REPRODUCTION AND ARTIFICIAL PROPAGATION OF FRESH -WATER MUSSELS. 1 87 



VII. INVESTIGATIONS ON THE UPPER MISSISSIPPI RIVER. 



A brief reference may here be made to certain field studies which were carried on 

 in connection with our mussel investigations during the months of June, July, and 

 August, in 1908, on the upper Mississippi River. The Bureau of Fisheries put at our 

 disposal for this purpose its substation, a small building provided with tanks and running 

 water, at La Crosse, Wis., and also its steamboat, the Curlew, which not only furnished 

 us with living quarters, but was of invaluable service for transportation from place to 

 place on the river (fig. 65, pi. xvi). The boat, which is ordinarily used in the work of 

 reclaiming young fish from the overflow of the river during the floods which occur in the 

 spring and early summer, is equipped with aerated tanks, seines, and other apparatus 

 and provided us with what was essentially a floating laboratory. With these facilities 

 much was accomplished that would have otherwise been impossible. In addition to the 

 usual crew of the Curlew, the party consisted, besides ourselves, of Messrs. W. E. Muns, 

 Howard Welch, F. P. Johnson, and W. E. Dandy, students in the University of Missouri, 

 who served as assistants. 



The primary object of the expedition was a determination of the breeding seasons of 

 the commercial species of mussels as far as possible at that time of the year and an 

 examination of the depleted mussel beds in the upper Mississippi River, which have 

 been all but destroyed as a result of the ravages of the mussel fisheries. 



With a clamming outfit of our own (fig. 69, pi. xvii), consisting of a flat-bottomed 

 skiff and "crow-foot " dredges^the usual apparatus employed by the mussel fishermen — 

 we were able to secure thousands of mussels, which were examined microscopically for 

 the purpose of determining their sex and the stage of development of the embryos. The 

 data thus obtained furnished a mass of detailed information, especially with respect to 

 those species which breed in the summer, but as they are incorporated in the account 

 already given of the breeding seasons, there is no need to refer to the subject again. 



The planting of young mussels in cages for a determination of the rate of growth 

 was also made during this summer, with the result as described in a preceding section. 



Some attempts were made to infect fish with glochidia, but this phase of the work 

 was greatly interfered with by the high water of the river, which remained at flood stage 

 unusually late in the summer of 1908 and made the seining of fish very difficult. Some 

 infections, however, were carried out with the glochidia of a few summer-breeding species, 

 the fish being retained in the tanks at the La Crosse station throughout the parasitic 

 period and the duration of the parasitism determined. 



A thorough survey of the mussel beds from Winona, Minn., to Lansing, Iowa, was 

 made, and records taken at each locality where mussels were collected. No large beds 

 at all were discovered, and in every instance where mussels were found indications of the 

 ravages worked by the clammers were apparent. An account of the distribution of the 

 species throughout this section of the Mississippi River and their relative abundance is 

 not presented here, as the results of our observations in these respects will be incorpo- 

 rated in the work of the several field parties which have been engaged in the study of 



