Variable Factors Affecting the Apparent Range and Estimated Concentration of Euphausiids in the North Pacific

Abstract

The quantitative and qualitative contents of a zooplankton sample are influenced by two kinds of variables: (1) natural variables such as temperature of the water, currents, latitudinal and seasonal variations in sunlight intensity, water transparency, amount of food or nutrients, oxygen content of the water, which may modify or maintain the horizontal and vertical distribution of species and condition their breeding and growth cycles; (2) artificial variables associated with (a) the method used to present the data, (b) the method used to take aliquots and count the plankton, and (c) the collecting method-type of net, depth of tow, hour of day of sampling.