Transactions - American Fisheries Society . ^ rapidlyfrom that depth. At 6 meters the oxygen begins to show an in-crease; at 8 meters a maximum of oxygen is reached amountingto more than the 11 cc. per liter. It does not begin to fall offvery greatly until 10 meters have been reached, and even at 12meters there is still a somewhat alnuidant supply. From thatpoint it declines until it practically reaches zero, although it doesnot get absolutely to zero at any point in this lake—at least notin August, so far as our observations go. So that in this lake alsothe stratum which is availal^le for ani
Transactions - American Fisheries Society . ^ rapidlyfrom that depth. At 6 meters the oxygen begins to show an in-crease; at 8 meters a maximum of oxygen is reached amountingto more than the 11 cc. per liter. It does not begin to fall offvery greatly until 10 meters have been reached, and even at 12meters there is still a somewhat alnuidant supply. From thatpoint it declines until it practically reaches zero, although it doesnot get absolutely to zero at any point in this lake—at least notin August, so far as our observations go. So that in this lake alsothe stratum which is availal^le for animal life is by this actionof the plants increased from a thickness of perhaps 6 meters to12 or more meters. Ainericdii Fisheries Society. 159 How great an effect the condition of the gases may have onlakes can perliaps he well illustrated l)y a lake whose gases havenot yet been investigated. Mr. Hankinson who is studying Wal-nut Lake in Michigan, has l)een telling me todav of the results. Fig. 11 —Elkhart Lake. Aug. 23, 1906. he has found in the study of the life of that lake. The lake habout a mile in length and half that in breadth, and ITO feet indepth. It is a lake that is not far different in tlieso conditionsfrom Rainljow liake, Okauchee Lake, Xagowicka Lake and num-erous other lakes in Wisconsin. In Walnut Lake as I am told, the bottom is verv thicklv 160 * Thirtij-ffth Annual Meeting covered with insect larvae which are living in the mnd and feed-ing on the lower organisms which live at all depths, and bothinsects and lower Crustacea supply food for fishes. I think thetrue whitefish is found in fair numbers in this lake. Xow oursouthern Wisconsin lakes lack oxygen in the l^ottom water; in-sect larvae, therefore, cannot live at the Iwttom. Oxygen is cutoff from the lower water early in July and does not increasethere again till October; and the result is that the bottom watersof our lakes are poor in life, and there is no possibility of rais-ing in these lakes
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