September 1966 Washington, D.C. Vol. 28, No. 9 



AN EVALUATION OF THE AIR BUBBLE CURTAIN 

 AS A BARRIER TO ALEWIVES 



By George A. Kupfer-i' and William G. Gordon^-*- 



ABSTRACT 



The effectiveness of an air bubble curtain to impede, redirect, or stop the annual 

 migration of alewives in the Milwaukee River was studied in the spring of 1964. Its 

 operation during a l--month period indicated that the curtain reduced the migration of 

 alewives. 



BACKGROUND 



The opening of Welland Canal provided a path for alewives to migrate into the upper Great 

 Lakes (Miller, 1957). Reaching Lake Michigan by the late 1940's, the alewives grew to phe- 

 nomenal numbers, each year apparently increasing several fold in numbers over the previ- 

 ous year. During the last 6 years, the City of Milwaukee has been plagued by large migra- 

 tions of alewives into the Milwaukee, Kinnickinnic, and Menomonee Rivers during May, June, 

 July, and part of August. Soon after entering these rivers they die in large numbers, and 

 cause an extensive sanitation problem. This discourages owners from improving their prop- 

 erties abutting the river in such a manner as to make the river an asset to the community. 



Mortalities of alewives in fresh water are not new. Although records of mortalities in 

 Lake Ontario date back to 1890 (Smith, 1892), no reasons are given for the possible cause of 

 death. Graham (1956) and Threinen (1958) suggest that mortalities are due to detrimental 

 changes in body metabolism probably following abrupt changes in water temperature. Obser- 

 vations and data from this study in 1964 indicate that a lack of sufficient dissolved oxygen is 

 also a contributing factor. 



An initial survey of the local situation in March 1964 revealed limitations to devices that 

 could be used to control migrations up the rivers. Because of low water and navigation in 

 the Menomonee, Kinnickinnic, and lower Milwaukee Rivers, barriers could not be used in 

 those portions generally navigated by large lake vessels. These rivers, from the junction of 

 the Milwaukee and Menomonee Rivers south and east to the lake, have become silted, and 

 maximum depth is about 25 feet. The Milwaukee River after it separates from the Menomo- 

 nee is navigable by smaller pleasure craft to the North Avenue Dam. 



The development of an air bubble curtain apparatus by the U. S. Bureau of Commercial 

 Fisheries demonstrated the practicality of guiding the Atlantic herring (Smith, 1961). Air 

 pumped through perforated polyethylene pipe made an air curtain that tended to direct the 

 movements of young herring in clear water. Upon review of this work, the city officials of 

 Milwaukee, Wis., implemented a study to determine the effectiveness of the air bubble cur- 

 tain and assess its possible application as a permanent control. 



* Assistant Director, Environmental Technical Services Division, Milwaukee Health Department, Milwaukee, Wis. 

 ** Fishery Biologist, Branch of Exploratory Fishing, U. S. Bureau of Commercial Fisheries, Ann Aibor, Mich. 



DEPARTMENT OF THE INTERIOR 

 Fish and Wildlife Service 

 Sep. No. 771 



