Migration and feeding ecology of dominant diel vertical migrants fishes, in the Canary Islands waters

Abstract

Diel vertical migrants (DVMs) are mainly zooplankton and micronekton migrating upward from 400-700 m depth every night to feed in the productive epipelagic zone and downward at dawn to the mesopelagic zone, where they release the ingested carbon. This is the so-called Active Flux, an important component of the Ocean Carbon Pump. Around 70% micronektonic DVMs biomass are lanternfishes (myctophidae). Therefore, myctophids might represent a pathway accounting for a substantial export of organic carbon to deeper waters. In order to assess the efficiency of the micronekton active flux, here we study the migration pattern and the feeding ecology in Hygophum hygomii and Lobianchia dofleini, two dominant myctophids in the Subtropical Eastern North Atlantic. Our results show that both populations are split in migratory and non-migratory individuals. The last ones were in a deprivation and post-digesting state with full stomachs of non-fresh food. This suggests that the evacuation rate is long enough to export efficiently most of the ingested food to the mesopelagic zone. The daily ration of the migratory individuals was 1.99 ±0.18 and 1.34 ±0.45 % of body dry weight of H. hygomii and L. dofleini respectively, feeding mainly on copepods and euphausiids. The feeding strategies and the migration patterns are discussed in order to provide further information concerning the micronekton active flux efficiency.