for the year 1928 are given in Table 80, which shows the abundance 

 of adult Crustacea (not nauplii) at one station in each of the 

 three sections. Station ll8 is located one mile north of Station 117. 

 The data in Table 80 show that the Crustacea were about equally- 

 abundant at Stations 25I( and 118 during the four periods of time for 

 which data are available. During the same periods, the abundance at 

 Station 126 was only 1/6 of that at Station 25ii, and l/7 of that at 

 Station 118. It is not possible to make a satisfactory comparison of 

 these stations with those in the Island Section, because the periods of 

 time covered agree in only two cases. 



The data obtained in 1929 and 1930 permit more adequate com- 

 parison. Table 8l was designed to facilitate such a comparison during 

 five two-week periods in 1929. In this table both adult Crustacea and 

 nauplii are included. Station 250 is not included in the computations 

 for Maumee Bay because conditions there are extremely variable, and the 

 station is less representative of the general area than are Stations 252 

 and 2511. Station 13U is excluded from the Detroit River Section in the 

 interest of simplicity. For each period represented, the Maumee Bay 

 Section had the highest counts, and the Detroit River Section had the 

 lowest counts. Counts in the River Raisin Section were sometimes 

 higher and sometimes lower than those in the Island Sectionj the mean 

 count was slightly higher. In the Maumee Bay Section the mean abundance 

 was 18 times that in the Detroit River Section, and nearly twice that of 

 the other two sections. 



Table 82 shows the same kind of comparison for 1930, except 

 that in this case there are six consecutive two-week periods represented. 

 Again the Detroit River Section had the lowest counts in each period 

 represented. The River Raisin Section showed greater abundance than the 

 Island Section in some periods, and less in others, and the mean again was 

 greater. The Maumee Bay Section had the largest mean count of all the 

 sections, but in certain of the two-week periods it had smaller counts 

 than the River Raisin and Island Sections, If the abundance in the 

 Detroit River Section be regarded as unity, the relative abundance in 

 the other sections would be as follows: Maumee Bay, 20; River Raisin, 17; 

 Island, 13. Thus, the different sections held the same relative positions 

 with respect to abundance of Crustacea in both years. The actual dif- 

 ferences between means in the same sections in the two years are strik- 

 ingly small in view of the short period of time involved. That is, the 

 difference of 11 individuals in the mean count for the Maumee Bay Section, 

 and the difference of 9 in the River Raisin Section, are not unexpectedly 

 large. 



2/iU 



