the transgression sets them moving, for thfv lannol tolerate warm ami salty waters. This is 

 a coastward movement and it coincides with the spawning period. Retreating before the 

 Atlantic waters, they climb along the valley lines of rivers that used to run in the undulating 

 [>lanes of the North Sea and the Irish Sea, before these latter subsided. This ascent is partly 

 anadronious in character. As a matter of fact these fishes never enter fresh water although 

 some races are restricted to estuaries fdled with brackish water. The main centres of concen- 

 tration are : the ancient estuary of the Rhine, to the east of Scotland, now the Fladen Ground ; 

 that of the Clyde, to the north of Ireland, near Inishtrahull ; and that of the Severn, at the 

 entrance to the Irish Sea, now Small's (Iround. Receding before the encroaching waters, the 

 shoals arrive at a particular date in definite regions. In August they are oil Aberdeen ; in Septem- 

 ber near Gullercoats ; in October, before Flamborough ; and in November near Yarmouth 

 and the Belgian coast. Later in winter they appear over the Banks of the Straits of Dover 

 and in the eastern English Channel as far as Cap d'Antifer. Each race has an habitual spawning- 

 ground and the eggs are always shed in continental waters with a salinity less than 35 "/oo- 



Herrings are exceptional among pelagic fishes in that their eggs are demersal ; they do not 

 float like those of other species. They are fastened singly or in small clumps on hydroids and 

 bryozoa or when spawning takes place close in-shore, on branched algae. Each female bears 

 more than 30,000 eggs. After spawning a feeding migration takes place and " spent " herrings^ 

 emptied of their sexual products, go in search of food. They fill up with diatoms and raven 

 on swarms of copepods. During years of extensive transgressions when, for instance, the 

 North Sea is invaded by warm water, it sometimes happens that the herrings find food hard 

 to come by. This occurred in 1922 after the great transgression of 1921. The starving, emac- 

 iated fishes, with their reserves of fat exhausted, perished in great numbers. 



Growth varies according to race. On an average a length of 5 inches is attained at 1 year. 

 7 ^/j inches towards 3 years, 11 inches at 6 years and 12 J inches at 9 years. Sexual maturity 

 is reached towards the fourth year. The maximum life-span is perhaps 20 years. 



The herring — the "king herring" of the British — is the most important fish from an 

 economic standpoint. At all times it has meant wealth for the Scandinavians. In 809 Charle- 

 magne founded Hamburg as a herring-fishing port, and in the same way the Normans established 

 Ostend, Dunkirk, Etaples, Dieppe and Fecamp (the "Fisk havn" of the Vikings). The clergy 

 levied tithes on these fishes, which stirred up revolts, notably in Flanders during the 12th 

 century. The Hanseatic League strove against the Scandinavian countries for the possession 

 of the herring fisheries. In France the sale was regulated by the royal decrees of Louis IX and 

 (Charles V, with the Parisian Corporation of the "Marchaiids de I'eau" having the monopoly. 

 The war between Holland and England in the 17th century was concerned with the maritime 

 ownership of the Dogger Bank. Conflicts have also raged about the Pacific herring. The 

 fishes in the Sakhalin region are vital for Japan and the war in 1902 against Russia was largely 

 undertaken to establish a supremacy over these fisheries. 



Herring are eaten fresh, while some are salted in barrels. There are also various ways of 

 smoking them, from the Dieppe craquelot to the kipper and the red herring. When marinated 

 in white wine they make an excellent preserved food. The partly preserved roll-mops and the 

 Scandinavian pickled herring are also much appreciated. 



Shoals of sprats (Cliiprn sprnlhis) — "brisling" to the Norwegians — are not so conspicuous 

 in the teeming life of northern .seas. The sjirat has a dark blue back and a silvery belly and does 

 not grow beyond a length of 6 inches. Like the herring it lives in cold waters and retreats before 

 the transgressions. It is abundant around Scandinavia, in the Baltic, the North Sea and the 

 Jinglish Channel. While rare in the Bay of Biscay it is found again olT the Galician coast. The 

 eggs are pelagic and the life-span is no more than 6 years. After maturing in a sweetened 

 pickling brine it becomes "Norwegian anchovy". 



All the cod-like fishes figure among these swarms of animals: there are whiting, haddock, 

 cod and ling. Demersal fishes are very numerous along the sea bottom. There are gurnards, 

 rays and various kinds of flat-fishes; turbot, brill, dabs and especially plaice. 



The plaice (Plenronecles pldlessa) lives pressed close to the gravel, sand or mud, lying on 

 its left side. The eyes and jaws are twisted towards the right side. These fishes are grey or 



48 A group of coral fishes from Hawuii. Photograph by 



Isy Schwart. 



A coral-dwcIling wrasse (Iridic), Hawaii. Photo- 

 graph by Giiiiter Scnfft. 



