310 American Fisheries Society 



an average of 833.8 mussels per fish. From the enclosure 

 made of poultry netting were recovered 1,152 living juveniles 

 and 5 pairs of valves of dead luteola, making a total of 1,157, 

 or an average of 231.4 mussels per fish. 



In view of the fact that the fishes in both enclosures had 

 received the same infection and doubtless had dropped the 

 same number of larval mussels, it appears that the enclosure 

 of fine-meshed screen prevented young mussels from being 

 washed out by waves, especially when, after releasing them- 

 selves from the host, they descended through the water to 

 the bottom, and as a result produced 3,012 more juveniles 

 than the other enclosure. It may be supposed that screen 

 sides of finer mesh than 12 to the inch would be even more 

 effective in confining the larval mussels within an enclosure. 



MAXIMUM DENSITY OF MUSSEL POPULATION IN ENCLOSURES 



Evidence regarding the maximum number of mussels 

 which will live and grow inside an enclosure is still being 

 sought. Records are available of such dense populations 

 of juvenile luteola on the bottom of a pen as 41 and 77 to 

 the square foot at the close of the first season, but the greatest 

 number of juvenile inhabitants which can advantageously pass 

 their second year in an enclosure has not been thus far satis- 

 factorily determined. The best record, however, obtained 

 from the work in Lake Pepin will be cited. 



On October 11, 1919, there were replanted in a half- 

 section of an enclosure 10 feet square, 1,060 live first season 

 luteola, this being at the rate of 21.2 for each of the 50 square 

 feet. These mussels ranged in size from 4.0 to 21.6 milli- 

 meters when replanted. After lying undisturbed for eleven 

 months, the enclosure was examined on September 10, 1920, 

 at which time 945 live second season luteola were recovered, 

 from 16.5 to 49.4 millimeters in length. Thus, the average 

 population was 18.9 for each of the 50 square feet. This 

 figure does not accurately represent the condition prevailing, 

 because the mussels were found crowded together in the cor- 



