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FISHERY BtJLLETIN OF THE FISH AND WILDLIFE SERVICE 



the surface-water temperature was "* * * prac- 

 tically at the freezing point." They expressed 

 the belief that spawning may have continued for 

 several days after ice covered the lake. 



Although the lake herring of Green Bay spawns 

 from mid-November to mid-December, considera- 

 able variation in the progress of spawning activi- 

 ties does take place. It is believed, however, that 

 some spawning is going on every year some place 

 in the bay during this entire period. 



An example of the dynamic situation during the 

 progress of spawning in Green Bay is offered by 

 records of catches of a single pound net at Sister 

 Bay in December 1950. On December 2 the catch 

 consisted mostly of ripe fish ready to spawn; on 

 December 3 about 50 percent of the fish were 

 spent; on December 4 all of the 112 lake herrmg 

 examined from the catch of this net were spent; 

 furthermore, their gonads were in an advanced 

 state of recovery — a condition typical of that 

 found in February. This observation suggests 

 that (1) Lake herring move in schools during the 

 spawning period in Green Bay; (2) fish of one 

 school do not necessarily complete spawning in 

 the place at which they have started; and (.3) 

 schools in one area do not all spawn at the same 

 time. 



Differences in progress of spawning between 

 various groups of fish most probably are the re- 

 sult of differences in the temperature regime in 

 the several parts of this hydrographically complex 

 bay (see General Features of Green Bay, p. 88). 

 Available temperature records are inadequate for 

 study of local differences during the spawning 

 season. Records that have been made, however, 

 show that the temperature drops through the 4° 

 to 3° C. range during the last half of November 

 and the first half of December when spawning 

 takes place. 



Spawning grounds 



Most reports, particularly those concerning in- 

 land lakes, indicate that eggs of lake herring are 

 laid in shoal areas 3 to 10 feet deep (Bean 1902; 

 Cahn 1927; Pritchard 1930; Stone 1938). Al- 

 though no evidence was given that spawning did 

 not occur in deeper water, the regularly observed 

 movement of fish into shoal areas and back to 

 deep water clearly indicates that the shallower 

 region must be the preferred spawning area. 

 Wagner (1911, p. 76) reported that in Green 



Lake, Wisconsin, which is 237 feet deep, "Local 

 fishermen generally believe that spawning takes 

 place at a depth of about seventy feet, on marly 

 bottom, but this is somewhat doubtful." Koelz 

 (1929) related that lake herring spawn in water 

 60 feet deep at the western end of Lake Erie and 

 in water 30 to 150 feet deep at the eastern end. 

 In Lake Ontario, Koelz said a deep-water form 

 spawns in 90 to 180 feet whereas shallow-water 

 lake herring spawn in 60 feet of water. In Green 

 Bay, spawning fish are most concentrated in water 

 10 to 60 feet deep but catches of both ripe and 

 spent fish are observed from nets fished at depths 

 down to at least 140 feet. Apparently, spawning 

 takes place over practically all depths and in all 

 sections of the bay. 



Spawning lake herring in general show no pref- 

 erence for a particular bottom type. Spawning 

 has been reported over boulders, gravel, sand, 

 marl, clay, mud, and aquatic vegetation. In 

 Green Bay, spawning takes place over areas of 

 boulders, sand, and mud, with no clear indication 

 of preference. The failure to select particular 

 bottom types probably stems from the fact that 

 lake herring are pelagic spawners. Evidence that 

 eggs are extruded a considerable distance above 

 the bottom is given by Pritchard (1930), who 

 found eggs evenly scattered over the bottom with 

 no evidence of local concentrations that would be 

 expected if eggs were deposited near the bottom. 



Spawning behavior 



Few observations have been made of the spawn- 

 ing act of lake herring. Cahn (1927) described 

 spawning activity of ciscoes in Lake Oconomowoc 

 as being slow and deliberate with no chasing or 

 darting about. In contrast with Cahn's observa- 

 tion, Bean (1902) described the night-time spawn- 

 ing activity of the tullibee in New York as being 

 accompanied by "* * * constant loud splashing 

 and fluttering." This type of activity has also 

 been reported by Washburn (see footnote 9, p. 

 125) in Birch Lake, Michigan, where "The fish 

 were seen darting about singly and in pairs, oc- 

 casionally coming to the surface and splashing 

 the water. The appearance of these fish on shoals 

 would take place just before dark at or about 

 sunset and continue until 10:00 p. m." Fishermen 

 of Green Bay tell of similar jumping and splashing 

 activity of lake herring during the spawning pe- 

 riod. No observations have been reported on 



