On the Biology of Calanus finmarchicus. Part IV. Seasonal Changes in the Weight and Chemical Composition in Loch Fyne

A. P. Orr
1934 Journal of the Marine Biological Association of the United Kingdom  
port. ---~-With 5 Figures in the Text. THE value of the zooplankton as a fish food depends not only on its distribution and numbers but also, to a large extent, on its chemical composition. Analyses of the marine plankton have already been made by Brandt (1898) , Brandt and Raben (1919-22), Meyer (1914), Moberg (1926) and Wimpenny (1929) . These authors worked on tow-nettings containing mixed plankton, both plant and animal. In the analyses of Brandt and of Brandt and Raben an attempt was made
more » ... n attempt was made to assess the value of the zooplankton and of the phytoplankton apart from one another. Seasonal variations have apparently been dealt with only by Wimpenny and Moberg who had the disadvantage of dealing with mixed catches; but the variation shown in some of the analyses given by Brandt and by Brandt and Raben suggests that seasonal variations in chemical composition take place. The analyses given by-the above authors, with the exception of those by Moberg and Wimpenny, were made on preserved material and no separation of individual species of plants and animals was possible; in any case, the large numbers they had to deal with would have rp.ade such an attempt extremely laborious even if the method of preservation adopted had allowed of it. However, by analysing a number of catches in which certain species of plants or animals predominated, Brandt, and Brandt and Raben, were able to give an approximate figure for the chemical composition of certain groups or species. The results in the following pages record an attempt to measure the variations in the composition of Oalanusfinmarchicus by itself. O.finmar-ch1"cusis an important food of certain fish and is widely distributed. In the Clyde Sea-Area it constitutes a considerable percentage of the zooplankton as a whole. The object of the work was to ascertain, in conjunction with the observations on size and distribution by Marshall (1933) and Nicholls (1933) recorded in Parts I and II of this series, what
doi:10.1017/s002531540004666x fatcat:ewctyzn4fvb2dkdjtznogxdyeu