Improving Conditions for Fish in Brown-Water Bog Lakes by Alkalization

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Abstract
By applying hydrated lime [Ca(OH)2 and Mg(OH)2] to an acid (pH 5.6) brown-water bog lake in n. Wisconsin in sufficient quantity to change the pH to 8.4 and maintaining it above pH 7.2,it was possible to remove enough of the brown color to double the light penetration and double the 02 concn. in the thermocline. These improved conditions produced a favorable habitat for trout by increasing the O2 values in cooler strata. Theoretically it would increase the volume of the food producing zone so that greater productivity for native spp. of fish would be realized as well. Knowing the volume of a lake, its pH and alkalinity, the amount of lime necessary can be estimated. This value was lower than the amount actually needed to produce alkaline conditions owing to the uptake of lime by the mud and inability to get all lime in soln. when it was scattered. In this instance (Cather Lake, Chippewa County, Wisconsin; 8 acres, 10 m. deep) it took twice the amount theoretically necessary. Care was taken not to over-alkalize. Clearing of the water set in soon. Within a month after alkalization Secchi disc readings had doubled. Bicarbonate also increased thus augmenting available CO2 for photosynthesis.

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