Cijanca can be as much as 6 feet in diameter. Chains of Salpa like crys- 

 talline garlands make their way through a slate-blue sea. Larval fishes, particularly the young 

 of cod, form seething yellowish patches amid this tremendously rich planktonic life, (llose-packed 

 silvery ranks of shoaling herring move through the lloating pastures, thrusting aside the salps 

 and jelly-fish. And as the herring move, they batten on the krill. 



The herring (CAiipca harciKjns) ranges over northern Atlantic waters, venturing as far as 

 80° N. and occurring in the Barents Sea and off the coasts of Greenland, It abounds along the 

 Scandinavian coasts, in the Baltic, in the North Sea and in the eastern English (Ihannel. In 

 the Bay of Biscay, where it is less common, it extends down to the latitude of La liochelle, OIT 

 the American coast it lives over the Banks of Newfoundland, Nova Scotia and Maine, reaching 

 the New York region. A closely related species (Clupea pallasii) replaces it in the Pacific. 

 We have already suggested how oceanic relicts of this species came to live in the White Sea 

 following an ancient warming up of the arctic. 



It used to be thought that the herring undertook long migrations. Dodd and Anderson 

 wrote of a vast shoal leaving the Arctic Ocean in the direction of Iceland and moving down 

 the Norwegian coast. After entering the North Sea and passing into the English Channel 

 the shoal returned polewards by way of the waters to the west of the British Isles. This fine 

 theory was demolished by the discovery of local races, which was due to the remarkable work of 

 the German Heincke and the Norwegian Hjort. Study of the average numbers of vertebrae 

 has enabled us to distinguisch the following races : the boreal race (Greenland, Iceland, Norway), 

 reaching a mean length of nearly 12 inches after 4 years and with a? to 58 vertebrae ; the Ameri- 

 can race (Labrador, Newfoundland and .Maine) also reaching 12 inches after I years and with 

 56 to 57 vertebrae ; the .\orlli Sea and eastern English Channel race, 10 inches after 4 years, 

 56 vertebrae ; the Bailie race 7 ^l^ to 10 inches after 4 years, 55 vertebrae and the Irish race 

 (Scotland, Wales and western English Channel), 10 inches after 4 years, 56 vertebrae. Other 

 local populations in the Zuyder-zee and Breton estuaries are comprised of small herring with 

 55 and 56 vertebrae. 



Above all, herrings are fishes of the polar seas and continental waters. In winter they 

 position themselves at the edge of the shelf at a depth of about ]i)() fathoms. But the arrival of 



47 



