BONY FISHES 283 



rich in oxygen. Hence the salmon, before depositing them, undertakes 

 regular migrations from the sea to the clear, cool woodland streams and 

 brooks. At certain times of the year (on the Bhine in May) it enters 

 the larger rivers, travels up-stream, and then goes up their tributaries 

 until it reaches a suitable spot for spawning. Its great bodily strength 

 enables it easily to leap over weirs and waterfalls up to the height of 

 13 feet. Should higher obstacles bar its way, artificial structures called 

 " salmon ladders" are provided for facilitating the ascent. These are 

 placed by the side of the obstacles, and consist of slanting gutters or 

 chutes, up which the fish can swim, or of reservoirs placed stepwise 

 above each other, so that the salmon can leap from one to the other. 

 After depositing the eggs, the salmon once more turns its course towards 

 the sea, whither it is followed by the young fish ; these, however, return 

 to the place of their birth as early as in their second year, for the 

 purpose of spawning in their turn. The salmon (like the trout) 

 produces very large eggs, but the number of eggs is on that account 

 much less than in most other fish (see carp), for the quiet pools in 

 which they are deposited are free from that violent incessant war of 

 extermination which prevails in the larger waters. The flesh of the 

 ascending or fresh-run salmon is of a pink-red colour, and highly 

 esteemed both fresh and in a smoked condition. 



A valuable member of the salmon family is the merry Trout '(S. fario), 

 which all the year round inhabits woodland streams, brooks, and ponds 

 traversed by running watercourses. The scaly coat of this fish is 

 generally of a brassy yellow colour, ornamented with numerous black 

 and red blue-bordered spots. In very shady brooks the trout is always 

 darker than in those which are exposed to the sunshine, and the colour 

 of the fish pales or darkens when it is transferred from the one kind of 

 water into the other. (Explain the significance of this.) By its body 

 structure the trout is a predatory fish, which lives by the incessant 

 pursuit of all the smaller kinds of aquatic animals. 



The Herring (Clupea harengus). 

 (Length 8 to 13 inches.) 



A. Importance to Man. 



Next to the cod, the herring is the most valuable product of the 

 Northern seas. To it Holland and the Hanseatic League largely owed 

 their former wealth and power (whence the saying, " Amsterdam is 

 built on herrings' heads ") ; and even at the present day hundreds of 



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