8 GEORGE V SESSIONAL PAPER No. 38a A. 1918 



in 



THE PEARLY FRESH-WATER MUSSELS OE ONTARIO. 

 By John D. Detweiler^ M.A., St. Andrew's College, Toronto. 



(With one figure in the text). 

 INTRODUCTION. 



As a part of the pearly fresh-water mussel investigation, conducted by the Bio- 

 logical Board of Canada, a number of localities, from which promising reports had 

 come in, were visited in August, 1916. 



The investigation had a twofold object: first, to determine the abimdance, species 

 cind commercial value of the mussels; and, second, to ascertain whether it would be 

 advisable to introduce artificial propagation in any Canadian waters. 



In order to facilitate the work, the Board decided to send the author to the Fair- 

 port Biological Station at Fairport, Iowa, so that he might thoroughly acquaint him- 

 self with the problem in hand. 



THE UNITED STATES FISHERIES BIOLOGICAL STATION, FAIRPORT, IOWA. 



This station was established in 1908, and is the centre of mussel propagation and 

 of the investigation of problems relating thereto. 



In the practical propagation of mussels the station serves as headquarters for field 

 operations conducted throughout the Mississippi basin, including the Mississippi river 

 and its tributaries. There may be in the field at one time from two to six field parties 

 operating near the station or at a distance of several hundred miles. For full account 

 see United States Bureau of Fisheries, Document 829, by Dr. Coker. 



METHODS AND TECHNIQUE OF ARTIFICIAL PROPAGATION. 



The methods of propagation are based upon the peculiar character of the normal 

 course of development of the fresh-water mussels. The young mussels, with rare excep- 

 tions, when first liberated from the mother clam must become parasitic upon a fish 

 in order to pass through the next stage of their development. To this end these young 

 mussels — glochidia, as they are called at this stage — attach themselves to the fins or 

 gills of a fish, if the opportunity presents itself. They already have two shells 

 which under proper stimulus work like a small trap, and a very slight wound seems to 

 be produced which after attachment begins at once to heal over. In this way the 

 glochidia become more or less safely encysted and now virtually live the life of para- 

 sites, subsisting on the juices of the fish. In the course of two weeks, more or less, 

 having completed their metamorphosis, they break away from their host, drop to the 

 bottom and begin an independent existence. 



If not over-infected, the fish seem to suffer no injurious effects. Naturally, the 

 limit of successful infection depends on the size and nature of the fish. , Careful 

 investigation of natural and artificial infection has shown that a moderate-sized fish 

 may carry successfully from 1,000 to 2,000 glochidia. 



Mussels do not attach themselves indiscriminately, but for each species of mussel 

 there is a limited number of species of fish that may serve as host. In some cases 

 the number that may act as a host is apparently very exclusive. In this connection 



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