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Species Composition by Age Groups and Stability of Fish Populations in Sections of Three Michigan Trout Streams during the Summer of 1937
Author(s) -
Shetter David S.,
Hazzard Albert S.
Publication year - 1939
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1938)68[281:scbaga]2.0.co;2
Subject(s) - streams , trout , fishery , fish <actinopterygii> , habitat , census , population , geography , tributary , table (database) , environmental science , hydrology (agriculture) , biology , ecology , geology , cartography , demography , computer network , geotechnical engineering , sociology , computer science , data mining
Intensive studies of the fish populations in three sections of the South Branch of the Pine River, two sections of the Little Manistee River, and three sections of the North Branch of the Boardman River were carried out monthly from June to September, 1937. The same sections were blocked and seined each month and the fish found there were enumerated by species, weighed, and measured. Scale samples were collected from all trout above age‐group O. The efficiency of the block‐and‐seining method of stream census was tested in the most difficult section to seine (lower census section on the South Branch of the Pine River). It was found to be 89.1 per cent effective, comparing favorably with results of similar tests conducted in New Hampshire trout streams. As far as could be determined, the method was 100 per cent efficient for the enumeration of the trout population. Only the very small minnows, muddlers, and suckers escaped the first seining. From the results of the seinings and from plane‐table maps of the census sections, monthly estimates were made of the populations per acre and per mile in the censused portions of each stream. No computations for entire streams have been made because the proportion of the habitats censused is not known for any of the streams in question. The estimates for various habitats must be considered as tentative in the light of the extreme variation found in the same section in different months. Recaptures of marked fish in subsequent months indicate that neither the trout nor the “coarse fish” tend to remain in the census areas. Calculations of stream populations on the basis of one or two counts in limited sections at any one time are therefore inaccurate. A study of the age of the trout collected in the census sections of the North Branch of the Boardman indicated an abnormal number of trout of age‐group O. In the South Branch of the Pine and in the Little Manistee the older age groups were present. The oldest trout represented by a few individuals were members of age‐group III, or in the fourth year of life.