Feeding patterns of transforming and juvenile myctophids that reach the neustonic layers

Abstract

43 Annual Larval Fish Conference, 21-24 May 2019, Palma, Balearic IslandsLanternfish of the family Myctophidae are one of the most abundant fish in the open ocean. Adult myctophids have a wide vertical distribution through the water column; with conspicuous differences in their day and night location, feeding at night in the epipelagic zone and being more disperse in the mesopelagic region during the day. Contrasting, larval stages are restricted to the upper 200 m, both day and night, performing restricted vertical displacements. Transforming stages show a less defined diel vertical and feeding pattern, while juveniles behave like adults. In this study we analysed the trophic ecology of transforming and juvenile stages of a particular group of myctophids known for reaching the neustonic layers in their adult night migration: Myctophum affine, M. asperun, M. nitidulum and Gonichthys cocco. Neuston samples were collected across the tropical and equatorial Atlantic, in 12 stations sampled day and night. Transforming and juvenile stages occurred at night in in the neuston, where they fed, and were absent from this layer during the day. The highest prey ingestion was observed for individuals collected mainly between 1-4 am. The incidence of feeding in the stages of transformation (60%) was lower than in the juveniles (66-100%). The number of prey ingested and their sizes did not show any increasing trend between stages, but there was great variability among individuals. Diet of the four species was mainly composed by a variety of genus of copepods, generally dominated by Oncaea spp species. For M. asperum there was almost no other type of prey in the stomachs. The high carbon content of preys like hyperiids made that the total carbon content per stomach was higher when these prey occur in the diet, such as in juveniles of M. nitidulumPeer Reviewe