160 BULLETIN OF THE BUREAU OF FISHERIES 



Table 11. — The five most abundant zooplanktons for each group of stations 



Genus 



Rank in 

 Group I 

 (stations 

 1, 8, 10, 

 and 12) 



Rank in 

 Group II 

 (stations 

 2, 11, and 

 14) 



Rank in 

 Group III 

 (stations 

 3, 5, 6, 7, 

 and 9) 



Genus 



Rank in 

 Group I 

 (stations 

 1, 8, 10, 

 and 12) 



Rank in 

 Group II 

 (stations 

 2, 11, and 

 14) 



Rank in 

 Group III 

 (stations 

 3, 5, 6, 7, 

 and 9) 



Cyclops 



3 

 3 

 1 

 4 



2 



2 

 1 

 3 

 4 

 5 



Ceriodaphnia 



2 



5 







Rotifer . 



Noteus __ 







Nauplii 



1 

 4 



Bosmina 



5 





Anursea 





4 





Polyarthra 















FISHES 



SUMMARY OF SEINING OPERATIONS AND RESULTS 



As stated in the introductory part of this report, the people of Minnesota and 

 Wisconsin claim that the number of fish has decreased in their section of the Missis- 

 sippi River, but no specific data are available to support this contention. Unfortu- 

 nately, the writer was not able to seine at all the stations, but the stations where 

 seining was done are so distributed that it is possible to determine whether there is 

 any correlation between the number of fish and the degree of pollution in the river. 

 Seine hauls were made at or near stations 1, 2, 4, 5, 6, 7, 9, and 10. The equipment 

 used consisted of a flat-bottomed gasoline launch, a rowboat, and a seine 150 by 6 

 feet of J^-inch mesh. The fish were preserved in 4 per cent formaldehyde and sent 

 to Dr. John Van Oosten, of the United States Bureau of Fisheries, for study. Doctor 

 Van Oosten's determinations were checked by Carl L. Hubbs, of the University of 

 Michigan zoological museum. 



Stations 1 and 2. — The seining at stations 1 and 2 was done on August 21. The 

 first haul at station No. 1 yielded the 362 fish shown in Table 12, in addition to one 

 18-inch common sucker and 75 crayfish. The second haul contained at least 1,500 

 small wall-eyed pike, numerous minnows, a few bullheads, a few suckers, and a 

 number of crayfish. The fish retained are listed in Table 12. 



The first haul at station No. 2 consisted of the 547 fish, shown in Table 12, one 

 10-inch pickerel, and one 6-inch smallmouth black bass. The second haul consisted 

 of a school of black bullheads, many wall-eyed pike, and several hundred shiners. 

 Part of this haul is listed in Table 12. The hauls at station No. 2 were made in 

 the left branch of the channel, which is less polluted locally than is the right branch. 

 Many fish were seen along the left bank (east side) of the river at station No. 2. A 

 few were seen also along the side of the island in the right branch of the channel. 



Station 4- — On August 17 three seine hauls were made in the Minnesota River 

 at station No. 4. The partial results of these hauls are shown in Table 12. In 

 one of the hauls 350 gizzard shad were taken but were thrown back. They do not 

 appear in the table. A number of shiners and sunfish likewise were thrown back 

 into the river. Crayfish seemed to be plentiful at this station. 



Station 5. — On August 20 three seine hauls were made at station No. 5. Only 

 one 1.5-inch stickleback was taken. 



