20 U. S. BUREAU OF FISHERIES. 



among other things that under favorable conditions the Lake Pepin 

 mucket {Lm)ipsilis luteola) makes as much growth in the first y€*ir 

 when kept at a density of 60 to the square foot as when planted only 

 half as closely. In various experiments to determine the practica- 

 bility of keeping young mussels in confinement during the winter ?, 

 survival of 83 to 93 per cent was obtained. 



Since in handling of live fish for any purpose slight injuries 

 occur, which, if the fish are held in confinement, lead to infections by 

 bacteria or water molds that cause the death of the fish, experiments 

 have been made in immersing the fish in a 1 to 1,000 solution of 

 copper sulphate after encystment of the glochidia. The results were 

 very favorable to the fish, and the solution apparently had no effect 

 upon the encysted mussel glochidia. 



Dr. L. B. Arey continued his study of the mechanism of encyst- 

 ment of mussel glochidia and of the relationship existing between 

 fish and mussel. He has been able to establish through his investiga- 

 tion that encystment is not the result of cell division but of cell 

 migration ; in other words, the rapidity with which the cyst of fish 

 tissue forms about the infecting glochidium results from the wander- 

 ing in and piling up of neighboring cells, not from multiplication of 

 those present. His study throws light upon the question as to what 

 the tissues of the host fish do, if anything, to provide special facilities 

 for the parasitic mussel embryos. Such information may have con- 

 siderable indirect value in possible improvements in methods of arti- 

 ficial culture of fresh-water mussels. 



PRACTICAL TESTS OF THE VALUE OF PROTECTION AND PROPAGATION. 



With the protective closure to mussel fishery of sections of the 

 Minnesota River and of other Minnesota streams in the spring of 

 1921 for the purpose of allowing them the opportunity of rehabitat- 

 ing their mussel beds naturally, a statistical examination of certain 

 mussel beds in the open and closed areas of the Minnesota River 

 near New Ulm' and Redw^ood Falls, Minn., was instituted. 



By careful method of catch with equipment of fixed measurements 

 and capacity, statistical information showing relative abundance and 

 ages of shells of different species has been obtained. These data 

 collected by Dr. A. D. Howard will serve for direct comparison with 

 similar records collected five years hence at the close of the pro- 

 tective period. Such comparison should indicate the value of legis- 

 lative closure of alternate sections of streams in the rchabitation of 

 mussel-bearing bottoms. 



A similar study of the Des Moines River in Iowa, closed to mussel 

 fishing in 1920, was carried out by H. W. Clark with the same pur- 

 pose in view. Careful studies are projected also for Lake Pepin, 

 in which alternate areas are now closed or open to conimercial fish- 

 ing, and in Lake Pokegama, Pine County, Minn., the closure of 

 which by administrative action five years ago has now been con- 

 tinued for another period. 



Through the cooperation of the Hawkeye Pearl Button Co., Mus- 

 catine, Iowa, records have been obtained of the relative frequencies 

 of the yellow sand-shell {Lampsilis anodontoidcs) and the nigger- 

 head mussel {Quadnda ehenus) in commercial carload shipments 

 from points on the White River, Ark., in the vicinity of Clarendon. 



