PROGRESS IN BIOLOGICAL INQUIRIES, 1921. 



REPORT OF THE DIVISION OF SCIENTIFIC INQUIRY FOR THE FISCAL YEAR 1921.' 



By R. E. CoKER," 

 Assistant in Charge of Scientific Inquiry. 



CONTENTS. 



Page. 



Introduction — 4 



Studies of fishes 5 



The Pacific salmon . 5 



Immature salmon in the ocean 6 



Results of marking experiments T 



Salmon investigation in Yukon River 7 



Chemical studies of salmon 9 



Life histories of marine fishes 10 



Fresh-v^ater fishes 11 



Whitefishes of the Great Lakes 13 



Fishes of Wisconsin lakes 13 



The paddlefish 14 



Poisonous action of gar roe 14 



Fishes of the Panama region ^ 15 



Pacific herring 16 



Use of fish in combating malaria 16 



Cooperation in antimalaria campaign , 16 



Conditions governing abundance of mosquito-destroying fish 17 



Mosquito control in northern waters 18 



Fish-cultural experiment work 19 



Experiments in propagating and rearing fish in ponds 19 



Water beetles in relation to pond culture 20 



Studies of Salmonidse in relation to fish culture 20 



Minnows in relation to fish culture 21 



A new form of pond outlet . 21 



Eradication of some objectionable plants 24 



Studies of fish disease 25 



Mortality in pike-perch eggs 25 



Abnormal conditions of fish ovaries 25 



Disease of rescued fish 26 



Parasitic flatworms of fresh-water fishes 26 



Treatment of Ichthyophthirius disease 27 



Oceanographic and limnological studies 28 



Investigations in the Atlantic 28 



Survey of Chesapeake Bay 29 



Survey of selected areas in Mississippi River 29 



Studies of inland lakes 30 



Agar-agar and other gelatins from seaweed 31 



The oyster 32 



Investigations of oyster culture 32; 



Effect of pollutions upon propagation of oysters 33: 



Fresh-water mussels 35; 



Propagation of mussels 35^ 



Protection of mussels 35. 



Mussel survey in upper Mississippi River 361 



Experiments relating to mussel propagation 36: 



Investigations in the Kentucky River 37 



The biological laboratories 37 



1 Appendix VIII to the Report of the U. S. Commissdoner of Fisheries for 1921. B. F.. 

 Doc. No. 911. 



2 With the collaboration of the investigators. 



3 



