PROGRESS IN BIOLOGICAL INQUIRIES, 193 4 371 



that some of the counts and measurements were valueless those prov- 

 ing not trenchant were dropped. Only 7 measurements and 2 counts 

 (lattu'al line scales and number of vertebrae) were retained as 

 indicative of possible racial ilill'crencos. 



Small a\era^e ditl'crcnccs betwcn the blue and yellow pike-perches 

 of Lake Erie have been noted, but the })ercentao;e of overlap is <rreat. 

 Differences between the blue pike-perch of Lake Erie and those of 

 Lake Ontario are as orreat as are the differences between the yellow 

 pike-})erch of Lake Erie and those of Lake Huron. In distinj^^uishing 

 the blue from the yellow pike-perch in Lake Erie the color and <rrowth 

 rate afford the best criteria. In Lake Erie these two species have a 

 dilFerent distribution, constitute distinct fisheries units, and because 

 of differences in irrowth rate and average size have different legal size 

 limits. From the standpoint of law enforcement it would be most 

 advantageous to have absolute morphological criteria Avhich would 

 differentiate the two species, but these apparently do not exist. 

 Further work on the racial question nmst include the age determina- 

 tion of all specimens and a study of morphological variations with 

 growth rate and with year classes. 



YELLOW PERCH 



F. W. Jobes continued the study of the life history of the yellow 

 perch. L"p to the present time scales of nearlj'^ 5,000 perch have been 

 analyzed for age and growth rate. The perch material was excep- 

 tionally^ well adapted to an investigation of the growth relationship 

 between the body of the fish and its scales. As a result of this work 

 a better conception will be obtained concerning this most difficult 

 problem that confronts nearly every investigator of the life history 

 of fishes. 



OTHER OUTSTANDING PROBLEMS 



Although some of the most controversial of the practical problems 

 on the Great Lakes, such as the proper mesh in trap nets and pound 

 nets, destructiveness of chub nets to trout, regulation of deep trap 

 nets, method of measuring mesh in gill nets, size limits of fish, and 

 pollution, have been solved, much remains to be done. The contro- 

 versial question of the destructiveness of hooks and bait nets to 

 immature fish needs investigation. Further experimental work 

 should be done on the proper mesh of gill nets employed in Lake 

 Erie. A satisfactory metliod for measuring the mesh of heavy twine 

 nnist be developed. 



UNIFORM REGULATION AND DEPLETION 



One of the most urgent needs on the Great Lakes today is con- 

 certed action by the various Commonwealths, both in this country and 

 in Canada, to regulate and jirotect the commercial fisheries of the 

 (ireat Lakes. Since 19:27 the Bureau has cooperated with the 

 various Commonwealths in some 10 interstate and international fish- 

 eries conferences. During this })eriod the Bureau, in cooperation 

 with various State conservation departments, has concentrated its 

 scientific research on the Great Lakes on those controversial practical 



