On the biology ofCalanus finmarchicus: XIII. Seasonal change in weight, calorific value and organic matter

Abstract

The length, weight, calorific value and organic matter content ofCalanus finmarchicus, Stage V, males and females, were measured in monthly samples taken from April 1962 to June 1963.There is considerable variation throughout the year and all stages had their maxima of weight and calorific value in spring, 1962, and winter 1962–63.The calorific value and weight are closely correlated so that, knowing the dry weight, the calorific value can be calculated from it. The correlation is closest in Stage V and, for these, only the dry weight need be known. Since the relation-ship is slightly different for males and females the sex of the adult must be known as well as the dry weight; curves showing these relationships are given.The calorific value obtained from organic-matter analysis at times deviates widely from the values obtained in direct bomb calorimetry, and it is concluded that in the method used not all the fat is accounted for.In weight, calorific value, and organic matter, but not in length, Stage V for a good part of the year show higher figures than adults.In comparing the weights with those of other years and other places, the annual pattern is found to vary considerably. The spring maximum seems to occur every year, but there may be either a maximum or a minimum in autumn and winter.