Does water calcium content influence the distinctness of daily growth increments in the otoliths of larval whitefish (Coregonus lavaretus L.)?

In larval and juvenile whitefish (Coregonus lavaretus L.) from Lake Constan ce, Germany, the otolith increments are deposited daily, whereas dairy depo sition could not be confirmed in larval whitefish from Lake Pyhaselka, Finl and. The calcium concentration in Lake Constance is high (around 1.3 mM), w hile calcium deficiency is typical for Finnish lakes (around 0.15 mM). Ther efore, the hypothesis that the distinctness of daily otolith increments in whitefish is related to water calcium content was tested by rearing three g roups of Lake Constance whitefish in water of 0.2, 1.3 and 4.7 mM Ca. The e ggs were incubated in lake water (1.3 mM Ca), and the larvae were acclimate d to the experimental calcium concentrations on the day of hatching. After 39 days of ad libitum-feeding with Artemia nauplii, the three groups did no t differ significantly in total length, wet and dry weight, and otolith len gth and width. The daily increments were easily recognizable, and contrast between dark (D)- and light (L)-zones was the same in the fish of all test groups. For the experimental set-up of this study, and particularly the ran ge of calcium concentrations tested, the hypothesis that water calcium cont ent influences the distinctness of daily otolith increments was rejected.