. Bulletin. Natural history; Natural history. 342 Illinois Natural History Survey Bulletin Vol. 26, Art. 4 In comparing the efficiency and selectiv- ity of the various entrapment devices, it was necessary to consider the average size of the fish taken, as well as the num- ber of commercial-sized or desirable-sized fish caught. A small-mesh net might take as many fish of commercial species as a large-mesh net; however, the catch of the small-mesh net might be largely of fish under commercial size. The large-mesh net taking only a few fish under commer- cial size would be a more efficient net to
. Bulletin. Natural history; Natural history. 342 Illinois Natural History Survey Bulletin Vol. 26, Art. 4 In comparing the efficiency and selectiv- ity of the various entrapment devices, it was necessary to consider the average size of the fish taken, as well as the num- ber of commercial-sized or desirable-sized fish caught. A small-mesh net might take as many fish of commercial species as a large-mesh net; however, the catch of the small-mesh net might be largely of fish under commercial size. The large-mesh net taking only a few fish under commer- cial size would be a more efficient net to the fisherman since it would require less time for the handling and releasing of small fish. The mean of the total lengths of indi-. JFig. 12.—The number of fish, all sizes, taken per net-day in entrapment devices fished in the Mississippi River between Burlington and Dubuque in 1946. Table 6.—Data (from table 13) on catches of wing nets of two different mesh sizes used in fisheries survey of the Caruthersville-Dubuque section of the Mississippi River, 1944, the data selected and presented to allow comparison of the sizes of carp taken by the two mesh sizes. Net Mean Total Length (x), Inches Number of Carp (n) Standard Deviation (s) l-inch-mesh 886 356 3 34 l)^-inch-mesh The following equations are based on the t-test for significance and the degrees of freedom () formulas on page 344. t = - 4 ()* ()2 V = 356 886 d-f- = V 356-886 - 1 = or 562 - 1 = 561. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Illinois. Natural History Survey Division. Urbana, State of Illinois, Dept. of Registration and Education, Natural History Survey Division
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