96 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



large numbers of "pin" herring were taken in 

 pound nets. Scales from 78 specimens taken at 

 Escanaba on May 27, 1945, revealed that all were 

 fish of the 1943 year class and were nearing the 

 end of their second year of life. Inasmuch as 

 this has been the only phenomenal occurrence of 

 small herring in smelt-type pound nets since they 

 came into common use, it can be assumed that the 

 appearance in numbers of young herring in 1945 

 could have resulted from a successful hatch in 

 1943 and that the abnormally plentiful young 

 herring extended beyond their normal range into 

 the shallow-water areas in which pound nets are 

 located. Although lake herring average about 5 

 inches long at the end of their first year of life, 

 which is within the size range of other small fish 

 taken, none were ever present in our pound-net 

 samples. 



The lake herring is a relatively short-lived 

 species. Hile (1936) reported the maximum age 

 of XII in Trout Lake, Wisconsin. Although no 

 other author has reported a fish this old, fish in 

 age group XI have been reported by Fry (1937) 

 in Lake Nipissing and by Hile in Clear Lake. 

 Lake herring in age group X have been reported 

 by Carlander (1945), Eddy and Carlander (1942), 

 Stone (1938), and Van Oosten (1929). The low- 

 est maximum age reached in any population was 

 reported by Hile for Muskellunge Lake where the 

 oldest fish belonged to age group IV. The oldest 

 age groups in these populations are represented 

 in the samples by only one or two individuals; in 

 most lake herring stocks heavy mortality starts 

 between the third and seventh years of life. 



The oldest lake herring taken in Green Bay 

 were two Vll-group fish caught in pound nets in 

 June 1951.^ Only 17 representatives of age group 

 VI were recorded during the course of this study. 



The observed age compositions of several North 

 American lake herring populations show that age 

 groups II to V are best represented in the samples 

 and that of these age groups III is usually the most 

 common. Some of the differences among samples 

 from various populations were undoubtedly the 

 result of selectivity of collecting gear. It appears, 

 nevertheless, that fish are much shorter lived in 

 some populations than in others. Hile (1936) 

 collected fish from several lakes with the same gill 



' One of the VH-group fish was in a selected sample collected on June 15, 

 1951, and does not appear In discussions dealing with age. The other VII 

 group flsh wa.s In the June 19, 1951, collection. 



nets, and his data should be well adapted to a 

 comparison of age composition in different bodies 

 of water. Hile's data show that age groups II 

 and III were best represented in the Muskellunge 

 and Clear Lake populations, but that the oldest 

 fish taken in Muskellunge Lake belonged to age 

 group rV, whereas in Clear Lake ciscoes lived as 

 long as 1 1 years and age group VII made up more 

 than 11 percent of the samples. The difference 

 between these two lakes in observed age composi- 

 tion is as great as that recorded elsewhere in the 

 literature. It is possible that differences reported 

 by other authors can be real and that the longev- 

 ity does vary with local conditions. 



Van Oosten (1929) showed that age group III 

 (age group IV under his system of age designation) 

 predominated in his samples from Saginaw Bay, 

 all of which were taken from pound nets during 

 the period October to December. This same age 

 group dominated samples taken from Green Bay 

 pound nets during the same time of the year 

 (table 5). 



SIZE AT CAPTURE 



The lengths of lake herring captured in pound 

 nets (table 7) and gill nets (table 8), varied both 

 as to average and range among collections of the 

 same year and of different years. Mean lengths 

 for samples, however, show no distinct seasonal 

 pattern, which is in marked disagreement with the 

 well-established, seasonal changes in age composi- 

 tion (see p. 94). The data on age would suggest 

 that the consistently older fish taken during the 

 first half of the year should be longer than the 

 predominantly younger fish taken in the second 

 half. The discrepancy is explained by the length 

 frequencies of age groups (table 9) which show a 

 wide overlap of length distribution where length 

 groups are frequently represented by fish of three 

 ages. Differences between mean lengths of age 

 groups III and V were only 0.4 to 0.7 inch in 

 different years. Thus, lake herring of these age 

 groups are similar in length regardless of age and 

 no great changes in length should be expected to 

 follow changes in age composition. 



That there is a greater growth than is indicated 

 by the average lengths of age groups is brought out 

 in a later discussion of computed growth. The 

 apparently poor growth suggested by the similar 

 average lengths of different-aged fish in the com- 

 mercial catch must be due either to a strong 



