16 PROTECTION OF FRESH- WATER MUSSELS, 



only one or two blanks can be cut out, leaving a larger bulk of shell 

 in proportion to the number of blanks gained. On the other hand, 

 in very large shells a high degree of waste is involved because of 

 excessive thickness, which must be ground from the blanks, and be- 

 cause of the extra weight of the discarded portion. Somewhere 

 between these extremes is the size of shell that yields the largest num- 

 l)er of blanks as compared with the waste or the weight of shell that 

 does not go into buttons. As shown by the data in the fifth column of 

 ihe table, the shells a little above 2 inches in size are those (for this 

 species) that make the best yield per ton for the small lines for which 

 there is the greatest general demand. 



REASONS FOR THE PROPOSED 2-INCH LIMIT. 



Argument might be made in favor of a higher size limit as being 

 still more favorable to the preservation of the mussels, but it is 

 sufficient to say that the economic conditions would not justify a 

 higher limit. At 2 inches a sufficiently severe restriction is placed 

 upon the fishery, and to go further would be practically to pro- 

 hibit the pui-suit of shelling in so many localities that excessive hard- 

 ship would be caused. 



As consideration thus far has been given almost exclusively to 

 the niggerhead shell, the question may well be raised. Will the same 

 limit apply to other species of shells? The minimum size of 2 inches 

 suggested can be taken as an absolute minimum, since there is no 

 species of any importance for which it would be too high. This 

 minimum would not, however, give the same degree of protection 

 to the larger forms, such as the washboard, the bluepoint, and the 

 mucket. Should a minimum size be fixed with particular reference 

 to any one of these varieties, it would necessarily be a good deal 

 higher. 



In the present paper recommendation is made for this one-size 

 limit alone, for the following reasons : 



1. All conditions considered, it is the most appropriate limit that 

 could be designated for the niggerhead mussel, which is at present 

 the most important species of wide distribution, and which is, further- 

 more, the species most liable to rapid extermination. This and spe- 

 cies closely like it, as the pigtoe, the pimple-back, and the maple- 

 leaf, are chiefly those that are now being taken in the very small sizes. 



2. The same size applies equally well to the related species just 

 mentioned, as well as to the "hickory-nut," or "Missouri nigger- 

 head," and the "butterfly." 



3. The larger species, as the "washboard," "bluepoint,'' and 

 "mucket," are generally so evidently valueless in the small sizes that 

 shellers do not take them. At least it is not yet of observation that 

 particular injury is being done to these species in this way. 



