Experimental test of an allometric method for estimating potential copepod production

Abstract

Phytoplankton and zooplankton, collected in November 1984 at the deepest point of Bedford Basin, Canada, were used in a 2 mo experiment in the Dalhousie tower tank to test the validity of estimating potential copepod production from allometric equations based on body size and temperature under food-saturated conditions (“maximum instantaneous growth, MIG” method). The development of the plankton community in the mesocosm was similar to fall and winter assemblages in a coastal Nova Scotian inlet. Predicted instantaneous rates of potential production were compared with average production of a mixed copepod assemblage measured over weekly intervals in the absence of predators. Predictions exceeded measured production by 1.9 to 136 times, but generally agreed within an order of magnitude. Whereas the MIG method facilitates automated estimation of potential copepod production, this advantage must be offset by the relative loss of accuracy compared to more labour-intensive methods. The method appears to be most useful for mesoscale surveys or neritic regions where the aim is to quickly obtain an order of magnitude estimate of secondary production.