Distribution of and biomass of macroplankton in the West Tropical Pacific

Thirty-five night-time samples were collected with an Isaacs-Kidd trawl at depths ranging from 40 to 1100 m on four fixed-position stations in the western equatorial Pacific. The catches were sorted into taxonomic groups and weighed. An attempt was made to exclude unwanted material obtained as the trawl was hauled in. Despite irregular variation in biomass from catch to catch, change with depth in percentage of different groups in total plankton biomass was the same in the entire region under study. There was a distinct alternation of layers, in which the major carnivorous groups, Decapoda, Cephalopoda, Myctophidae, and other fishes dominate.