Inter-comparison of Bongo and Juday Nets Size-fractionated Zooplankton Biomass Collected in the Gulf of Alaska During 2019

Abstract Excerpt:
In the North Pacific, the zooplankton data sets in the western and eastern parts were collected using different sampling gears, most often by Bongo and Juday nets. While preliminary taxonomic zooplankton inter-comparison between nets was performed, the biomass comparison is still unavailable. During winter (February–March) 2019, in the Gulf of Alaska (GoA) 34 paired zooplankton samples were collected using Bongo and Juday nets (Fig. 1). On board of R/V Professor Kaganovskiy, Bongo (0.5 m^-2 mouth area mesh 0.250 mm) and Juday (0.1 m^-2 mouth area, mesh 0.160 mm) nets were towed vertically from 250–0 m and 200–0 m, respectively. On board, the Bongo fresh zooplankton sample was size fractionated using 0.25, 0.5, 1, 2, and 4 mm sieves (Fig. 2). Juday nets samples were fixed in a 4% formaldehyde-seawater solution and size fractionated later using the same set of sieves. Size-fractions were then oven-dried at 50°C to the constant weight and weighed to the nearest 0.1 mg. Biomass was calculated by dividing size-fraction mass by the volume filtered estimated either using flowmeter (Bongo) or by the distance travelled multiplied by the mouth area (Juday).