Diel variation of zooplankton distributions in Hawaiian waters favors horizontal diel migration by midwater micronekton

摘要: Micronekton in deep-scattering layers around the Hawaiian Islands undergo diel migrations with both vertical and horizontal components. We sought to determine whether resource availability provides an adaptive explanation for this migration. simultaneously measured spatio-temporal patterns of micronekton, using acoustics imaging optics, their potential zooplankton prey, net tows, acoustics, optics. Zooplankton biomass, density, total abundance were higher at night than prior sunset nearshore sites, whereas relatively little variation was observed offshore. All measures 5 6 times offshore during nighttime hours when migrating micronekton species nearshore. There no significant nearshore-offshore gradient sunset, leading 2 possible explanations day-night zooplankton: benthic emergence migration coupled motion. Analysis taxonomic from tows did not support hypothesis. 3 assessment techniques supported conclusion that distribution could favor by given pressures micronketon be deep water daylight avoid predators. Recently pub- lished work has shown small animals (2 10 cm length) scattering comprised travel distances least 11 km roundtrip each night, often against currents, obtain these increased food resources. The length likely cost journey some insight about importance feeding gains.