LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 



125 



Lake (1,103 eggs per ounce of fish). Lake Erie 

 (1,546 eggs per ounce of age group II fish), and 

 Irondequoit Bay (1,369 eggs per ounce of fish) as 

 computed from data given by Brown and Moffett 

 (1942), Scott (1951), and Stone (1938), respec- 

 tively. 



Table 39. — Relation between the length of the individual 

 lake herring and the number, weight, and size of the eggs 

 it produces 



(Number of fish In parentheses] 



I Records of weight were lacking for 11 flsh. 



The average egg diameters showed no tendency 

 to change with increase of length but were larger 

 in fish of the spa^vning run in November (1.88 

 mm.) than in the prespawning October specimens 

 (1.62 mm.). Other analyses revealed no correla- 

 tion between egg diameter and total number of 

 eggs in individual fish. 



SPAWNING 

 Time and factors of spawning 



According to available records, lake herring in 

 the latitude of the Great Lakes spawn sometime 

 between mid-November and mid-December, and 

 spawning activity at one location usually covers 

 a period of 1 to 2 weeks. That the spawning date 

 may differ with latitude is indicated by Dymond 

 (1933), who found evidence that the lake herring 

 of Hudson and James Bays spawn as early as 

 September 10. Water temperature unquestion- 

 ably is an important factor influencing the time of 



388748 O 57 6 



spawning. Cahn (1927) stated that ciscoes did 

 not begin to spawn in Lakes Mendota and Oco- 

 nomowoc, Wisconsin, until water temperature had 

 dropped below 4° C, and that the temperature 

 was either 3.1° or 3.0° C. at the time spawning 

 ended (5 years of observations). To verify this 

 apparent relation between temperature and spawn- 

 ing, Cahn (p. 100) held 25 ciscoes in tanks with 

 the following results: 



* * * The water was kept at a temperature of 4.5° C. 

 during a period of four months [weeks?], covering the 

 breeding season. In spite of the fact that fifteen of the 

 confined fish were females, all heavy with eggs, not a 

 single egg was laid during this time. In a second tank, 

 exactly similar to the first, and with the same water sup- 

 ply, but cooled by means of ice to a temperature of 3.5° C, 

 females from the first tank spawned within ten minutes 

 after transfer. 



\ second experiment consisted in transferring two 

 females into the second tank while the water was 4.5° C. 

 After two hours in this tank, a large piece of ice was 

 added and a careful record of the temperature kept. The 

 first female spawned with the temperature at 3.6° C, the 

 second at 3.4° C. 



Monti (1929) found that whitefish did not 

 spawn in Italian lakes where winter temperatures 

 remained above 7° or 8° C. Evidence supporting 

 the hypothesis of a critical breeding temperature 

 was given by Pritchard (1930). During the spawn- 

 ing period of the lake herring, which starts in raid- 

 November, the temperatures at a hatchery intake 

 near Belleville in the Bay of Quinte, Lake Ontario, 

 were — 



Stone (1938) recorded a temperature of 3.8° C. 

 shortly before ciscoes started to spawn in Ironde- 

 quoit Bay, Lake Ontario. He observed also that 

 spawning started earlier in the southern end of 

 the bay where water temperatures dropped sooner 

 than in the northern end. Washburn ' reported 

 water temperatures near 3.3° C. during cisco 

 spawning in Birch Lake, Michigan. Brown and 

 MofFett (1942) found spawning at its peak in 

 Swains Lake, Mich., on December 14, 1937, when 



• Washbrnn, Oeorge N. 1944. Experimental gill netting In HIrch Lake, 

 Cass County, Michigan, Michigan Department of Conservation, Institute 

 tor Fisheries Research, Rept. No. 948, 33 pp. (Typewritten.] 



