MAXIMUM DAILY RATION OF GREAT-LAKES BLOATER

Maximum daily consumption rates of bloater Coregonus hoyi from Lake Mi chigan were measured in the laboratory for 1-, 5-, 10-, 25-, 50-, 100- , and 200-g fish at 4, 8, 12, and 16-degrees-C. These represent most o f the ranges in bloater size and temperature likely to be encountered in Lake Michigan. Bloaters were raised from eggs in the laboratory and acclimated to test temperatures for 22-23 d prior to the experiments. Maximum daily consumption rates were determined by feeding the fish s urplus amounts of brine shrimp Artemia sp. at 4-h intervals for 24 h. Specific daily ration increased with temperature up to 16-degrees-C fo r all size-groups. At 12 and 16-degrees-C, the maximum daily ration of small bloaters (about 1 g) exceeded 120% of body weight per day (base d on wet weight; equivalent to 79%/d based on dry weight); the maximum daily ration of large bloaters (over 100 g) ranged between 5 and 12%/ d (2-7%/d based on dry weight). As percentage of maximum consumption a t 16-degrees-C, consumption rates averaged 82% at 12-degrees-C, 45% at 8-degrees-C, and 28% at 4-degrees-C. These results can be described b y the equation: C(max) = 1.61 . W-0.138. F(T), where C(max) is specifi c maximum consumption rate (g.g-1.d-1), W is fish weight (g), and F(T) is a dome-shaped temperature dependence function with an optimum temp erature of 16.8-degrees-C (R2 = 0.957, N = 27).