350 U.S. BUREAU OF FISHERIES 



catch by species, the kind and amount of gear lifted, the length of 

 time the gear was fished, and the location of the fishing grounds. 

 The reports for the years 1927 and 1928 were by no means complete, 

 but since the beginning of 1929 there has been available a virtually 

 complete record of all commercial fishing activities in the State. 



For the purpose of analysis of the statistical data the Great Lakes 

 waters of the State of Michigan have been divided into statistical 

 districts which, as far as possible, represent natural geographical 

 divisions. There are 7 districts in Lake Superior, 11 in Lake 

 Michigan, 6 in Lake Huron, 1 in Lake St. Clair, and 1 in Lake Erie. 

 The analyses have been directed toward a stud}^ of fluctuations in 

 the total catch and total intensity of the fishery and also in the 

 relative abundance of the several important species from year to 

 year and from one locality to another. Abundance is calculated in 

 terms of yield per unit of fishing effort. 



The use of identical types of gear in totally unrelated fisheries 

 and important variations both from one region to another and from 

 one time of year to another in the amount of time gear is fished 

 before it is lifted have made necessary the development of special 

 methods of analysis for the study of Great Lakes fisheries sta- 

 tistics. The former difficulty was met by an allocation of effort 

 in the direction in which it was actually exerted, that is, a particu- 

 lar unit of gear is considered to have fished for a given species onlj' 

 when some quantity of that species is included in its catch. The 

 latter of the above mentioned difficulties was obviated through the 

 introduction of the time element in the computation of fishing 

 effort. Thus the fishing effort represented by a day's lift is not 

 merely the amount of gear lifted, but rather is the product of the 

 amount of gear lifted and tlie time the gear has fished. The sum 

 of these separate products can be considered to represent the true 

 fishing intensity for a given district or a given period of time. A 

 detailed explanation and justification of these methods has appeared 

 in a special publication. 



At the present time the statistical studies are being confined chiefly 

 to Lake Huron. In the near future a report will be prepared on 

 the statistics of the commercial fisheries of that lake for the 5-vear 

 period, 1929-33. 



PIKE-PERCHES 



H. J. Deason was detailed to make a brief survey of the com- 

 mercial lifts of trap nets operated during the period, April 3-14, 

 1933, in the vicinity of Sandusky, Ohio, and the islands of western 

 Lake Erie. Particular emj)hasis was placed on the percentage of 

 illegal saugers taken in these nets.. Counts were made in the 

 field of all legal and illegal saugers, yellow pike-perch, and yellow 

 perch taken in 10-t commercial trap nets operated at Sandusky, 

 Put-in-Bay, and Toledo. Many saugers were also weighed, meas- 

 ured, and sexed at these three localities. 



In addition much work has been done on the life history studies 

 of the pike-perches of Lake Erie. A publication on these species 

 was completed and presented at the annual session of the American 

 Fisheries Society. It was observed that dominant age-groups oc- 

 curred in the collections made in 1927 and 1928, The 1926 yeav 

 class was dominant in both collections in the case of the yellow and 



