Although the use of isotopes is expensive, 

 it is believed that in the near future the 

 cost will decrease greatly. 



5. Investigate littoral currents more 

 thoroughly and determine the relationship 

 between lake morphometry and currents. 



6. Undertake the determination of 

 subsurface currents and the relationship 

 between subsurface and surface currents. 



Costs of such a program would be high 

 both in money and time. It will, however, 

 be necessary if the true nature of currents 

 is to be found and predictions of currents 

 made possible. 



ACKNOWLEDGMENTS 



The following agencies and individuals 

 contributed to this study: the crews of 

 the U. S. Fish and Wildlife Service research 

 vessels Cisco and Musky assembled and re- 

 leased drift bottles; the crews of the 

 Michigan Department of Conservation Patrol 

 Boats Nos. 2 and 3 assisted in releasing 

 drift bottles; the U. S. Coast Guard made 

 wind records available; many, many persons 

 returned the cards from the bottles; Mr. 

 William Cristanelli drafted the figures; 

 James Moffett, Ralph Hile, and Stanford 

 Smith of the Great Lakes Fishery Investiga- 

 tions and John Ayers of the Great Lakes 

 Research Institute made suggestions in the 

 preparation of this manuscript. 



SUMMARY 



1. The U. S. Fish and Wildlife Service 

 and the Michigan Department of Conservation, 

 in a cooperative project, conducted a com- 

 prehensive liranological survey in Saginaw 

 Bay and adjacent Lake Huron waters in the 

 summer and fall of 1956. As a part of this 

 project in order to gain information on 

 surface currents, drift bottles were used 



in Saginaw Bay, and drift bottles together 

 with the dynamic-height method were used in 

 lower Lake Huron area. 



2. The drift bottle consisted of a 

 4-ounce Boston round bottle corked, sealed 

 with beeswax, and fitted with a metal drag 

 suspended 12 inches below the neck of the 

 bottle by a piece of black iron wire. The 

 purpose of the drag was to reduce the direct 



influence of the wind upon bottle movement. 

 For the most part drags appeared to func- 

 tion properly up to at least 30 days, after 

 which time many broke away from their drift 

 bottles. 



3. A total of 2,650 of these units 

 were released from the U. S. Fish and Wild- 

 life Service research vessels Cisco and 

 Musky and Michigan Department of Conserva- 

 tion Patrol Boats Nos. 2 and 3. Subsequent- 

 ly 1,843 (69.5 percent) reply cards from 

 the recovered bottles were returned. Of 

 these, 240 were returned after the cut-off 

 date of February 28, 1957, and were not 

 used in studies of surface currents. 



4. Recovery of bottles during the 

 summer and fall was greatest over weekends 

 with this becoming more pronounced after 

 August. Percentage return of bottles re- 

 leased from any one of the nine cruise 

 periods decreased as the season progressed. 



5. Wind records at the Tawas Point, 

 Bay City, and Harbor Beach, Michigan Coast 

 Guard stations were used in drafting wind 

 tracks . 



6. There appeared to be a high corre- 

 lation in Saginaw Bay between direction of 

 surface currents that moved these bottles 

 and direction of winds. In Lake Huron this 

 correlation applied to a lesser extent 

 although the drift of bottles was generally 

 from west to east, apparently under the 

 influence of the prevailing westerly winds 

 of this area. 



7. Use of the dynamic-height method 

 in Lake Huron was restricted because of the 

 paucity of stations covered. It appeared, 

 however, from results using this method 

 along with drift bottles that the surface 

 currents in Lake Huron are much more com- 

 plicated than has been suspected. 



8. Greatest rates of drift were 

 obtained from bottles drifting clockwise 

 around the top of the Michigan Thumb, 

 thence south along the east coast of the 

 Thumb. 



LITERATURE CITED 



ADAMS, MILTON P. 



1937. Saginaw Valley report. Michigan 

 Stream Control Coram., 104 pp. 



27 



