Coloration. 59 



bottom and a luxurious growth of water weeds, conditions 

 exceedingly favorable for the growth and increase of the 

 shrimp. 



A striking instance of the difference in coloring of the 

 flesh from the influence of age or season, is related by the 

 European ichthyologist, Dr. Fric, in regard to the salmon 

 of Bohemia. He says that there are three different ascents 

 of the salmon during the year : The first ascent begins in 

 February or March under the ice, and lasts till May. These 

 salmon weigh from twenty-five to fifty pounds, and are 

 famous under the name of " violet-salmon." The second 

 ascent begins in June and lasts till August. These fish 

 have a reddish flesh, and weigh from twelve to twenty-two 

 pounds, and are known as " rose-salmon." The third as- 

 cent is from September until December. These fish are 

 mostly weak, weighing from three to fifteen pounds. 

 Their flesh is pale, and they are usually called "silver- 

 salinon." 



The trout of the mountain lakes of the Alps, according 

 to the season and the nature of the water they inhabit, have 

 their flesh whitish or reddish. 



The color and condition of the water has likewise a very 

 marked effect upon the external appearance of the Salmon- 

 idcB. Agassiz found that the color of book trout of 

 neighboring streams was influenced by the color and quan- 

 tity of the water, and that even trout of the same stream 

 differed in color as they frequented the shady or sunny 

 side. He also found that fish in clear, sunny waters, with 

 gravelly bottoms, were highly and brightly colored; while 

 those in shady streams, or where the bottom was dark or 

 muddy, and the water not so clear, were correspondingly 

 dusky in hue ; and that bright fish taken from waters of 

 the former character and placed in those of the latter, 



