Comparing the catch efficiency with different types of plankton nets in the high production zones of the Pacific Ocean

Abstract

A comparison of the qualitative and quantitative characteristics of zooplankton caught by five different types of plankton nets was performed on the basis of the data of plankton surveys in various high production zones of the Pacific Ocean (392 zooplankton samples) in order to determine conversion coefficients for a more adequate quantitative estimation of plankton. In epipelagic zones, both the abundance and biomass of zooplankton caught by a Juday net were practically everywhere higher as compared to those estimated with the use of JuOM and Norpak nets but lower than the values obtained with Bongo nets. For the sake of the comparison of the quantitative estimations with different nets, we suggest coefficients equal to the ratios of the zooplankton biomass from a Juday net to the biomasses from other nets: from 0.4 to 1.5 for the total biomass values and from 0.3 to 2.3 for individual groups of zooplankton. The coefficients applied at the TINRO to account for the plankton underhauling with big Juday nets are reasonable and reliable for most of the dominating groups except for chaetognats, which are twice overestimated.