164 BULI.ETIN OF THE BUREAU OF FISHERIES. 



insure the optimum infection and are not well suited for work on a large scale because 

 of their behavior during infection. Fish which rest upon the bottom are sometimes not 

 so favorable as they might seem because they do not move about enough to keep the 

 glochidia in motion. While other features may be of greater importance, the behavior 

 of the fish as affecting the distribution of the glochidia in the water should always be 

 considered in deciding how useful any fish may be for purposes of infection. . 



INFECTION OF FISH IN LARGE NUMBERS. 



The infection of fish in large numbers has been attempted with a view to determining 

 the feasibility of extending the methods described above to wholesale infections of fish 

 in a hatchery. As a result of two such attempts, we have no doubt that the successful 

 development of the methods needed for infection in connection with the artificial propa- 

 gation of mussels is only a matter of a little study in a properly equipped station. In 

 December, 1907, about 25,000 small fish, under 6 inches in length, were placed at our 

 disposal at the substation of the Bureau at La Crosse, Wis., and we were able on this 

 occasion to infect by wholesale methods about 12,000 blue-gill sunfish, 3,700 yellow 

 perch, 7,000 catfish, 2,000 crappie, 150 rock bass, 150 carp, and 100 roach. The greater 

 number of these fish were infected with the glochidia of Lampsilis ligamentina, and, 

 considering the fact that this was our first experience with so large a number of fish, the 

 results were satisfactory. Smaller lots were infected with the glochidia of L. anodon- 

 toides and L. recta, the results giving every indication that these two species are essen- 

 tially like L. ligamentina in the conditions of their development. The most successful 

 infections were obtained by placing from 100 to 200 fish in a common galvanized iron 

 washtub about two-thirds full of water. It was found that by adding to this body of 

 water the glochidia obtained from two or three specimens of Lampsilis, and, when it 

 seemed necessary, stirring the water by hand, tolerably constant results could be secured. 

 Our difficulties were with over- rather than with under-infection. It was also possible 

 to use the same tub a number of times without changing the water or adding to the stock 

 of glochidia. Infection was also attempted by lowering the water in the large retaining 

 tanks of the station to a depth of 4 inches and confining the whole number of fish which 

 had been held in the full tank to this much smaller body of water. This method was 

 found, in the absence of any attempt to keep the glochidia properly distributed through 

 the water, quite inadequate and it became necessary to reinfect these fish in the tubs. 



The mortality of the fish in these experiments was decidedly in excess of what one 

 might expect for uninfected fish kept under similar conditions, a result clearly due to 

 the over- infection which is the one thing most to be guarded against. At the end of six 

 weeks some of the remaining fish were liberated in the west channel of the Mississippi 

 River at La Crosse, a locality which we then believed might be suitable for this species 

 of Lampsilis. 



These infections were made under conditions of limited time and equipment and 

 were wholly tentative, the aim being to make a test of our methods on a large scale. 

 We revisited La Crosse a month after the infection, making careful examinations of the 



