File:The crustacea of the plankton, July, 1894-Dec., 1896 (1897) (14774777935).jpg

Identifier: crustaceaofplank00birg (find matches)
Title: The crustacea of the plankton, July, 1894-Dec., 1896
Year: 1897 (1890s)
Authors: Birge, E. A. (Edward Asahel), 1851-1950
Subjects: Plankton
Publisher: (Madison : s.n.)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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ng this time Cyclops begins its rapid increase towardsthe spring maximum, if the multiplication has not already begununder the ice. Its swarms of young are in the upper strata ofthe water. It may be laid down as a general rule that largenumbers of young of any species of Crustacea appear first in theupper levels of the water, and the animals later pass towardthe middle of the lake; and later still, occupy the water towardthe bottom. It may be said, therefore, in general, that thepresence in the upper water of a very high percentage of thecatch of any species indicates the beginning of a period of re- X xx XI 8. pa 1. oin > l 1 O • i l 55 /;/ f 4 / // / H // o O // ■ > /. \ H \ Ph \ H \ aj \\ // // d / 1 P<5 < s • / 1 H \ & 1-5 \ \ s^ \ \, \ ^ ^ ^ ^ <^y * .••■ HB P i-s yf i <s V, N H •» V \ ■«J N ■-•.._ a N \ ;-» ^ 08:52, 23 September 2015 (UTC)^<Z2- V\ 4 V M a ^^ Ph \ <j a go ft 68 O 02 S3 o ooq ©*~ B3ft02 o c8O 00 .2 S3• i—i in02 > d s 00 2
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GOCO W. u © 02U © ft © a ooo cT aa ft 02 o ;-! © c3O 02 to CO o•i—i 3•i—i -♦-».°2 a•i—i CM 6 h-1 Vertical Distribution of the Crustacea—Spring. 381 production of the species, while the presence of a larger numberin the bottom water of the lake than in the surface water indi-cates that the species is past its maximum and is already be-ginning to decline in numbers. In both years the numbers of Crustacea in the upper watershow an increase during April, due to the multiplication ofCyclops. This increase went on, as was shown in the early partof this paper, much more rapidly in 1896 than in 1895. As aresult, the population both of the surface water and of thelower levels increased much more rapidly in 1896, and the latterpart of April, 1896, represents about the same condition of thedevelopment of the Crustacea, as does the first half of May in1895. In each case more than 40 per cent, of the Crustaceawere present in the upper stratum, while the 15-18 m. levelhad not

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