I040 FRESH-WATER BIOLOGY 



birth to living young which liave been carried far beyond the 

 " hatching " point. 



A. Migration. As the spawning season approaches, fishes under- 

 take a general migratory movement. The migration may be of 

 great or very limited extent. The movement is in general one of 

 going upstream to small brooks and shoreward to shallow water. 

 In some cases the migration may mean the movement for a few 

 feet only. Some minnows and darters move to a favorably-placed 

 rock or weed. The skipjack in our small lakes moves to the zone 

 of pickerel weeds near shore. The sunfishes, black bass, and many 

 others move shoreward to shallow water. Some minnows move to 



Fig. I5.)0. SucKer, Cahilomiis contmcrsoni (Lacepc-di?). Actual si2c, 232 mm. long. 



riffles from neighboring pools. The upstream movement of suckers 

 is powerful in California, and has become proverbial in Illinois and 

 neighboring waters. 



The limit in the extent of migratory movements upstream is 

 reached by the Pacific coast salmons. The Ciuinnat salmon of the 

 Pacific coast is the king of the migrants. It enters the Columbia 

 River at the age of four years, in March and April. The entire 

 summer is taken up, without food, in ascending to its spawning 

 grounds. It spawns a thousand miles and more from the ocean, 

 or in Alaska two thousand miles from the sea, in shallow riffles of 

 small streams at the headwaters of the streams it ascends. Alturas 

 Lake, near one of its spawning places, has an elevation of 7,335 

 feet. After spawning the adult dies. It ne\'er succeeds in regaining 

 the ocean. The Atlantic slope salmon {Saliiw salar) ascends from 

 the ocean to the headwaters of streams north of Cape Cod. The 

 relative of the salmons, the cisco of Tippecanoe Lake, in December 

 ascends its tributary streams to spawn. The marine lamprey as- 

 cends streams from the Atlantic Ocean. The landlocked lamprey 

 {PelromyzoH mariitns imicolor) of central New York migrates eight 



