PRODUCTION OF THE FRESH WATER MUSSEL. 



By H. L. Canfield, 



Homer, Minnesota. 



The Mississippi and its tributary rivers are the greatest 

 producers of warm water fishes in the world, and practically 

 all commercial fresh water mussels are produced in the 

 waters of the Mississippi basin. In time of spring flood the 

 Mississippi overflows its banks and inundates the islands and 

 adjacent lowlands in which are located sloughs, pools and 

 other depressions, and into this territory many fishes go to 

 feed and spawn. Later in the season the river recedes into 

 its banks and becomes quite low, leaving many of the fishes 

 in the depressions. As the season advances and the land- 

 locked waters become low and stagnant due to the low stage 

 of the river and to seepage, millions of fish are left high and 

 dry to perish unless removed to live waters. 



During the fiscal year 1922, the U. S. Bureau of Fisheries 

 rescued from these land-locked pools of the Mississippi 

 River over 139,000,000 stranded game and commercial fish- 

 es of various ages and sizes, and released on the gills of suit- 

 able host fishes, in a state of parasitism, over two billion 

 larval commercial mussels. 



The fresh water mussel is in great demand for use in the 

 manufacture of pearl buttons and the supply has become so 

 short that mussels sold at $10.00 and $15.00 per ton ten 

 years ago are now easily disposed of at $60.00 to $90.00 per 

 ton. The necessity for protecting measures and artificial 

 propagation of mussels is therefore easily understood. In 

 mussel infection work, quantities of fishes are required, so 

 the rescue of stranded food fishes and mussel infection are 

 combined to great economic advantage. 



The larval mussel is developed in the adult female 

 mussel, then freed as a parasite into the water. To live it 

 must within a very limited time attach itself on the gill of a 

 proper host fish. Here it encysts and passes through a met- 

 amorphosis which changes its internal structure. In about 

 two weeks or more, according to the water temperature, it 

 releases itself as a juvenile mussel, to commence its ince- 

 pendent life. Th larval mussel is of light weight and is 

 therefore held in suspension by the water for a short ti^e. 

 This is a very critical period of the larval mussel's life, fcr it 



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