An intercomparison of the taxonomic and size composition of tropical macrozooplankton and micronekton collected using three sampling gears

Abstract

A micronekton intercalibration experiment was conducted off the southwest coast of Oahu Island, Hawaii in October 2004. Day and night samples were collected in the epipelagic and mesopelagic zones using three micronekton sampling gears: the Cobb Trawl, the Isaacs-Kidd Midwater Trawl (IKMT), and the Hokkaido University Frame Trawl (HUFT). Taxonomic composition and contribution by main size groups to total catch varied among gear types. However, the three gears exhibited similar taxonomic composition for macrozooplankton and micronekton ranging from 20 to 100 mm length (MM20–100). The HUFT and IKMT captured more mesozooplankton and small MM20–100, while the Cobb trawl selected towards larger MM20–100 and nekton. Taxonomic composition was described and inter-compared among gears. The relative efficacy of the three gears was assessed, and size dependent intercalibration coefficients were developed for MM20–100.