Counting and identifying copepod species with an in situ electronic zooplankton counter

Abstract

The potential for identifying and separating copepod species and stages with an in situ electronic zooplankton counter, which was developed and tested as a biological tool, has been examined. The instrument was mounted on the Batfish, a depth-controllable towed body equipped to measure chlorophyll a, temperature, salinity, and depth. Zooplankton length and diameter distributions measured by the zooplankton counter were compared with measurements made using a microscope. Detailed analysis of the data shows that the electronic counter has sufficient resolution to separate and identify dominant species of copepods consisting of Clausocalanus arcuicornis, Metridia lucens, Calanus finmarchicus, and Euchirella rostrata sampled from the Scotian Shelf, and Centropages brachiatus, Calanus chiliensis, and Eucalanus inermis sampled from the Peruvian Shelf. The examples of Batfish data included show the separation of dominant species and copepod abundance estimates from the Peruvian Shelf. The relative merits of the electronic measurements and microscope analysis are discussed.