l895- ^O- 9- HVDR.-BIOL. STUDIES OF THE NORW. FISHERIES. 



Chapter IV. 



Are the Lives of Fishes and their Migrations dependent on 

 the Ocean Currents? 



In Chap. I, we saw that all the species of fish which give rise to our 

 great periodical fisheries, such as the Cod, Herring and Mackerel, have 

 their true home in the open seas, the Northern and Atlantic Oceans. 

 At certain periods of the year they commence their migrations thence 

 towards the coasts, the influxions«, either for the purpose of spawning, 

 or to seek nourishment in the coastal waters and the Fjords. The fish 

 thus spend a great part of their lives under the coast. The eggs of 

 the Mackerel and Cod are spawned freely in the sea, while the ova of 

 the Herring are attached to the bottom in shallow water, and all these 

 eggs thus undergo their first development near land. They subsequently 

 wander about as fr}-, in bays and sounds, until, after a shorter or larger 

 period, they proceed to the open sea as almost fully grown fish. 



In the previous Chapters we saw that the open sea is, in man}- 

 respects, widely different from the waters of the coast. A comparatively 

 more uniform temperature, and great salineness exists there throughout 

 the year, whilst the coastal waters are vastly exposed to periodical 

 (seasons) and non-periodical changes. Do these variations play any 

 part in the cycle of life of the fish and their migrations .- 



The one circumstance, alone, that the influxions are tied to certain 

 periods of the year, so that they may be expected with a considerable 

 amount of certainty at a fixed time, appears to me to prove that there must 

 exist a connection between the sea and the life of the fish. Only owing 

 to the fish having, through countless generations, been exposed to, and 

 affected by the same changing conditions in the sea, can one ex- 

 plain the development of the wonderful conformity to rule of their 



