378 U.S. BUKEAU OF FISHERIES 



The spawning habits of the Arkansas f anshell have been definitely 

 determined and confirmed by observations in three different years 

 by Thomas K. Chamberlain. In the field studies the formation of 

 winter colonies has been discovered and significant observations on 

 the method of fertilization obtained. Over 400 marked individual 

 mussels have been collected from such colonies for study. 



Internal and external activities as vndices of condition. — The 

 studies at Columbia of the mussel heart by H. L. Motley have pro- 

 vided normals with which the condition of mussels in the various 

 experiments is readily compared. This heart test has also proved 

 very helpful in field examinations as well as in the laboratory 

 studies, and new information concerning the successful shipment of 

 mussels has been one of the advances made through the application 

 of these heart data. By slowing the heart action with cold, dry 

 air (5°-10° C.) it was found that the metabolism of the animals 

 could be reduced to almost the hibernation level. Applying this 

 fact, living mussels have been kept out of water in dry air for over 

 80 days, and have remained in good condition throughout the tests, 

 thus indicating a new safe method for the shipment of mussels over 

 long distances and with no care on the part of the carrier. The 

 survival in shipment tests has been practically 100 percent. 



The observations on mussel activities under normal and adverse 

 conditions have been greatly extended and are now being revised for 

 publication. 



POLLUTION STUDIES 



Erosion silt. — The review of the mass data on erosion silt and its 

 bearing on fisheries problems has been completed and the scientific 

 results organized for publication. Particular attention has been 

 given to the effects of erosion silt on light transmission, conductivity, 

 water temperature, and salt content, as bearing on fisheries problems. 



Arsenic investigations near Gardiner^ Mont. — The study of arsenic 

 pollution in Bear Creek, a tributary of the Yellowstone River near 

 Gardiner, Mont., was made with reference to stream pollution and 

 to possible storage of arsenic by certain aquatic insects which are 

 eaten by the trout and whitefish. These investigations were par- 

 ticularly important to the program of pollution in that they pointed 

 to an unlooked for source of storage which must be considered in 

 future studies of other heavy metals as well as arsenic. 



Cooperative projects with United' States engineers. — The coopera- 

 tive work with the United States engineers has been continued 

 during- the year. Plans are now being made for a continuation of 

 these projects as requested by the office of the Chief of Engineers. 

 This work consists in the investigation of stream conditions with 

 reference to erosion and pollution and supplies much information 

 on our inland waters. 



Neir method for studying pollution effects. — As a result of dif- 

 ficulties encountered in previous studies of pollution problems and 

 in view of the various discrej^ancies between existing observations on 

 pollution and relative toxicity of pollution agents, experiments have 

 been in progress for some time looking to the development of more 

 satisfactor}^ methods of study and to the standardization of results. 

 New apparatus has been devised and new technique perfected which 



