CULTURE OF FRESH-WATER MUSSELS. 



6 9 



Table i. — Increase in Length op Juvenile Mussels in a Floating Crate During the Growing 



Season of the First Year, 1914.' 



Date collected. 



Lernnh. Increase in length. 



Pate cullected. 



June 10.. 

 July 18 . 

 Aug. 17. 



Mm. 



Per cent. 



3-95 



8.8 



1,580.0 

 209.5 



Length. 



Sept. 12. 

 Oct. 10.. 

 Nov. 24. 



Mm. 



22. i 

 27. 2 

 32 



Inctease in length. 



Mm. 



9-3 



4.9 

 48 



Ptr cetit. 



71-5 

 21.0 

 17.6 



' The mussels measured were taken at random, with the exception of the last one. which was selected as the maximum. 



The length of 32 millimeters at the close of the season (1914) is one hundred and 

 twenty-eight times that of the original juvenile at the beginning of free life. This cer- 

 tainly compares favorably with the total length of 3 millimeters reported by Herbers 

 (1913), which was the largest in his culture of juveniles, while the mussels in the experi- 

 ment of which this paper treats were still alive and vigorous at the end of the season. 

 Figure 70 is a photograph of the contents of a basket at the end of the season reduced 

 to five-twelfths natural size. The mussels range in size from 32 to 15.5 millimeters. 

 The variation is considerable, but it should be noted that less than 27 per cent are under 

 three-fourths of the maximum size. The last mussel in the series, and one of the 

 smallest, is deformed, probably restricted in growth by lodging in a crevice. Two more 

 small mussels were found when the mud was passed through a sieve. Of these one 

 measured 14. 1 millimeters and the other the remarkably small size of 6.9 millimeters. 

 The latter was living at the time of removal from the river. These few cases of dwarf- 

 ing are doubtless due to lodgment in unfavorable locations — under crowded conditions — 

 in the basket. 



During the last month, from October 20 to November 20, a record of growth was 

 taken to determine to what extent growth takes place as the water temperatures fall. 

 Measurements of 10 mussels from the basket were taken. After marking and measuring 

 each they were returned to the crate. The results are presented in Table 2, following 

 which are given the water temperature averages, maximum, minimum, and range 

 for the period. It will be seen that the growtli for the period was very slight. 



Table 2. — Increase in LENGTH of Juvenile Mi SSELS In a Floating Crate During the Last 



Month of the Growing Season, 1914. 



Specimen number. 



Length. 



Specjmen Dumber. 



Oct. 20. 



Average. 



Mm. 

 95-4 



23 3 

 29 4 



93 s 



Nov. 



Mm. 

 95 8 

 23. 6 

 29 7 

 34. o 



Increase 

 in length. 



o. 4 

  3 



• 3 



• 5 



water TEMPERATURE For period of MEASURED GROWTH. 

 Average : °f. 



For 1 1 days, Oct. 20 to 31 54. 9 



For 10 days, Nov. 1 to 10 50. 9 



For 10 days, Nov. 1 1 to 20 43. 2 



For whole period , Oct. 20 to Nov. ->o 49-2 



Maximum for whole period , Oct. 20 to Nov. 20 60 



Minimum for whole period, Oct. 20 to Nov. 20 32 



Range for whole period, Oct. 20 to Nov. 20 28 



7631G — 22 2 



