LAKE HERRING OF GREEN BAY, LAKE MICHIGAN 



95 



without exception strongly represented (74.2 to 

 87.1 percent) and made up 77.8 percent of all fish 

 taken over the period 1949-52. In April-June 

 collections the IV-group was still strongest in 3 

 years (67.5 to 73.3 percent) and made up 42.2 

 percent of the sample in the remaining year. The 

 percentage of IV-group fish dropped from 77.8 in 

 the first quarter to 64.0 in the second, whereas the 

 Ill-group increased from 9.2 to 25.3 percent. 

 Age group III was dominant in the summer quar- 

 ter (July-September) in one of the two samples 

 (50.8 percent) as well as in combined data of 

 1950-51 (45.4 percent). The transition to domi- 

 nance by age group III was complete in the fourth 

 quarter (October-December) , where it maintained 

 this position in both years (68.9 and 76.3 percent) 

 and in combined data for 1949-50 (73.0 percent). 

 The dominance of the Ill-group (73.0 percent), 

 which advances to age group IV on January 1, is 

 only slightly less than that of the IV-group of the 

 first quarter of the following year (77.8 percent). 

 The mid-year shift of dominance from age group 

 IV to age group III is also shown clearly by the 

 average ages (table 5). 



The much less extensive data on gill-net sam- 

 ples ' (table 6 and fig. 2) suggest that the trend of 

 age composition is much the same as for pound 

 nets. Age group IV was dominant, but the 

 average age was decreasing in the first three 

 quarters and age group III was dominant in all 

 samples of the fourth quarter. 



Despite similar trends in the seasonal shift of 

 age composition, gill nets in general took older 

 fish than did pound nets. The small differences 

 where large numbers of fish were concerned, how- 

 ever, indicated that during the years of this study 

 both gears were cropping a similar segment of the 

 population. 



The age composition of the commercial catch 

 demonstrated for Green Bay requires that a differ- 

 ent year class be a major contributor to the 

 fishery each year. The fishery, in turn, must then 

 be very sensitive to fluctuations in success of year 

 classes. Because of the resulting instability in the 

 economy of small fishing communities it would be 

 advantageous to devise some method of predicting 

 good and poor year classes before they enter the 

 fishery so that problems of high or low production 



' Collections from experimental and commercial gear are shown together 

 In Elll-net data. Figures presented In a later discussion on length at capture 

 show that lake herring taken In the two types of gears at the same time of 

 year have similar length distributions. 



could be anticipated. Unfortunately, this study 

 has been conducted during a period of high and 

 relatively stable production (see Economic Impor- 

 tance of the Fishery, p. 90) and no fluctuations or 

 means of their detection were discernible. The 

 catch and abundance (expressed as catch per unit- 

 of-effort), however, are normally subject to wide 

 fluctuations (Hile, Lunger, and Buettner, 1953). 



The age composition of a representative sample 

 of an entire population should normally show a 

 preponderance of fish in the youngest age group, 

 with progressively decreasing numbers as age 

 increases. This pattern of diminishing numbers 

 with age must exist in lake herring populations 

 (even though it has never been demonstrated), for 

 a population that regularly has fewer young fish 

 than old must soon disappear. Since young lake 

 herring have to be abundant, their scanty repre- 

 sentation in samples of the population must be 

 attributed either to the inability of collecting gear 

 to capture them or to their absence from the area 

 sampled. 



It is believed that the scarcity of young herring 

 in the 1948-52 samples was largely the result of 

 their scarcity on the fishing grounds. A principal 

 gear of capture, the pound net, was fully capable 

 of taking lake herring as young as 1 or 2 years old 

 had they been present in abundance. Pound nets 

 from which lake herring were taken for this study 

 were also designed to capture smelt. Because of 

 their small size and slender form, smelt require 

 smaller mesh sizes than do the lake herring and 

 yellow perch {Perca flavescens), which constitute 

 important portions of the commercial catch. 

 Mesh sizes ranging from 1 }i to 2 inches, extension 

 measure as manufactured, made even smaller by 

 treatment with preservative, have been used in 

 Green Bay since smelt became an important com- 

 mercial species about 1940 (Hile, Lunger, and 

 Buettner, 1953). Although this mesh was far 

 smaller than was previously considered satisfac- 

 tory to catch commercial-sized herring, its intro- 

 duction did not result in any continuous appear- 

 ance of smaller herring in the catch even though 

 it regularly captured yearling smelt and perch. 

 In southern Green Bay, large numbers of trout- 

 perch (Percopsis omiscomaycus) 3 to 4 inches long 

 are regularly taken. 



The ability of pound nets to catch young herring 

 was clearly demonstrated in the winter of 1944-45 

 when, according to Hile, Lunger, and Buettner, 



