88 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Because of its varied form in different localities, 

 the lake herring is known by more than one com- 

 mon name. Names used in this work where other 

 authors are quoted are sometimes cisco or tullibee 

 rather than lake herring. These names are most 

 often applied to the deep-bodied forms that occur 

 in inland lakes and Lakes Erie and Ontario. Most 

 lake herring from the upper Great Lakes, however, 

 are of the characteristically shallow-bodied form 

 that is most commonly termed "lake herring." 



The lake herring is of major importance in the 

 commercial fishery of Green Bay. Fluctuations in 

 its abundance bring a degree of economic uncer- 

 tainty to the people who depend upon this fish for 

 part of their livelihood. Although the lake herring 

 has been important in the commercial catch of 

 Green Bay, little has been known about it. 

 Knowledge of this species provides greater under- 

 standing of its reactions to changing environ- 

 mental conditions, and also is required to develop 

 management principles that would allow maximum 

 utilization of the species without depleting the 

 population. 



A study of the life history of the Green Bay 

 lake herring was initiated in 1948 when field collec- 

 tions of scales were made by Dr. Ralph Hile, of 

 the United States Fish and Wildlife Service, as 

 part of a cooperative project with the Wisconsin 

 Conservation Department for the study of Green 

 Bay fish populations. After 1950, field work was 

 carried on by the author with the help of Leonard 

 S. Joeris and Donald Mraz of the Sturgeon Bay 

 field station of the Service's Great Lakes Fishery 

 Investigations. During 1952, the research vessel 

 FWS Cisco, operated by the Great Lakes Fishery 

 Investigations, was available for approximately 

 1 week each in May, July, and October for the 

 study of the distribution of lake herring in Green 

 Bay. Some material on the lake herring of Green 

 Bay was collected during parts of two other cruises 

 of the Cisco in May and June. 



The author is most grateful to Drs. Ralph Hile, 

 John Van Oosten, and James W. Moffett, U. S. 

 Fish and Wildlife Service, and to Dr. Karl F. 

 Lagler, University of Michigan, for valuable 

 guidance during the conduct of the study. 



GENERAL FEATURES OF GREEN BAY 



Green Bay is a nearly detached arm of Lake 

 Michigan with its long axis roughly parallel to 

 the northeast shore of the lake. Morphometric 



features of Green Bay and Lake Michigan are 

 compared in table 1 . The two bodies of water are 

 similar in that they are long and narrow, but they 

 differ greatly in depth and area. The greatest 

 length of Green Bay is about 118 miles on a 

 northeast-southwest axis between the upper end 

 of Big Bay de Noc and the city of Green Bay, 

 Wis. (fig. 1). The greatest width, about 23 miles, 

 is on a northwest-southeast axis in the region of 

 the northern island passages. The area of Green 

 Bay included within a line drawn between the 

 town of Fairport and the tip of the Door Peninsula 

 near Gills Rock is approximately 1,590 square 

 miles. The greatest depth, about 160 feet, is 

 just northwest of Washington Island. The bay 

 is relatively shallow — mean depth, 51 feet. One- 

 third of its area is less than 30 feet deep and only 1 1 

 percent is more than 100 feet deep. 



Table I. — Morphometric features of Lake Michigan and 

 Green Bay 



[Data from the U, S, Lake Survey Chart Nos. 7 and 70, 1953 edition] 



Measurement 



Greatest length (miles) . 

 Greatest width (miles). 

 Shoreline length (miles) 



Area (squarf miles) 



Volume (cubic miles) __ 

 Greatest depth (feet)... 

 Mean depth (feet) 



LakeMich- 

 igan 



307 



ng 



1,661 

 22.400 



1,165 

 932 

 274 



Green 

 Bay 



118 

 23 



379 

 1,590 



15 

 160 



51 



Four major channels in the northern island area 

 with depths of 45 to 130 feet connect Green Bay 

 with Lake Michigan. The manmadc Sturgeon 

 Bay Canal which is 160 feet wide and 20 feet deep 

 joins the two bodies of water in the southern area 

 at Sturgeon Bay. A study being carried on by 

 the Great Lakes Fishery Investigations of the 

 United States Fish and Wildlife Service has pro- 

 vided some data about the exchange of water 

 between Green Bay and Lake Michigan. Al- 

 though not as comprehensive as might be desired, 

 the data do give a general idea of the water -ex- 

 change system between the lake and bay, and of 

 water movements within the bay. 



An outstanding feature of the water movements 

 in Green Bay is tlie high degree of irregularity in 

 direction and velocity. The direction and rate of 

 water movements are believed to be governed . 

 mainly by wind and barometric pressure. Flow 

 of water into the bay from rivers is believed to be 

 of minor importance in the major water move- 

 ments except during spring runoff. Movement 



