September 1966 



COMMERCIAL FISHERIES REVIEW 



were fished a shorter time on days when many fish were present in the netting area. Both 

 nets, however, were fished for the same length of time and during the same period to obtain 

 comparable results. Because of strong currents, a line was attached between the pilings of 

 the bridges, along which a small barge was operated for setting and picking up the nets (fig. 

 8). As the nets were picked out of the water, the enmeshed alewives were counted and re- 

 corded, 



FISHING RESULTS 



Gill-netting during the first week gave inconsistent results (fig. 9). At first, the net a- 

 bove the air curtain would have greater numbers of fish than the net below. From May 18 



through June 15, 1964, the down- 



LEGEND: 





- 



Upslream net 





- Downslream rwt. 



Flui)iing tunnel began opcrat 



DATE OF SAMPLE 



Fig. 9 - Number of alewives caught by gill nets above and below the air- 

 bubble curtain during summer 1964. 



stream net consistently caught more 

 fish than the upstream net. The first 

 erratic results may have resulted 

 from fish in the river before the 

 study began. 



The results of gill -netting on 

 June 19 indicated that a large run of 

 alewives apparently moved up the 

 river on about June 18 or 19. The 

 upstream net had about 285 fish, 

 while the downstream had over 800 

 (estimated) fish. The downstream 

 net at the North Water Street bridge 

 was lost because personnel could not 

 lift it out of the water owing to the 

 many alewives in the net. A flushing 

 station, the outlet of which was lo- 

 cated just below the North Avenue 

 dam on the Milwaukee River, was 

 turned off at the beginning of the 

 study. The flushing station is used 

 during dry weather in the summer to alleviate the stagnant condition of the river by discharg- 

 ing about 18 million gallons of water per hour through the outlet. The intake for this flushing 

 station was located in the main harbor adjacent to the Milwaukee Yacht Club. A small self- 

 cleaning screen over the intake was not considered feasible for such a short experiment; 

 therefore, the pumps at the flushing station were turned off and remained off until 9:00 a.m. 

 on June 16, 1964. Then, because of dry weather flow and adverse river conditions, the flush- 

 ing tunnel was used. As a result, alewives were pumped into the river behind the air curtain 

 at the rate of about 2,000 fish a day. Undoubtedly these fish contributed to the catch of the 

 net upstream. 



A commercial minnow dealer who regularly fished in the entire river and had daily con- 

 tact with these areas reported that the alewives were present in the rivers before this study 

 began. He reported netting small numbers of alewives as far upstream as the dam. He stated, 

 however, that about Ij to 2 weeks after the air curtain installation, no alewives were found in 

 that stretch of the river which extended from the curtain to the dam. He stated that after June 

 16, he again began to catch alewives in his minnow nets. This fisherman believed that the 

 curtain was successful. His observations would again tend to lend credence to the experi- 

 ences of City personnel and to explain some of the early results. 



CHEMICAL AND PHYSICAL TESTS OF WATER QUALITY 



To provide data from this study which might be comparable with like studies at a future 

 time, basic chemical and physical determinations of the water quality in the study area were 

 made. Surveys were made on Mondays, Wednesdays, and Fridays to measure temperature 



