REPORT OF THE COMMISSIONER OF FISHERIES. 17 
ARTIFICIAL PROPAGATION OF FRESH-WATER MUSSELS. 
The work of propagating fresh-water pearly mussels at various 
places in the basin of the Mississippi River was conducted as usual 
under the direction of the Fairport laboratory. The number of 
young mussels (glochidia) liberated in a condition of parasitism on 
fishes was 209,132,800, as compared with 252,478,700 in the fiscal year 
1917. The decrease was largely accounted for by the fact that dur- 
ing a considerable portion of the season most favorable for collecting 
the fish hosts very few of the mussels were gravid. This was espe- 
cially the case with the mucket, the principal mussel handled. The 
tens of fishes infected prior to release was 252,259, of which 
159,190 were seined in open waters, 83,982 were rescued from land- 
locked pools and lakes, and 9,087 were propagated and reared at the 
Fairport station. 
Three new fields for mussel propagation were opened during the 
year, namely, New Boston, IIl., on the Mississippi, a point on the 
Ohio River near Louisville, and Lake Pokegama, Minn. The col- 
lecting of juvenile mussels in Lake Pepin indicated that the arti- 
ficial propagation of the local species of mucket in that water is pro- 
ducing good results. Collecting done in the White River, Ark., 
yielded numbers of young niggerheads and yellow sandshells but no 
muckets. 
The cost of mussel propagation in 1918 was considerably in excess 
of that in the previous year. The cost of glochidia planted was 
$0.0536 per thousand, as compared with $0.373 per thousand in 1917. 
The increased cost of equipment, material, and labor contributed 
largely to the increased expense oi the propagation work. ‘This 
computed cost of propagation includes salaries of permanent em- 
ployees actually engaged, overhead charges, and depreciation of 
$0.004 per thousand. The overhead charges include one-third the 
director’s salary; one-half the superintendent’s salary, and one-half 
the clerk’s salary. 
The experimental propagation of mussels at the Fairport station 
was continued. Especially gratifying results were obtained in one 
pond, from which a total of 1,391 young of the Lake Pepin mucket 
were obtained when drained October 8 to 16, 1917. These mussels 
were the result of plants in the preceding season from fish held in 
open-bottom crates over an especially prepared bottom of sand. 
They varied considerably in size, measuring from about 1 inch to 24 
inches in length, indicating that they resulted from several plants. 
These results are especially important, as this is by far the largest 
number of mussels ever reared under artificial conditions at one time. 
Fish infected with this mucket had also been placed in crates in two 
other ponds in the spring of 1917, and when these were drained in 
the fall 382 mussels were recovered. Specimens resulting from a 
plant made in 1914 continued to grow in the station ponds, and by 
October, 1917, some had reached a length of more than 34 inches. 
